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• TableofContents• Index• Reviews• ReaderReviews• Errata• Academic

JavaServlet&JSPCookbookByBruceW.Perry

Publisher :O'ReillyPubDate :January2004

ISBN :0-596-00572-5Pages :746

Withliterallyhundredsofexamplesandthousandsoflinesofcode,theJavaServletandJSPCookbookyieldstipsandtechniquesthatanyJavawebdeveloperwhousesJavaServerPagesorservletswilluseeveryday,alongwithfull-fledgedsolutionstosignificantwebapplicationdevelopmentproblemsthatdeveloperscaninsertdirectlyinto

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theirownapplications.

• TableofContents• Index• Reviews• ReaderReviews• Errata• Academic

JavaServlet&JSPCookbookByBruceW.Perry

Publisher :O'ReillyPubDate :January2004

ISBN :0-596-00572-5Pages :746

Copyright Preface What'sintheBook

Audience

Organization

ConventionsUsedinThisBook

UsingCodeExamples

CommentsandQuestions

Acknowledgments

Chapter1.WritingServletsandJSPs Introduction

Recipe1.1.WritingaServlet

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Recipe1.2.WritingaJSP

Recipe1.3.CompilingaServlet

Recipe1.4.PackagingServletsandJSPs

Recipe1.5.CreatingtheDeploymentDescriptor

Chapter2.DeployingServletsandJSPs Introduction

Recipe2.1.DeployinganIndividualServletonTomcat

Recipe2.2.UsingaContextElementinTomcat'sserver.xml

Recipe2.3.DeployinganIndividualServletonWebLogic

Recipe2.4.DeployinganIndividualJSPonTomcat

Recipe2.5.DeployinganIndividualJSPonWebLogic

Recipe2.6.DeployingaWebApplicationonTomcat

Recipe2.7.DeployingaWebApplicationonWebLogicUsingAnt

Recipe2.8.UsingtheWebLogicAdministrationConsole

Recipe2.9.UsingWebLogicBuildertoDeployaWebApplication

Recipe2.10.Usingtheweblogic.DeployerCommand-LineTool

Chapter3.NamingYourServlets Introduction

Recipe3.1.MappingaServlettoaNameinweb.xml

Recipe3.2.CreatingMoreThanOneMappingtoaServlet

Recipe3.3.CreatingaJSP-TypeURLforaServlet

Recipe3.4.MappingStaticContenttoaServlet

Recipe3.5.InvokingaServletWithoutaweb.xmlMapping

Recipe3.6.MappingAllRequestsWithinaWebApplicationtoaServlet

Recipe3.7.MappingRequeststoaControllerandPreservingServletMappings

Recipe3.8.CreatingWelcomeFilesforaWebApplication

Recipe3.9.RestrictingRequestsforCertainServlets

Recipe3.10.GivingOnlytheControllerAccesstoCertainServlets

Chapter4.UsingApacheAnt Introduction

Recipe4.1.ObtainingandSettingUpAnt

Recipe4.2.UsingAntTargets

Recipe4.3.IncludingTomcatJARfilesintheBuildFileClasspath

Recipe4.4.CompilingaServletwithanAntBuildFile

Recipe4.5.CreatingaWARFilewithAnt

Recipe4.6.CreatingaJARFilewithAnt

Recipe4.7.StartingaTomcatApplicationwithAnt

Recipe4.8.StoppingaTomcatApplicationwithAnt

Chapter5.AlteringtheFormatofJSPs

Introduction

Recipe5.1.PrecompilingaJSPinTomcat

Recipe5.2.PrecompilingaJSPinWebLogic

Recipe5.3.PrecompilingJSPswiththePrecompilationProtocol

Recipe5.4.MappingaJSPtoItsPageImplementationClass

Recipe5.5.CreatingaJSPfromScratchasaJSPDocument

Recipe5.6.GeneratinganXMLViewfromaJSP

Chapter6.DynamicallyIncludingContentinServletsandJSPs Introduction

Recipe6.1.IncludingaResourceEachTimeaServletHandlesaRequest

Recipe6.2.UsinganExternalConfigurationtoIncludeaResourceinaServlet

Recipe6.3.IncludingResourcesNestedatMultipleLevelsinaServlet

Recipe6.4.IncludingaResourcethatSeldomChangesintoaJSP

Recipe6.5.IncludingContentinaJSPEachTimetheJSPHandlesaRequest

Recipe6.6.UsinganExternalConfigurationFiletoIncludeaResourceinaJSP

Recipe6.7.IncludinganXMLFragmentinaJSPDocument

Recipe6.8.IncludingContentfromOutsideaContextinaJSP

Chapter7.HandlingWebFormDatainServletsandJSPs Introduction

Recipe7.1.HandlingaPOSTHTTPRequestinaServlet

Recipe7.2.HandlingaPOSTHTTPRequestinaJSP

Recipe7.3.SettingthePropertiesofaJavaBeaninaJSP

Recipe7.4.SettingaScopedAttributeinaJSPtotheValueofaFormParameter

Recipe7.5.PostingDatafromaServlet

Recipe7.6.PostingDatafromaJSP

Recipe7.7.UsingaServlettoAddaParametertoaQueryString

Recipe7.8.UsingaJSPtoAddaParametertoaQueryString

Recipe7.9.UsingaFiltertoReadParameterValues

Chapter8.UploadingFiles Introduction

Recipe8.1.PreparingtheHTMLPageforFileUploads

Recipe8.2.Usingthecom.oreilly.servletLibrary

Recipe8.3.UploadingOneFileataTime

Recipe8.4.UploadingMultipleFiles

Recipe8.5.RenamingFiles

Recipe8.6.UsingaJSPtoHandleaFileUpload

Chapter9.HandlingExceptionsinWebApplications

Introduction

Recipe9.1.DeclaringExceptionHandlersinweb.xml

Recipe9.2.CreatinganException-HandlingServlet

Recipe9.3.SendinganErrorfromaServlet

Recipe9.4.SendinganErrorfromaJSP

Recipe9.5.CreatinganError-HandlingJSP

Recipe9.6.DeclaringaSpecialException-HandlingJSPforOtherJSPs

Chapter10.ReadingandSettingCookies Introduction

Recipe10.1.SettingaCookiewithaServlet

Recipe10.2.CreatinganArrayfromAlloftheRequest'sCookies

Recipe10.3.SettingaCookiewithaJSP

Recipe10.4.ReadingCookieValueswithaServlet

Recipe10.5.ReadingCookieValueswithaJSP

Recipe10.6.AlteringorRemovingaCookieThatHasAlreadyBeenSet

Chapter11.SessionTracking Introduction

Recipe11.1.SettingtheSessionTimeoutinweb.xml

Recipe11.2.SettingtheSessionTimeoutinAllTomcatWebApplications

Recipe11.3.SettingtheSessionTimeoutProgrammatically

Recipe11.4.CheckingifaSessionExistsinanHttpServletRequest

Recipe11.5.TrackingSessionActivityinServlets

Recipe11.6.TrackingSessionActivityinJSPs

Recipe11.7.UsingURLRewritinginaJSP

Recipe11.8.UsingURLRewritinginaServlet

Recipe11.9.UsingaListenertoTracktheSessionLifecycle

Recipe11.10.UsingaListenertoMonitorSessionAttributes

Recipe11.11.UsingaFiltertoMonitorSessionAttributes

Chapter12.IntegratingJavaScriptwithServletsandJSPs Introduction

Recipe12.1.IncludingJavaScriptModulesinaServlet

Recipe12.2.IncludingJavaScriptModulesinaJSP

Recipe12.3.CreatingaNewWindowwithJavaScriptinaServlet

Recipe12.4.CreatingaNewWindowwithJavaScriptinaJSP

Recipe12.5.UsingJavaScripttoValidateFormValuesinaServlet

Recipe12.6.UsingJavaScripttoValidateFormValuesinaJSP

Chapter13.SendingNon-HTMLContent Introduction

Recipe13.1.SendingaPDFFile

Recipe13.2.SendingaWordProcessingFile

Recipe13.3.SendinganXMLfile

Recipe13.4.SendinganAudioFile

Recipe13.5.ViewingInternalResourcesinaServlet

Chapter14.LoggingMessagesfromServletsandJSPs Introduction

Recipe14.1.LoggingWithoutLog4j

Recipe14.2.SettingUpLog4j

Recipe14.3.UsingaLoggerWithoutaConfigurationFile

Recipe14.4.AddinganAppendertotheRootLogger

Recipe14.5.UsingaPatternwithaLogger'sAppender

Recipe14.6.Usinglog4jinaJSP

Recipe14.7.LoggingMessagesUsingaServletContextEventListener

Recipe14.8.LoggingMessagesUsingaSessionEventListener

Chapter15.AuthenticatingClients Introduction

Recipe15.1.CreatingUsersandPasswordswithTomcat

Recipe15.2.SettingUpSSLonTomcat

Recipe15.3.UsingBASICAuthentication

Recipe15.4.UsingForm-BasedAuthentication

Recipe15.5.LoggingOutaUser

Recipe15.6.UsingJAAStoCreateaLoginModule

Recipe15.7.CreatingtheJAASConfigurationFile

Recipe15.8.UsingJAASinaServlet

Recipe15.9.UsingJAASinaJSP

Chapter16.Binding,Accessing,andRemovingAttributesinWebApplications Introduction

Recipe16.1.SettingServletContextAttributesinServlets

Recipe16.2.SettingServletContextAttributesinJSPs

Recipe16.3.AccessingorRemovingServletContextAttributesinServlets

Recipe16.4.AccessingorRemovingServletContextAttributesinJSPs

Recipe16.5.SettingSessionAttributesinServlets

Recipe16.6.SettingSessionAttributesinJSPs

Recipe16.7.AccessingorRemovingSessionAttributesinServlets

Recipe16.8.AccessingorRemovingSessionAttributesinJSPs

Recipe16.9.SettingRequestAttributesinServlets

Recipe16.10.SettingRequestAttributesinJSPs

Recipe16.11.AccessingorRemovingRequestAttributesinServlets

Recipe16.12.AccessingorRemovingRequestAttributesinJSPs

Chapter17.EmbeddingMultimediainJSPs Introduction

Recipe17.1.EmbeddinganAppletinaJSPUsingjsp:plugin

Recipe17.2.EmbeddinganAppletinaJSPUsingtheHTMLConverter

Recipe17.3.AutomaticallyCreatingHTMLTemplateforIncludingFlashFiles

Recipe17.4.WritingHTMLTemplatetoEmbedaFlashFile

Recipe17.5.EmbeddingFlashinaServlet

Recipe17.6.EmbeddingaQuickTimeMovieinaJSP

Recipe17.7.EmbeddinganSVGFileinaJSP

Recipe17.8.EmbeddingaBackgroundSoundtrackinaJSP

Chapter18.WorkingWiththeClientRequest Introduction

Recipe18.1.ExaminingHTTPRequestHeadersinaServlet

Recipe18.2.ExaminingHTTPRequestHeadersinaJSP

Recipe18.3.UsingaFiltertoAlterRequestHeaders

Recipe18.4.AutomaticallyRefreshingaServlet

Recipe18.5.AutomaticallyRefreshingaJSP

Recipe18.6.CountingtheNumberofWebApplicationRequests

Chapter19.FilteringRequestsandResponses Introduction

Recipe19.1.MappingaFiltertoaServlet

Recipe19.2.MappingaFiltertoaJSP

Recipe19.3.MappingMoreThanOneFiltertoaServlet

Recipe19.4.ChangingtheOrderinWhichFiltersareAppliedtoServlets

Recipe19.5.ConfiguringInitializationParametersforaFilter

Recipe19.6.OptionallyBlockingaRequestwithaFilter

Recipe19.7.FilteringtheHTTPResponse

Recipe19.8.UsingFilterswithRequestDispatcherObjects

Recipe19.9.CheckingFormParameterswithaFilter

Recipe19.10.BlockingIPAddresseswithaFilter

Chapter20.ManagingEmailinServletsandJSPs Introduction

Recipe20.1.PlacingtheEmail-RelatedClassesonyourClasspath

Recipe20.2.SendingEmailfromaServlet

Recipe20.3.SendingEmailfromaServletUsingaJavaBean

Recipe20.4.AccessingEmailfromaServlet

Recipe20.5.AccessingEmailfromaServletUsingaJavaBean

Recipe20.6.HandlingAttachmentsfromanEmailReceivedinaServlet

Recipe20.7.AddingAttachmentstoanEmailinaServlet

Recipe20.8.ReadingaReceivedEmail'sHeadersfromaServlet

Chapter21.AccessingDatabases Introduction

Recipe21.1.AccessingaDatabasefromaServletWithoutDataSource

Recipe21.2.ConfiguringaDataSourceinTomcat

Recipe21.3.UsingaDataSourceinaServletwithTomcat

Recipe21.4.CreatingaDataSourceonWebLogic

Recipe21.5.UsingaJNDILookuptogetaDataSourcefromWebLogic

Recipe21.6.UsingaDataSourcefromWebLogicinaJSP

Recipe21.7.CallingaStoredProcedurefromaServlet

Recipe21.8.CallingaStoredProcedurefromaJSP

Recipe21.9.ConvertingaResultSettoaResultObject

Recipe21.10.ExecutingSeveralSQLStatementsWithinaSingleTransaction

Recipe21.11.UsingTransactionswithJSPs

Recipe21.12.FindingInformationaboutaResultSet

Chapter22.UsingCustomTagLibraries Introduction

Recipe22.1.CreatingaClassicTagHandler

Recipe22.2.CreatingaJSP1.2TLDforaClassicTagHandler


Recipe22.4.PackagingaTagLibraryinaWebApplication

Recipe22.5.PackagingtheTagLibraryinaJARFile

Recipe22.6.UsingtheCustomTaginaJSP

Recipe22.7.HandlingExceptionsinaCustomTagClass

Recipe22.8.CreatingaSimpleTagHandler

Recipe22.9.CreatingaTLDforaSimpleTagHandler

Recipe22.10.UsingaSimpleTagHandlerinaJSP

Recipe22.11.CreatingaJSPTagFile

Recipe22.12.PackagingtheJSPTagFileinaWebApplication

Recipe22.13.PackagingtheJSPTagFileinaJAR

Recipe22.14.UsingaCustomTagAssociatedwithaTagFile

Recipe22.15.AddingaListenerClasstoaTagLibrary

Chapter23.UsingtheJSTL Introduction

Recipe23.1.DownloadingtheJSTL1.0andUsingtheJSTLTagsinJSPs

Recipe23.2.DownloadingtheJavaWebServicesDeveloperPack

Recipe23.3.UsingtheCoreJSTLTags

Recipe23.4.UsingtheXMLCoreJSTLTags

Recipe23.5.UsingtheXMLTransformTags

Recipe23.6.UsingtheFormattingJSTLTags

Recipe23.7.UsingASQLJSTLTagwithaDataSourceConfiguration

Recipe23.8.UsingASQLJSTLTagWithoutaDataSourceConfiguration

Recipe23.9.AccessingScopedVariableswiththeEL

Recipe23.10.AccessingRequestParameterswiththeEL

Recipe23.11.UsingtheELtoAccessRequestHeaders

Recipe23.12.UsingtheELtoAccessOneRequestHeader

Recipe23.13.AccessingCookieswiththeEL

Recipe23.14.UsingtheELtoAccessJavaBeanProperties

Recipe23.15.UsingJSTLFunctions

Chapter24.Internationalization Introduction

Recipe24.1.DetectingtheClientLocaleinaServlet

Recipe24.2.DetectingtheClient'sLocalesinaJSP

Recipe24.3.CreatingaResourceBundleasaPropertiesFile

Recipe24.4.CreatingaResourceBundleasaJavaClass

Recipe24.5.UsingtheResourceBundleinaServlet

Recipe24.6.UsingtheResourceBundleinaJSP

Recipe24.7.FormattingDatesinaServlet

Recipe24.8.FormattingDatesinaJSP

Recipe24.9.FormattingCurrenciesinaServlet

Recipe24.10.FormattingCurrenciesinaJSP

Recipe24.11.FormattingPercentagesinaServlet

Recipe24.12.FormattingPercentagesinaJSP

Recipe24.13.SettingtheLocalizationContextintheDeploymentDescriptor

Chapter25.UsingJNDIandEnterpriseJavaBeans Introduction

Recipe25.1.ConfiguringaJNDIObjectinTomcat

Recipe25.2.AccessingtheTomcatJNDIResourcefromaServlet

Recipe25.3.AccessingtheTomcatJNDIResourcefromaJSP

Recipe25.4.ConfiguringaJNDIResourceinWebLogic

Recipe25.5.ViewingtheJNDITreeinWebLogic

Recipe25.6.AccessingtheWebLogicJNDIResourcefromaServlet

Recipe25.7.AccessingtheWebLogicJNDIResourcefromaJSP

Recipe25.8.AccessinganEJBUsingtheWebLogicJNDITree

Chapter26.HarvestingWebInformation Introduction

Recipe26.1.ParsinganHTMLPageUsingthejavax.swing.textSubpackages

Recipe26.2.UsingaServlettoHarvestWebData

Recipe26.3.CreatingaJavaBeanasaWebPageParser

Recipe26.4.UsingtheWebPageParsingJavaBeaninaServlet

Recipe26.5.UsingtheWebPageParsingJavaBeaninaJSP

Chapter27.UsingtheGoogleandAmazonWebAPIs Introduction

Recipe27.1.GettingSetUpwithGoogle'sWebAPI

Recipe27.2.CreatingaJavaBeantoConnectwithGoogle

Recipe27.3.UsingaServlettoConnectwithGoogle

Recipe27.4.UsingaJSPtoConnectwithGoogle

Recipe27.5.GettingSetUpwithAmazon'sWebServicesAPI

Recipe27.6.CreatingaJavaBeantoConnectwithAmazon

Recipe27.7.UsingaServlettoConnectwithAmazon

Recipe27.8.UsingaJSPtoConnectwithAmazon

Colophon Index

Copyright

Copyright©2004O'ReillyMedia,Inc.

PrintedintheUnitedStatesofAmerica.

PublishedbyO'ReillyMediaInc.,1005GravensteinHighwayNorth,Sebastopol,CA95472.

O'Reilly&Associatesbooksmaybepurchasedforeducational,business,orsalespromotionaluse.Onlineeditionsarealsoavailableformosttitles(http://safari.oreilly.com).Formoreinformation,contactourcorporate/institutionalsalesdepartment:(800)[email protected].

NutshellHandbook,theNutshellHandbooklogo,andtheO'ReillylogoareregisteredtrademarksofO'ReillyMedia,IncTheCookbookseriesdesignations,JavaServletandJSPCookbook,theimageofafennecfox,andrelatedtradedressaretrademarksofO'Reilly&Associates,Inc.

JavaandallJava-basedtrademarksandlogosaretrademarksorregisteredtrademarksofSunMicrosystems,Inc.,intheUnitedStatesandothercountries.O'ReillyMedia,Inc.isindependentofSunMicrosystems,Inc.

Manyofthedesignationsusedbymanufacturersandsellerstodistinguishtheirproductsareclaimedastrademarks.Wherethosedesignationsappearinthisbook,andO'Reilly&Associateswasawareofatrademarkclaim,thedesignationshavebeenprintedincapsorinitialcaps.

Whileeveryprecautionhasbeentakeninthepreparationofthisbook,thepublisherandauthorsassumenoresponsibilityforerrorsoromissions,orfordamagesresultingfromtheuseoftheinformationcontainedherein.

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mailto:[email protected]

PrefaceOnahistoricaltimeline,thesagaofJavaasaserver-sideprogrammer'stoolofchoicebeganinearly1997whenSunMicrosystemsreleasedthe"Java™WebServer"betaandJavaServletDevelopersKit.[1]ServletsareatypeofJavaclassthatexecutesonaserver.Servletsdynamicallyhandlenetworkedrequestsandresponses,mostlyusingtheHypertextTransferProtocol(HTTP).InJune1999,SunintroducedJavaServerPages(JSPs),whichintermingledJavacodewithJavaScriptandHTMLtemplatetext.

[1]SeeSunMicrosystemsJavamilestonesandhistoryat:http://java.sun.com/features/2000/06/time-line.html.

JSPs,astheyarenowevolving(withJSPVersion2.0),aredesignedtoencapsulatedomainlogicinstandardandcustomtags,andseparatethisdomainlayerfromtheJSPcomponent'spresentationlogic.Thelatterconceptmeans"thestuffthatpeoplesee"whentheyinteractwithawebapplication,suchasHTML-relatedscreenwidgets.Ideally,aJSPusestagstointeractwithdatabasesandencapsulatedomainrules,andstaticordynamicallygeneratedtemplatetext,suchasXMLorXHTML,tocreatethevisualpagefortheuser.

Duringthelate1990s,Iwasafreelance,backendwebdeveloperusinganumberofdifferentlanguages.Whenserver-sideJavaappearedonthescene,Igreetedthenewswithasmuchreliefasjoy.Designedfromthebottomupasobject-orientedandmodular,Javarepresentedareassuringalternativetotheadhoc,ill-designed,albeitwell-intentionedmassesofweb-relatedcodeIwouldoftenencounterwhenanorganizationbroughtmeintothemidstofaproject.

Notonlycanyoueasilycreateyourownreusablecomponentsfor,say,sendingemailsimplybydesigninganduploadingtoyourwebapplicationoneormoreJavaclasses,[2]butyouhavetheentireJavaAPIatyourdisposalfordealingwithessential,low-levelitemssuchasString-

http://java.sun.com/features/2000/06/time-line.html

handling,fileI/O,andMathcalculations.Whatadeal!

[2]Forexample,theinstallationofabinaryActiveServerPages(ASP)componentoftenrequiredthescrutinyandpermissionofthehostingInternetServiceProvider(ISP),becauseabadlywrittenormaliciousASPcomponentcouldwreakhavocontheservermachine.

TheotherbigbenefitJavaprovidesisitscross-platformnature.Webdeveloperscandesigntheirwebapplications,neatlypackagetheminaspecialJARfileforwebcomponentscalledaWebApplicationArchivefile,theninstalltheWARsonvariousservershostedbydifferentoperatingsystems(OSes).JavawebcomponentsarenotboundtoasingleOSortoaparticularvendor'sserversoftwarelikeotherweb-relatedsoftwaretechnologies.

Jumpaheadtothepresent.Bylate2003,Javahasachievedstatusasthegranddaddyofserver-sidedevelopment.ServletsandJSPsareincludedintheJava2EnterpriseEdition(J2EE),awidelyacceptedenterprisetechnologyfornetwork-basedanddistributedcomputing.Hundredsofthousandsofdevelopersthroughouttheworldworkonthe"webtier"ofJ2EE-basedtechnologies,usingservlets,JSPs,andsometimesspecialwebframeworkssuchasStruts.

Infact,manywebdevelopersnowspendafairamountoftimegettingtoknowvarious"applicationservers"likeBEAWebLogic,JBoss,orIBM'sWebSpherethatpulltogetherthewebtier,businessordomainobjects(suchascomponentsthathandleweatherdataoracustomer'sfinancialaccounts),andEnterpriseInformationSystems(EIS).TheseapplicationserversrepresentthesoftwarehostforservletsandJSPs.Manywebdevelopers,includingmyself,spendalotoftimeworkingonwebcomponentsthatarehostedonTomcat,apopularopensource(http://www.opensource.org)servletengineand"referenceimplementation"forthenewservletandJSPAPIs.[3]

[3]Areferenceimplementationissoftwarethatisbasedonacommonlyagreeduponspecification,andisfreelyavailabletosoftwaredevelopersandothersasademonstrationofhowthespecifiedsoftwaresystemisdesignedtofunction.

http://www.opensource.org/default.htm

Therapidmaturationandwell-establishednatureofJavahasnaturallyledtoa"cookbook"approachforourbook.Thiscookbookfocusesonhowtoinitiatecertainweb-relatedtasksinJava,ratherthantutoringthereaderonhowtousetheJavalanguage,orexplainingtheservletandJSPAPIsinfinelygraineddetail.Countlesstutorial-orientedJavabooksstillexist,however,inneworreissuedform,whichatteststothepopularityofJavaasaweb-developmentplatform.

What'sintheBook

Increatingtherecipesforthisbook,ItriedtocoverasmanycommonandadvancedwebdevelopertasksasIcouldpracticallyfitintoonebook.Thisamountstoabout230differentrecipes.Eachrecipeshowshowtoimplementaparticulartaskusingservlets,JSPs,and,inmanycases,oneormoresupportingJavaclasses.

Therecipesshowhowto:

Authenticatewebclients

Interactwithdatabases

Sendemail

Handlesubmitteddatafromawebform

Readandset"cookies"

Uploadfilesfromtheclient

IntegrateJavaScriptwithservletsandJSPs

EmbedmultimediafileslikedigitalmoviesandmusicinJSPsandservlets

Handlewebclientswhoseusersspeakdifferentlanguages(internationalization)

LogmessagesfromservletsandJSPs

Dynamicallyincludechunksofcontent,asintraditionalserver-side

include(SSI)code

InteractwithEnterpriseJavaBeans(EJBs)fromaJSPandservlet

UseAmazon.com'sandGoogle.com'sWebServicesAPIsfromaservletorJSP

Ihavealsoincludednumeroustechnology-specificrecipes,suchas:

Using"sessions"inyourJavawebapplications(aconceptthatrepresentsthetrackingofauser'sprogressthroughawebsite)

Workingwith"filters"

UsingtheopensourceANTtooltobuildwebapplications

BindingJavaobjectstoasessionorwebapplicationsotheycanbeusedasinformationordatacontainers

CreatingyourowncustomtagsforJSPs

UsingtheJavaServerPagesStandardTagLibrary(JSTL),whichisalargesetofprebuilttagsyoucanuseinJSPs

Inshort,thebookisdesignedtohelpguideJavawebdevelopersintheireverydaytasks,andtoprovidequicksolutionstotypicalweb-relatedproblems.

BEAWebLogicRecipes

BecauseJavawebdeveloperstendtoworkwithbothTomcatandaproprietaryapplicationserver,I'veincludedanumberofdifferentrecipestoshowhowtoimplementcommontaskswithBEAWebLogic.Asa

practicalmatter,Icouldnotcovertheseveralotherapplicationserversthatareavailable,suchasIBM'sWebSphere,JBoss,Jetty,Oracle9iapplicationserver,orcommercialservletenginessuchasNewAtlantaServletExecandCauchoResin.ButIwantedtoincluderecipescovering"howtheotherhalflives"intermsofusingvariousvendortoolsformanagingeverydayweb-applicationtasks.SolutionsinvolvingthedeploymentorrevisionofwebcomponentsanddeploymentdescriptorsusingvisualinterfacessuchasWebLogic'sAdministrationConsoleorWebLogicBuildercanbequitedifferentfromthoseusedwithTomcat.

Asaresult,thisbookincludesacollectionofbasicWebLogic-relatedrecipes,suchasdeployingwebapplicationsonWebLogic,andusingaservlettoaccessaWebLogicDataSource.Chapter25showshowaservletcaninteractwithanEJBinstalledonWebLogic.

Audience

Therecipesaremainlydesignedforexperienceddeveloperswhodesign,build,deploy,andreviseJava-basedwebapplications.ThisincludesJSP,servlet,andJavaBeandevelopers.

ThebookisalsoappropriateforexperiencedwebdeveloperswhoarejustlearningJavaandmigratingfromanotherwebprogrammingplatform,suchasActiveServerPages,PHP,orPerl.Thesedevelopersareusuallyknowledgableabouttheunderlyingmechanisms,suchassessions,cookies,fileuploads,loginauthentication,andhandlingHTTPPOSTrequests,butmaynotyetknowhowtoimplementthesetasksinJava.Thecookbookallowsthemtoquicklylookupasolutiontoaproblemthattheyhaveprobablyalreadydealtwithusinganotherlanguage.

JavadeveloperswhoneedtoknowhowtoimplementnewservletAPI2.4andJSP2.0features(suchassomeofthenewweb.xmlfilter-mappingelementsforrequestdispatchersandembeddingtheExpressionLanguage[EL]inaJSP'stemplatetext)willalsofindthecookbookhandy.

WhatYouNeedtoKnow

ReadersshouldknowthebasicsoftheJavalanguageorbelearninghowtoprogramwithJava.

Chapter1,includesbriefintroductionstoservlets,JSPs,anddeploymentdescriptorsforreaderswhoarenotyetuptospeedontheseconcepts.However,sincethecookbook'sfocusisonconcisesolutionstospecificproblems,itdoesnotincludelongtutorialsontheservletandJSPAPIs.Eachrecipeincludesanintroductionthatprovidesenoughinformationtogetstartedwiththevarioustechnologiesandcodesamples.Therecipesalsoincludenumerousreferencestoonlineinformationresources,suchasJavadocpagesandtutorials,forreaderswhoneedtoexploreatopic

ingreaterdepth.

ReaderswillbenefitfromhavingalreadybeenintroducedtovariousJ2EEsubjectareassuchasJavaDatabaseConnectivity(JDBC),theJavaNamingandDirectoryInterface(JNDI),andEnterpriseJavaBeans(IhaveincludedonerecipethatinvolvesconnectingawebcomponentwithEJBsusingJNDI).

Finally,aworkingknowledgeofXMLisalsohelpful,asJavawebdevelopmentinvolvesXML-baseddeploymentdescriptorsandconfigurationfiles.

Organization

ThebookbeginswiththreechaptersthatcoverthenutsandboltsofwritingservletsandJSPs,deployingservletsandJSPs,namingorregisteringyourservlets,andusingtheAnttool.

Ithenexploreseveralbasictopicsonwebdevelopment,suchasdynamicallyincludingcontentinwebpages,uploadingfiles,handlingdatathathasbeenpostedfromanHTMLform,readingandsettingcookies,trackingsessions,andintegratingJavaScriptwithJSPsandservlets.

Next,thebookincludessomemoreadvancedrecipes,suchasloggingmessages,authenticatingclients,bindingattributes,workingwiththeclientrequest,andcreatingservletfilters.Chapter20,andChapter21,covertwocommonandcomplexweb-developmenttaskswith20differentrecipes.

Chapter22,andChapter23describecustomtagsandtheJSTL.Chapter24,discussesthecrucialtopicofinternationalizingyourwebapplicationswithservletsandJSPs.

ForwebdeveloperswhosewebcomponentsmustinteractwithEJBsusingtheJavaJNDI,Chapter25,showshowtoconfigureJNDIinbothTomcatandWebLogic,aswellashowtoaccessJNDIobjectsusingbothservers.

ThebookconcludeswithtwochaptersthatdescribedifferentstrategiesforextractingdatafromwebsitesusingJavawebcomponents.Chapter26,hasrecipesonharvestingor"scraping"datafromwebpages.Chapter27,describeshowtouseGoogle'sandAmazon.com'swebservicesAPIs.

ConventionsUsedinThisBook

Thefollowingtypographicalconventionsareusedinthisbook:

Italic

Indicatesnewterms,exampleURLs,emailaddresses,filenames,fileextensions,pathnames,directories,andUnixutilities.

Constantwidth

Indicatescommands,options,switches,variables,attributes,keys,functions,types,classes,namespaces,methods,modules,properties,parameters,values,objects,events,eventhandlers,XMLtags,HTMLtags,macros,thecontentsoffiles,ortheoutputfromcommands.

Constantwidthbold

Showscommandsorothertextthatshouldbetypedliterallybytheuser,andisusedtoemphasizecodeinexamples.

Constantwidthitalic

Showstextthatshouldbereplacedwithuser-suppliedvalues.Insomecaseswheretextisalreadyitalicized,user-suppliedvaluesareshowninangledbrackets(<>)

Thisiconsignifiesatip,suggestion,orgeneralnote.

Thisiconindicatesawarningorcaution.

UsingCodeExamples

Thisbookisheretohelpyougetyourjobdone.Ingeneral,youmayusethecodeinthisbookinyourprogramsanddocumentation.Youdonotneedtocontactusforpermissionunlessyou'rereproducingasignificantportionofthecode.Forexample,writingaprogramthatusesseveralchunksofcodefromthisbookdoesnotrequirepermission.SellingordistributingaCD-ROMofexamplesfromO'Reillybooksdoesrequirepermission.Answeringaquestionbycitingthisbookandquotingexamplecodedoesnotrequirepermission.Incorporatingasignificantamountofexamplecodefromthisbookintoyourproduct'sdocumentationdoesrequirepermission.

O'Reilly&Associatesandtheauthorbothappreciate,butdonotrequire,attribution.Anattributionusuallyincludesthetitle,author,publisher,andISBN.Forexample:"JavaServletandJSPCookbook,byBrucePerry.Copyright2004O'Reilly&Associates,Inc.,0-596-00572-5."

Ifyoufeelyouruseofcodeexamplesfallsoutsidefairuseorthepermissiongivenabove,[email protected].


CommentsandQuestions

Pleaseaddresscommentsandquestionsconcerningthisbooktothepublisher:

O'Reilly&Associates,Inc.1005GravensteinHighwayNorthSebastopol,CA95472(800)998-9938(intheUnitedStatesorCanada)(707)829-0515(internationalorlocal)(707)829-0104(fax)

O'Reillyhasawebpageforthisbook,whereerrata,examples,andanyadditionalinformationislisted.Youcanaccessthispageat:

http://www.oreilly.com/catalog/jsvltjspckbk

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http://www.oreilly.com/default.htm

Acknowledgments

Onenight,morethanayearago,IdispatchedanemailtoO'Reillywithanideaforabook.Atthattime,thelikelihoodthatthiscasualemailwouldeventuallygiverisetoapublishedbookseemedveryremote.Afternumerousemailed"backandforths"betweenmeandacoupleofO'ReillyJavaeditors,andthenseveralmonthsofgentlenudging,solidediting,occasionalreconceptualizations,and(ofcourse)writing,writing,andmorewriting,theseedofthebookideagerminatedandreachedfruition.Voilá,acookbookisborn!

Theshapingofabookisalwaysacollaborationamongseveralpeople.ThisbookprobablywouldnothaveleftthelaunchingpadwithoutmyeditorBrettMcLaughlin'ssuccinctandcontinuousremindersaboutwhatdifferentiatesacookbookfromotherbooktypes.Brettisalsoafine"wordbyword"copyeditor,andhavinganeditorialbackgroundmyself,Iappreciatedhiseffortsfromthewriter'sside.Also,Brett'sknowledgeofJavaisdeep,andhiscommentshelpedmeavoidsomeawkwardcodedesigndecisions.

IamveryfortunatetohaveJasonHunterandSangShinastechnicaleditors.Theyarebothwell-knownJavaexperts,andthisisamuchbetterbooksincetheyhavereadandcommentedonlargechunksofit.Theirreviewhadareallyshortdeadline,andthisisabigbook.Iwasamazedatthecomprehensivecoveragewithsuchashortturnaround.Asatechnicalwriter,Iamindebtedtothosewhorescuemefromembarrassingmistakes!

Someofussaveourfamilymembersforlastinacknowledgingthosewhohelpus.Maybethatisbecausethelastparagraphisthefoundationonwhichtherestofthelanguagesits,justasthefamilyiseverywriter'sfoundation,givingthemsupportandshieldingthemfromdistractionsastheyimmersethemselvesinproseandtechnology.ThisbookwouldnothavebeencreatedwithoutthehelpfrommywifeStacy,daughterRachel,andevenScott,whoinspiresmefromthetendervantagepointofbeinglessthanoneyearold.I'llalsorepeatwhatIsaidinmyAppleScriptbook;

IthankmyparentsRobertandAnnePerryforinstallinginmealoveofwritingandbooks.

Chapter1.WritingServletsandJSPs

Introduction

Recipe1.1.WritingaServlet

Recipe1.2.WritingaJSP

Recipe1.3.CompilingaServlet

Recipe1.4.PackagingServletsandJSPs

Recipe1.5.CreatingtheDeploymentDescriptor

Introduction

Thepurposeofthischapteristobringrelativenewcomersuptospeedinwriting,compiling,andpackagingservletsandJSPs.IfyouhaveneverdevelopedaservletorJSPbefore,orjustneedtobrushuponthetechnologytojumpstartyourdevelopment,thentheupcomingrecipesprovidesimpleprogrammingexamplesandanoverviewofthecomponentsthatyourequireontheuserclasspathtocompileservlets.

Recipe1.1andRecipe1.2provideabriefintroductiontoservletsandJSPs,respectively.AcomprehensivedescriptionofaservletorJSP'sroleintheJava2Platform,EnterpriseEdition(J2EE),isbeyondthescopeoftheserecipes.However,informationthatrelatesdirectlytoJ2EEtechnology,suchasdatabasesandJDBC;usingservletswiththeJavaNamingandDirectoryInterface(JNDI);andusingservletswithJavaMail(oremail)isdistributedthroughoutthebook(andindex!).

The"SeeAlso"sectionsconcludingeachrecipeprovidepointerstocloselyrelatedchapters,anonlinetutorialmanagedbySunMicrosystems,andotherO'Reillybooksthatcoverthesetopicsindepth.

Recipe1.1WritingaServlet

Problem

Youwanttowriteaservletthatispartofawebapplication.

Solution

CreateaJavaclassthatextendsjavax.servlet.http.HttpServlet.Makesuretoimporttheclassesfromservlet.jar(orservlet-api.jar)you'llneedthemtocompiletheservlet.

Discussion

AservletisaJavaclassthatisdesignedtorespondwithdynamiccontenttoclientrequestsoveranetwork.IfyouarefamiliarwithCommonGatewayInterface(CGI)programs,thenservletsareaJavatechnologythatcanreplaceCGIprograms.Oftencalledawebcomponent(alongwithJSPs),aservletisexecutedwithinaruntimeenvironmentprovidedbyaservletcontainerorwebcontainersuchasJakartaTomcatorBEAWebLogic.

Awebcontainercanbeanadd-oncomponenttoanHTTPserver,oritcanbeastandaloneserversuchasTomcat,whichiscapableofmanagingHTTPrequestsforbothstaticcontent(HTMLfiles)aswellasforservletsandJSPs.

Servletsareinstalledinwebcontainersaspartofwebapplications.

TheseapplicationsarecollectionsofwebresourcessuchasHTMLpages,images,multimediacontent,servlets,JavaServerPages,XMLconfigurationfiles,Javasupportclasses,andJavasupportlibraries.Whenawebapplicationisdeployedinawebcontainer,thecontainercreatesandloadsinstancesoftheJavaservletclassintoitsJavaVirtualMachine(JVM)tohandlerequestsfortheservlet.

Aservlethandleseachrequestasaseparatethread.Therefore,servletdevelopershavetoconsiderwhethertosynchronizeaccesstoinstancevariables,classvariables,orsharedresourcessuchasadatabaseconnection,dependingonhowtheseresourcesareused.

Allservletsimplementthejavax.servlet.Servletinterface.Webapplicationdeveloperstypicallywriteservletsthatextendjavax.servlet.http.HttpServlet,anabstractclassthatimplementstheServletinterfaceandisspeciallydesignedtohandleHTTPrequests.

Thefollowingbasicsequenceoccurswhenthewebcontainercreatesaservletinstance:

1. Theservletcontainercallstheservlet'sinit()method,whichisdesignedtoinitializeresourcesthattheservletmightuse,suchasalogger(seeChapter14).Theinit()methodgetscalledonlyonceduringtheservlet'slifetime.

Theinit()methodinitializesanobjectthatimplementsthejavax.servlet.ServletConfiginterface.Thisobjectgivestheservletaccesstoinitializationparametersdeclaredinthedeploymentdescriptor(seeRecipe1.5).ServletConfigalsogivestheservletaccesstoajavax.servlet.ServletContextobject,withwhichtheservletcanlogmessages,dispatchrequeststootherwebcomponents,andgetaccesstootherwebresourcesinthesameapplication(seeRecipe13.5).

Servletdevelopersarenotrequiredtoimplementtheinit()methodintheirHttpServletsubclasses.

3. Theservletcontainercallstheservlet'sservice()methodinresponsetoservletrequests.IntermsofHttpServlets,service()automaticallycallstheappropriateHTTPmethodtohandletherequestbycalling(generally)theservlet'sdoGet()ordoPost()methods.Forexample,theservletrespondstoausersendingaPOSTHTTPrequestwithadoPost()methodexecution.

WhencallingthetwoprincipalHttpServletmethods,doGet()ordoPost(),theservletcontainercreatesjavax.servlet.http.HttpServletRequestandHttpServletResponseobjectsandpassestheminasparameterstotheserequesthandlermethods.HttpServletRequestrepresentstherequest;HttpServletResponseencapsulatestheservlet'sresponsetotherequest.

Example1-1showsthetypicalusesoftherequestandresponseobjects.ItisagoodideatoreadtheservletAPIdocumentation(athttp://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/package-summary.html),asmanyofthemethodnames(e.g.,request.getContextPath())areself-explanatory.

5. Theservletorwebcontainer,notthedeveloper,managestheservlet'slifecycle,orhowlonganinstanceoftheservletexistsintheJVMtohandlerequests.Whentheservletcontainerissettoremovetheservletfromservice,itcallstheservlet'sdestroy()method,inwhichtheservletcanreleaseany

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/package-summary.html

resources,suchasadatabaseconnection.

Example1-1showsatypicalservletidiomforhandlinganHTMLform.ThedoGet()methoddisplaystheformitself.ThedoPost()methodhandlesthesubmittedformdata,sinceindoGet(),theHTMLformtagspecifiestheservlet'sownaddressasthetargetfortheformdata.

Theservlet(namedFirstServlet)specifiesthatthedeclaredclassispartofthecom.jspservletcookbookpackage.Itisimportanttocreatepackagesforyourservletsandutilityclasses,andthentostoreyourclassesinadirectorystructurebeneathWEB-INFthatmatchesthesepackagenames.

TheFirstServletclassimportsthenecessaryclassesforcompilingabasicservlet,whicharetheemphasizedimportstatementsinExample1-1.TheJavaclassextendsHttpServlet.TheonlydefinedmethodsaredoGet(),whichdisplaystheHTMLforminresponsetoaGETHTTPrequest,anddoPost(),whichhandlestheposteddata.

Example1-1.AtypicalHttpServletusedforhandlinganHTMLform

packagecom.jspservletcookbook;

importjava.io.IOException;

importjava.io.PrintWriter;

importjava.util.Enumeration;

importjavax.servlet.ServletException;

importjavax.servlet.http.HttpServlet;

importjavax.servlet.http.HttpServletRequest;

importjavax.servlet.http.HttpServletResponse;

publicclassFirstServletextendsHttpServlet{

publicvoiddoGet(HttpServletRequestrequest,

HttpServletResponseresponse)throwsServletException,

java.io.IOException{

//settheMIMEtypeoftheresponse,"text/html"

response.setContentType("text/html");

//useaPrintWritertosendtextdatatotheclientwhohasrequestedthe

//servlet

java.io.PrintWriterout=response.getWriter();

//BeginassemblingtheHTMLcontent

out.println("<html><head>");

out.println("<title>HelpPage</title></head><body>");

out.println("<h2>Pleasesubmityourinformation</h2>");

//makesuremethod="post"sothattheservletservicemethod

//callsdoPostintheresponsetothisformsubmit

out.println(

"<formmethod=\"post\"action=\""+request.getContextPath()+

"/firstservlet\">");

out.println("<tableborder=\"0\"><tr><tdvalign=\"top\">");

out.println("Yourfirstname:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"firstname\"size=\"20\">");

out.println("</td></tr><tr><tdvalign=\"top\">");

out.println("Yourlastname:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"lastname\"size=\"20\">");


out.println("Youremail:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"email\"size=\"20\">");


out.println("<inputtype=\"submit\"value=\"SubmitInfo\"></td></tr>");

out.println("</table></form>");

out.println("</body></html>");

}//doGet

publicvoiddoPost(HttpServletRequestrequest,



//displaytheparameternamesandvalues

EnumerationparamNames=request.getParameterNames();

StringparName;//thiswillholdthenameoftheparameter

booleanemptyEnum=false;

if(!paramNames.hasMoreElements())

emptyEnum=true;



//useaPrintWritertosendtextdatatotheclient




out.println("<title>SubmittedParameters</title></head><body>");

if(emptyEnum){

out.println(

"<h2>Sorry,therequestdoesnotcontainanyparameters</h2>");

}else{

out.println(

"<h2>Herearethesubmittedparametervalues</h2>");

}

while(paramNames.hasMoreElements()){

parName=(String)paramNames.nextElement();

out.println(

"<strong>"+parName+"</strong>:"+

request.getParameter(parName));

out.println("<br/>");

}//while


}//doPost

}

YoumighthavenoticedthatdoGet()anddoPost()eachthrowServletExceptionandIOException.TheservletthrowsIOExceptionbecausetheresponse.getWriter()(aswellasPrintWriter.close())methodcallcanthrowanIOException.ThedoPost()anddoGet()methodscanthrowaServletExceptiontoindicatethataproblemoccurredwhenhandlingtherequest.Forexample,iftheservletdetectedasecurityviolationorsomeotherrequestproblem,thenitcouldincludethefollowingcodewithindoGet()ordoPost():

//detectsaproblemthatpreventsproperrequesthandling...

thrownewServletException("Theservletcannothandlethisrequest.");

Figure1-1showstheoutputdisplayedbytheservlet'sdoGet()methodinabrowser.

Figure1-1.Theservlet'soutputfordoGet()method

Figure1-2showstheservlet'soutputforthedoPost()method.

Figure1-2.Theservlet'soutputforthedoPost()method

SeeAlso

Recipe1.3oncompilingaservlet;Recipe1.4onpackagingservletsandJSPs;Recipe1.5oncreatingthedeploymentdescriptor;Chapter2on

deployingservletsandJSPs;Chapter3onnamingservlets;thejavax.servlet.httppackageJavaDoc:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/package-summary.html;theJ2EEtutorialfromSunMicrosystems:http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/J2eeTutorialTOC.html;JasonHunter'sJavaServletProgramming(O'Reilly).

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/package-summary.html

http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/J2eeTutorialTOC.html

Recipe1.2WritingaJSP

Problem

YouwanttocreateaJSPandincludeitinawebapplication.

Solution

CreatetheJSPasatextfileusingHTMLtemplatetextasneeded.StoretheJSPfileatthetoplevelofthewebapplication.

Discussion

AJavaServerPages(JSP)componentisatypeofJavaservletthatisdesignedtofulfilltheroleofauserinterfaceforaJavawebapplication.WebdeveloperswriteJSPsastextfilesthatcombineHTMLorXHTMLcode,XMLelements,andembeddedJSPactionsandcommands.JSPswereoriginallydesignedaroundthemodelofembeddedserver-sidescriptingtoolssuchasMicrosoftCorporation'sASPtechnology;however,JSPshaveevolvedtofocusonXMLelements,includingcustom-designedelements,orcustomtags,astheprincipalmethodofgeneratingdynamicwebcontent.

JSPfilestypicallyhavea.jspextension,asinmypage.jsp.WhenaclientrequeststheJSPpageforthefirsttime,orifthedeveloperprecompilestheJSP(seeChapter5),thewebcontainertranslatesthetextualdocumentintoaservlet.

TheJSP2.0specificationreferstotheconversionofaJSPintoaservletasthetranslationphase.WhentheJSP(nowaservletclass)respondstorequests,thespecificationcallsthisstagetherequestphase.Theresultingservletinstanceis

calledthepageimplementationobject.

AJSPcompiler(suchasTomcat'sJaspercomponent)automaticallyconvertsthetext-baseddocumentintoaservlet.Thewebcontainercreatesaninstanceoftheservletandmakestheservletavailabletohandlerequests.Thesetasksaretransparenttothedeveloper,whoneverhastohandlethetranslatedservletsourcecode(althoughtheycanexaminethecodetofindoutwhat'shappeningbehindthescenes,whichisalwaysinstructive).

ThedeveloperfocusesontheJSP'sdynamicbehaviorandwhichJSPelementsorcustom-designedtagssheusestogeneratetheresponse.DevelopingtheJSPasatext-baseddocumentratherthanJavasourcecodeallowsaprofessionaldesignertoworkonthegraphics,HTML,ordynamicHTML,leavingtheXMLtagsanddynamiccontenttoprogrammers.

Example1-2showsaJSPthatdisplaysthecurrentdateandtime.TheexampleJSPshowshowtoimportanduseacustomtaglibrary,whichChapter23describesingreatdetail.Thecodealsousesthejsp:useBeanstandardaction,abuilt-inXMLelementthatyoucanusetocreateanewJavaobjectforuseintheJSPpage.HerearethebasicstepsforwritingaJSP:

1. Openupatexteditor,oraprogrammer'seditorthatoffersJSPsyntaxhighlighting.

IfyouaredevelopingaJSPforhandlingHTTPrequests,theninputtheHTMLcodejustasyouwouldforanHTMLfile.

IncludeanynecessaryJSPdirectives,suchasthetaglibdirectiveinExample1-2,atthetopofthefile.Adirectivebeginswiththe<%@s.

Typeinthestandardactionsorcustomtagswherevertheyare

needed.

Savethefilewitha.jspextensioninthedirectoryyouhavedesignatedforJSPs.Atypicallocationisthetop-leveldirectoryofawebapplicationthatyouaredevelopinginyourfilesystem.

SomeJSPsaredevelopedasXMLfiles,orJSPdocuments,consistingsolelyofwell-formedXMLelementsandtheirattributes.TheJSP2.0specificationrecommendsthatyougivethesefilesa.jspxextension.SeeRecipe5.5forfurtherdetailsonJSPdocuments.

Example1-2.AJSPfilethatdisplaysthedate

<%--usethe'taglib'directivetomaketheJSTL1.0coretagsavailable;usetheuri

"http://java.sun.com/jsp/jstl/core"forJSTL1.1--%>

<%@tagliburi="http://java.sun.com/jstl/core"prefix="c"%>

<%--usethe'jsp:useBean'standardactiontocreatetheDateobject;theobjectisset

asanattributeinpagescope

--%>

<jsp:useBeanid="date"class="java.util.Date"/>

<html>

<head><title>FirstJSP</title></head>

<body>

<h2>Hereistoday'sdate</h2>

<c:outvalue="${date}"/>

</body>

</html>

Toviewtheoutputofthisfileinabrowser,requestthefilebytypingthe

URLintothebrowserlocationfield,asin:http://localhost:8080/home/firstJ.jsp.ThenameofthefileisfirstJ.jsp.IfthisisthefirsttimethatanyonehasrequestedtheJSP,thenyouwillnoticeadelayastheJSPcontainerconvertsyourtextfileintoJavasourcecode,thencompilesthesourceintoaservlet.

YoucanavoiddelaysbyprecompilingtheJSP.IfyourequesttheJSPwithajsp_precompile=trueparameter,TomcatconvertstheJSP,butdoesnotsendbackaresponse.Anexampleishttp://localhost:8080/home/firstJ.jsp?jsp_precompile=true.

Figure1-3showstheJSPoutputinabrowser.

Figure1-3.OutputfromthefirstJ.jsppage

Ifyouselect"ViewSource"fromthebrowsermenutoviewthepage'ssourcecode,youwon'tseeanyofthespecialJSPsyntax:thecommentcharacters(<%----%>),thetaglibdirective,thejsp:useBeanaction,orthec:outtag.Theservletsendsonlythetemplatetextandthegenerateddatestringtotheclient.

SeeAlso

Recipe5.1-Recipe5.3onprecompilingJSPs;Chapter2ondeployingservletsandJSPs;Recipe1.1andRecipe1.3onwritingandcompilingaservlet;Recipe1.4onpackagingservletsandJSPs;Recipe1.5oncreatingthedeploymentdescriptor;theJ2EEtutorialfromSunMicrosystems:http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/J2eeTutorialTOC.html;HansBergsten'sJavaServerPages(O'Reilly).


Recipe1.3CompilingaServlet

Problem

Youhavewrittenaservlet,andnowyouwanttocompileitintoaclassfile.

Solution

Makesurethatservlet.jar(forTomcat4.1.24)orservlet-api.jar(forTomcat5)isonyouruserclasspath.UsejavacasyouwouldforanyotherJavasourcefile.

Discussion

Ataminimum,youhavetoplacetheservletclassesonyourclasspathinordertocompileaservlet.TheseclassesarelocatedintheseJavapackages:

javax.servlet

javax.servlet.http

Tomcat5supportstheservletAPI2.4;theJARfilethatyouneedontheclasspathislocatedat<Tomcat-5-installation-directory>/common/lib/servlet-api.jar.Tomcat4.1.24usestheservlet2.3API.Theservletclassesarelocatedat:<Tomcat-4-installation-directory>/common/lib/servlet.jar.

ForBEAWebLogic7.0,theservletclassesandmanyothersubpackages

ofthejavaxpackage(e.g.,javax.ejb,javax.mail,javax.sql)arelocatedat:<WebLogic-installation-directory>/weblogic700/server/lib/weblogic.jar.

IfyouareusingAnttocompileservletclasses,thenproceedtoRecipe4.4,donotpassGo,donotcollect$200.ThatrecipeisdevotedspecificallytothetopicofusingAnttocompileaservlet.IfyouuseanIDE,followitsinstructionsforplacingaJARfileontheclasspath.

Thefollowingcommandlinecompilesaservletinthesrcdirectoryandplacesthecompiledclass,nestedwithinitspackage-relateddirectories,inthebuilddirectory:

javac-classpathK:\tomcat5\jakarta-tomcat-5\dist\common\lib\servlet-api.jar

-d./build./src/FirstServlet.java

Forthiscommandlinetorunsuccessfully,youmustchangetotheparentdirectoryofthesrcdirectory.

Recipe1.4explainsthetypicaldirectorystructure,includingthesrcdirectory,fordevelopingawebapplication.

Iftheservletdependsonanyotherlibraries,youhavetoincludethoseJARfilesonyourclasspathaswell.Ihaveincludedonlytheservlet-api.jarJARfileinthiscommandline.

YoualsohavetosubstitutethedirectorypathforyourowninstallationofTomcatforthislineofthepriorcommand-linesequence:

K:\tomcat5\jakarta-tomcat-5\dist\common\lib\servlet-api.jar

Thiscommandlineusesthebuilt-injavaccompilerthatcomeswiththe

SunMicrosystemsJavaSoftwareDevelopmentKit(JDK).Forthiscommandtoworkproperly,youhavetoincludethelocationoftheJavaSDKthatyouareusinginthePATHenvironmentvariable.Forexample,onaUnix-basedMacOSX10.2system,thedirectorypath/usr/binmustbeincludedinthePATHvariable.OnmyWindowsNTmachine,thePATHincludesh:\j2sdk1.4.1_01\bin.

SeeAlso

Chapter2ondeployingservletsandJSPs;Chapter3onnamingservlets;Recipe1.4onpackagingservletsandJSPs;Recipe1.5oncreatingthedeploymentdescriptor;theJ2EEtutorialfromSunMicrosystems:http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/J2eeTutorialTOC.html;JasonHunter'sJavaServletProgramming(O'Reilly).


Recipe1.4PackagingServletsandJSPs

Problem

YouwanttosetupadirectorystructureforpackagingandcreatingaWebARchive(WAR)fileforservletsandJSPs.

Solution

Setupadirectorystructureinyourfilesystem,thenusethejartoolorAnttocreatetheWAR.

Discussion

Exceptintherarestofcircumstances,you'llusuallydevelopaservletorJSPaspartofawebapplication.Itisrelativelyeasytosetupadirectorystructureonyourfilesystemtoholdweb-applicationcomponents,whichincludeHTMLfiles,servlets,JSPs,graphics,JARlibraries,possiblymoviesandsoundfiles,aswellasXMLconfigurationfiles(suchasthedeploymentdescriptor;seeRecipe1.5).

Thesimplestorganizationforthisstructureistocreatetheexactlayoutofawebapplicationonyourfilesystem,thenusethejartooltocreateaWARfile.

AWARfileislikeaZIParchive.YoudeployyourwebapplicationintoawebcontainerbydeployingtheWAR.SeeChapter2forrecipesaboutvariousdeploymentscenarios.

ThewebapplicationstructureinvolvingtheWEB-INFsubdirectoryisstandardtoallJavawebapplicationsandspecifiedbytheservletAPIspecification(inthesectionnamedWebApplications.Hereiswhatthisdirectorystructurelookslike,givenatop-leveldirectorynameofmyapp:

/myapp

/images

/WEB-INF

/classes

/lib

TheservletspecificationspecifiesaWEB-INFsubdirectoryandtwochilddirectories,classesandlib.TheWEB-INFsubdirectorycontainstheapplication'sdeploymentdescriptor,namedweb.xml.TheJSPfilesandHTMLliveinthetop-leveldirectory(myapp).Servletclasses,JavaBeanclasses,andanyotherutilityclassesarelocatedintheWEB-INF/classesdirectory,inastructurethatmatchestheirpackagename.Ifyouhaveafullyqualifiedclassnameofcom.myorg.MyServlet,thenthisservletclassmustbelocatedinWEB-INF/classes/com/myorg/MyServlet.class.

TheWEB-INF/libdirectorycontainsanyJARlibrariesthatyourwebapplicationrequires,suchasdatabasedrivers,thelog4j.jar,andtherequiredJARsforusingtheJavaServerPagesStandardTagLibrary(seeChapter23).

OnceyouarereadytotesttheapplicationinWARformat,changetothetop-leveldirectory.Typethefollowingcommand,namingtheWARfileafterthetop-leveldirectoryofyourapplication.Thesecommand-linephrasesworkonbothWindowsandUnixsystems(IusedthemwithWindowsNT4andMacOSX10.2):

jarcvfmyapp.war.

Don'tforgetthefinaldot(.)character,whichspecifiestothejartooltoincludethecurrentdirectory'scontentsanditssubdirectoriesintheWARfile.Thiscommandcreatesthemyapp.warfileinthecurrentdirectory.

TheWARnamebecomestheapplicationnameandcontextpathforyourwebapplication.Forexample,myapp.waristypicallyassociatedwithacontextpathof/myappwhenyoudeploytheapplicationtoawebcontainer.

IfyouwanttoviewthecontentsoftheWARatthecommandline,typethis:

jartvfalpine-final.war

IftheWARfileisverylargeandyouwanttoviewitscontentsonepageatatime,usethiscommand:

jartvfalpine-final.war|more

Hereisexampleoutputfromthiscommand:

H:\classes\webservices\finalproj\dist>jartvfalpine-final.war

0MonNov1814:10:36EST2002META-INF/

48MonNov1814:10:36EST2002META-INF/MANIFEST.MF

555TueNov0517:08:16EST2002request.jsp

914MonNov1808:53:00EST2002response.jsp

0MonNov1814:10:36EST2002WEB-INF/

0MonNov1814:10:36EST2002WEB-INF/classes/

0TueNov0511:09:34EST2002WEB-INF/classes/com/

0TueNov0511:09:34EST2002WEB-INF/classes/com/parkerriver/

CONTINUED...

ManydevelopmentteamsareusingAnttocompileandcreateWARfilesfortheirservletsandJSPs.Recipe2.6describesusingAntfordevelopingandupdatingwebapplications.

Ijumpstartyourprogresstowardthatrecipebyshowingthekindofdirectorystructureyoumightuseforacomprehensivewebapplication,onethatcontainsnumerousservlets,JSPs,staticHTMLfiles,aswellasvariousgraphicsandmultimediacomponents.WhenusingAnttobuildaWARfilefromthiskindofdirectorystructure,youcanfilteroutthe

directoriesthatyoudonotwanttoincludeinthefinalWAR,suchasthetop-levelsrc,dist,andmetadirectories.

myapp

/build

/dist

/lib

/meta

/src

/web

/images

/multimedia

/WEB-INF

/classes

/lib

/tlds

/jspf

TheWEB-INF/tldsandWEB-INF/jspfoptionaldirectoriesmaycontainTagLibraryDescriptorfilesandJSPfragments(chunksofJSPsthataredesignedtobeincludedinotherJSPs,suchasserver-sideincludes),respectively.

SeeAlso

Chapter2ondeployingservletsandJSPs;Chapter3onnamingservlets;ThedeploymentsectionsofTomcat:TheDefinitiveGuide,byBrittainandDarwin(O'Reilly);theJ2EEtutorialfromSunMicrosystems:http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/J2eeTutorialTOC.html.


Recipe1.5CreatingtheDeploymentDescriptor

Problem

Youwanttocreatethedeploymentdescriptorforyourapplication.

Solution

NametheXMLfileweb.xmlandplaceitintheWEB-INFdirectoryofyourwebapplication.Ifyoudonothaveanexistingexampleofweb.xml,thencutandpastetheexamplesgivenintheservletv2.3or2.4specificationsandstartfromthere.

Discussion

Thedeploymentdescriptorisaveryimportantpartofyourwebapplication.ItconveystherequirementsforyourwebapplicationinaconciseformatthatisreadablebymostXMLeditors.Theweb.xmlfileiswhereyou:

RegisterandcreateURLmappingsforyourservlets

Registerorspecifyanyoftheapplication'sfiltersandlisteners

Specifycontextinitparametername/valuepairs

Configureerrorpages

Specifyyourapplication'swelcomefiles

Configuresessiontimeouts

Specifiysecuritysettingsthatcontrolwhocanrequestwhichwebcomponents

Thisisjustasubsetoftheconfigurationsthatyoucanusewithweb.xml.Whileanumberofchaptersinthisbookcontaindetailedexamplesofweb.xml(refertothe"SeeAlso"section),thisrecipeshowssimplifiedversionsoftheservletv2.3andv2.4deploymentdescriptors.

Example1-3showsasimplewebapplicationwithaservlet,afilter,alistener,andasession-configelement,aswellasanerror-pageconfiguration.Theweb.xmlinExample1-3usestheservletv2.3DocumentTypeDefinition(DTD).Themaindifferencebetweenthedeploymentdescriptorsof2.3and2.4isthat2.3usesaDTDand2.4isbasedonanXMLschema.You'llnoticethattheoldversionofweb.xmlhastheDOCTYPEdeclarationatthetopofthefile,whilethe2.4versionusesthenamespaceattributesoftheweb-appelementtorefertotheXMLschema.TheXMLelementsofExample1-3havetobeinthesameorderasspecifiedbytheDTD.

Example1-3.ThedeploymentdescriptorforservletAPI2.3

<?xmlversion="1.0"encoding="ISO-8859-1"?>

<!DOCTYPEweb-app

PUBLIC"-//SunMicrosystems,Inc.//DTDWebApplication2.3//EN"

"http://java.sun.com/dtd/web-application_2_3.dtd"

>

<web-app>

<display-name>Servlet2.3deploymentdescriptor</display-name>

<filter>

<filter-name>RequestFilter</filter-name>

<filter-class>com.jspservletcookbook.RequestFilter</filter-class>

</filter>

<filter-mapping>


<url-pattern>/*</url-pattern>

</filter-mapping>

<listener>

<listener-class>com.jspservletcookbook.ReqListener</listener-class>

</listener>

<servlet>

<servlet-name>MyServlet</servlet-name>

<servlet-class>com.jspservletcookbook.MyServlet</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/myservlet</url-pattern>

</servlet-mapping>

<session-config>

<session-timeout>15</session-timeout>

</session-config>

<error-page>

<error-code>404</error-code>

<location>/err404.jsp</location>

</error-page>

</web-app>

Example1-3showstheweb.xmlfileforanapplicationthathasjustoneservlet,accessedatthepath<contextpath>/myservlet.Sessionstimeoutin15minuteswiththisapplication.IfaclientrequestsaURLthat

cannotbefound,thewebcontainerforwardstherequesttothe/err404.jsppage,basedontheerror-pageconfiguration.ThefilternamedRequestFilterappliestoallrequestsforstaticanddynamiccontentinthiscontext.Atstartup,thewebcontainercreatesaninstanceofthelistenerclasscom.jspservletcookbook.ReqListener.

EverythingaboutExample1-4isthesameasExample1-3,exceptthattheweb-appelementatthetopofthefilereferstoanXMLschemawithitsnamespaceattributes.Inaddition,elementscanappearinarbitraryorderwiththeservletv2.4deploymentdescriptor.Forinstance,ifyouweresoinclinedyoucouldlistyourservletsandmappingsbeforeyourlistenersandfilters.

Example1-4.Aservletv2.4deploymentdescriptor


<web-appxmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation=

"http://java.sun.com/xml/ns/j2ee

http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"version="2.4">



</web-app>

Theservlet2.4versionofthedeploymentdescriptoralsocontainsdefinitionsforvariouselementsthatarenotincludedintheservlet2.3web.xmlversion:jsp-config,message-destination,message-destination-ref,andservice-ref.ThesyntaxfortheseelementsappearsinthespecificationsforJSPv2.0andJ2EEv1.4.

SeeAlso

Chapter2ondeployingservletsandJSPs;Chapter3onnamingservlets;Chapter9onconfiguringthedeploymentdescriptorforerrorhandling;theJ2EEtutorialfromSunMicrosystems:http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/J2eeTutorialTOC.html.


Chapter2.DeployingServletsandJSPs

Introduction

Recipe2.1.DeployinganIndividualServletonTomcat

Recipe2.2.UsingaContextElementinTomcat'sserver.xml

Recipe2.3.DeployinganIndividualServletonWebLogic

Recipe2.4.DeployinganIndividualJSPonTomcat

Recipe2.5.DeployinganIndividualJSPonWebLogic

Recipe2.6.DeployingaWebApplicationonTomcat

Recipe2.7.DeployingaWebApplicationonWebLogicUsingAnt

Recipe2.8.UsingtheWebLogicAdministrationConsole

Recipe2.9.UsingWebLogicBuildertoDeployaWebApplication

Recipe2.10.Usingtheweblogic.DeployerCommand-LineTool

Introduction

ThischapterdescribeshowtotakeservletsorJavaServerPages(JSPs)andmakethemavailabletoreceivewebrequestsonTomcat'sservletcontainerorBEAWebLogicServer7.0.ThisdiscussionbeginswithdeployingservletsandJSPs;inotherwords,gettingthemrunningonTomcatorWebLogic,eitheraloneoraspartofawebapplication.

DevelopingandcompilingaservletorJSPwithinanintegrateddevelopmentenvironment(IDE)isonething.HavingthewebcomponentrespondtoHTTPrequestsisanother.Thisiswhatdeploymentisallaboutwithweb-relatedsoftware:placingthesoftwareintoservicewithinawebcontainerlikeTomcatoranapplicationserversuchasBEAWebLogicServer7.0.ThefollowingrecipesdetaildeploymentofservletsandJSPsonthesewebcontainers,firstindividually,andthenaspartofawebapplication.

ThewonderfulopensourceJakartaAntbuildandautomationtooliscommonlyusedforthispurpose.Itismentionedwhereveritisrelevantinthefollowingrecipes,andChapter4iscompletelydevotedtoinstallingandusingAnt.

Recipe2.1DeployinganIndividualServletonTomcat

Problem

YouwanttotakeacompiledservletandinstallitinTomcattofindoutifitisworking.Youaredoingapreliminarytestanddonotwanttotakethetimetobuildacompletewebapplicationfortheservlet.

Solution

CopyandpastetheclassfileintoTomcat'sdefaultwebapplication(orintoawebapplicationthatyouhavealreadyinstalled),thenrequestitusingtheinvokerservlet.OruseanAntbuild.xmlfiletomovethefiletemporarilyintotheTomcatdefaultwebapplication.

Discussion

Sometimesyoudesignaservletandareanxioustoseeiftheservletworks.Unlesstheservletdependsonotherservletsorcomponentsintheapplication,youcantestitonTomcatbypastingtheclassfile(includingitspackage-relateddirectories)intothedefaultTomcatwebapplication.Bydefault,thisapplicationislocatedatthepath<Tomcat-installation-directory>/webapps/ROOT.

Ifthefullyqualifiedclassnameoftheservletisjspservletcookbook.CookieServlet,thenhereistheentireprocessformanuallygettingasingleservletgoingonTomcat:

ShutdowntheTomcatserverbyexecutingtheshellscript<tomcat-

installation-directory>/bin/shutdownorbyexecutingashellscriptyourserveradministratorhasprovided.Analternativeisto"stop"thedefaultapplicationbyrequestingthisURLinyourbrowser:http://localhost:8080/manager/stop?path=/.

Createthejspservletcookbookdirectoryinthe<Tomcat-installation-directory>/webapps/ROOT/WEB-INF/classesdirectory(maketheclassesdirectoryifitdoesnotalreadyexist).

PastetheCookieServletclassfileintothe<Tomcat-installation-directory>/webapps/ROOT/WEB-INF/classes/jspservletcookbookdirectory.

StartuptheTomcatserverbyexecutingtheshellscript<Tomcat-installation-directory>/bin/startuporashellscriptthatyourserveradministratorhasprovided.AnalternativeistostartthedefaultapplicationbyrequestingthisURLinyourbrowser:http://localhost:8080/manager/start?path=/.

RequesttheservletinyourbrowserwiththeURLhttp://localhost:8080/servlet/jspservletcookbook.CookieServlet.

Bynowyouareprobablysaying,"Theremustbeamoreelegantalternativetothisslow,manualinstallationofasingleservlet!"Youarecorrect,andcanuseJakartaAnttoconvertthismanualprocesstoanautomatedone.

Thebuild.xmlfileinExample2-1accomplishesthesametestingprocess,assumingyouhavedownloadedandinstalledAntasdescribedinChapter4.Placethisbuildfileinaconvenientdirectory.Createinthatdirectoryaglobal.propertiesfilethatiscustomizedaccordingtoyourneeds(seeExample2-2).Changetothatdirectoryinacommand-linewindowandtypeant.Anttakescareoftherestofthetasks,includingstartingandstoppingTomcat'sdefaultwebapplication.

Example2-1.Installingaservletinthedefaultwebapplication

<projectname="Cookbook"default="deploy-servlet"basedir=".">

<taskdefname="start"classname="org.apache.catalina.ant.StartTask"/>

<taskdefname="stop"classname="org.apache.catalina.ant.StopTask"/>



<propertyfile="global.properties"/>

<targetname="init"description="Initializessomeproperties.">

<echomessage="Initializingproperties."/>

<propertyname="build"value=".\build"/>

<propertyname="src"value=".\src"/>



<propertyname="context-path"value=""/>

</target>

<targetname="prepare"depends="init">

<echomessage="Cleaningupthebuilddirectory."/>

<deletedir="${build}"/>

<mkdirdir="${build}"/>

</target>



<pathid="classpath">

<filesetdir="${tomcat.dir}/common/lib">

<includename="*.jar"/>

</fileset>

<filesetdir="${tomcat.dir}/common/endorsed">


</fileset>

</path>



<targetname="start"

description="StartsthedefaultWebapplication">

<echomessage="Startingthedefaultapplication...."/>

<start

url="${url}"

username="${username}"

password="${password}"

path="/${context-path}"

/>

</target>



<targetname="stop"

description="StopsthedefaultWebapplication">

<echomessage="Stoppingtheapplication...."/>

<stop

url="${url}"



path="/${context-path}"

/>

</target>



<targetname="deploy-servlet"depends="prepare"

description=

"Compilethespecifiedservlet,thenmoveitintoTomcat'sdefault

Webapplication.">

<echomessage="StoppingthedefaultTomcatapplication...."/>

<antcalltarget="stop"/>

<echomessage="Compilingtheservlet...."/>

<javacsrcdir="${src}"destdir="${build}">

<includename="${compiled.servlet}.java"/>

<classpathrefid="classpath"/>

</javac>

<echomessage=

"CopyingtheservlettoTomcatROOTwebapplication..."/>

<copytodir="${tomcat.webapps}/WEB-INF/classes">

<filesetdir="${build}"/>

</copy>

<echomessage="Startingthedefaultapplication...."/>

<antcalltarget="start"/>

</target>

</project>

Theglobal.propertiesfilethatsitsinthesamedirectoryasbuild.xmllookslikeExample2-2.

Example2-2.global.propertiesfileforAnt

tomcat.webapps=k:/jakarta-tomcat-4.1.12/webapps/ROOT

tomcat.dir=k:/jakarta-tomcat-4.1.12

url=http://localhost:8080/manager

compiled.servlet=CookieServlet

username=tomcat

password=tomcat

global.propertiesisjustalistofproperty-name=valuepairs.Inotherwords,eachlineiscomposedofastringofcharactersthatrepresentsthepropertyname(optionallyincludingaperiodcharacter),followedbyan

"="signandanotherbunchofcharactersthatrepresentsthevalue.

JakartaAnt'sonlinemanualislocatedat:http://jakarta.apache.org/ant/manual/index.html.

Hereiswhatbuild.xmldoes:

1. DefinestwotaskswithataskDefelement,calledstartandstop.Thesetaskswillbeusedbythetargetsstartandstoplateroninthebuild.xmlfile.ThesetasksallowyoutousetheTomcat"manager"application-deploymenttoolfromyourAntfiles.

Usesapropertytasktoloadinthesetofpropertiesthataredefinedintheglobal.propertiesfile.Thismeansthatthepropertynametomcat.dirisnowavailableforuselateroninthebuild.xmlfile.Thepathelementusesthetomcat.dirpropertybyincludingitsvalue(intheexample,"k:/jakarta-tomcat-4.1.12")aspartofaclasspathdefinition.Yougetthevalueoftheseimportedpropertiesbyusingareferencelike${tomcat.dir}.AnytimeyouwanttogivethepropertyadifferentvaluebeforeexecutinganAntfile,youcanjustchangethepropertiesfilebytypinginanewvalueinatexteditor.

Createsaninittargetthatechoesamessagetotheconsoleandcreatesthreeproperties(build,src,andcontext-path).Thevaluesofthesepropertiesareavailableonlyaftertheinittargethasbeenexecuted.Forexample,ifthepreparetargetdoesnothave"init"asthevalueofitsdependsattribute,thedeploy-servlettarget,whichdependsonprepare,cannotusethepropertyvaluesdefinedbyinit.

Definesatargetcalledprepare.

http://jakarta.apache.org/ant/manual/index.html

Buildsareusableclasspath(withtheID"classpath")outofalloftheJARfileslocatedinacoupleofTomcatdirectories.

Createsthestartandstoptargets.Thesetargetsechoamessagetotheconsoleandthencallthetasks(suchasstop)thatweredefinedwithtaskDefelementsatthetopofthebuild.xmlfile.Thestartandstoptargetsareactuallyinvokedbytheall-in-onetargetdeploy-servlet.

Createsthedeploy-servlettarget.Thistargetdoesallthemajorworkinsidethebuild.xmlfile.Noticethatitsdependsattributehasthevalue"prepare."Thismeansthatpriortoexecutingtheinstructionscontainedwithinthedeploy-servlettarget,Antfirstexecutestheinitandpreparetargets.Sincethepreparetargetdependsontheinittarget,deploy-servletcallsprepare,whichitselfcallsitowndependency,theinittarget.Sojustbylaunchingthedeploy-servlettarget,youhavetriggeredatargetchainthatlookslikeinit

prepare deploy-servlet.Usinganelementcalledantcallwithwhichatargetmayexplicitlycallanothertarget,deploy-servletcallsboththestopandstarttargets.Inthiswayitcan:

a. StopthedefaultTomcatapplication.

Compiletheservletusingthejavactask.Thejavactaskincludestheservletthatisspecifiedbythecompiled.servletproperty,whichissetinsidetheglobal.propertiesfile.

CopiesthecompiledservlettotheWEB-INF/classesdirectoryofTomcat'sdefaultwebapplication.Thecopytaskcreatesthisclassesdirectoryifitdoesnotalreadyexist.

Startsthedefaultwebapplicationsothatyoucanrequestyourservletinthebrowser.

SeeAlso

ThedeploymentsectionsofTomcat:TheDefinitiveGuide,byBrittainandDarwin(O'Reilly);Recipe2.2,Recipe2.4,andRecipe2.6;theJakartaAntonlinemanualat:http://jakarta.apache.org/ant/manual/index.html

http://jakarta.apache.org/ant/manual/index.html

Recipe2.2UsingaContextElementinTomcat'sserver.xml

Problem

YouwanttodeployandredeployaservletonTomcat4.1.xwithoutrestartingtheTomcatwebcontainer.

Solution

DeploytheservletaspartofaContextelementinTomcat'sserver.xmlfile.

Discussion

YoucanpastearecompiledservletclassoveranexistingservletclassandinvoketheservletwithoutrestartingTomcat:

1. LocatetheContextelementforyourwebapplicationorcreateanewContextelementinthe<tomcat-installation-directory>/conf/server.xmlfile.ContextelementsmustbenestedwithintheHostelementthatrepresentsthevirtualhostunderwhichyourwebapplicationisrunning.

SetthereloadableattributeofyourContextelementtotrue.ThissignalsTomcattomonitorthecontentsofWEB-INF/classesandWEB-INF/libforanychanges.Ifchangesaredetected,Tomcatautomaticallyreloadsthewebapplication.

TheContextelementinserver.xmllookslikethis:

<ContextclassName="org.apache.catalina.core.StandardContext"

crossContext="false"reloadable="true"

mapperClass="org.apache.catalina.core.StandardContextMapper"

useNaming="true"debug="0"swallowOutput="false"

privileged="false"displayName="HomeWebApp"

wrapperClass="org.apache.catalina.core.StandardWrapper"

docBase="h:\home"cookies="true"path="/home"

cachingAllowed="true"

charsetMapperClass="org.apache.catalina.util.CharsetMapper"

>

Thepathattributerepresentsthecontextpathfortheapplication.ThedocBaseattributepointstothedirectorythatrepresentsthetoplevelofthiswebapplication.Mostoftheexample'sotherattributeshavevaluesthataresharedbyotherContexts.Forexample,cookies="true"indicatesthattheContextwillusecookiesforthesessionidentifier,andcrossContext="false"preventstheservletsinthiswebapplicationfromobtainingrequestdispatchersforotherwebapplicationsrunninginthevirtualhost.

Settingthereloadableattributetotrueincurssignificantruntimeoverhead,sothisconfigurationisrecommendedonlyforwebapplicationsindevelopmentmode.

Underthisconfiguration,Tomcat4.1.xdisplaysaconsolemessageafteraslightdelaywhenyoupasteanewservletclassovertheoldoneinthewebapplication.Hereisanexampleofaconsolemessageinresponsetoadynamicservletreload:

WebappClassLoader:Resource'/WEB-INF/classes/com/jspservletcookbook/OracleTest.

class'wasmodified;

Dateisnow:SunFeb0222:17:41EST2003Was:SunFeb0221:38:52EST2003

SeeAlso

ThedeploymentsectionsofTomcat:TheDefinitiveGuide,byBrittainandDarwin(O'Reilly);Recipe2.1,Recipe2.4,andRecipe2.6;JakartaTomcatdocumentationfortheContextelement:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/config/context.html.

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/config/context.html

Recipe2.3DeployinganIndividualServletonWebLogic

Problem

YouwanttotakeyourcompiledservletandinstallitinBEAWebLogicServer7.0tofindoutifitisworking.

Solution

CopyandpastetheclassfileintoWebLogic'sdefaultwebapplication(orintoawebapplicationthatyouhavealreadyinstalled).UsetheWebLogicAdministrationConsoletoaltertheweb.xmlfileandgivetheservletasensiblenamewithwhichtorequestitinabrowser,oruseanAntbuildfiletomovethefiletemporarilyintotheWebLogicdefaultwebapplication.

Discussion

WebLogic7.0'sdefaultwebapplicationislocatedonthefollowingpath:<WebLogic-installation-directory>/user_projects/<mydomain>/applications/DefaultWebApp.InthedefaultinstallationoftheWebLogic7.0server,notmuchexistsinthedefaultwebapplicationbutaweb.xmldeploymentdescriptor,andsomeimagefiles.Toaddaservlettothedefaultapplication,pasteyourservletclass,includingitspackage-relateddirectories,intotheDefaultWebApp/WEB-INF/classesdirectory.Youmighthavetocreateaclassesdirectorythefirsttimeyoudothis.Changetheweb.xmlfiletogivetheservletaname(whichiseasierthroughtheAdministrationConsole)beforeredeployingthewebapplicationasdescribedinRecipe2.4.

UsetheAdministrationConsoletoedittheweb.xmlfileinordertogivethenewservletaregisterednameandservlet-mappingelement.Youcanalsouseanotheravailabletool,suchasWebLogicBuilder(Recipe2.9)oratexteditor.Figure2-1showstheDefaultWebAppintheAdministrationConsole.Clickon"EditWebApplicationDeploymentDescriptors...".

Figure2-1.WebLogicServerAdministrationConsole

ThisdisplaysthescreenshowninFigure2-2.Thisscreenprovidesaneasygraphicalmethodofeditingtheweb.xmlfileforanywebapplication(inthiscase,theWebLogicdefaultwebapplication).

Figure2-2.Editingtheweb.xmlfilegraphically

Withthisgraphicaleditor,createtheservletandservlet-mappingelementsfortheservletthatyoujustadded.Makesuretoclickonthe"WebDescriptor"buttonintheleftcolumnoftheFigure2-2windowandthenpersistthechangesthatyoumadeintheweb.xmlfile.Thisactionrewritestheweb.xmlfile,addingthenewservletandservlet-mappingelements.

Nowredeploythewebapplication,whichisjustamatterofclickingafewhypertextlinksintheConsole.ChoosethenameofyourwebapplicationintheleftcolumnoftheConsole,underthemydomain Deployments

WebApplicationsnodeofthetreenavigationstructureinthislefthandcolumn.Figure2-3showstheresultingwindow.

Figure2-3.UsingtheConsoletoredeployawebapplication

Clickonthe"Deploy"tab,thenclickthe"Undeploy"buttonintheresultingHTMLtable.Thewebapplicationisnowunavailableforservice.

Toredeploytheapplication,clickthe"Deploy"tab,thenselectthe"Deploy"button,asshowninFigure2-4.

Figure2-4.Graphicallydeployingaservlet

Iftheservletthatyouareworkingonalreadyexistsinthewebapplication,thenyoucanalsocopyandpasteanewservletclassovertheoldoneintheWEB-INF/classesdirectoryofthewebapplication.Thenewservletversionbecomesavailableimmediately,withoutusingtheConsoletoredeploytheentirewebapplication.

YoucanalsouseanAntfiletocompiletheservletandcopyitintoWebLogic'sdefaultwebapplication.ThebuildfileinExample2-3isverysimilartotheoneusedanddescribedinRecipe2.1;it'sjustrevisedforusewithWebLogic'swebcontainerinsteadofTomcat's.

Example2-3.UsinganAntfilewithaWebLogicservlet

<projectname="Cookbook"default="deploy-servlet"basedir=".">

<propertyfile="wl.properties"/>

<target

name="init"

description="Initializessomeproperties.">




</target>





</target>


<filesetdir="${wl.dir}\server\lib">


</fileset>

</path>

<targetname="deploy-servlet"depends="prepare"

description="Compilethespecifiedservlet,thenmoveitinto

WL'sdefaultWebapplication.">

<echomessage="Compilingtheservlet${compiled.servlet}...."/>




</javac>

<echomessage="CopyingtheservlettoWLdefaultwebapplication..."/>

<copytodir="${wl.webapp}/WEB-INF/classes">


</copy>

</target>

</project>

ThisAntbuildfilefirstloadsasetofpropertiescontainedinafilecalledwl.properties,whichislocatedinthesamedirectoryasthebuildfile.Thebuildfiletypicallyhasthenamebuild.xml;however,youcancallanotherbuildfileinthesamedirectorybyusingthe-buildfilecommand-lineoption,asinant-buildfilewl_build.xml.Thewl.propertiesfileforthisexampleisshowninExample2-4.

Example2-4.wl.propertiesforWebLogicAntbuildfile

wl.webapp=k:/bea/user_projects/bwpdomain/applications/DefaultWebApp

wl.dir=k:/bea/weblogic700

compiled.servlet=test

Thedeploy-servlettargetdependsonatargetnamedpreparethatisalsodefinedinthisbuildfile.Thepreparetargetinturnhas"init"asitsdependsattribute,whichmeansthattheinittargetexecutespriortothepreparetarget.Socallingthedeploy-servlettargetcreatesa

chainofexecutingtargets:init prepare deploy-servlet.Inall,thisiswhatthebuildfileaccomplishes:

1. initcreatesacoupleofproperties(buildandsource)thatpointtodirectories.

Thepreparetargetdeletesandthenremakesthebuilddirectory,sothatyoustartwithacleanbuild.

deploy-servletcompilestheservletintothebuilddirectory,thencopiesitintothedirectoryspecifiedbythewl.webappproperty(whichcontainsitsvalueinthewl.propertiesfile).

ThepathelementcreatesaclasspathoutoftheJARfilesfoundinthek:/bea/weblogic700/server/libdirectory.ThisdirectorypathishowAntresolvesthephrase"${wl.dir}\server\lib,"whichisparsedbyattachingthevalueofthepropertywl.dirtothestring"\server\lib."

SeeAlso

Recipe2.5,Recipe2.7-Recipe2.10;thedeploymentsectionsofWebLogic:TheDefinitiveGuide,byMountjoyandChugh(O'Reilly);WebLogic'sServer7.0programmerdocumentation:http://e-docs.bea.com/wls/docs70/programming.html.

http://e-docs.bea.com/wls/docs70/programming.html

Recipe2.4DeployinganIndividualJSPonTomcat

Problem

YouwanttoplaceaJSPfileintoawebapplication.

Solution

CopytheneworrevisedJSPfileintothetop-leveldirectoryofthedefaultTomcatwebapplicationorofanotherdeployedwebapplication.

Discussion

TheeasiestwaytotestanewJSPfileistoplaceitatthetoplevelofTomcat'sdefaultwebapplication.Thisapplicationislocatedinthe<Tomcat-installation-directory>/webapps/ROOT/directory.Tomcat4.1.xcompiles(orrecompiles,ifyouarepastinganewJSPfileoveranoldone)theJSPanddisplayitsresponseinawebpage.YoudonothavetostopandstartTomcatusingtheTomcatmanagerapplicationforthenewJSPfiletobeavailabletoyourwebapplication.

PlacingaJSPfileinadeployedwebapplicationwillnotworkiftheJSPdependsonapplication-specificresourcessuchasservlets,customtags,orotherJavaclasses,becausethereisnoguaranteethatthetemporaryhostwebapplicationyouareusingfortheJSPhasaccesstothoseresources.

IfyouhavetodeployaJSPseparatelyfromitswebapplication,youcan

alsoplaceaJSPfileinadeployedwebapplicationotherthantheTomcatdefaultapplication.ThismakestheJSPpageavailabletoapplicationuserswithouthavingtostopandrestartTomcat.RememberthattheJSPfilesbelonginthetoplevelofthewebapplication,whichhasthefollowingdirectorystructure:

index.html

default.jsp

anotherJsp.jsp

images/logo.jpeg

WEB-INF/classes/jspservletcookbook/myservlet.class

WEB-INF/lib/helperclasses.jar

WEB-INF/lib/utilities.jar

WEB-INF/web.xml

WEB-INF/mytags.tld

Inotherwords,thetoplevelofthedirectorycontainstheHTMLandJSPfiles,aswellastheWEB-INFdirectory.TheWEB-INFdirectorycontains:

Theweb.xmldeploymentdescriptor

Theclassesdirectory,whichcontainspackage-relateddirectoriesandservletorsupportclasseslikeJavaBeans

Thelibdirectory,whichstoresanyJavaArchive(JAR)filescontainingutilityorhelperclassesthatyourwebapplicationuses

Optionally,anyTagLibraryDescriptorfiles(fileswith.tldsuffixes)

Anyoptionaldirectoriesforimages,videofiles,XMLfiles,orotherwebresources

SeeAlso

ThedeploymentsectionsofTomcat:TheDefinitiveGuide(O'Reilly);Recipe2.1,Recipe2.2,andRecipe2.6.

Recipe2.5DeployinganIndividualJSPonWebLogic

Problem

YouwanttoquicklytestaJSPwithoutdeployingitaspartofanewwebapplication.

Solution

CopyandpastetheJSPintothetop-leveldirectoryofBEAWebLogicServer7.0'sdefaultwebapplication,thenrequesttheJSPinabrowser.

Discussion

AJSPfilecanbe"hotdeployed"onWebLogic7.0'sdefaultwebapplicationwithouthavingtoredeploytheentirewebapplication.Thisdefaultwebapplicationislocatedat<WebLogic-installation-directory>/user_projects/<name-of-your-domain>/applications/DefaultWebApp.IfyoupasteyourJSPfileintothisdirectory(DefaultWebApp),itwillbeavailabletoreceiverequestswithoutredeployingthedefaultwebapplication.IfyourJSPfileisnamednewfile.jsp,thentheURLforrequeststothispagewouldbehttp://localhost:7001/newfile.jsp.NotetheabsenceofacontextpathorapplicationnameintheURL.Iftherequestisforthedefaultwebapplication,thentheJSPfilesappearfollowingtheforwardslash(/)afterthehost:portpartoftheURL(inotherwords,afterthelocalhost:7001/part).

Torepeatapriorcaveat:placingaJSPfileinadeployedwebapplicationinorder

totestitwillnotworkiftheJSPdependsonapplication-specificresourcessuchasservlets,customtags,orotherJavaclasses,becausethereisnoguaranteethatthetemporaryhostwebapplicationyouareusingfortheJSPhasaccesstothoseresources.

Inmostcases,theJSPisalreadypartofawebapplication,andseveraltoolsexisttoredeployawebapplication,includingAnt,BEAWebLogicBuilder,andtheWebLogicAdministrationConsole.

Finally,youcanalsocopyandpasteaJSPfileintoanotherWebLogicwebapplication.However,thatapplicationmustbedeployedinexplodeddirectoryformat,meaningthattheapplicationhasnotbeendeployedinarchiveform(asaWARorEARfile).Therefore,placetheJSPfileintheapplication'stop-leveldirectory.Iftheapplicationisnamed"newapp,"thisdirectoryisnamed<WebLogic-installation-directory>/user_projects/<name-of-your-domain>/applications/newapp.

SeeAlso

Recipe2.3;Recipe2.7-Recipe2.10;WebLogic'sServer7.0programmerdocumentation:http://e-docs.bea.com/wls/docs70/programming.html.


Recipe2.6DeployingaWebApplicationonTomcat

Problem

YouwanttodeployanentirewebapplicationonTomcat4.1.x.

Solution

CreateaJakartaAntbuildfile.Antcanautomaticallycompileyourservletclasses,createawebapplicationarchive(.war)file,thendeploytheWARtotheTomcat4.1.xserver.

Discussion

TherecommendedmethodforthecompilationanddeploymentofwebapplicationsistousetheJakartaAntautomationtool.Ifyouchangeanythingintheapplication(suchasalteringaservletorJSP),thenallittakesisasinglecommand-lineexecutionofanttocompile,package,andredeploytheapplicationonTomcat.Youdonothavetogotothetroubleofmanuallyrecompilingachangedservlet,creatinganewWARfile,startingandstoppingTomcat,andredeployingtheapplication.

AnothermethodofdeployingawebapplicationonTomcatistoplaceadirectorycontainingawebapplicationintherequireddirectorystructureintheTomcatwebappsfolder.Thenameofthewebapplicationdirectory(suchasmyapp)thenbecomesthecontextpathornameofthenewwebapplication.Thisdeploymentmethodisnotguaranteedtoworkwithotherapplicationservers,however,soitisanineffectivestrategyforcreatingportableapplications.Inaddition,sincethismanualmethodisnotautomatedinanymanner,itisawkwardtoreplaceandkeeptrackofany

changedservletorJavaBeanclassesinthesewebapplicationdirectories.

TheendofthisdiscussiondescribeshowtoconfigureTomcat'sserver.xmlconfigurationfilesothatacontextpathpointstoanunpackedwebapplicationdirectoryelsewhereontheserver.Asanalternativetocreatinganarchivedapplication(aWARfile),Tomcatdeveloperscanusethismethodofdeploymentduringdevelopmentandtesting.

UsingAntfordeployment

UsingAnttocompileanddeployanapplicationinvolvesthefollowingsteps:

1. ChooseadirectorytoholdtheAntbuild.xmlfile,anybuild.propertiesfiles,andallofthecontentsofyourwebapplication.

CreatethedirectoriestoholdtheJavaservletsourcefiles,anyJSPorHTMLfiles,JavaArchive(JAR)filesforcomponents(suchasdatabasedrivers)andthewebapplicationarchivefile(WARfile).OnewaytocreatethisdirectorystructureisshowninFigure2-5.

Figure2-5.Webapplicationdirectorystructure

3. Inthisexample,thesrcdirectorycontainstheJavasourcefilesforservletsandJavaBeans.Thewebdirectorycontainsthefiles

thatresideatthetoplevelofthewebapplication,suchasJSPandHTMLfiles.ThemetadirectoryholdsXMLdeploymentdescriptors(attheveryleast,web.xml).ThebuilddirectoryiswhereAntcompilestheJavasourcefiles.ThesefileswillendupintheWEB-INF/classesdirectoryofthewebapplication.ThelibdirectoryisforanyJARfilesthatyourwebapplicationuses,suchasdatabasedriversand/ortaglibraries.Finally,thedistdirectorycontainstheWARfile.

CreatetheJavasourcecodefortheapplicationandmoveanyotherrelatedfiles(likeJSPsandweb.xml)intotheirspecifieddirectories.

Createanynecessarypropertyvaluesinthebuild.propertiesfilethatbuild.xmlwilluseduringthecompilationanddeploymentprocess.Thesepropertieswillbedescribedinmoredetailintheupcomingdiscussion.

Runthebuild.xmlfileonthecommandlinebychangingtothedirectorycontainingthebuild.xmlfileandtypingant.

Example2-5isthebuild.propertiesfilethatisreferencedinstep5.

Thefiledoesnothavetobecalledbuild.properties;thisnameisusedpurelybyconvention.Youcouldcallitglobal.props,forinstance.

Example2-5.build.propertiesforwebapplicationdeployment

tomcat.webapps=k:/jakarta-tomcat-4.1.12/webapps/



username=tomcat

password=tomcat

manager.path=${tomcat.dir}/work/standalone/localhost/manager

Eachofthesepropertiesismadeavailabletoorimportedintothebuild.xmlfilebythefollowinglinewithinthisfile:

<propertyfile="build.properties"/>

ThislinerepresentsapropertytaskorXMLelementwithinthebuild.xmlXMLfile.Forexample,thevalueofthetomcat.dirpropertyinsidetheAntXMLfileis"k:/jakarta-tomcat-4.1.12."

Example2-6istheentirebuild.xmlfile.ItcanbeusedtocompileJavaclasses,createaWARfile,anddeployittoTomcatjustbyexecutingantonthecommandline.ThechiefadvantageofusingAntisthatitautomatesanotherwisecomplicatedprocess.Ifyouhavetochangeoraddaservletinthewebapplication,forinstance,youcanrecompileandredeploythewebapplicationsimplybyrunningAnt.Thisbuild.xmlfileisfairlycomplexandintroducessomeadvancedfeaturesofAnt.

Example2-6.AnAntbuildfilefordeployingawebapplication

<projectname="DeployProject"default="deploy-application">

<taskdefname="deploy"classname="org.apache.catalina.ant.DeployTask"/>

<taskdefname="undeploy"classname="org.apache.catalina.ant.UndeployTask"/>





</fileset>



</fileset>

</path>

<targetname="init"





<propertyname="dist"value=".\dist"/>

<propertyname="lib"value=".\lib"/>

<propertyname="web"value=".\web"/>

<propertyname="meta"value=".\meta"/>

<propertyname="context-path"value="myapp"/>

</target>


<echomessage="Cleaningupthebuildanddistdirectories."/>



<deletedir="${dist}"/>

<mkdirdir="${dist}"/>

</target>

<targetname="deploy"

description="DeploysaWebapplication">

<deployurl="${url}"username="${username}"password="${password}"

path="/${context-path}"war="file:${dist}/${context-path}.war"

/>

</target>

<targetname="undeploy"

description="UndeploysaWebapplication"if="already.deployed">

<undeployurl="${url}"username="${username}"password="${password}"

path="/${context-path}"/>

</target>

<targetname="create-war"description="createsawebapplicationarchivefile">

<wardestfile="${dist}/${context-path}.war"webxml="${meta}/web.xml">

<classesdir="${build}"/>

<libdir="${lib}"/>

<filesetdir="${web}"/>

</war>

</target>

<targetname="deploy-application"depends="prepare"

description="Compilethewebapplication....">

<echomessage="Undeployingtheapplicationonlyifit'sdeployed..."/>

<availablefile="${manager.path}/${context-path}.war"property="already.deployed"/>

<antcalltarget="undeploy"/>

<echomessage="Compilingtheapplicationfiles..."/>


<includename="*.java"/>


</javac>

<echomessage="creatingtheWARfile...."/>

<antcalltarget="create-war"/>

<antcalltarget="deploy"/>

</target>

</project>

Thecreate-wartargetusesthewarAnttasktogeneratetheWARfile,basedoncertainattributevaluesandnestedelements.Forexample,theweb.xmlfilethatwillbeincludedintheWARisspecifiedasthevalueforthewartask'swebxmlattribute.Inaddition,theclassesthatwillbeincludedintheWARfile'sWEB-INF/classesdirectoryarespecifiedbythisnestedelementofthewartask:


Thenicethingaboutthisclasseselement,alongwiththelibandfilesetnestedelements,isthatallofthenesteddirectoriesinsidethebuild,lib,andwebdirectoriesareautomaticallyincludedintheWAR.Forexample,thewebdirectoryincludesanimagesdirectorycontainingtheapplication'svariousGIFfiles.TheimagesdirectoryisincludedatthetopleveloftheWARfile,alongwithanyHTMLorJSPfilesthatarestoredin

thewebdirectory,justbyincludingthisnestedelement:


Alsoexaminethedeploy-applicationtarget,whichembodiesthemeatofthisbuild.xmlfile.AslongasyouproperlysetthePATHenvironmentvariabletopointattheAntcomponent,thedeploy-applicationtargetiscalledbydefaultwhenyoutypeantatthecommandline.

First,thetargetfindsoutwhetherthewebapplicationhasalreadybeendeployedonTomcat.Thisfunctionisincludedbecausethisbuildfilewillpresumablyberunoverandoveragain,notjustthefirsttimethewebapplicationisdeployed.Thislineusesanavailabletask,whichsetsapropertytothevalue"true"onlyifthefilespecifiedinitsfileattributeexists:

<availablefile="${manager.path}/${context-path}.war"

property="already.deployed"/>

<antcalltarget="undeploy"/>

Ifthisparticularfileisfound,itmeansthattheTomcatManagerapplicationhasalreadydeployedtheWARfile,andthatthealready.deployedpropertyissettotrue.Thisallowsthebuild.xmlfiletoconditionallyundeploytheapplication,beforetheapplicationisredeployedafteranychanges.Inotherwords,itundeploystheapplicationonlyifthewebapplicationisalreadydeployed(otherwise,runningtheundeploytargetraisesanerrorandhaltsexecutionofthebuildfile).Theundeploytargetrunsonlyifthealready.deployedpropertyissettotrue:

<targetname="undeploy"

description="UndeploysaWebapplication"

if="already.deployed">

Thehandyantcalltaskcallsanothertargetinthefile,similartocallingamethod.Finally,thedeploy-applicationtargetusesthejavac

tasktocompiletheapplication'sservletsintothebuilddirectory,thenusestheantcalltasktocreatetheWARfileanddeploytheneworchangedapplicationtoTomcat.Thetargetechoesvariousmessagestotheconsoletohelpindicatetothedeveloperwhatitisdoing:



...





</javac>



<antcalltarget="deploy"/>

</target>

Asanalternativetousingthepriordeploymentmethod,youcanconfigureTomcattopointtoanexternaldirectorythatcontainsavalidwebapplication.ThisstrategydeploysthewebapplicationthenexttimeTomcatisrestarted.Itisanacceptablestrategywhentheapplicationisunderdevelopment,becauseyoucanconfigureTomcattoautomaticallyreloadtheapplication(Recipe2.2)whenaservletischanged,orwhenaJARfileisaddedtoWEB-INF/lib.However,developersshoulddeployapplicationsasWARfileswhenthetimecomestoruntheapplicationonaproductionserver.

CreateafilethatcontainsaContextelementasthiselementwouldappearinserver.xml.Givethisfilea.xmlextension.Itissensibletocallthisfilethesamenameasthecontextpathorapplicationname(forexample,myapp.xml),butnotrequired.Yourfilecontentmightlooklikethis:

<ContextclassName="org.apache.catalina.core.StandardContext"

crossContext="false"reloadable="true"

mapperClass="org.apache.catalina.core.StandardContextMapper"

useNaming="true"debug="0"swallowOutput="false"

privileged="false"

wrapperClass="org.apache.catalina.core.StandardWrapper"

docBase="h:\book\cookbook\sec1\sec1_1\dist"

cookies="true"path="/newapp"cachingAllowed="true"

charsetMapperClass="org.apache.catalina.util.CharsetMapper">

</Context>

Thereloadableattributevalueof"true"configuresTomcattomonitortheclassesinWEB-INF/classesandthecomponentsinWEB-INF/libforanychanges.Tomcatautomaticallyreloadsthewebapplicationifitdetectsanychanges.

ThevalueforthedocBaseattributecanbeanabsolutepathtothedirectorythatcontainsthewebapplication,orthecontextroot.ItcanalsobethepathtoaWARfile.ThedocBaseattributecanalsobeapathnamerelativetotheappBasedirectoryoftheenclosingHostelementinserver.xml,suchasrelativetothe<Tomcat-installation-directory>/webappsdirectory.Thepathattributedeclaresthecontextpathforthenewapplication,asinhttp://localhost:8080/newapp/(where/newappisthecontextpath).

Placethisfileinthe<Tomcat-installation-directory>/webappsdirectory(orwhicheverdirectoryisconfiguredastheappBaseintheenclosingHostelementinconf/server.xml)andrestartTomcat.ThiswebapplicationcannowbeinvokedonTomcat.

SeeAlso

ThedeploymentsectionsofTomcat:TheDefinitiveGuidebyBrittainandDarwin(O'Reilly);Recipe2.1,Recipe2.2,andRecipe2.4.

Recipe2.7DeployingaWebApplicationonWebLogicUsingAnt

Problem

YouwanttodeployawebapplicationonWebLogicServer7.0usingJakartaAnt.

Solution

CreateaJakartaAntbuildfile.Antcanautomaticallycompileyourservletclasses,createaweb-applicationarchive(.war)file,andthendeploytheWARtoWebLogicServer7.0.

Discussion

YoucaneithermanuallycutandpastewebcomponentsintotheWebLogicapplicationsdirectory(asdescribedinthesidebar),oruseAnttoautomatetheprocessofcompiling,generatingaWARfile,andcopyingtheWARtothisdirectory.Anexampledirectorypathtoapplicationsisk:\bea\user_projects\bwpdomain\applications.Thismethodwouldentailaminoreditofthebuild.xmlandbuild.propertiesfilesdescribedinRecipe2.6.

ManuallyDeployingaWebApplication

WhenBEAWebLogicServer7.0isrunningindevelopmentmode,ifaWARfile,anenterprisearchiveapplication(EAR)file,oradirectorythatcontainsavalidwebapplicationisplacedintheapplicationsdirectory,thenthoseapplicationsareautomaticallydeployedandbecomeavailableontheserver.

AvalidwebapplicationcontainsaWEB-INF/web.xmldeploymentdescriptorthatdoesnotgenerateanyparsingexceptions.Ifthedirectorythatyouplaceintheapplicationsfolderdoesnotcontainadeploymentdescriptor,thenWebLogicwillnotautomaticallydeploytheapplication,eveniftheserverisrunningindevelopmentmode.WebLogicraisesanexceptionsimilartothisoneintheconsoleinwhichtheserverwasstartedup:

<Unabletoactivateapplication,_appsdir_dist_dir,fromsource,K:\bea\user_

projects\bwpdomain\applications\dist.Reason:NoJ2EEdeploymentdescriptor

foundat"K:\bea\user_projects\bwpdomain\applications\dist".>

Thisdeploy-applicationAnttargetiseditedinbuild.xmltodeployonWebLogic7.0:







</javac>



<copytodir="${wl.applications}">

<filesetdir="${dist}"/>

</copy>

</target>

Inaddition,thebuild.propertiesfilecoulddefinethewl.applicationspropertywithavaluesuchas"k:\bea\user_projects\bwpdomain\applications".OncetheWARfileiscopiedtothisspecialdirectory,aWebLogicserverthatisstartedin

developmentmodewillautomaticallydeployit.

Inthe\user_project\bwpdomaindirectory(dependingonyourserverdomainname)theWebLogicstartscriptiscalledstartWebLogic.cmdonWindowsandstartWebLogic.shonUnix.Tostarttheserverindevelopmentmode,thelineinthestartscriptshouldbesetSTARTMODE=(thevalueisanemptystringhere)orsetSTARTMODE=false.TheserverstartsinproductionmodeifitissetSTARTMODE=true.

SeeAlso

Recipe2.3;Recipe2.8-Recipe2.10;WebLogic'sServer7.0programmerdocumentation:http://e-docs.bea.com/wls/docs70/programming.html.


Recipe2.8UsingtheWebLogicAdministrationConsole

Problem

YouwanttodeployawebapplicationusingWebLogic'sAdministrationConsole.

Solution

BringuptheAdministrationConsoleinyourwebbrowseranduseitsgraphicalinterfacetodeployeitheraWARfileoraweb-applicationdirectory.

Discussion

TheWebLogicAdministrationConsoleisaservlet-andbrowser-basedtoolformanagingWebLogicserverresourcesandJava2EnterpriseEdition(J2EE)applications.TousetheConsole,WebLogicServermustberunning.First,requesttheURLhttp://localhost:7001/console(orwhicheveryourserveraddressandportis,asinhttp://<weblogic-server-address>:<port>/console).Thenenteryourloginnameandpasswordtogainentrytothebrowser-basedtool.TheresultingscreenlookslikeFigure2-6,withahierarchicallistofchoicesinthelefthandcolumnandthecurrentscreenchoiceintherighthandcolumn.

Figure2-6.WebLogicAdministrationConsole

Intheleftcolumn,choosethenameofyourdomainbyclickingontheplussign(+),whichdisplaysthedomain'ssubnodes.ThesubnodesofthedomainincludeServers,Clusters,Machines,NetworkChannels,Deployments,Services,andSecurity.Thenchoosethe"Deployments"node,whichgivesyouthechoiceofselectingits"WebApplications"subnode.Openupthe"WebApplications"nodebyclickingonitsplussign.TheresultingscreenlookslikeFigure2-7.

Figure2-7.WebApplicationsnode

IntheWebApplicationswindow,clickthe"ConfigureaNewWebApplication..."hyperlink.ThenextscreengivesyoutheoptionofuploadingtheWebApplicationArchive(WAR)orEnterpriseApplication

Archive(EAR)filethroughyourbrowsertotheserver'sfilesystem,asshowninFigure2-8.

Figure2-8.DeployingawebapplicationasaWARorEARfile

Initiatethisuploadandthenclickonthe"select"linknexttotheWARfile.CompletethethreestepsthatFigureFigure2-9shows:clickthearrowbuttonstodeploytheapplicationfromthe"AvailableServers"columntothe"TargetServers"column,nametheapplication(leavethenamethesameastheWARfilenameminusthe.warsuffix),thenpressthe"ConfigureandDeploy"button.ThatisallittakestodeploytheWARfiletothetargetserver.

Figure2-9.FinalstepsfordeployingtheWARfile

Nowtestthedeploymentbyrequestingoneoftheservletsinthebrowser,usingthenamethatyougavetheapplicationasthecontextpath.AnexampleURLishttp://localhost:7001/cookbook/cookieservlet.ThisURLrequestsaservletthathasbeenmappedtothename"/cookieservlet."Theweb-applicationcontextpathis/cookbook.

RedeployingapreviouslyundeployedwebapplicationusingtheWebLogicAdministrationConsoleinvolvesthefollowingsteps:

1. SelectthenameofyourapplicationundertheWebApplicationsnodeintheConsole'slefthandcolumn.ThisshowsascreensimilartoFigure2-10.

Figure2-10.SelectingawebapplicationintheConsole

2. Clickthe"Deploy"buttonintherighthandscreen.Thisreactivatestheapplication,sothatitcanreceiverequestsintheWebLogicwebcontainer.

IfyouwanttodeleteawebapplicationusingtheWebLogicAdministrationConsole,clickonthenameofyourdomaininthelefthandcolumnoftheConsolescreen,thenonthe"Deployments"and"WebApplications"nodes.Clickingthetrashcaniconassociatedwiththeapplication,asshowninFigure2-11,deletestheapplicationfromtheWebLogicserver.

Figure2-11.Deletingawebapplication

DeletingawebapplicationinthismannermeansthattheapplicationisnolongeravailabletoreceiverequestsintheWebLogicwebcontainer.

SeeAlso

Recipe2.3andRecipe2.7;Recipe2.9andRecipe2.10;WebLogic'sServer7.0programmerdocumentation:http://e-docs.bea.com/wls/docs70/programming.html.


Recipe2.9UsingWebLogicBuildertoDeployaWebApplication

Problem

YouwanttouseWebLogicBuildertodeployawebapplication.

Solution

WebLogicBuilderinstallswiththeWebLogic7.0Server,soyoucanlaunchtheBuilderapplicationanduseitsgraphicaltoolstodeploythewebapplication.

Discussion

WebLogicBuilderisagraphicaltoolthatinstallswithWebLogicServer7.Itcanbeusedtoeditdeploymentdescriptorfilessuchasweb.xmlandweblogic.xml,aswellasfordeployingwebapplicationstoaserver.UsingWebLogicBuilder,youcanopenup,edit,anddeploywebapplicationsthatexistaseitherWARfilesorinexplodeddirectoryformat.

Explodeddirectoryformatisaweb-applicationdirectorystructureasitwouldappearinyourfilesystem,butthatisnotinarchivedorinWARform.TobedeployedonWebLogicasawebapplication,therootdirectorymustcontaintheWEB-INF/web.xmldeploymentdescriptorandanyotherproperlystructuredapplicationcomponents,suchasatheWEB-INF/classesdirectorycontainingyourservlets(includinganypackage-relateddirectories).

YoucanlaunchWebLogicBuilderonWindowsfromeitherthe"Start"menuorthecommandline.ThestartscriptforBuilderisat:<BEA_HOME>/weblogic700/server/bin/startWLBuilder.cmd(orstartWLBuilder.shonUnix).<BEA_HOME>isthedirectorywhereWebLogicServer7.0isinstalled.

ItiseasytoopenupandeditthedeploymentdescriptorforawebapplicationinWebLogicBuilder.GototheFile OpenmenuandnavigatetotheWARfileorrootdirectoryfortheapplication.

TheresultisthewindowdepictedinFigure2-12.Thenavigationtreeintheupper-leftwindowletsyouconfigurewebresources(suchasservlets)anddeploymentdescriptorelements(suchassecurityconstraints),thensavethechangestoweb.xml.

Figure2-12.OpeningaWARfileinWebLogicBuilder

Youcanaddordeleteelementsforservlets,servletmappings,andfilters,forinstance.ThechangesarepersistedtothedeploymentdescriptorifyoumakeandsavechangestotheapplicationfromwithinWebLogicBuilder.Youcanthenoptionallyconnecttotheserverfromthe"Tools"menu,anddeploytheapplication.

The"DeployModule"windowindicateswhethertheapplicationisalreadydeployed.Figure2-13showsthiswindow.Ifyouhavealreadydeployed

theapplication,youcanstillmakedeployment-descriptorchangesinBuilder,thendeploytheapplicationagainfromthe"Tools"menu.WebLogicBuilderspecificallyundeploystheapplication,thenredeploysitwiththechangesthatyouincludedinweb.xml.

Figure2-13.WebLogicBuilder'sDeployModulewindow

WebLogicBuilderdoesnotshowanyJSPfilesthatmaybepartofthewebapplication.ItwillshowanyservletmappingsthatareassociatedwithJSPfiles.

SeeAlso

Recipe2.3,Recipe2.7,Recipe2.8,andRecipe2.10;WebLogic'sServer7.0programmerdocumentation:http://e-docs.bea.com/wls/docs70/programming.html;thelocalWebLogicBuilderHelpdocumentation:<BEA_HOME>\weblogic700\server\builder\index.html.


Recipe2.10Usingtheweblogic.DeployerCommand-LineTool

Problem

YouwanttousethecommandlinetodeployawebapplicationonWebLogicServer7.0.

Solution

UsetheJava-basedweblogic.Deployercommand-lineutility,whichisinstalledwithWebLogicServer7.0.

Discussion

Fordevelopersoradministratorswhoneedtousethecommandlineorshellscriptsfordeployingandredeployingwebapplications,WebLogicServer7.0providestheJava-basedDeployerutility.ThisutilityaccomplishesthesametasksasusingthegraphicalinterfaceoftheWebLogicAdministrationConsoletodeployorredeployawebapplication.First,thisrecipedescribeshowtodeployandredeployawebapplicationonthecommandlineusingtheDeployerutility.ThentherecipeprovidesanexampleofaWindowsbatchfilethatinvokestheDeployerutility.

TheDeployerutilitycaninitiateothertasks,suchasredeployingindividualwebcomponentsinawebapplication.TheonlinedocumentationfortheDeployerutilitycanbefoundathttp://e-docs.bea.com/wls/docs70/programming/deploying.html#1094693.

http://e-docs.bea.com/wls/docs70/programming/deploying.html#1094693

TheDeployerutilityisaJava-basedprogramthatrequiresthefollowingJARfileonyourclasspathbeforetheprogramcanrun:<BEA_HOME>\server\lib\weblogic.jar."><BEA_HOME>representsthedirectorywhereWebLogicServer7.0wasinstalled.Thefollowingcommand-linescriptonaWindowsNT4.0machineredeploysthecookbook.warwebapplicationonaservernamedbwpserver:

java-cpk:\bea\weblogic700\server\lib\weblogic.jar;

%CLASSPATH%weblogic.Deployer

-adminurlhttp://localhost:7001

-userbwperry-namecookbook-source.\dist\cookbook.war

-targetsbwpserver-activate

Thiscommand-lineinvocationdeploysthewebapplicationrepresentedbythearchivefilecookbook.war,sotheapplicationisnowavailabletoreceiverequestswiththecontextpath/cookbook.Whenrunonthecommandline,theprogrampromptstheuserforapasswordifyouhavenotincludeditinthescriptwiththe-passwordoption.The-sourceoptionspecifiesthelocationoftheWARfileorweb-applicationdirectory.The-targetsoptionspecifiesoneormoreserversonwhichtodeploythewebapplication.Thefinalcommandfordeployingtheapplicationis-activate.

Thiscommand-lineinvocationdeactivates(makesunavailable)anexistingwebapplicationontheserverbwpserver.Itpromptsfortheuserpasswordfirst,unlessyouaddthe-passwordoptiontothecommandline:



-adminurlhttp://localhost:7001

-userbwperry-namecookbook

-targetsbwpserver-deactivate

The-cpoptionspecifiestheclasspathtouseforrunningtheDeployer

mailto:<BEA_HOME>

Javautility,andmustincludetheweblogic.jarJARfile.The-adminurlswitchspecifiestheadministrationserver(thedefaultvalueishttp://localhost:7001,soitdoesnothavetobeincludedhere).The-nameoptionspecifiesthenameoftheapplicationtobedeactivated,andthe-targetsoptionnamestheserverwheretheapplicationisrunning.Thefollowingcommand-lineinvocationredeploysthesame"cookbook"application:



-userbwperry-namecookbook-activate

Thistime,the-adminurland-targetsoptionswereomitted.Thedefaultvaluesfortheseswitchesarehttp://localhost:7001andallcurrenttargets(ifthedeveloperisredeployinganexistingapplication),respectively.Iftheapplicationisbeingdeployedforthefirsttime,thedefaulttargetforthe-targetsoptionistheadministrationserver.

Itiseasiertorunshellcommandsfromabatchfile,becausethereislesstypingforcomplicatedcommand-lineprogramsandtheshellscriptscanbepermanentlysaved.Example2-7isthefirstexamplerewrittenasabatchfileonWindowsNT4.0.

Example2-7.Deployinganapplication

@echooff

setWL_HOME=K:\bea\weblogic700

setBEA_CLASSPATH=%WL_HOME%\server\lib\weblogic.jar;%CLASSPATH%

java-cp%BEA_CLASSPATH%weblogic.Deployer-adminurlhttp://localhost:7001-userbwperry

-namecookbook-source.\dist\cookbook.war-targetsbwpserver-activate

Thisbatchfilesetstwoenvironmentvariables:WL_HOMEandBEA_CLASSPATH.Theseareusedtomakesurethattheclasspathincludestheweblogic.jarfile,whichcontainstheDeployerutility.Ifthe

scriptwassavedasdeploy.bat,thisishowitwouldberunonthecommandline:

H:\book\cookbook>deploy

Theresultingconsoleoutputlookslikethis.

Enterapasswordfortheuser"bwperry":bwpserver_1968

Operationstarted,waitingfornotifications...

....

#TaskIDActionStatusTargetTypeApplicationSource

15ActivateSuccessbwpserverServercookbookH:\book\

cookbook\.\dist\cook

SeeAlso

Recipe2.3andRecipe2.5;Recipe2.7-Recipe2.9;WebLogic'sServer7.0programmerdocumentation:http://e-docs.bea.com/wls/docs70/programming.html.


Chapter3.NamingYourServletsIntroduction

Recipe3.1.MappingaServlettoaNameinweb.xml

Recipe3.2.CreatingMoreThanOneMappingtoaServlet

Recipe3.3.CreatingaJSP-TypeURLforaServlet

Recipe3.4.MappingStaticContenttoaServlet

Recipe3.5.InvokingaServletWithoutaweb.xmlMapping

Recipe3.6.MappingAllRequestsWithinaWebApplicationtoaServlet

Recipe3.7.MappingRequeststoaControllerandPreservingServletMappings

Recipe3.8.CreatingWelcomeFilesforaWebApplication

Recipe3.9.RestrictingRequestsforCertainServlets

Recipe3.10.GivingOnlytheControllerAccesstoCertainServlets

Introduction

Animportantwebapplicationconfigurationtaskistocreatethepathbywhichyourservletisrequestedbywebusers.Thisiswhattheusertypesintotheaddressfieldofhisbrowserinordertomakearequesttotheservlet.Whilethisissometimesthefullnameoftheservlet,thatconventionoftenresultsinanawkwardURI.Forexample,awebsitemighthaveaservletthatdynamicallyassemblesa"Resources"page,insteadofastaticresources.htmlpage.Usingthefullservletname,therequestURLmightbehttp://www.myorganization.com/servlet/com.organization.servlets.resources.ResourceServletThisisquiteapathtotypein;itmakesmuchmoresensetomapthistoaservletpath,whichisanaliasfortheservlet.Usingtheservletpath,the(new)addressforthedynamicpagemightbehttp://www.myorganization.com/resources.Theservletpath,inthiscase,is/resources.

ThisservletpathisalsotheidentifierusedbyotherservletsorJSPsthatforwardrequeststothisparticularservlet,aswellastheaddressthatanHTMLformtagusesinitsactionattributetolaunchparameternamesandvaluestowardtheservlet.TheservletspecificationoffersanintuitiveandflexiblewaytomapHTTPrequeststoservletsintheweb.xmldeploymentdescriptor.

Thischapterdescribeshowyoucanusetheweb.xmldeploymentdescriptortocreateoneormorealiases(servletpaths)toyourservlet.ItalsodiscusseshowtoinvoketheservletwithothertypesofURLs,suchasonethatlookslikeaJSPpagerequest(e.g.,info.jsp)oronethatlookslikeanHTMLpagerequest(info.html).Recipe3.5alsodescribeshowtoaccessaservletwithoutamappinginweb.xml,forexample,forthedeveloperwhowantstodebugherservletwithoutmodifyingtheweb.xmlfile.

Finally,Recipe3.7,Recipe3.9,andRecipe3.10showhowtomapallrequeststoone"controller"servlet(Recipe3.7),restricttherequestsforcertainservletstoauthenticatedusers(Recipe3.9),andblockall

requeststocertainservletsexceptthoseforwardedfromthecontroller(Recipe3.10).

Recipe3.1MappingaServlettoaNameinweb.xml

Problem

Youwanttocreateanalias,orservletpath,toyourservlet.

Solution

Createservletandservlet-mappingelementsinweb.xml.

Discussion

Creatinganaliastotheservlettakesplaceinthedeploymentdescriptor'sservlet-mappingelement.Allservletelementsmustcomebeforeanyoftheservlet-mappingelementsintheservlet2.3web.xmldeploymentdescriptor.Theservlet-mappingelementreferstothenameoftheservletthatappearsintheservlet-nameelement,suchas:

<servlet><servlet-name>myservlet</servlet-name></servlet>

Thisisreferredtoastheservlet'sregisteredname.Theservlet-mappingthenprovidesthename,orURLpattern,whichwebapplicationuserscantypeintotheirbrowserstoaccesstheservlet.Example3-1showsaweb.xmlfilewithaservletandservlet-mappingelement.Theregisterednameinthiscaseis"CookieServlet".

Example3-1.servletandservlet-mappingelements


<!DOCTYPEweb-app



>

<web-app>

<servlet>

<servlet-name>CookieServlet</servlet-name>

<servlet-class>com.jspservletcookbook.CookieServlet</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/cookieservlet</url-pattern>

</servlet-mapping>

</web-app>

Inthisexample,theservletelementregistersthename"CookieServlet"byusingtheservlet-nameelement.Theclassnameisspecifiedbytheservlet-classelement.TheactuallocationofthisservletclassmaybeWEB-INF/classes/com/jspservletcookbook/,orinsideaJARfilethatresidesinWEB-INF/lib."CookieServlet"becomestheregisterednamebywhichtheservletcom.jspservletcookbook.CookieServletisreferredtointherestoftheweb.xmlfile.

Nowcreatetheservletpathbywhichthewebapplicationuserswillaccessthisservletintheirwebbrowsers.Thisaliasingisaccomplishedwiththeservlet-mappingelement.servlet-nameidentifiestheregisterednamebywhichtheservletisreferredtoinweb.xml,andtheurl-patternelementcreatestheURLthatisusedtoaccessthisservlet.The/characterinsidethe/cookieservletpatternmeans"beginattheweb-applicationroot."Forexample,ifthecontextpathforthesitehttp://www.mysite.orgis"cookbook,"thenthecompleteaddressforaccessingtheCookieServletservletishttp://www.mysite.org/cookbook/cookieservlet.The/cookbookpartofthe

URListhecontextpathforyourwebapplication.Theservletisthenidentifiedwiththe/cookieservletpatternwithinthatcontext.

Lookingatthismoregenerally,youhavethefollowingURLforanygivenservlet:

http://<host>:<port>/<contextpath>/<servlet-path>

Mostservletcontainersallowforadefaultcontext,wherethecontextpathis/.Inthiscase,theURLisinthisform:

http://<host>:<port>/<servlet-path>

Forexample,ifyouareusingTomcat4.1.xonyourlocalmachineandhavecreatedanapplicationcalled"myapp"andaservletURLpatternof/myservlet,theentirewebaddressforthatservletlookslikehttp://localhost:8080/myapp/myservlet.

YoucanalsoaccessaservletwithaURLlikethis:

http://host:port/contextpath/servlet/registered-servlet-name

Soiftheregisteredservletnamewas"MyServlet,"thentherequestappearsashttp://localhost:8080/myapp/servlet/MyServlet.

Someservletenginesuseadifferentservletpaththan/servlet,andothersallowthispathtobechangedbyanadministrator.Youshouldconsultthedocumentationforyourservletcontainertoensurethecorrectpathforyoursetup.Whatiftheexampleservlet-mappingelementappearedintheweb.xmlfilefortheserver'sdefaultwebapplication,inwhichthecontextpathis/?Inthiscase,userswouldaccesstheCookieServletservletbyusingtheaddresshttp://www.mysite.org/cookieservlet.

Theurl-patternthatyoucreateforaservletinsideofaservlet-mappingelementiscase-sensitiveinTomcatandWebLogic.AccordingtoChapterSRV.11.1oftheservletv2.3specificationandv2.4proposedfinaldraft,"The

containermustusecase-sensitivestringcomparisonsformatching."Iftheuserrequestshttp://www.mysite.org/cookbook/cookieSERVLETinsteadofhttp://www.mysite.org/cookbook/cookieservlet,thentherequestisnotdirectedtothemappedservlet(CookieServlet).InTomcat4.1.xandWebLogic7.0,therequestreturnsanHTTP404errorcode,whichisthe"Filenotfound"typeerrorreturnedbyawebserver.

Theurl-patterninsidetheservlet-mappingelementcantakeondifferentforms,whicharediscussedintheupcomingrecipes.

SeeAlso

Chapter1onweb.xml;Recipe3.2-Recipe3.8;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets.

Recipe3.2CreatingMoreThanOneMappingtoaServlet

Problem

YouwanttocreateseveralnamesorURLpatternsthatwebuserscanusetorequestasingleservlet.

Solution

Associatetheservletelementwithmorethanoneservlet-mappingelementinthedeploymentdescriptor.

Discussion

Youcancreateanumberofservlet-mappingelementsforasingleservlet,asshowninExample3-2.Ausercanaccessthisservletbyusingoneoftwoaddresses:http://www.mysite.org/cookbook/cookieservletorhttp://www.mysite.org/cookbook/mycookie.

Example3-2.Twoservlet-mappingtags


<!DOCTYPEweb-app



>

<web-app>

<servlet>


<servlet-class>com.parkerriver.cookbook.CookieServlet</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/cookieservlet</url-pattern>

</servlet-mapping>

<servlet-mapping>


<url-pattern>/mycookie</url-pattern>

</servlet-mapping>

</web-app>

Rememberthattheservlet-mappingelementshavetoappearafteralloftheservletelementsintheservlet2.3deploymentdescriptor.

OnlyexactmatchestotheURLpatternwillwork.Ifauserrequests/cookieservlet/(notethefinalforwardslash)insteadof/cookieservlet,shereceivesanHTTPerrorcodeinsteadoftheservlet-generatedpageshewasexpecting.

Youcanuseawildcardcharacter(*)toextendyourmappingpattern.ThemappingsinExample3-3invoketheCookieServletforalloftheURLsthatbeginwith/cookie/,andthenoptionallyincludeanynamesaftertheforwardslash.Forexample,CookieServletcanbeinvokedwithaURLofhttp://www.mysite.org/cookbook/cookie/youusingthisdescriptor.Thisisbecausetheurl-patternmatchesanyHTTPrequestsendingwiththe"/cookie/"string.

Example3-3.UsinganasteriskintheURLpattern


<!DOCTYPEweb-app



>

<servlet>


<servlet-class>com.jspservletcookbook.CookieServlet</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/cookie/*</url-pattern>

</servlet-mapping>

Youcannotusetheasteriskcharacterasawildcardsymbolinsidetheservlet-nameelement.Theasteriskcanbeusedonlyasawildcardsymbolintheurl-patternelement(asin<url-pattern>/cookie/*</url-pattern>),orinpatternsthatpointtoallfileswithacertainextensionorsuffix(asin<url-pattern>*.jsp</url-pattern>).Thelatterpatterniscalledanextensionmapping.

SeeAlso

Chapter1onweb.xml;Recipe3.1;Recipe3.3-Recipe3.8;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets.

Recipe3.3CreatingaJSP-TypeURLforaServlet

Problem

YouwanttolinkaURLpatternthatlookslikeaJSPfilerequesttoaservlet.

Solution

Createaservlet-mappingelementthatincludesaJSP-styleURLpattern.

Discussion

Imentionedinthepreviousrecipesthatyouhavealotoflatitudewhencreatingaliasesthatpointtoservlets.Forinstance,arequestthatappearstoaccessaJSPfilecaneasilybemappedtoaservlet.ThedeploymentdescriptorinExample3-4mapstheURLpattern/info.jsptotheJspInfoservlet.

Example3-4.DeploymentdescriptorexampleofmappingaJSP-styleURLtoaservlet


<!DOCTYPEweb-app



>

<web-app>

<servlet>

<servlet-name>JspInfo</servlet-name>

<servlet-class>com.parkerriver.cookbook.JspInfo</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/info.jsp</url-pattern>

</servlet-mapping>

</web-app>

TheforwardslashthatbeginstheURLpattern/info.jspmeans"beginattherootofthewebapplicationthatusesthisdeploymentdescriptor."SotheentireURLfortheJspInfoservletlookslikethisforthecookbookwebapplication:http://www.mysite.org/cookbook/info.jsp.

YoucanalsomapallreferencestoJSPpagestoasingleservlet,asshowninExample3-5,whichusesaweb.xmlentrywithanextensionmapping.

Example3-5.MappingallJSPURLstoasingleservlet


<!DOCTYPEweb-app



>

<web-app>

<servlet>


<servlet-class>com.parkerriver.cookbook.JspInfo</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>*.jsp</url-pattern>

</servlet-mapping>

</web-app>

Makesuretoexcludetheslash(/)intheURLpattern,asanextensionmappingthatusesafileextensionsuffixbeginswithanasteriskandendswithaperiodandthesuffixitself,asin<url-pattern>*.jsp</url-pattern>.ThistypeofmappingmaybeusefulifyouweremigratinganapplicationfromoneversionthatusedalotofJSPpagestoanewversionthatreliedentirelyonservlets.ThistakescareofuserswhohavebookmarkedmanyURLsthatinvolveJSPfiles.

Tomcat4.1.xincludesanimplicitmappingtoitsownJSPpagecompilerandexecutionservletforanyrequestendingin.jsp.Ifyouincludeamappingsuchastheoneinthepreviousweb-appfragment,thenyourmappingwilloverrideTomcat'simplicitmapping.

SeeAlso

Chapter1onweb.xml;Recipe3.1andRecipe3.2;Recipe3.4-Recipe3.8;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets.

Recipe3.4MappingStaticContenttoaServlet

Problem

YouwantrequestsforstaticcontentsuchasHTML-styleURLstorequestaservlet.

Solution

Useaservlet-mappingelementinweb.xmltomaptheservletnametothestaticcontent.

Discussion

Itoftenseemsoddtothecasualprogrammer,butyoucanhaveaservletrespondtoaURLthatappearstobestaticcontent,suchasanHTMLfile.Example3-6mapstheservletHtmlServlettoallURLsendinginthe.htmlsuffix.Anyrequestwithinthewebapplicationthatcontainsthisdeploymentdescriptorandspecifiesafileendingwith.htmlisdirectedtoHtmlServlet.

Example3-6.Mappingstaticcontenttoaservletinweb.xml


<!DOCTYPEweb-app



>

<web-app>

<servlet>

<servlet-name>HtmlServlet</servlet-name>

<servlet-class>com.jspservletcookbook.HtmlServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>HtmlServlet</servlet-name>

<url-pattern>*.html</url-pattern>

</servlet-mapping>

</web-app>

Theservlet-mappingelementinthislistingcontainsanextension-mappingURLpattern:itbeginswithanasteriskandendswith.html.IfyouwanttomaptheservlettojustoneHTMLfile,useXMLthatlookslikethis:

<url-pattern>myfile.html</url-pattern>.

Usingthispattern,onlyrequestsforthemyfile.htmlfilearedirectedtoHtmlServlet.

MakesurethatURLpatternsneverbeginwithaslash(/)whenyouarecreatingextensionmappings.

SeeAlso

Chapter1onweb.xml;Recipe3.3;Recipe3.5-Recipe3.8;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets.

Recipe3.5InvokingaServletWithoutaweb.xmlMapping

Problem

Youwanttorequestaservletthatdoesnothaveaservlet-mappingelementintheweb.xmldeploymentdescriptor.

Solution

Useaninvoker-styleURLoftheformhttp://www.mysite.org/mywebapp/servlet/com.jspservletcookbook.MyServlet

Discussion

Someservletsmaynothaveapathmappinginthewebapplication'sdeploymentdescriptor.Sohowcanauserrequestthisservlet?WhatnameandURLdotheyuse?

Tomcatandotherservletcontainersprovideamethodforinvokingservletsthatarenotmappedinweb.xml.YoucanuseaURLofthefollowingform:

http://www.mysite.org/mywebapp/servlet/<fullyqualifiedclassnameofservlet>

Aservletwiththeclassandpackagenameofjspservletcookbook.MyServletisinvokedashttp://www.mysite.org/mywebapp/servlet/jspservletcookbook.MyServlet.Ensurethatthepathsegmentfollowingthenameofyourwebapplicationis/servlet/andnot/servlets/.Iftheservletisstoredinthedefaultwebapplication(generallyatthetopleveloftheservletcontainer),theURL

forinvokingitishttp://www.mysite.org/servlet/jspservletcookbook.MyServlet.

Theweb.xmlfilelocatedin<Tomcat_install_directory>/confincludesthisdefinitionandmappingfortheinvokerservlet:

<servlet>

<servlet-name>invoker</servlet-name>

<servlet-class>org.apache.catalina.servlets.InvokerServlet</servlet-class>

<init-param>

<param-name>debug</param-name>

<param-value>0</param-value>

</init-param>

<load-on-startup>2</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>invoker</servlet-name>

<url-pattern>/servlet/*</url-pattern>

</servlet-mapping>

Theinvokerservletcanalsobeusedtoinvoketheservletsthatareregisteredinweb.xml.TheseURLslooklikehttp://www.mysite.org/cookbook/servlet/<RegisteredServletName>.Forinstance,imagineyouhaveaservletelementlikethis:

<servlet>

<servlet-name>myservlet</servlet-name>

<servlet-class>jspservletcookbook.MyServlet</servlet-class>

</servlet>

Considerthatthewebapplicationcontextpathis/cookbook.IftheTomcatinvokerservletisenabledinthisapplication,thenthisservletcanbeinvokedwithitsregisterednameathttp://www.mysite.org/cookbook/servlet/myservlet.

InTomcat4.1.x,theinvokerservletmappingmaybecommentedoutinsideofthe

<tomcat-installation-directory>/conf/web.xmlfile.Thepurposeofthusdisablingtheinvokeristoensurethatservletscanbeinvokedusingonlythepathsspecifiedbytheservlet-mappingelementsinweb.xml.

Ifaservletisrequestedusingtheformhttp://www.mysite.org/myapp/servlet/<fully-qualified-classname>,ratherthanusingtheservlet'sregisteredname,anyinitializationparametersprovidedforthatservletintheweb.xmlfilearenotavailable.Example3-7showsaregisteredservletwithinitparameters.

Example3-7.Aregisteredservletwithinitparameters

<servlet>

<servlet-name>Weather</servlet-name>

<servlet-class>home.Weather</servlet-class>

<init-param>

<param-name>region</param-name>

<param-value>NewEngland</param-value>

</init-param>

</servlet>

Becauseitistheregisterednameoftheservletthathastheregionparameterassignedtoit,onlyarequestforthatregisteredname(oraservletpathmappedtothatname)triggerstheregionparameters.AccessingtheservletthroughitsfullyqualifiednamewillnotresultintheregionparameterbeingpassedtotheWeatherservlet.

SeeAlso

Chapter1onweb.xml;Recipe3.1-Recipe3.4;Recipe3.6-Recipe3.8;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets.

Recipe3.6MappingAllRequestsWithinaWebApplicationtoaServlet

Problem

Youwanttohaveallwebapplicationrequestsgotoasinglecontrollerservlet.

Solution

Useaservlet-mappingelementinyourdeploymentdescriptor,withaurl-patternelementof<url-pattern>/*</url-pattern>.

Discussion

Insomecases,youmightwanttohaveallrequestsrelatedtothewebapplicationtogoasingleservlet.Thisservletcontrollermaylogrequests,implementsecurity,orexamineandoptionallyaltertherequestobjectbeforeitforwardstherequesttoanotherlocation(usuallyanotherservletorJSP).

FortheSunMicrosystemsdescriptionoftheFrontControllerdesignpattern,whichisamethodforusingaservletasacentralprocessingpoint,seetheCoreJ2EEBlueprintspageathttp://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html.

Onceagain,web.xmlistheplacetoconfigureaservlettoreceiveallweb

http://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html

applicationrequests.Example3-8showshowtouseaURLpatterntoaimallrequestsatacontrollerservlet.

Example3-8.Aimingallrequestsatacontrollerservlet


<!DOCTYPEweb-app



>

<web-app>

<servlet>

<servlet-name>Interceptor</servlet-name>

<servlet-class>com.jspservletcookbook.Interceptor</servlet-class>

</servlet>



<servlet-mapping>



</servlet-mapping>

<servlet-mapping>



</servlet-mapping>

</web-app>

Youmayalsohavetooverrideanydefaultinvokerservletwithyourownmapping:


Maptheservletthatyouwanttoreceiveallwebapplicationrequeststo

thisURLpatternaswell.Ifyoukeeptheinvokerservletthewayitis,userscouldbypassthecontrollerservletbyusingaURLlikehttp://www.mysite.org/myapp/servlet/com.jspservletcookbook.CookieServlet

InTomcat,youcanalsodisabletheinvokerservletinthetop-levelweb.xmlfile(in<Tomcat_install_directory>/conf)bycommentingouttheservlet-mappingelement.ThisaffectsallotherwebapplicationsrunningunderthatTomcatinstance,however,sothisdecisionshouldbemadecollectivelyamongadministratorswhodeployapplicationsonthatserver.

Youmustalsoremove,alter,orcommentoutotherservlet-mappingelementsthatallowservletrequeststobypassthecontrollerservlet.Ifamorespecificmapping(suchastheoneinExample3-9)isincludedinweb.xml,requestsfortheCookieServletwillbypasstheInterceptorservlet.

Example3-9.Specificmappingsoverridemappingsusingwildcardsymbols


<!DOCTYPEweb-app



>

<web-app>

<servlet>


<servlet-class>jspservletcookbook.Interceptor</servlet-class>

</servlet>

<servlet>


<servlet-class>

com.jspservletcookbook.CookieServlet

</servlet-class>

</servlet>

<servlet-mapping>



</servlet-mapping>

<servlet-mapping>


<url-pattern>/CookieServlet</url-pattern>

</servlet-mapping>

</web-app>

Theservlet-mappingelementforCookieServletinthisexamplewouldcausetheservletpathof/CookieServlettobypasstheInterceptorservlet,becausetheservletpathof/CookieServlet(aspartofarequestthatlookslikehttp://host:port/context-path/CookieServlet)isamoreexactmatchtotheURLpatternof/CookieServletthanitisto/*.

Therequestsforstaticcontentsuchaswelcomefiles(e.g.,index.html)arealsointerceptedbytheURLpattern/*.Therequestsforthesestaticfileswillalsogotothecontrollerservlet.

SeeAlso

Chapter1onweb.xml;Recipe3.1-Recipe3.4;Recipe3.6-Recipe3.8;

Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets;theCoreJ2EEBlueprintspage:http://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html


Recipe3.7MappingRequeststoaControllerandPreservingServletMappings

Problem

Youwanttomapallrequeststoasinglecontrollerservlet,whilepreservingtheservletmappingsforotherservletsinasecuremanner.

Solution

Usesecurity-constraintelementsinweb.xmltopreventwebusersfrommakingrequeststothenoncontrollerservlets.

Discussion

Whatifthecontrollerservletthatreceivesallrequestswantstoconditionallyforwardtherequestalongtoanotherservletforspecializedprocessing?Ifalloftheotherservletmappingsareremovedfromweb.xmlandtheinvoker-styleURLpattern(/servlet/*)ismappedtothecontrollerservletitself,eventhecontrollerservletispreventedfromforwardingarequesttoanotherservlet!Howcanyougetaroundtheserestrictions?

Asolutionistoretaintheindividualservletmappingsinweb.xml.Thenyoucanusesecurity-constraintelementstopreventwebusersfrommakingrequeststothesenoncontrollerservlets.Whenthecontrollerservletwantstoforwardarequesttoanotherservlet,itusesanobjectthatimplementsthejavax.servlet.RequestDispatcherinterface.RequestDispatchersarenotrestrictedfromforwardingrequests(usingtheRequestDispatcher.forward(request,response)

method)toURLpatternsthatarespecifiedbysecurity-constraintelements.Example3-10showsaservletnamedControllerthatusesaRequestDispatchertoforwardarequesttoanotherservlet.

Recipe3.9describeshowtoprotectservletsfromreceivinganyweb-userrequestswiththesecurity-constraintelement,soIwon'trepeatthatinformationhere.

Example3-10.UsingRequestDispatchertoforwardarequest

importjavax.servlet.*;

importjavax.servlet.http.*;

publicclassControllerextendsHttpServlet{

publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)

throwsServletException,java.io.IOException{

RequestDispatcherdispatcher=null;

Stringparam=request.getParameter("go");

if(param==null)

thrownewServletException("MissingparameterinController.");

elseif(param.equals("weather"))

dispatcher=request.getRequestDispatcher("/weather");

elseif(param.equals("maps"))

dispatcher=request.getRequestDispatcher("/maps");

else

thrownewServletException(

"ImproperparameterpassedtoController.");

//ifwegetthisfar,dispatchtherequesttothecorrectURL

if(dispatcher!=null)

dispatcher.forward(request,response);

else


"Controllerreceivedanulldispatcherfromrequestobject.");

}

}

Theservletchecksthegoparameterforitsvalue.Arequesttothisservletmightlooklike:

http://localhost:8080/home?go=weather

Inthisexample,theControllerservletismappedtoreceiveallwebrequeststothe"home"webapplication.Inotherwords,thecontroller'sservlet-mappinginweb.xmlhasaurl-patternof/*.

Basedonthegoparametervalue,ControllercreatesaRequestDispatcherobjectwithadifferentspecifiedURLforforwarding.TheservletgetsaRequestDispatcherobjectfirstbycallingtherequestobject'sgetRequestDispatcher(Stringpath)method.Thepathparametercanberelativetothecontextrootofthewebapplication,asitishere,butitcannotextendbeyondthecurrentservletcontext.SupposetheURLpattern/weatherismappedtotheregisteredservletname"Weather":

<servlet-mapping>


<url-pattern>/weather</url-pattern>

</servlet-mapping>

Inthiscase,thepathpassedtothegetRequestDispatcher()methodlookslikegetRequestDispatcher("/weather").Ifthegoparameteriseitherwrongormissing,theControllerthrowsaServletExceptionwithanappropriatemessage.TheWeatherservlet,though,cannotbeaccessedbywebusersdirectlybecauseitisrestrictedbyasecurity-constraintelementbuttheRequestDispatcher.forward(request,response)methodisnotlimitedbytheseconstraints.

Youcanalsousethejavax.servlet.ServletContext.getNamedDispatcher(String

name)methodtogetaRequestDispatcherobjectforforwarding.Usingthismethod,youdonothavetoincludeanyservlet-mappingelementsforthetargetservlet.ThegetNamedDispatcher()methodtakesasitsparametertheregisterednameoftheservletinweb.xml.Example3-11showsthepriorservletexamplealteredtousegetNamedDispatcher("Weather"),usingtheweatherservlet'sregisterednameinstead.

Example3-11.UsinggetNamedDispatcher()toforwardarequest



publicclassControllerextendsHttpServlet{


HttpServletResponseresponse)


RequestDispatcherdispatcher=null;

Stringparam=request.getParameter("go");

if(param==null)

thrownew

ServletException("MissingparameterinController.");

elseif(param.equals("weather"))

dispatcher=getServletContext().

getNamedDispatcher("Weather");

elseif(param.equals("maps"))

dispatcher=getServletContext().

getNamedDispatcher("Maps");

else


"ImproperparameterpassedtoController.");

/*checkforanulldispatcher,then

dispatchtherequesttothecorrectURL*/

if(dispatcher!=null)


else


"Controllerreceivedanulldispatcher.");

}

}

ThedoGet()methodhasbeenchangedtouseaRequestDispatcherreceivedfromtheServletContext.getNamedDispatcher(Stringregistered-servlet-name)method.Insteadofaservletpath,thedispatcherobjectusesthatservlet'sregisteredname("Weather")fromweb.xml,asin:

<servlet>


<servlet-class>com.jspservletcookbook.Weather

</servlet-class>

</servlet>

IftheServletContextreturnsanulldispatcherbecausesomeoneleftoutthenecessaryXMLelementinweb.xml,thendoGet()throwsaServletExceptionexplainingthatthedispatcherobjectisnull.

Analternatestrategyistousealistenertochecktherequestbeforeitfindsitswaytoaservlet.Chapter19describeshowtousealistenertoexamineanHTTPrequest.

SeeAlso

Chapter1onweb.xml;Recipe3.1-Recipe3.5;Recipe3.8;Chapter19onusingalistenertoexaminetherequest;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets;theCoreJ2EEBlueprintspage:http://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html


Recipe3.8CreatingWelcomeFilesforaWebApplication

Problem

Youwanttoconfigureoneormorewelcomefilesforawebapplication.

Solution

Useawelcome-file-listelementinyourdeploymentdescriptor.

Discussion

AwelcomefileisatraditionasoldasthehypertextualInternet.Manysiteshavehomepagesorotherwelcomefilesthataredesignedtobetheentrypageorfrontdoorfortheirwebsites.Thesepagesusuallyhavenameslikeindex.html,welcome.html,ordefault.html.Youcanconfigureyourwebapplicationtodirectrequeststowardthesepagesbyaddingawelcome-file-listelementtoyourwebapplication'sdeploymentdescriptor.Setupawelcomefilelistinweb.xmlinthemannerdemonstratedbyExample3-12.Thewelcome-file-listelementmustcomeafteranyservletandservlet-mappingelements,andprecedeanyerror-pageortaglibelementsintheservlet2.3deploymentdescriptor.

Example3-12.Settingupwelcomefilesinweb.xml


<!DOCTYPEweb-app

>

<web-app>



<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

</web-app>

WhenevertheservletcontainerencountersaURLforawebapplicationthatspecifiesonlyadirectory,notaparticularfilenameorservlet,thenitlooksforawelcome-file-listelementintheapplication'sdeploymentdescriptor.Theservletv2.3specificationcallsthesekindsofURLsvalidpartialrequests.Theservletcontainerattachesanywelcomefilenamesthatitfindsinweb.xmltotherequest(intheorderthattheyappearinweb.xml)andreturnsthosefilestotheclient.

Forexample,let'ssayTomcatreceivesarequestforhttp://www.mysite.org/cookbook/.Alsoimaginethattheweb.xmlfileforthecookbookwebapplicationcontainsthewelcome-file-listshowninExample3-12.Tomcatthenreturnshttp://www.mysite.org/cookbook/index.htmlifthatfileexists;ifitdoesnot,Tomcatlooksforthedefault.jspfileinthecookbookdirectoryandreturnsthatfileinstead.

Theservletcontainerinitiatesthissearchinresponsetoanydirectory-styleURLthatitreceives(suchashttp://www.mysite.org/cookbook/bookinfo/).Inotherwords,aslongasanindex.htmlordefault.jsp(orwhicheverfilenamesyouchoose)existsinawebapplication'srootdirectory,andthewebdeveloperhasproperlyconfiguredthewelcome-file-listelement,thenthosefilesare

invokedbydefaultinresponsetodirectory-stylerequests.

SeeAlso

Chapter1onweb.xml;Recipe3.1-Recipe3.6;Recipe3.9;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets.

Recipe3.9RestrictingRequestsforCertainServlets

Problem

Youwanttoallowonlyauthenticateduserstorequestcertainservlets.

Solution

Usethesecurity-constraintelementintheweb.xmldeploymentdescriptor.

Discussion

Somewebapplicationscontainservletsthatshouldnotbeinvokeddirectlybywebusers,becausetheyhandlesensitivedataandmayhavespecialjobs(suchasadministeringtheserverorwebapplication).Forexample,youcoulddesignaservletthatisaccessedonlybyserveradministrators.Howdoyouprotecttheseservletsfrombeinginvokedimproperlyorbyunauthorizedusers?

Inthelattercase,youcanusedeclarativesecurity,orcontainer-managedsecurity.Thisstrategyinvolvesconfiguringtheweb.xmldeploymentdescriptorwithyourapplication'ssecurityinformation,therebydecouplingsecurityinformationfromyourservlet'scode.AnysecuritychangesforawebapplicationcanthenbemadeintheXMLconfigurationfiles(orviatheWebLogicServer7.0AdministrationConsole)withoutmessingwiththeservlet'ssourcecode.Thesecurityconfigurationisthenloadedandimplementedbytheservletcontainer.

Youcanalsouseprogrammaticsecurity,whichinvolvesincluding

security-relatedcodewithinservlets,suchascheckingtheHttpServletRequestobjecttoseeifauserisauthorizedtouseacertainwebresource.

ForTomcat,usingthesecurity-constraintelementinweb.xmlrequirescreatingausernameandpasswordintheXMLfilelocatedat<Tomcat-installation-directory>/conf/tomcat-users.xml.ThisisanXMLfileinwhichyoudefineinternalusersandpasswords.ItmightlooklikeExample3-13.

Example3-13.Atomcat-users.xmlfile

<?xmlversion='1.0'encoding='utf-8'?>

<tomcat-users>

<rolerolename="manager"/>

<rolerolename="tomcat"/>

<rolerolename="developer"/>

<userusername="tomcat"password="tomcat"roles="tomcat,manager"/>

<userusername="bruce"password="bruce1957"

roles="tomcat,manager,developer"/>

<userusername="stacy"password="stacy1986"roles="tomcat"/>

</tomcat-users>

ThisXMLfragmentincludesatomcat-usersrootelementcontainingoneormoreroleanduserelements,dependingonhowmanyusersaredefinedforthewebapplicationshandledbythatinstanceofTomcat.Thistomcat-users.xmlconfigurationfileisaccessiblebyallofthecontainedwebapplications.

Youthencreatesecurity-constraint,login-config,andsecurity-roleelementsinsideofthewebapplication'sdeploymentdescriptor,orweb.xml.

Ifyouarenotusingtheservletv2.4deploymentdescriptor,thesecurity-relatedelementshavetoappearinthisorderandfollowmostoftheotherelementsthatcanappearinweb.xml,oryourdeploymentdescriptorwillnotbeavalidXMLfile.

Specifically,theonlyelementsthatcancomeaftersecurity-roleareenv-entry,ejb-ref,andejb-local-ref.

Thesecurity-constraintelementlookslikeExample3-14,giventhattheprotectedURLpatterninthiscaseis<url-pattern>/CookieServlet</url-pattern>.

Example3-14.Thesecurity-constraintelement

<security-constraint>

<web-resource-collection>

<web-resource-name>CookieInfo</web-resource-name>


<http-method>GET</http-method>

<http-method>POST</http-method>

</web-resource-collection>

<auth-constraint>

<description>Thisappliesonlytothe

"developer"securityrole</description>

<role-name>developer</role-name>

</auth-constraint>

<user-data-constraint>

<transport-guarantee>NONE</transport-guarantee>

</user-data-constraint>

</security-constraint>

Thesecurity-constraintelementmustcontainoneormoreweb-resource-collectionelements.Theweb-resource-collectionelementdescribeswhichwebresourcesinthewebapplicationareprotectedbythespecifiedsecurityconstraint.Inotherwords,arequestovertheInternetforawebresource,suchasaservlet,triggersanysecurityconstraintthathasbeenmappedtotheresource.Inthisexample,thesecurityconstraintprotectsanyrequestthatfitstheURL

pattern,<web-application-root-directory>/CookieServlet.Thehttp-methodelementsspecifytheHTTPmethodsthatthissecurityconstraintcovers.Intheexample,aGETorPOSTrequestfor/CookieServlettriggerstheconfiguredsecuritymechanism.Ifyoudonotincludeanyhttp-methodelementsunderthesecurity-constraintelement,theconstraintwillapplytoanyHTTPmethod(suchasPUTorDELETE,inadditiontoGETandPOST).

Theobjectsthatimplementthejavax.servlet.RequestDispatcherinterfacemayforwardHTTPrequestsfromoneservlettoaprotectedservletwithouttriggeringthesesecurityconstraints.

Theauth-constraintelementisdesignedtodescribethesecurityrolesthatpermitaccesstothewebcomponent.Asecurityroleisanamethatrepresentsthesecurityprivilegesauserorgroupofusershaveinrelationtoaparticularresource,suchasaservlet.Examplesofsecurityrolesareadmin,manager,ordeveloper.Inthecaseofthetomcat-users.xmlfile,usersareassignedtoroles.Withinthesecurity-constraintelementexample,onlyusersthataremappedtothedeveloperroleinthetomcat-users.xmlfilehaveaccesstoCookieServlet.

Howdoesawebapplicationauthenticateauserinthefirstplace?Forinstance,howcanthewebapplicationfindouttherequester'susernameandpassword,andtherebydetermineifhecanbegivenaccesstotheservlet?Incontainer-managedsecurity,thisiswhatthelogin-configelementisusedfor.Thiselementappearsafterthesecurity-constraintelementintheweb.xmlfile.BothelementsmightlooklikeExample3-15inawebapplication'sdeploymentdescriptor.

Example3-15.Usinglogin-configwithasecurity-constraintelement



<web-resource-name>CookieInfo</web-resource-name>





<auth-constraint>

<description>Thisappliesonlytothe

"developer"securityrole</description>


</auth-constraint>


<transport-guarantee>NONE</transport-guarantee>



<login-config>

<auth-method>BASIC</auth-method>

</login-config>

<security-role>


</security-role>

Thelogin-configelementspecifiestheauthenticationmethodthatisusedtoauthenticateanyuserrequestsforprotectedwebresources.Protectedwebresourcesarethosespecifiedbyaweb-resource-collectionelement,insidethesecurity-constraintelement.Intheexample,BASICauthenticationisusedforanyrequeststhatmatchtheURLpattern/CookieServlet.BASICisafamiliarformofwebauthenticationinwhichthebrowserpresentstheuserwithadialogwindowforenteringtheusernameandpassword.Tomcatcomparesthegivennameandpasswordwiththeuserinformationconfiguredinthetomcat-users.xmlfile,andthenusesthewebapplication'ssecurity-constraintconfigurationtodeterminewhethertheusercanaccesstheprotectedservlet.

Theauth-methodchildelementoflogin-configcanalsobegiventhevaluesFORM,CLIENT-CERT,orDIGEST.

Onemoreingredientisnecessarytocompletethisservletsecurityconfiguration:thesecurity-roleelement.Example3-15createsasecurityrolenameddeveloper.Thedevelopervaluealsoappearsinthesecurity-constraintchildelementauth-constraint.Thismeansthatonlyuserswhoaremappedtothesecurityroledeveloperareabletoaccesswebresourceswhichareprotectedbythesecurityconstraint(i.e.,thatareidentifiedbyaweb-resource-collectionchildelementofsecurity-constraint).Inotherwords,thisauthenticationmethodisactuallyatwo-stepprocess:

1. Checkiftheprovidedusernameandpasswordarecorrect.

Determineiftheuserismappedtothespecifiedsecurityrole.Forexample,theusermightprovideacorrectusernameandpassword,butshemaynotbemappedtothespecifiedsecurityrole.Inthiscase,sheispreventedfromaccessingthespecifiedwebresource.

TheusersaremappedtosecurityrolesinTomcatinthepreviouslymentionedtomcat-users.xmlfile.Hereisanexampleofwhatauserelementmightlooklikeinthetomcat-users.xmlfile:

<username="bwperry"password="bruce2002"

roles="developer,standard,manager"/>

Thisuserisassignedthreedifferentroles:developer,standard,andmanager.TheTomcatservletcontainerusestheseXMLelementsinthetomcat-users.xmlfiletodeterminewhethercertainusername/passwordcombinationshavebeenassignedparticularroles.Figure3-1isdesignedtounraveltheseconfusingcross-references.Justthinkofasecurityroleasawaytofurtherrefineagroupofapplicationusers,orgroupthemintermsoftheiruserprivileges.

Figure3-1.Usingasecurityconstraintelement

ThesecurityconfigurationdepictedbyExample3-15sXMLtextcanbeusedwithWebLogic7.0,buttheWebLogic-specificconfigurationfileiscalledweblogic.xml.

Theweblogic.xmlfileaccompaniestheweb.xmldeploymentdescriptorinsideyourwebapplication'sWEB-INFdirectory.

Example3-16showstheXMLwithintheweblogic.xmldeploymentdescriptor.

Example3-16.Securityroleinweblogic.xml



<security-role-assignment>


<principal-name>bwperry</principal-name>

</security-role-assignment>

InWebLogic7.0,youcanalsoestablishusers,groups,andsecurityrolesthatareglobaltoaparticularWebLogicserverthroughtheAdministrativeConsole.

Thisrecipedescribedhowtorestricttherequestsforcertainservlets.Thenextrecipeshowsonewaytopreventallrequestsexceptthoseforwardedfromacontrollerservletfromreachingotherservlets.

SeeAlso

Chapter1onweb.xml;Recipe3.1-Recipe3.8;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets;theCoreJ2EEBlueprintspage:http://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html


Recipe3.10GivingOnlytheControllerAccesstoCertainServlets

Problem

Youwanttosetupthewebapplicationsothatonlyacontrollerservlethasaccesstocertainservlets.

Solution

Createasecurity-rolethatdoesnothaveanyusersmappedtoit,thenspecifyinthesecurity-constraintelementtheservletsthatyouwanttopreserveforthecontroller.

Discussion

Thisrecipeshowshowyoucancreateasecurity-constraintelementthatforbidsanyrequestsfromreachingspecifiedURLpatterns.

TheservletsmappedtothoseURLpatternsareforwardedrequestsonlyfromoneormorecontrollerservletsthatuseanobjectthatimplementsthejavax.servlet.RequestDispatcherinterface.Recipe3.7includesanexamplecontrollerservletthatforwardsarequesttoanotherservletusingaRequestDispatcher.Example3-17showshowyoucansetupthesecurity-constraintelementforanexampleservletwiththeregisteredname"Weather".

Example3-17.Asecurity-constraintthatallowsonlyRequestDispatcher.forward-relatedrequests

<!DOCTYPEweb-app


"http://java.sun.com/dtd/web-application_2_3.dtd">

<web-app>



<servlet>


<servlet-class>

com.jspservletcookbook.Weather

</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/weatherurl-pattern>

</servlet-mapping>





<web-resource-name>Weather

</web-resource-name>

<url-pattern>/weather</url-pattern>




<auth-constraint>

<role-name>nullrole</role-name>

</auth-constraint>


<transport-guarantee>NONE

</transport-guarantee>



<login-config>


</login-config>

<security-role>


</security-role>

</web-app>

ThenextstepinprotectingtheWeatherservletistomakesurethatthetomcat-users.xmlfiledoesnotmapanyuserstothe"nullrole"securityrole.Thesecurity-roleelementlookslikethis:

<security-role>


</security-role>

Hereiswhatatypical<Tomcat-installation-directory>/conf/tomcat-users.xmlfilelookslike:


<tomcat-users>


<rolerolename="tomcat"/>

<rolerolename="developer"/>

<userusername="tomcat"password="tomcat"roles="tomcat,manager"/>

<userusername="bruce"password="bruce1957"

roles="tomcat,manager,developer"/>

</tomcat-users>

InwebapplicationsconfiguredinthemannerofExample3-17,anydirectrequesttotheURLpattern/weatherreceivesaresponseinthecategoryof"HTTPStatus403Accesstotherequestedresourcehasbeendenied."However,acontrollerservletcanstillusetheRequestDispatcher.forward(request,response)methodtoforwardarequesttothe/weatherURLforprocessing.Recipe3.7andExample3-10showaservletthatusesthisforwardmethod,soIwon't

repeatthatcodehere.

Makesuretoconfigurefriendlyerrorpagesfortheuserswhomakerequeststorestrictedservlets.Chapter9describeshowtodesignateerrorpagesforcertainHTTPresponsecodesinthewebapplication'sdeploymentdescriptor.Youmaywanttoprovideautomaticrefreshesafteraspecifiedintervalfromtheerrorpagetothecontrolleroranyloginpages.

SeeAlso

Chapter1onweb.xml;Recipe3.1-Recipe3.9;Chapter11oftheServletv2.3and2.4specificationsonmappingrequeststoservlets;theCoreJ2EEBlueprintspage:http://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html


Chapter4.UsingApacheAnt

Introduction

Recipe4.1.ObtainingandSettingUpAnt

Recipe4.2.UsingAntTargets

Recipe4.3.IncludingTomcatJARfilesintheBuildFileClasspath

Recipe4.4.CompilingaServletwithanAntBuildFile

Recipe4.5.CreatingaWARFilewithAnt

Recipe4.6.CreatingaJARFilewithAnt

Recipe4.7.StartingaTomcatApplicationwithAnt

Recipe4.8.StoppingaTomcatApplicationwithAnt

Introduction

ApacheAnt(http://ant.apache.org/)isaJava-andXML-basedautomationtoolthatisavailableasopensourcesoftwarefromtheApacheSoftwareFoundation.AntbeganitslifeaspartoftheTomcatcodebase.Thetool'sfirstofficialreleaseasastandalonesoftwareproductwasinJuly2000,accordingtotheAntFAQ(http://ant.apache.org/faq.html).TheoriginalcreatorofbothAntandTomcatisJamesDuncanDavidson.

AnthasevolvedintothebuildtoolofchoiceforautomatingJavasoftwareprojects,whichmeansbuildingtheseprojectsfrombeginningtoend.ThisincludescompilingJavaclasses,creatingJARorWARfiles,andinitiatingfilesystem-relatedtaskssuchascreatingdirectoriesandmovingorcopyingfiles.AllofthesetasksarecontrolledbytheAntbuildfileforaspecificproject.

AnAntbuildfileisanXMLfilethatislaunchedfromthecommandlineandexecutesJavaclassesbehindthescenes.Antisalsoextensible;youcancustomizethistooltosuityourownpurposes.Inaddition,Antiscross-platformandveryportable,sinceitisbasedonXMLandJava.Oncewebdevelopersbecomefamiliarwiththishandyandpowerfultool,theyfindthatitgreatlyeasesthetaskofcompiling,packaging,andinevitablyalteringandredeployingtheirwebapplications.

ThischapterfirstdescribeshowtodownloadAntandsetituponyoursystem,andthenexplainsAnttargetsandtasksforthosewhoarenewtoAnt.TherestofyoucanmerrilymoveontootherrecipesdescribinghowtocreateaclasspaththatincludesthenecessaryTomcatJARfiles,createWARandJARfiles,anduseAnttoexecuteTomcat'sManagerapplication.

http://ant.apache.org/default.htm

http://ant.apache.org/faq.html

Recipe4.1ObtainingandSettingUpAnt

Problem

YouwanttodownloadandsetupApacheAntonyourcomputer.

Solution

Pointyourbrowsertohttp://ant.apache.org/,downloadthebinaryorsourcedistributionofAnt,thenfollowtheinstructionsgiveninthisrecipeandontheAntsupportsite.

Discussion

ThebinarydistributionofApacheAntcanbedownloadedfromhttp://ant.apache.org/bindownload.cgi.Youcanalsodownloadthesourcedistribution,whichcontainstheJavasourcefilesforAnt,fromhttp://ant.apache.org/srcdownload.cgi.YoumusthavetheJavaSoftwareDevelopmentKit(SDK)installed.

Antv1.5.3willbethelastreleasethatsupportsJDK1.1.Antv1.5.1canrunwithJDK1.1,althoughsometasksworkonlyonJDK1.2.

TouseAnt,youmusthaveaJavaAPIforXMLProcessing(JAXP)-compliantXMLparseravailableonyourclasspath.ThebinaryAntdistributionincludestheApacheXerces2XMLparser.IfyouoptforadifferentJAXP-compliantparser,youshouldremovexercesImpl.jarand


http://ant.apache.org/bindownload.cgi

http://ant.apache.org/srcdownload.cgi

xmlParserAPIs.jarfromAnt'stop-level/libdirectory(asinjakarta-ant-1.5.1/lib)andputtheJARfile(s)forthealternativeparserintoAnt's/libdirectory.Youcanalsoaddthemdirectlytoyouruserclasspath.

TheuserclasspathistheclasspathrepresentedbytheCLASSPATHenvironmentvariableonyourmachine.Thisclasspathoverridesthedefaultvaluefortheuserclasspath(.,orthecurrentdirectory).Thejavacommand-linetool's-cpor-classpathswitchesoverridetheCLASSPATHenvironmentvariable.TheuserclasspathcanalsobesetbyaJARfilespecifiedbythejavatool's-jarswitch.Thisdesignationinturnoverridestheotherwaysofspecifyingaclasspath.Thebottomlineisthatitiseasiertoplaceyourparserofchoiceinthejakarta-ant-1.5.1/libdirectoryinsteadoffoolingaroundwiththeseclasspathissues.

ThecompleteinstallationdirectionsforAntandlinkstorelatedWebpagesareathttp://ant.apache.org/manual/index.html.

TakethefollowingstepstogetAntrunningonyourmachine:

1. Unpackthecompressedfile(inZIPorTARformat)containingtheAnttool.WithAntv1.5.1,unpackingthedistributionfilecreatesadirectorycalledjakarta-ant-1.5.1.

SettheANT_HOMEenvironmentvariabletothedirectorywhereyouinstalledAnt.OnUnix,thiscanbeaccomplishedbytypingacommand-linephrase:

exportANT_HOME=/usr/local/jakarta-ant-1.5.1

OnWindowstype:

setANT_HOME=h:\jakarta-ant-1.5.1

Addthe<Ant-installation-directory>/bindirectorytoyourPATHenvironmentvariable.Thisallowsthedevelopertochangetoanyworkingdirectorywithabuild.xmlfileandtypeanttorunthisfile(readthenextrecipeforadescriptionofexecutingabuild.xmlfile).The<Ant-

http://ant.apache.org/manual/index.html

installation-directory>/bindirectorycontainsthescriptswhichlaunchtheJavaclassesthatformthebasisofAnt.

Optionally,settheJAVA_HOMEenvironmentvariabletothedirectorywhereyourJDKisinstalled.YoumightaswellsettheJAVA_HOMEenvironmentvariable,becausethescriptsthatareprovidedwithAntinits/bindirectorycanthenautomaticallyaddtherequiredJDK-relatedclasseswhenyouwanttousethejavacorrmictasks.TasksareXMLelementsthatdocertainjobsinAntfiles,suchaswar(tocreateWebArchivefiles)andjavac(tocompileJavaclasseswithAnt).

Testyourinstallationbytypingant-version.Ifeverythinggoeswell,thiscommandproducesareturnvaluelikethis:

K:\>ant-version

ApacheAntversion1.5.1compiledonOctober22002

SeeAlso

Recipe4.2onusingAnttargets;Recipe4.3onincludingTomcatJARfilesintheAntclasspath;Recipe4.4oncompilingaservletwithAnt;Recipe4.5oncreatingaWARfilewithAnt;Recipe4.6onusingAnttocreateJARfiles;Recipe4.7andRecipe4.8onstartingandstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theApacheAntmanual:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.



Recipe4.2UsingAntTargets

Problem

YouwanttocreatetargetelementsfordevelopingwebapplicationswithanAntbuildfile.

Solution

Createoneormoretargetelementsaschildelementsofaprojectelement.Makesurethetargetshavetherequirednameattributeandvalue.

Discussion

AnAntbuildfileisanXMLfileinotherwords,aplaintextfilethatincludeselementsandattributes.Example4-1showsanAntfilethatechoesamessagetotheconsole.Asmentionedintheintroduction,AntfilesexecuteJavacodebehindthescenes.Thewayyoucontrolthedesiredactionsofyourbuildfileisbyarrangingoneormoretargetelementsinsidetheprojectrootelement.

Example4-1.AnAntbuildfilethatechoesaconsolemessage

<projectname="Cookbook"default="echo-message"basedir=".">

<targetname="echo-message"

description="Echoingamessagetotheconsole">

<echomessage="HellofromthefirstAntfile"/>

</target>

</project>

Antfileshaveoneprojectrootelement,whichmusthaveadefaultattributeandvalue.Thedefaultattributespecifiesthetargetthatrunsifnoothertargetsareidentifiedonthecommandline.Thenameandbasedirattributesareoptional.Thenameattribute,asyoumighthaveguessed,givestheprojectelementadescriptivename.Thebasedirattributespecifiesthedirectorybywhichpathsthatarereferredtointhefilearecalculated.Itsdefaultvalueisthedirectorycontainingthebuildfile.

Whataretargets?Theyaregroupsoftasks,representedinAntbyatargetelement.Targetsgrouponeormoretasks(whichareinturnrepresentedbyataskelement)intologicalandnamedunitsofcontrol,similartoJavamethods.

TasksincludeactionsthatcompileJavafiles(thejavactask),copyfilesfromonelocationtoanother(copy),andcreateJARorWARfiles(aptlynamedjarandwar).Forinstance,theecho-messagetargetinExample4-1callstheechotask.

Thetarget'snameinExample4-1isecho-message,whichisjustanamethatIcreatedforit.Atarget'sdescriptionattributeisoptional,asarethreeotherattributes:depends,if,andunless.I'llexplainthepurposeofdependsshortly;theifandunlessattributesallowtheconditionalexecutionoftargets.

AslongasAntisproperlysetuponyourcomputer,hereiswhatthecommand-linesequenceforexecutingthisexamplebuild.xmlfilemightlooklike:

H:\book\cookbook\sec1\sec1_3>ant

Buildfile:build.xml

echo-message:

[echo]HellofromthefirstAntfile.

BUILDSUCCESSFUL

Totaltime:3seconds

First,theXMLfilewiththeprojectrootelementissavedwiththefilenamebuild.xml.Thentheuserchangestothedirectorythatcontainsthisfileandtypesant,withoutanyoptions.Antthenlooksforafilecalledbuild.xmlinthecurrentdirectoryandrunstheproject'sdefaulttarget(inExample4-1,theecho-messagetarget).

Youcangivethebuildfileanameotherthanbuild.xml,butthenyouneedtorunAntwiththe-buildfileoption:

ant-buildfiledev.xml

MostbuildfilesinvolveseveraltargetsthatexecuteinacertainsequencetoinitiateJavadevelopmenttasks.Example4-2demonstratesthedependsattribute.Thisexampleshowshowtoexecuteseveraltargetsinaspecifiedsequence.

Example4-2.Usingthedependstargetattributetolaunchasequenceoftargets

<projectname="Cookbook"default="echo-message"basedir=".">

<targetname="init">

<propertyname="name"value="BrucePerry"/>

</target>

<targetname="show-props"depends="init">

<echomessage=

"The'name'propertyvalueis:${name}"/>

<echomessage=

"OSnameandversionis:${os.name}${os.version}"/>

<echomessage=

"YourJavahomeis:${java.home}"/>

</target>

<targetname="echo-message"depends="show-props">

<echomessage=

"HellofromthefirstAntfileindirectory:${basedir}"/>

</target>

</project>

Thistime,insteadofjustonetarget,theprojectelementhasseveralnestedtargets.Theecho-messagetargetisstillthedefaulttarget,butitsbehaviorhaschangedduetothevalueofitsdependsattribute.ThisoptionalattributespecifiesthenameofoneormoreAnttargetsthatmustbeexecutedpriortothecurrenttarget.Inotherwords,theecho-messagetargetspecifies,"Idependontheshow-propstarget,soexecuteitbeforeme."Theshow-propstarget,however,alsohasadependsattributethatindicatesarelianceontheinittarget.Asaresult,thisbuildfileestablishesasequenceforexecutingitstargets:init show-props echo-message.

Theresultofrunningthepriorbuildfileatthecommandlineisshownhere:

H:\book\cookbook\sec1\sec1_3>ant

Buildfile:build.xml

init:

show-props:

[echo]The'name'propertyvalueis:BrucePerry

[echo]OSnameandversionis:WindowsNT4.0

[echo]YourJavahomeis:h:\jdk1.3.1_02\jre

echo-message:

[echo]HellofromthefirstAntfileindirectory:

H:\book\cookbook\sec1\sec1_3

BUILDSUCCESSFUL

Totaltime:2seconds

Hereiswhatthisbuildfileaccomplishes:

1. Theinittargetfirstcreatesanamepropertythatcontainsthevalue"BrucePerry".Thetargetusesthepropertytasktoaccomplishthis.RecallthattasksdotherealworkinAnt;targetsaresimplygroupingelementsthatcalloneormoretasks.

Theshow-propstargetthenechoesthevaluesofthenameproperty(createdbytheinittarget)andthreebuilt-inproperties:os.name,os.version,andjava.home.

Theecho-messagetargetissuesitsmessagetotheconsoleandreturnsthevalueofthebasedirproperty.Allofthetargetsusetheechotasktodelivertheirmessages.

Notethatthenamepropertywouldnotbesetiftheinittargetwasneverexecuted.Iftheshow-propstargetisdefinedasseenhere,therewillbeproblems:

<targetname="show-props">

...</target>

However,itisproperlydefinedasfollows:

<targetname="show-props"depends="init">

...</target>

Withoutthedependsattribute,theinittargetwouldneverbeexecuted,becausethebuildfile'sexecutionsequencewouldlooklikeshow-props echo-message.Thenamepropertywouldneverbegivenavalue.

Antbuildfilesareusuallymuchmorecomplexthantheseexamples,whichismoreofatestamenttoAnt'spowerthanevidenceofpoordesign.Chapter2showshowtodeployindividualservletsandwebapplicationswithmoreextensiveAntfiles.

SeeAlso

Recipe4.1ondownloadingandsettingupAnt;Recipe4.3onincludingTomcatJARfilesintheAntclasspath;Recipe4.4oncompilingaservletwithAnt;Recipe4.5oncreatingaJARfilewithAnt;Recipe4.7andRecipe4.8onstartingandstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theAntmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.

http://ant.apache.org/manual/CoreTasks/property.html

http://ant.apache.org/manual/using.html#targets



Recipe4.3IncludingTomcatJARfilesintheBuildFileClasspath

Problem

YouwanttoestablishanAntclasspaththatincludesvariousTomcatJARfiles.

Solution

Useapath-likestructuretodefinetheclasspath,thenrefertothisclasspathwheneveryouneedit.SpecifythedirectorieswherethenecessaryJARfilesarelocatedwithanexternalpropertiesfile.

Discussion

BeforeyoucancompileaservletusingAnt,youmustensurethattheservletAPIclassesareavailableontheclasspaththattheAntbuildfileisusingforcompilation.Forexample,the<Tomcat-installation-directory>/common/libdirectorycontainsservlet.jar,whichincludesthenecessaryclassesforcompilingaservlet.Inaddition,youmightwanttoincludethemail.jarcomponentfromthesamedirectorytocompileaservletthatusestheJavaMailAPI.Adifferentdirectory<Tomcat-installation-directory>/common/endorsedincludesthexmlParserAPIs.jarfile,whichyoumightspecifyontheclasspathtousetheassociatedSAXandDOMXMLprogrammingclasses.

Example4-3definesaclasspathusingapathXMLelement.Acompile-servlettargetfurtherdownintheXMLfilethenusesthedefinedclasspathtocompileaservlet.

Example4-3.DefiningaclasspathincludingTomcatJARfiles

<projectname="Cookbook"default="compile-servlet"basedir=".">




<pathid="servlet-classpath">



</fileset>



</fileset>

</path>

<targetname="compile-servlet">

<echomessage="Compilingtheservlet...."/>



<classpathrefid="servlet-classpath"/>

</javac>

</target>

</project>

Usingthepathelement,theclasspathcanbedefinedsimilarlytoaninstancevariableofaJavaclass,anditsvaluecanthenbeusedthroughoutthebuildfile.Theadvantageofthisapproachisthattheclasspathmaybeverycomplex,butithastobedefinedonlyonce.WheneverthereisaneedforaclasspathinanAntfile,theclasspathelementanditsrefidattributecanbeusedtopullinthedefinedclasspath.InExample4-3,thepathelementisgivenauniqueID,"servlet-classpath."Thedevelopercreatesthisnametouniquelyidentifythepath-likestructure.

AnothercoretypeofAnttaskisafileset.filesetsareelementsthatrepresentgroupsoffiles.ThetwonestedfilesetsintheexamplehavedirattributesthatspecifytwodirectoriesundertheTomcatinstallationdirectory:./common/liband./common/endorsed.ThesearedirectoriesthatcontainmanyimportantJavalibraries,suchasservlet.jarandmail.jar.Afilesetelement'snestedincludeelementcreatesapattern(withthenameattribute)thatspecifiesthetypesoffilestoincludeineachfileset.Theexampleincludesallfilesinthespecifieddirectoriesendingin".jar".

IfyouwantedtofurtherrefinethetypesofJARfilesthatareincludedinafileset,youcouldusethefileset'snestedexcludeelement:



<excludename="commons*.jar"/>

</fileset>

Thepattern"commons*.jar"excludesalltheJARfilesfromtheclasspaththatbeginwiththeword"commons,"followedbyzeroormorecharactersanda".jar"suffix.

Thecompile.servlettargetinExample4-3echoesamessagetotheconsole,thenusesthejavactasktocompileaservlet.

ThiscodefromExample4-3makestwopropertiesthataredefinedinanotherfileavailabletotheAntbuildfile:


Hereiswhattheglobal.propertiesfilelookslike:


compiled.servlet=MyTask

src=.\src

build=.\build

Thepropertycompiled.servletevaluatestothenameoftheJava

sourcefilethatisbeingcompiled.Thetomcat.dirfileisthefilepathtotheTomcatrootdirectory.

InExample4-3,theclasspathelementisnestedinsidethejavactask,asin:




</javac>

Theclasspathelement'srefidattributepullsintheclasspaththatwasdefinedearlierinthebuildfile(includingalltheTomcatJARsin./common/liband./common/endorsed).Thevalueoftherefidattributeistheidofthepathelement("servlet-classpath").Inotherwords,thepathelementinExample4-3representsaclasspath;theelement'sidornameis"servlet-classpath."

IfitisnecessarytoaddmoreclassesorJARstotheclasspaththatyouaredefininginanAntfile,thenaddanothernestedfilesettothepathelement.Example4-4addsallofthecontentsofthebuilddirectorytotheclasspathdefinedbyExample4-3(alongwiththeTomcat-relatedJARs)byaddingathirdnestedfileset.

Example4-4.Nestingthreefilesetsinapathstructure




</fileset>



</fileset>

<filesetdir="./build"/>

</path>

Anidiomthatoftenappearsinpath-relatedpatternsis**,whichmeanszeroormoredirectories.Forexample,thefollowingfilesettagincludesallofthefilescontainedinanynestedimagesfolders(srcisapropertynamepointingtothesourcedirectoryofthisfileset),nomatterhowdeeplytheyarenested:

<filesetdir="${src}">

<includename="**/images/*"/>

</fileset>

SeeAlso

Recipe4.1ondownloadingandsettingupAnt;Recipe4.2onwritingAnttargets;Recipe4.4oncompilingaservletwithAnt;Recipe4.5oncreatingaWARfilewithAnt;Recipe4.6onusingAnttocreateJARfiles;Recipe4.7andRecipe4.8onstartingandstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theAntmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.





Recipe4.4CompilingaServletwithanAntBuildFile

Problem

Youwanttosetupasimplebuildfilethatyoucanusetocompileindividualservlets,withouthardcodingservletnames.

Solution

DesignabuildfilesothatthenameoftheJavaclasstocompilecanbesetfromanexternalpropertiesfileorfromthecommandline.

Discussion

IfyouarenotusinganIDEtodevelopandcompileyourservlets,anAntbuildfilecanautomatethecompilingofyoursourcefiles.Inordertomakethisbuildfilereusable,youshoulddesignittogetthenameofthefilefromanexternalpropertiesfileorfromthecommandline.

Ant'sadvantagescometotheforewhenitisusedtoautomatealloftheaspectsofbuilding,archiving,anddeployingawebapplication.However,youcanalsouseAntasakindofbatchprocessor.Inthisrecipe,IuseAnttodynamicallychooseaJavafiletocompile.

Thebuild.xmlfileinExample4-5importsacoupleofpropertiesfromabuild.propertiesfile,includingthenameoftheservlettobecompiled.OnewaytochooseadifferentJavafiletocompileistochangethevalueofthecompiled.servletpropertyinthisfile,withouttouchingthebuildfile:

tomcat.dir=/users/bruceper/java/jakarta-tomcat-4.1.12

compiled.servlet=MyServlet

TorunExample4-5,changetothedirectorywherethebuild.xmlfileislocatedandtypeantwithoutanyoptions.

IfyouarerunninganAntbuildfilewithadifferentname,thenlaunchitwiththiscommandline:

ant-buildfileant_compiler.xml

First,thisfileimportsthetomcat.dirandcompiled.servletpropertiesfromabuild.propertiesfile.Thisfileislocatedinthesamedirectoryasthebuildfile.Thetomcat.dirpropertyisusedtocreateaclasspathcomposedoftheJARfilesintwodirectoriesthatareapartofTomcat'sdirectorytree(seeRecipe4.2).

Example4-5.CompilingaservletwithanAntbuildfile

<projectname="servletcompiler"default="compile"basedir=".">





</fileset>



</fileset>

</path>

<targetname="init"



<propertyname="build"value="./build"/>

<propertyname="src"value="./src"/>

</target>





</target>

<targetname="compile"depends="prepare"

description="Compiletheservlet">

<echomessage="CompilingtheJavafile"/>

<echomessage="${compiled.servlet}.java..."/>




</javac>

</target>

</project>

Theinittargetcreatestwopropertiesrepresentingthesource(src)anddestination(build)directoriesofthetargetservlet.TheJavafilewaitingtobecompiledislocatedinansrcdirectory.Atypicalbuildfilealsohasaninittargetthatinitializesseveralmoreproperties.Sincethecompiletargethasadependsattributethatspecifiesthepreparetarget,andthepreparetargetdependsoninit,thenthebuildsequencelookslikeinit prepare compile.

Thepreparetargetjustcleansupthebuilddirectorytoensurethatthebuilddirectorycontainsthelatestcompiledclasses.

ThecompiletargetusesthejavactasktoactuallycompiletheJava

file.javachasattributesthatspecifythesourceanddestinationdirectoriesoftheJavafile(s)thatitwillattempttocompile.Example4-5usesthesrcandbuildpropertiestoprovidevaluesfortheseattributes.Twonestedelementsofthejavactaskcompilethespecifiedservletfileandprovidetheclasspaththatthejavactaskuses(seeRecipe4.2).

Hereistheconsoleoutputafterrunningthisbuildfile(withsomeeditingforreadability):

init:

[echo]Initializingproperties.

prepare:

[echo]Cleaningupthebuilddirectory.

[delete]Deletingdirectory

/Users/bruceper/books/cookbook/sec1/sec1_3/build

[mkdir]Createddir:


compile:

[echo]CompilingtheJavafileMyServlet.java...

[javac]Compiling1sourcefileto


BUILDSUCCESSFUL

Totaltime:6seconds

Usingthecommandlinetodeclarethetargetservlet

Whatifyouwanttochangetheservletthatyouarecompiling,butarenotinclinedtotypethenewJavafilenameintothebuild.propertiesfile?Runningthebuild.xmlAntfilefromthecommandlineinthefollowingmannerwilloverridetheimportedcompiled.servletproperty:

ant-Dcompiled.servlet=AnotherServlet

AnotherServlet.javaisthefilenameinthisexampleoftheJavafilethatawaitscompilationinthesrcdirectory.Thisfragmentofoutputshowsthatanypropertiespassedinfromthecommandlineoverridepropertiesofthesamenamecreatedwithinorimportedintothebuildfile:

compile:

[echo]CompilingtheJavafileAnotherServlet.java...

[javac]Compiling1sourcefileto


Thejavactaskcompilesonlyonlythejavafilesinthesrcdirectorythatdonothaveacorrespondingclassfile,orincaseswheretheclassfileisolderthanitscorresponding.javafile.Asalways,checktheAntmanualtofindoutaboutallthedifferentvariationsandattributesofjavac:http://ant.apache.org/manual/CoreTasks/javac.html.

Ifyouwanttocopythecompiledservletclasstoawebapplicationdirectory,youcouldaddadeploy-servlettargetthatusesthecopyAnttask:

<targetname="deploy-servlet"depends="compile">

<echomessage=

"CopyingtheservlettoTomcatwebapp"/>

<copytodir="${tomcat.webapps}/WEB-INF/classes">


</copy>

</target>

Thecopytasktakesitsnestedfileset,whichrepresentsthecontentsofthedirectorynamedbythebuildpropertyvalue,andcopiestheseclassfilestotheWEB-INF/classesdirectoryofTomcat'sdefaultwebapplication.

SeeAlso

Recipe4.1ondownloadingandsettingupAnt;Recipe4.2onwritingAnttargets;Recipe4.3oncreatingaclasspathforanAntfile;Recipe4.5oncreatingaWARfilewithAnt;Recipe4.6onusingAnttocreateJARfiles;Recipe4.7andRecipe4.8onstartingandstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;the

http://ant.apache.org/manual/CoreTasks/javac.html

Antmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject,http://ant.apache.org.





Recipe4.5CreatingaWARFilewithAnt

Problem

YouwanttouseAnttocreateaWebARchive(WAR)file.

Solution

UsetheAntwartask.

Discussion

AWARfileisawebapplicationarchivethatcontainsservletclasses,JSPfiles,HTMLfiles,imagedirectories,JARfiles,XMLconfigurationfiles,andotherresourcesthatawebapplicationdependson.TheWARisdeployedonawebcontainerlikeTomcatinordertomakethewebapplicationavailabletothecontainer'susers.AntincludesawartaskthatmakesiteasytogenerateaWARfromadirectorystructurethatcontainsthenecessarywebapplicationfiles.

Example4-6isastandalonebuildfilethatcreatesaWARfile.ItcouldeasilycompriseonetargetinacomplexbuildfilethatcompilesJavafiles,createstheWAR,anddeploystheapplication(seeRecipe2.6).

Thisexamplecreatesabuildsequenceofinit preparecreate-war.Theinittargetcreatesseveralpropertiesthatrefertodirectories,suchasthebuilddirectorycontainingtheservletclassfiles.Thecontext-pathpropertyprovidesthecontextpathforthewebapplication,andinthiscase,thenameoftheWARfile(myapp.war).

Youexecutethisbuildfilefromacommandpromptwhoseworking

directoryisthewebapplication'srootortop-leveldirectory.

Example4-6.AnAntfileusingthewartask

<projectname="war-task"default="create-war"basedir=".">

<targetname="init"





<propertyname="dist"value=".\dist"/>

<propertyname="lib"value=".\lib"/>

<propertyname="web"value=".\web"/>

<propertyname="meta"value=".\meta"/>

<propertyname="context-path"value="myapp"/>

</target>


<echomessage=

"Cleaningupthebuildanddistdirectories."/>





</target>

<targetname="create-war"description=

"createsawebapplicationarchivefile"

depends="prepare">

<wardestfile="${dist}/${context-path}.war"

webxml="${meta}/web.xml">


<libdir="${lib}"/>


</war>

</target>

</project>

Ifthebuildfilewascalledwar-task.xml,thentheAntfileisexecutedwiththiscommandline:

ant-buildfilewar-task.xml

Thecreate-wartargetcallsthewartask.

Thewartask'sdestfileattributeisrequired;itspecifiesthelocationoftheresultingWARfile.Example4-6createstheWARinthedistdirectory.Thewebxmlattributespecifiesthelocationofthewebapplication'sdeploymentdescriptor.Thiswebapplication'sweb.xmlfile(inthisexample)islocatedinthemetadirectory.

Theexamplewartaskhasthreenestedelements:classes,lib,andfileset.ThedirattributeoftheclasseselementpointstothedirectorythatcontainstheJavaclassesthatarelocatedintheWEB-INF/classesdirectory.ThewartaskautomaticallycreatestheWEB-INF/classesdirectoryintheWARfile.Thistaskalsoreproducesallthepackage-relateddirectoriesinthebuilddirectorywhenitcreatesWEB-INF/classes.Inotherwords,ifthebuilddirectoryincludesacom/jspservletcookbookdirectorystructure,thentheWARwillhavethesamestructureinWEB-INF/classes.

ThelibelementgrabsandstoresanyJARfilesthatwillbelocatedintheWARfile'sWEB-INF/libdirectory.Finally,thefilesetnested

element,inthiscase,pullsinallthestaticfilesandanynestedimagedirectoriesthatarecontainedin/webandplacesthematthetopleveloftheWAR'sdirectorytree.Hereiswhattheoutputofthisbuildfilelookslike(withsomeeditingforreadability):

init:

[echo]Initializingproperties.

prepare:

[echo]Cleaningupthebuildanddistdirectories.


/Users/bruceper/books/cookbook/build

[mkdir]Createddir:

/Users/bruceper/books/cookbook/build


/Users/bruceper/books/cookbook/dist

[mkdir]Createddir:

/Users/bruceper/books/cookbook/dist

create-war:

[war]Buildingwar:

/Users/bruceper/books/cookbook/dist/myapp.war

ThewartaskhasnumerousotheroptionalattributesthatareexplainedintheAntmanualathttp://ant.apache.org/manual/CoreTasks/war.html.

SeeAlso

Recipe4.1ondownloadingandsettingupAnt;Recipe4.2onwritingAnttargets;Recipe4.3oncreatingaclasspathforanAntfile;Recipe4.4oncompilingaservletwithAnt;Recipe4.6onusingAnttocreateJARfiles;Recipe4.7andRecipe4.8onstartingandstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theAntmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;

http://ant.apache.org/manual/CoreTasks/war.html



theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.



Recipe4.6CreatingaJARFilewithAnt

Problem

YouwanttocreateaJARfilewithAnt.

Solution

Usethebuilt-injartask.

Discussion

ThejartaskautomatesthecreationofJARfiles.LikethewartaskforWARs,thejartaskallowsyoutoautomatethecommand-linephrasesyouwouldhavetotypeinforcreatingJARs.Inthisway,buildfilesusingthejartaskaresomewhatlikeshellscriptsorbatchfilesforcreatingJARs.TheSunMicrosystemsJARfilespecificationcanbefoundathttp://java.sun.com/j2se/1.4/docs/guide/jar/jar.html.

Inwebapplications,JARfilesareusedtocontainseparatecodelibrariesthatthewebapplicationdependson,suchasadatabasedriver.Theyarelocatedinawebapplication'sWEB-INF/libdirectory.Example4-7showsanAnttargetthatusesthejartasktocreateaJAR,andthencopiestheJARfiletothelibdirectoryofawebapplication.TheseactionsprecedethearchivingofthewebapplicationintoaWARfile,whichcanbeincludedinthesamebuildfiletoautomateeverythingatonce(seeRecipe4.5oncreatingWARfiles).

Example4-7.CreatingaJARfilewithAnt

http://java.sun.com/j2se/1.4/docs/guide/jar/jar.html

<projectname="jar-task"default="create-jar"basedir=".">

<targetname="init"



<propertyname="dist"value="dist"/>

<propertyname="web"value="web"/>

<propertyname="meta"value="meta"/>

<propertyname="jar-name"value="myutils"/>

</target>


<echomessage=

"Cleaningupthebuildanddistdirectories."/>



</target>

<targetname="create-jar"

description="createsaJARarchivefile"

depends="prepare">

<jardestfile="${dist}/${jar-name}.jar"

basedir="../../"

includes="**/*.class**/${web}/*.html">

<filesetdir="../../images"/>

</jar>

</target>

</project>

Thisbuildfilecontainsthreetargetsinthebuildsequenceinitprepare create-jar.ThesetargetscreatesomepropertiesandcleanupadirectorycalleddistthatcontainstheresultantJARfile.Thecreate-jartargetcallsthejartask,whichlookslike:

<jardestfile="${dist}/${jar-name}.jar"basedir="../../"

includes="**/*.class**/${web}/*.html">

<filesetdir="../../images"/>

</jar>

ThedestfileattributeofthejarelementspecifiesthelocationandnameoftheJARfileafteritiscreated.Iusedapropertycalledjar-namehere,sothattheusercanrunthisAntfilefromthecommandlineandfeedanewJARfilenameintothebuildfileifneedbe,asin:

ant-Djar-name=mynewjar.jar

Rememberthatanypropertiesspecifiedwiththe-Dswitchoverridethepropertiesofthesamenamedefinedinsidethebuildfile.

Thebasedirattributeofthejartaskidentifiesthetop-leveldirectoryoffilesthatwillbeincludedintheJAR.Intheexample,thepattern../../means"gouptwodirectoriesfromthebasedirofthisproject";inotherwords,gouptwodirectoriesfromwheretheAntbuildfileislocated.

Theincludesattributehastwospace-separatedpatterns(youcanalsoseparatethemwithacomma).ThepatternsfurtherrefinethetypesoffilesthatwillbeincludedintheJARfile.Thefirstpatternspecifiesthe

inclusionofallthefilesendingwiththe.classsuffixthatarelocatedinzeroormoredirectoriesbeneaththebasedirlocation.ThisJAR,asaresult,containsalloftheJavaclassfilesinalldirectoriesnestedbeneaththebasedirectory;theJARreproducesanynesteddirectoriesthatitfindswiththeclassfiles.Theotherpattern(**/${web}/*.html)takesalldirectoriesnestedbeneaththebasedirectorycalledwebandincludesanyfilesthatendwith.htmlintheJAR.Onceagain,thenesteddirectorieswillbeincludedwiththeJARandtheHTMLfiles.

Finally,afilesetelementnestedwithinthejartaskgrabsallthecontentsofthe../../imagesfolderandincludesthemintheJAR,butitdoesnotincludetheimagesfolderitself.AwaytoincludetheimagesfolderanditscontentsatthetopleveloftheJARistochangethejartaskto:

<jardestfile="${dist}/${jar-name}.jar"basedir="../../"

includes="**/*.class**/${web}/*.html**/images/*.gif

Thistaskaddsathirdpatterntotheincludesattribute(**/images/*.gif),whichgrabsalltheGIFfilescontainedbyanyimagesdirectoriesthatarenestedinthebasedirectory(thevalueofthejarelement'sbasedirattribute).AnimagesdirectorywillbeincludedintheJARifoneisfound.

The**patternisoftenusedinAntelements;itmeans"zeroormoredirectories."

Manifest

ThejartaskcreatesaMETA-INF/MANIFEST.MFfilefortheJARifthejartask'smanifestattributedoesnotappear.Thedefaultmanifestlookslikethis:

Manifest-Version:1.0

Created-By:ApacheAnt1.5.1

IfyouwanttospecifythelocationofyourownmanifestfileforreasonssuchassigningaJARfileorspecifyingthefilethatcontainsthemain()methodinanexecutableJAR,usethejartask'smanifestattribute.ThisoptionalattributecanbeeitherthefilelocationofthemanifestorthenameofanotherJARthathasbeenaddedbyusinganestedfilesetelement.IfitisaJAR,thetasklooksinthatJARfortheMETA-INF/MANIFEST.MFmanifest.

SeeAlso

Recipe4.1ondownloadingandsettingupAnt;Recipe4.2onwritingAnttargets;Recipe4.3oncreatingaclasspathforanAntfile;Recipe4.4oncompilingaservletwithAnt;Recipe4.7andRecipe4.8onstartingandstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theAntmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.





Recipe4.7StartingaTomcatApplicationwithAnt

Problem

YouwanttostartawebapplicationonTomcatusinganAntfile.

Solution

UsetheTomcat-suppliedStartTasktasksothatAntcanmanageTomcat.

Discussion

TheTomcatservletandJSPcontainerincludesabuilt-inwebapplicationcalled"Manager"thatyoucanusetostart,stop,deploy,andinitiateotheradministrativetaskswithwebapplications.Tomcatmakesthisapplicationavailablefromthe/managercontextpath.

TomcatVersion4(andlater)includesJavaclassesthatallowdeveloperstousetheManagerapplicationfromtheirAntbuildfiles.TheadvantageofusingtheManagerapplicationfromAntisthatyoudonothavetoconfiguretheconf/server.xmlfiletomakethewebapplicationdynamicallyreloadable(seeRecipe2.2).Inaddition,youcanstartorstopasinglewebapplicationwithoutdisruptingotherTomcatapplications.

TheManagerdocumentationisfoundonlineathttp://jakarta.apache.org/tomcat/tomcat-4.1-doc/printer/manager-howto.html

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/printer/manager-howto.html

TakethesestepstostartTomcatfromAnt:

1. MakesureyouhavethenecessaryJARfilerequiredtousetheAnttaskforstartingTomcat:<Ant-installation-directory>/lib/catalina-ant.jar.CopythisJARfromthe<Tomcat-installation-directory>/server/libdirectorytoyour<Ant-installation-directory>/libdirectory(otherwiseknownasANT_HOME/lib).

MakesuretheTomcatuserdatabaseincludesausernamethatislinkedtothemanagerrole.OnlyadministrativeusersshouldbeauthorizedtostartandstopwebapplicationsusingtheManagertool.Theconf/tomcat-users.xmlfilemapsusersandpasswordstoroles.AuserhastobemappedtothemanagerroletobeabletousetheManagertool.Hereisanexampleofoneoftheseusermappingsintomcat-users.xml:

<userusername="doug"password="_1968dgw"roles="manager,dbadmin"/>

UsethetaskdefelementintheAntfiletodefinethecustomtaskandgiveitaname.Example4-8givesthetaskthenamestart,whichisusedbythetargetthatisresponsibleforstartingTomcat.

RuntheAntfileatthecommandlinebychangingtoitsdirectoryandtypingant.

Example4-8showsthetaskdefelementthatdefinesthestarttask,followedbythetargetthatstartsthespecifiedTomcatapplication.

Example4-8.StartingTomcatusinganAntfile

<projectname="MyProject"default="start-tomcat"basedir=".">

<taskdefname="start"classname="org.apache.catalina.ant.StartTask"/>




<targetname="start-tomcat"

description="StartstheWebapplication">

<echomessage="Startingthedefaultapplication${context-path}..."/>

<start

url="${url}"




</target>

</project>

ThestarttaskhasfourattributesthatExample4-8setsusingaglobal.propertiesfile.Thisisatextfilecontainingfourname/valuepairs,whichareimportedintotheAntfileusingthepropertytask:


Theglobal.propertiesfileislocatedinthesamedirectoryastheAntbuildfile.Herearethecontentsoftheglobal.propertiesfile:


username=bruce

password=bruce1957

context-path=home

TheurlpropertyspecifiestheTomcatManagerURL,theusernameandpasswordidentifytheuserwhoismappedintheTomcatuserdatabasetothemanagerrole,thecontext-pathpropertyspecifiesthecontextpathofthewebapplicationyouarestarting,andtheAntfileitselfspecifiestheopeningslash(/)characterforthecontextpath.

AnotherwaytopasspropertiestoanAntfileisonthecommandline:

ant-Dusername=bruce-Dpassword=bruce1957

-Durl=http://localhost:8080/manager

-Dcontext-path=home

Propertiesaddedonthecommandlineoverridethosespecifiedbythepropertytask.

LaunchthisAntfilebychangingtoitsdirectoryatthecommandlineandtypingantorant-buildfilebuildfile-name.Hereisthecommand-lineoutput:

H:\book\cookbook\code\chap4>ant-buildfilestart.xml

Buildfile:start.xml

start-tomcat:

[echo]Startingthedefaultapplicationhome...

[start]OK-Startedapplicationatcontextpath/home

BUILDSUCCESSFUL

Totaltime:4seconds

Ifanapplicationisstopped,itisunavailabletowebusers(seeRecipe4.8).Whentheapplicationisstartedagain,itcanreceiverequestsnormally.

TheTomcatmanagerapplicationcaninitiatemanyothercommonadministrativetaskssuchasdeployingapplications(seeRecipe2.6).

SeeAlso

TheTomcatManagerapplicationdescription:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/manager-howto.html;Recipe4.1ondownloadingandsettingupAnt;Recipe4.2onwritingAnttargets;Recipe4.3oncreatingaclasspathforanAntfile;Recipe4.4oncompilingaservletwithAnt;Recipe4.5andRecipe4.6oncreatingWARandJARfiles;Recipe4.8onstoppingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theAntmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/manager-howto.html





Recipe4.8StoppingaTomcatApplicationwithAnt

Problem

YouwanttouseAnttostopaspecificTomcatwebapplication.

Solution

DefineataskintheAntfileusingataskdefelementandtheJavaclassorg.apache.catalina.ant.StopTask.

Discussion

Duringdevelopment,youmightneedtostopaTomcatwebapplicationsothatyoucanaddnewservletsordeployment-descriptorentries,andthenrestarttheapplication,allowingthechangestotakeeffect.Intheabsenceofaconf/server.xmlconfigurationtomaketheapplicationdynamicallyreloadable(seeRecipe2.2),youcanuseanAnttargettostopaparticularwebapplicationwithoutdisruptingtheotherrunningwebapplications.Thisistheoppositeofstartinganapplication(Recipe4.7);theapplicationistakenoutofserviceuntilyoustartitagain.

Theorg.apache.catalina.ant.StopTaskclassprovidesaconnectionbetweenAntandtheTomcatManagerapplication.Managerisabuilt-inwebapplication(atcontextpath/manager)thatyoucanusetoadministerotherTomcatwebapplications.

ImplementthesamefourstepsdiscussedinRecipe4.7tousethisstoptask:

1. MakesureyouhavethenecessaryJARfilerequiredtousetheAnttaskforstoppingTomcat:<Ant-installation-directory>/lib/catalina-ant.jar.CopythisJARfromthe<Tomcat-installation-directory>/server/libdirectorytoyour<Ant-installation-directory>/libdirectory(otherwiseknownasANT_HOME/lib).

MakesuretheTomcatuserdatabaseincludesausernamethatislinkedtothemanagerrole(seestep2ofRecipe4.7ifyouneedmoredetails).

Example4-9usesataskdefelementtogivethetaskthenamestop,whichisusedbythetargetthatisresponsibleforstoppingTomcat.

RuntheAntfileatthecommandlinebychangingtoitsdirectoryandtypingantorant-buildfilebuildfile-name.

Example4-9.UsingAnttostopawebapplication

<projectname="MyProject"default="stop-tomcat"basedir=".">

<taskdefname="stop"classname="org.apache.catalina.ant.StopTask"/>




<targetname="stop-tomcat"

description="StopstheWebapplication">

<echomessage="Stoppingtheapplication${context-path}..."/>

<stop

url="${url}"


</target>

</project>

Thetaskdefdefinesataskforthisbuildfilecalledstop.Thedefinedtaskisthenusedinthebuildfile:

<stopurl="${url}"username="${username}"password="${password}"


Example4-9getsitspropertyvaluesfromapropertytaskthatimportsglobal.properties(thepropertyfileislocatedinthesamedirectoryastheAntbuildfile).Thepropertiesrepresent:

Theusernameandpasswordofauserwhoismappedtothemanagerroleinconf/tomcat-users.xml

TheURLtotheManagerapplication,asinhttp://localhost:8080/manager

Thecontextpathforthewebapplicationthatyouarestopping

TheTomcatmanagerapplicationcaninitiatemanyothercommonadministrativetaskssuchasdeployingapplications(seeRecipe2.6).

SeeAlso

TheTomcatManagerapplicationdescription:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/manager-howto.html;

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/manager-howto.html

Recipe4.1ondownloadingandsettingupAnt;Recipe4.2onwritingAnttargets;Recipe4.3oncreatingaclasspathforanAntfile;Recipe4.4oncompilingaservletwithAnt;Recipe4.5andRecipe4.6oncreatingWARandJARfiles;Recipe4.7onstartingTomcatwithAnt;Recipe2.1andRecipe2.6ondeployingwebapplicationsusingAnt;theAntmanualsectiononthepropertytask:http://ant.apache.org/manual/CoreTasks/property.html;theAntmanualsegmentontargets:http://ant.apache.org/manual/using.html#targets;theApacheAntmanualindexpage:http://ant.apache.org/manual/index.html;theApacheAntProject:http://ant.apache.org.





Chapter5.AlteringtheFormatofJSPs

Introduction

Recipe5.1.PrecompilingaJSPinTomcat

Recipe5.2.PrecompilingaJSPinWebLogic

Recipe5.3.PrecompilingJSPswiththePrecompilationProtocol

Recipe5.4.MappingaJSPtoItsPageImplementationClass

Recipe5.5.CreatingaJSPfromScratchasaJSPDocument

Recipe5.6.GeneratinganXMLViewfromaJSP

Introduction

ThischaptercoverstwomeansofworkingwithJSPsthatfallslightlyoutsidethenorm.ThefirstmethodprecompilesJSPsandturnsthemintoservletsourcecode.TheseconddevelopsJSPsasXMLdocuments.

PrecompilingJSPs

PrecompilingaJSPinvolvesusingaserver-providedcommand-linetooltoconverttheJSPpageintoaservletclassfile.AJSPisconvertedintoaservlet,oftencalledaJavaServerPageimplementationclass,beforeithandlesanyHTTPrequests.TheJSPspecificationreferstothestagebywhichtheJSPcontainerconvertsJSPpagesyntaxintoaservletasthetranslationphase.InTomcat,ifyouwanttoexaminewhattheJSPpageimplementationclasslookslikeafterthisconversion,gotothisdirectory:

Tomcat-install-directory/work/Standalone/name-of-host/name-of-web-app

name-of-hostcouldbelocalhost,oranyotherhostnamethatreferstotheserverTomcatisinstalledon.Thenameofthewebapplicationisalsothenameofthecontext;thisisusuallysomethinglikeexamples,ROOT,orstorefront.

Theindicateddirectorycontains.javafiles,suchasdefault_jsp.java.ThesearetheJavasourcefilesthatarecompiledintoclassfiles,andthenexecutedasservletstorespondtorequests.

ThereasonswhyaJSPdevelopermaywanttoprecompileaJSPpageinclude:

1. AvoidingtheperceptibledelaycausedwhenaJSPisfirstrequestedfromthewebcontainer,duringwhichtheJSPcompilerconvertstheJSP'ssourcecodeintoaservlet.

AllowingthedevelopertoexaminetheJavasourcecodefortheJSPpageimplementationclass,andoptionallyworkonthecodewiththeirservletIDE'ssourcecodeeditor.

InbothTomcatandWebLogic,acommand-linetoolcanbeusedtoprecompileaJSP.Recipe5.4coversthemappinginweb.xmlofaJSPpagetoitsservletimplementationclass.

JSPsasXMLDocuments

ThelaterrecipesinthischapterdescribecreatingJSPsasXMLfiles.BoththeJSPspecificationsv1.2and2.0describethegenerationanduseofJSPsaspureXMLdocuments.ThismeansthatratherthancreateJSPsintypicalJSPpagesyntax,theyareinsteadcodedaswell-formedXMLdocuments.AccordingtotheJSPspecification,aJSPdocumentisanamespace-awareXMLdocument.TheJSPcontainerdifferentiatesJSPdocumentsfromtraditionalJSPpagesinatleastoneofthreeways.

1. Ajsp-property-groupelementinweb.xmlspecifiesaJSPdocumentwiththeis-xmlchildelement.(Thejsp-property-groupelementisoneoftheJSPconfigurationelementsthattheJSP2.0specificationhasproposedaddingtoweb.xml.)

Thefilehasa.jspxextension.

TheJSPpagehasarootelementofjsp:root.

Recipe5.5showswhatthesefileslooklike.

TheJSPspecificationdescribesanXMLviewasadescriptionofaJSPpageinXMLform.AnXMLviewisgeneratedbytheJSPcontainerduringthetranslationphase.Asubclassofjavax.servlet.jsp.tagext.TagLibraryValidatorcanusetheXMLviewtoparseaJSPinordertovalidatethatcustomtagshavebeenusedcorrectly,beforethecontainerfinallyconvertstheJSPintoitspage

implementationclass(aservlet).Recipe5.6showshowtogenerateXMLviewsforaJSP,andhowtosavetheresultingXMLfiles.

JSPscanbecreatedasXMLfilesforthefollowingreasons,amongothers:

WebcontainerscanacceptJSPdocumentsinwebapplications,meaningthatthewebapplicationcancontainXMLfilesinsteadofthepagesintraditionalJSPsyntax.JSPdocumentscanthusbeintegratedwithotherXMLcontent,suchasXHTMLfiles,ScalableVectorGraphics(SVG),andtheXMLfilesthatarepartofwebservicestransactions.

YoucanuseXMLeditorstoworkwithJSPdocuments.

YoucanuseotherXMLtechnologieswithJSPdocuments,suchasXSLT,SimpleObjectAccessProtocol(SOAP),SAX,andDOM.

Recipe5.1PrecompilingaJSPinTomcat

Problem

YouwanttoconvertJSPsintoservletsusingTomcat4.1.x.

Solution

UsetheJspCcommand-linetoolfoundin<Tomcat-installation>/bin.

Discussion

UsingtheJspCcommand-linetoolisthefirststepinprecompilingTomcatJSPs.Thistoolisofferedintheformofashellscriptjspc.shonUnixsystemsandjspc.batonWindowsandcreatestheJavasourcefilesfortheJSPpageimplementationclasseswithwhichitissupplied.Theresultant.javafilesstillhavetobecompiledintoservletclassfiles,usingjavacoranotherJavacompiler.SinceprecompilingJSPsisatwo-stepprocess,Irecommendabatchfileforconvenience.However,let'sfirstexaminehowtousetheJspCutility.

TheWindowsshellscriptforrunningJspC(<Tomcat-install-directory>/bin/jspc.bat)requiresthataJASPER_HOMEenvironmentvariablebesettotheTomcatinstallationdirectory.Setthisenvironmentvariablewiththefollowingcommandline:

setJASPER_HOME=k:\jakarta-tomcat-4.1.12

RuntheJspCutilitybychangingtothe%JASPER_HOME%\bindirectoryandtypingthefollowingcommand(specifyyourowndirectorypathsandissuethecommandononeline):

jspc-dH:\book\cookbook-webincH:\book\cookbook\map.xml

-webapph:\book\cookbook\dist

The-dswitchspecifiesthedirectorywhereyouwouldlikethesourcefilestobegenerated,andthe-webincswitchspecifiesthenameofanautomaticallygeneratedfilewhereJspCwillcreatetheservletandservlet-mappingelementsfortheservletfiles.IfyoucompileaJSPpagethatiscalledprecomp.jsp,themappingswouldlooklikeExample5-1.

Example5-1.ServletmappingforaprecompiledJSP

<servlet>

<servlet-name>org.apache.jsp.precomp_jsp</servlet-name>

<servlet-class>org.apache.jsp.precomp_jsp</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/precomp.jsp</url-pattern>

</servlet-mapping>

Youcanthencutandpastetheseservletandservlet-mappingelementsintotheweb.xmldeploymentdescriptorforyourwebapplication.

The-webappswitchspecifiesaweb-applicationdirectory,whichmustinturnhavea/WEB-INFsubdirectorycontainingyourapplication'sweb.xmlfile.JspCfindsallofthe.jspfilesatthetoplevelofthisweb-applicationdirectoryandtranslatesthemintoservletsourcefiles,alongwithanyJSPsinnestedsubdirectories.Theresulting.javafilesareplacedinthedirectoryspecifiedwiththe-dswitch.Unlike-webinc,the-webxmlswitchcreatesanentireweb.xmlfilethatincludesthenewservletsandservletmappings.SeveralotherJspCoptionsaredescribedhere:http://cvs.apache.org/viewcvs/~checkout~/jakarta-tomcat-4.0/jasper/doc/jspc.html.

http://cvs.apache.org/viewcvs/~checkout~/jakarta-tomcat-4.0/jasper/doc/jspc.html

You'llthenneedtocompilethegeneratedsourcefiles.Irecommendusingabatchfiletotakecareofbothstepsatonce.TheWindowsbatchfileinExample5-2generatesthesourcefilesandusesthejavactooltocompiletheservlets.

Example5-2.UsingabatchfiletoprecompileJSPswithTomcat

@echooff

jspc-dH:\book\cookbook\classes-webincH:\book\cookbook\map.xml-webapph:\book\

cookbook\dist

setPRECLASSPATH=%CATALINA_HOME%\common\lib\servlet.jar;

%CATALINA_HOME%\common\lib\jasper-runtime.jar;%CLASSPATH%

javac-classpath%PRECLASSPATH%-d./classes*.java

Savethisfileinatextfilewithanamelikeprecomp.bat.Changetothedirectorycontainingthebatchfileandtypeprecomp.ThisbatchfilerunstheJspCcommandonall.jspfilesexistingbeneaththeh:\book\cookbook\distweb-applicationdirectory.Usingthe-webincswitch,thecommandcreatesanXMLfragmentofservletandservlet-mappingelementsasshownearlierinthisrecipe.Iftherearenoproblems,thecompiledfileswillbestoredintheh:\book\cookbook\classesdirectory.

ThecodethencreatesaPRECLASSPATHenvironmentvariablethatincludestheservlet.jarandjasper-runtime.jarcomponents,alongwithanydirectoriesorJARsthatarepartoftheexistingCLASSPATHenvironmentvariable.Theservlet.jarcomponentisnecessarytoimporttheseJavapackagesduringcompilation:

javax.servlet

javax.servlet.http

javax.servlet.jsp

Addingthejasper-runtime.jarisnecessarytoimporttheorg.apache.jasper.runtimepackage.OnWindows,youmayhavetosetaJASPER_HOMEenvironmentvariabletotheTomcatinstallationdirectorybeforethisbatchfilerunsproperly.

Example5-3showsaUnixshellscriptthataccomplishesthesametask.Thisscriptexecutesthejspc.shfileinTomcat's/bindirectory,precompilingalloftheJSPfilesthattheJspCtoolfindsinthecurrentworkingdirectory.Thescriptstorestheresulting.javafilesinthe./classesdirectory.

Example5-3.AshellscriptforprecompilingJSPfiles

#!/bin/sh

$CATALINA_HOME/bin/jspc.sh-d./classes-webinc./map.xml-webapp./;

PRECLASSPATH=$CATALINA_HOME/common/lib/servlet.jar:$CATALINA_HOME/common/lib/jasper-

runtime.jar;

exportPRECLASSPATH;

javac-classpath$PRECLASSPATH-d./classes./classes/*.java

SeeAlso

Recipe5.3ontheprecompilationprotocol;Recipe5.4onmappingthecompiledJSP(s)inweb.xml;theJSPprecompilationsectionofJavaServerPagesbyHansBergsten(O'Reilly);ChapterJSP.11.4oftheJSP2.0specification.

Recipe5.2PrecompilingaJSPinWebLogic

Problem

YouwanttoprecompileaJSPinWebLogic.

Solution

Usetheweblogic.jspcJavautilitythatinstallswithWebLogicServer7.0.

Discussion

WebLogicServer7.0installswithitsownJavautilityforprecompilingJSPs:weblogic.jspc.ThisutilityispartoftheJARfilethatcanbefoundatthislocation:<WebLogic-install-directory>/weblogic700/server/lib/weblogic.jar.WhenyouprecompileJSPsusingweblogic.jspc,itplacestheclassfilesinthespecifieddestinationdirectory.Example5-4showsasimplebatchfileonWindowsNTthatprecompilesanexample.jspJSPpageintoitsservletimplementationclass.

Example5-4.PrecompilingaJSPwithweblogic.jspc

@echooff

setWLCLASSPATH=k:\bea\weblogic700\server\lib\weblogic.jar;%CLASSPATH%

java-cp%WLCLASSPATH%weblogic.jspc-d.\classesexample.jsp

ThesecondlineofExample5-4setsanenvironmentvariable,WLCLASSPATH.Thisvariableprependsareferencetoweblogic.jartotheexistingCLASSPATHvariable.Thenextlineoftheexampleusesthis

combinedclasspathtorunweblogic.jspc.The-dswitchtellstheprogramwheretostoretheresultingclassfiles,inthiscase,intheclassesdirectorybeneaththedirectorycontainingthebatchfileandexample.jsp.ThisprogramgeneratesaJavaclassfilenamedjsp_servlet.__example.class(includingthepackagename).Ifyoudonotspecifyapackageforthecompiledservlet,jsp_servletisusedasthedefaultpackagename(seeExample5-6).Example5-5showsashellscriptthatiswrittenonMacOSXforprecompilingaJSPwithWebLogic.

Example5-5.PrecompilingJSPswithweblogic.jspcandashellscript

#!/bin/sh

WLCLASSPATH=/Users/bruceper/java/weblogic_jar/weblogic.jar:$CLASSPATH;

exportWLCLASSPATH;

java-cp$WLCLASSPATHweblogic.jspc

-d/Users/bruceper/books/cookbook/code/chap5/classesnewfile.jsp

weblogic.jspcisdifferentfromTomcat'sJspCutilityinthatitcompilesafileinJSPpagesyntaxintotheservletclassfileinasingleoperation.UsingTomcat'sJspCfromthecommandlinerequirestheuseofacompiler,suchasjavac,tocompilethe.javafilesgeneratedbyJspCintoclassfiles.ThissecondcompilationstepwhenusingJspCishandledautomaticallywhenusingweblogic.jspc.

TheWindowsbatchfileinExample5-6specifiesajspservletcookbookpackageforalltheJSPpagesfoundinthewebapplicationspecifiedbythe-webappswitch.

Example5-6.Usingweblogic.jspctoprecompileallJSPpagesinawebapplication

@echooff

setWLCLASSPATH=k:\bea\weblogic700\server\lib\weblogic.jar;%CLASSPATH%

java-cp%WLCLASSPATH%weblogic.jspc-d.\classes-packagejspservletcookbook-compileAll

-webapph:/home

Example5-7showsaUnixshellscriptthatdoesthesamething.

Example5-7.PrecompilingallJSPpagesinawebapplicationwithashellscript

#!/bin/sh

WLCLASSPATH=/Users/bruceper/java/weblogic_jar/weblogic.jar:$CLASSPATH;

exportWLCLASSPATH;

java-cp$WLCLASSPATHweblogic.jspc-d/Users/bruceper/books/cookbook/code/chap5/classes

-packagejspservletcookbook-compileAll-webapp/Users/bruceper/books/cookbook/code/chap5

Notethisportionoftheinstructionintheexample:

-compileAll-webapph:/home

The-compileAllswitch,alongwithanargumentto-webapp,tellsweblogic.jspctoprecompilealltheJSPfilesfoundinthewebapplicationconfiguredintheh:\homedirectory,includinganyJSPfilesnestedinsubdirectories.Thiswebapplicationisinexplodeddirectoryformat(notarchivedintoaWARfile).InExample5-6,thecompiledclassesarestoredinthe\classes\jspservletcookbookdirectorypath.

SeeAlso

Recipe5.3ontheprecompilationprotocol;Recipe5.4onmappingthecompiledJSP(s)inweb.xml;theJSPprecompilationsectionofJavaServerPagesbyHansBergsten(O'Reilly);ChapterJSP.11.4oftheJSP2.0specification.

Recipe5.3PrecompilingJSPswiththePrecompilationProtocol

Problem

Youwanttousethe"precompilationprotocol"thatispartoftheJSPspecificationtoprecompileoneormoreJSPfiles.

Solution

SendarequesttotheJSPcontainerthatincludesajsp_precompileparameter.

Discussion

TheJSP1.2and2.0specificationsrequirecompliantJSPcontainerstosupporttheuseofthejsp_precompilerequestparameter.ThisparametersuggeststhatthecontainerprecompiletherequestedJSP.HereishowitworksinTomcat:

1. RequesttheJSPthatyouwantprecompiledwiththejsp_precompileparameteraddedtotheURL,asinhttp://localhost:8080/home/url_rewrite.jsp?jsp_precompile=true.

TheJSPcontainerisnotsupposedtoexecutetheJSPpage;itjustprecompilesit.Theresultoftherequest,ifyouweremakingitinawebbrowser,isablankpage.

IftheJSPfileinJSPpagesyntaxhasnotyetbeencompiled,oriftheJSPfilehasbeenchangedandhasalatermodificationdatethanany

existingpageimplementationclass,TomcatcreatesanewJavasourceandclassfilefortheJSPinthe<Tomcat-install-directory>/workdirectory.IftheJSPfileisnamedurl_rewrite.jsp,TomcatcallstheJavasourceandclassfilesurl_rewrite_jsp.javaandurl_rewrite_jsp.class.

Supplyingtherequestparameterjsp_precompile(withoutthe"=true"part)isthesameasrequestingjsp_precompile=trueintheURL.

TheprecompilationprotocolinTomcatwillbothcreatethe.javafileandcompilethatfileintotheJSPpageimplementationclass.UsingtheJspCtoolasdescribedinRecipe5.1willgenerateonlya.javafile.

ThisprotocolisbestusedwithanautomatedtoolthatcanmakeHTTPrequests,suchastheJakartaCommonsHttpClientcomponent.UsingsuchatoolallowsyoutoautomatetheprecompilationofdozensofJSPsbysendingseveralHTTPrequestsfromasingleJavaprogram.

SeeAlso

Recipe5.1onusingTomcat'sJspCutility;Recipe5.2onprecompilingwithWebLogicServer;Recipe5.4onmappingthecompiledJSPsinweb.xml;Chapter7onsendingHTTPrequestsfromaservletoraJSP;theJakartaCommonsHttpClienthomepageathttp://jakarta.apache.org/commons/httpclient/;TheJSPprecompilationsectionofJavaServerPagesbyHansBergsten(O'Reilly);ChapterJSP.11.4oftheJSP2.0specification.

http://jakarta.apache.org/commons/httpclient/default.htm

Recipe5.4MappingaJSPtoItsPageImplementationClass

Problem

YouhavealreadyprecompiledaJSPandwanttospecifyamappingtotheJSPpageimplementationclassinyourdeploymentdescriptor.

Solution

Cutandpastetheservletandservlet-mappingelementsgeneratedautomaticallybyJspCintoweb.xml.Createtheproperpackage-relateddirectoriesintheWEB-INF/classesdirectoryofyourwebapplication,thenplacetheprecompiledJSPsintothatdirectory.

Discussion

PrecompilingJSPsallowsyoutoremovetheJSPpagesyntaxfilesfromyourwebapplicationandjustusetheresultingservletclassfiles.Youcanthenusetheservlet-mappingelementinweb.xmltomapaJSP-styleURL(e.g.,default.jsp)tothecompiledservletclass.Hereishowtoaccomplishthistask:

1. PrecompiletheJSP(s)asdescribedinRecipe5.1orRecipe5.2,includingthecompilationofJavasourcefilesintoclassfilesusingjavacoranothercompilertool.

Cutandpastetheservletandservlet-mappingelementsgeneratedautomaticallybyJspCintoyourdeploymentdescriptor(ifyouareusingTomcat),oraddthoseelementsmanuallytoweb.xml(ifyouare

usingWebLogicoranothercontainer).

Makesuretheservlet-mapping'surl-patternelementpointstoaJSP-stylefilename,suchasdefault.jsp,oranextensionmappingsuchas*.jsp.

Placetheclassorclasses,includingthepackage-relateddirectories,inWEB-INF/classes,orinsideofaJARfilethatisstoredinWEB-INF/lib.

WhenthewebusersrequesttheURLspecifiedbytheservlet-mappingforthatJSPpageimplementationclass,thewebcontainerwillnowdirectthatrequesttothemappedservletclass.

Example5-8showsaservletconfigurationforaprecompiledJSP.

Example5-8.Aweb.xmlentryforaprecompiledJSP

<servlet>


<servlet-class>org.apache.jsp.precomp_jsp</servlet-class>

</servlet>

<servlet-mapping>


<url-pattern>/precomp.jsp</url-pattern>

</servlet-mapping>

Thedirectorystructureforthisclassinyourwebapplicationshouldbesomethinglike:/WEB-INF/classes/org/apache/jsp/precomp_jsp.class.Ifthecontextpathforyourwebapplicationis/home,userscanrequestthisJSP'simplementationclass(aservlet,behindthescenes)withaURLsimilartohttp://localhost:8080/home/precomp.jsp.

SeeAlso

Recipe5.1-Recipe5.3;ChapterJSP.11.4oftheJSP2.0specification.

Recipe5.5CreatingaJSPfromScratchasaJSPDocument

Problem

YouwanttocreateaJSPdocumentinanXMLeditor'stool.

Solution

OpenupyourXMLeditorofchoiceandcreatetheJSPusingonlyXMLelements.

Discussion

AJSPdocumentisanamespace-aware,well-formedXMLfilethatcontainsJSPstandardactions(suchasjsp:includeandjsp:useBean),customactions(suchasJSTLcustomtags),andtheXMLequivalentsofJSPdirectives.Table5-1specifiestheXMLequivalentsforcommonJSPdirectives.WritetheJSPdocumentinanXMLeditor,preferablyonewhereyoucancheckitswell-formedness.TheJSPdocumenthastobeawell-formedXMLdocumenttobeeligibleforplacementintoaJSPcontainerandexecution.

Table5-1.XMLequivalentsforJSPdirectives

Directive Example JSPdocumentequivalent

<page><%@pageimport="java.util.Date"%> <jsp:directive.pageimport="java.util.Date"/>

<include><%@includefile="footer.html"%> <jsp:directive.includefile="footer.html"/>

<taglib>

<%@tagliburi="WEB-INF/tlds/xml_gen.tld"prefix="t"%>

<jsp:rootjsp:id="0"xmlns:jsp="http://java.sun.com/JSP/Page"version="2.0"xmlns:t="urn:jsptld:/WEB-INF/tlds/xml_gen.tld">

InJSP1.2,theonlywaytoidentifyaJSPpageasXMLisbyhavingajsp:rootelementastheroot.However,JSP2.0offersseveralnewoptionstheJSP2.0specificationstatesthataJSPdocumentcanalsobedistinguishedfromaJSPinnon-XMLsyntaxbyajsp-property-groupelementinthedeploymentdescriptor,a.jspxfileextension,orajsp:rootrootelement.

ThisrecipeshowsasimpleJSPpageanditsXMLequivalent,thenrepeatsthecomparisonwiththeadditionofacustomtagandaruntimeexpressionforaJSPelementattribute.Example5-9isasimplefileinJSPpagesyntaxshowingthewebserver'slocaltime.

Example5-9.AsimpleJSPpage-syntaxfile

<%@pagecontentType="text/html"%>

<%@pageimport="java.util.Date"%>

<html>

<head><title>WelcometotheWeb</title></head>

<body>

<h2>WelcometotheWeb</h2>

Theserver'slocaltimeis<%=newDate()%>.

</body>

</html>

ThisJSPhastwopagedirectivesandaJSPexpressionthatdisplaysadateandtimestringonthebrowserpage.Figure5-1showstheexecutionofthispageinabrowser.

Figure5-1.SimpleJSPbeforeXMLconversion

ThispagecanbeconvertedintoaJSPdocumentbycuttingandpastingthecodeintoanXMLeditorandreplacingnon-XMLconstructswithXMLelements.Example5-10istheJSPdocumentequivalentofExample5-9.

Example5-10.AsimpleJSPdocumentaswell-formedXML

<jsp:rootxmlns:jsp="http://java.sun.com/JSP/Page"version="2.0">

<jsp:directive.pagecontentType="text/html"/>

<jsp:directive.pageimport="java.util.Date"/>

<html>


<body>


Theserver'slocaltimeis<jsp:expression>newDate()</jsp:expression>.

</body>

</html>

</jsp:root>

Example5-10hasjsp:directive.pageelementsinsteadoftraditionalJSPdirectives,whicharenotvalidXMLelementsbecauseofthe<%@syntax.AnythinginaJSPpagethatuses<%-styledelimiterscannotbeusedtodistinguishJSPelements,becausethentheJSPdocumentwillnotpassanXMLwell-formednesstest.

Example5-11isamorecomplexJSPpagewithataglibdirectivethatspecifiesthecoretaglibraryfromJSTL1.0;thepagealsouses

ExpressionLanguage(EL)code.Further,thepagehasajsp:useBeanelementthatsetsajava.util.DatevariabledateStringtopagescope.

Example5-11.AJSPpagepresentingacomplexXMLconversion



<html>


<body>


Hello,<c:outvalue="${param.firstName}${param.lastName}"/><br><br>

<jsp:useBeanid="dateString"class="java.util.Date"/>

Thetimeis<c:outvalue="${dateString}"/>.<br><br>

Thevalueof10+24+35=<c:outvalue="${10+24+35}"/>

</body>

</html>

Example5-12isthesameJSPpageconvertedtoaJSPdocument.

Example5-12.Referringtotaglibraries(taglibs)inaJSPdocument

<jsp:rootxmlns:jsp="http://java.sun.com/JSP/Page"

xmlns:c="http://java.sun.com/jstl/core"version="2.0">


<html>


<body>


<jsp:text>Hello</jsp:text>

<c:outvalue="${param.firstName}${param.lastName}"/><br></br><br></br>


<jsp:text>Thetimeis</jsp:text><c:outvalue="${dateString}"/>.

<br></br><br></br>

<jsp:text>Thevalueof10+24+35=</jsp:text>

<c:outvalue="${10+24+35}"/>

</body>

</html>

</jsp:root>

InaJSPdocument,anytaglibrariescanbeincludedasnamespaceattributes,suchasinthejsp:rootelement,asshownhere:


xmlns:c="http://java.sun.com/jstl/core"version="2.0">

Thejsp:textelementcanbeusedtocontainanytemplatedataintheJSPdocument.YoucanusetheJSPstandardactionssuchasjsp:useBeanandcustomtagslikec:outwiththesamesyntaxusedinaJSPpage.

Figure5-2showsthebrowseroutputoftheJSPdocumentinExample5-12.ThispagewasrequestedbyusingthisURL:http://localhost:8080/home/example_xml2.jsp?firstName=Bruce&lastName=Perry.

Figure5-2.OutputfromExample5-11

HereiswhattheHTMLsourcecodelookslike,ifyouchose"ViewSource"fromthebrowsermenu(withsomecarriagereturnsaddedforreadability):

<html><head><title>WelcometotheWeb</title></head>

<body>


HelloBrucePerry<br/><br/>

ThetimeisMonFeb1016:20:05EST2003.<br/><br/>

Thevalueof10+24+35=69

</body></html>

SeeAlso

Recipe5.6ongeneratinganXMLviewfromaJSP;ChapterJSP.6(JSPdocuments)oftheJSP2.0specification;ChapterJSP.10(XMLviews)oftheJSP2.0specification.

Recipe5.6GeneratinganXMLViewfromaJSP

Problem

YouwanttoautomaticallygenerateanXMLviewfromaJSPpage.

Solution

CreateacustomtagandaTagLibraryValidatorclass,fromwhichyoucanoutputtheXMLviewofaJSPtoafile.

Discussion

AnXMLviewisanXMLformofaJSPpagethattheJSPcontainergeneratesduringthetranslationphase,anintermediarystagebeforethecontainerconvertstheJSPtoitspageimplementationclass(aservlet).ATagLibraryValidatorclasscanusetheXMLviewtovalidatetheuseofcustomtagsintheJSPpriortotheJSP'sconversiontoaservlet.AnXMLviewisverysimilartoaJSPdocument,whichisanXMLformofaJSPpagethatJSPdeveloperscanwriteandaddtotheirwebapplications.ThedifferencesbetweenthetwoXMLfilesaccordingtotheJSPspecificationv2.0are:

AnXMLviewexpandsanyincludedirectivesthataJSPdocumentcontainsintotheircorrespondingJSPfragments.

AnXMLviewprovideseachXMLelementwithajsp:idattribute.

AnXMLviewaddsajsp:rootelementastherootelementofthedocumentifthedocumentdoesnotalreadyhaveajsp:root

element.

AnXMLviewaddsajsp:directive.pageelementandpageEncodingattributeiftheydonotalreadyexist,andsetsthevalueofpageEncodingto"UTF-8".

AnXMLviewaddsajsp:directive.pageelementandcontentTypeattributeiftheydonotalreadyexist,andsetsthevalueofcontentTypeaccordingtoChapterJSP.4.2,"ResponseCharacterEncoding,"oftheJSP2.0specification(e.g.,"text/xml"foraJSPdocument).

Javadeveloperscanaddsubclassesofjavax.servlet.jsp.tagext.TagLibraryValidatortotheirwebapplicationsastoolsforvalidatingtheapplication'suseofcustomtags.TheJSPcontainer(JasperisthenameoftheTomcatJSPcontainer)makesavailabletotheTagLibraryValidatoranXMLviewofaJSPpageforthepurposeofparsingXMLelementsinthepageandvalidatingwhetherornottheyhavebeenusedcorrectly.

ItisusefultoexaminetheXMLviewofaJSPpageinordertodebugaTagLibraryValidatorclassthatyouareusinginacustomtaglibrary,ortoopenupyourJSPinanXMLeditorandevaluateitssyntaxfromanXMLperspective.Hereisaniceway(okay,abitofahack!)toautomaticallygenerateafilerepresentingtheXMLviewofaJSPpage.Thisrecipeusesajavax.servlet.jsp.tagext.PageDataobject,whichautomaticallyreturnstheXMLviewofaJSPpageasajava.io.InputStream.Hereishowitworks:

1. Createaclassthatextendsjavax.servlet.jsp.tagext.TagLibraryValidator.Theseclassesareusedtovalidatetheuseofcustomtags,andareexplainedinmoredetailinChapter23.

OverridetheTagLibraryValidator.validate(Stringprefix,Stringuri,PageDatapage)methodtowritetheXMLview

informationfromthePageDataparametertoafile.

Createasimplecustomtagbyextendingjavax.servlet.jsp.tagext.TagSupport.Thistag"marks"aJSPpagesothatitsXMLviewcanbeoutputtoafile.Thetagincludesa"filename"attributefromwhichyourvalidatorclasswillgetthefilenamefortheXMLview.Thetaglookslikethis:

<t:toxmlfilename="myxml_view"/>

CreateaTagLibraryDescriptor(TLD)fileforthistaglibrary,specifyingtheTagLibraryValidatorclassyoucreatedasthevalidatorforthislibrary:

<validator>

<validator-class>

com.jspservletcookbook.ToXmlValidator

</validator-class>

<description>

SavesXMLviewsofJSPpagestothe

specifieddirectory.

</description>

</validator>

PlaceboththeTagLibraryValidatorandtheTagSupportclassesintheWEB-INF/classesdirectoryofthewebapplication,orinsideaJARfilethatisstoredinWEB-INF/lib(theexamplesinthisrecipeassumethisformat,ratherthanplacingtheclassesinaJAR).

PlacetheTLDfileintheWEB-INF/tldsdirectory.

AddataglibelementreferringtoyourtagsandTLDtotheWEB-INF/web.xmldeploymentdescriptor.

Thetaglibelementinweb.xmlisnotneededwithJSPVersion1.2and2.0,sincetheJSPcontainerautomaticallysearchesWEB-INF,aswellastheMETA-INF

directoryofyourapplication'sJARfiles,foranyfilethatendswiththeextension.tld.

8. CreateapropertiesfilecontainingthedirectorypaththatyouwanttousefortheautomaticallygeneratedXMLview.StorethispropertiesfileinWEB-INF/classesusingtheappropriatepackagenames.Thispropertiesfileisusedtoavoidthehardcodingofanabsolutedirectoryinthevalidatorclass'scode.

UsethecustomtagintheJSPfile(s)forwhichyouwanttheXMLviewsgeneratedasfiles.

First,Example5-13showstheXMLview-relatedcustomtaginaJSPfile.

Example5-13.GeneratingtheXMLviewofaJSPpage

<%@tagliburi="/toxml_view"prefix="t"%>

<html>

<head>

<title>Testtld</title>

</head>

<bodybgcolor="#ffffff">

Hello,thispageisusingthetoxmltagtolookatitsXMLView.

<t:toxmlfilename="my_xmlview"/>

</body>

</html>

Thet:toxmltagisanemptyelementthatsignalsthevalidatorclasstogenerateafilecontaininganXMLview.Thefilewillbenamedmy_xmlview.xml(thevalidatorclassaddsthe.xmlextension).Thetag

otherwisehasnoeffectontheappearanceorbehaviorofthisJSP.ThefollowingfragmentofthedeploymentdescriptorshowsthetaglibelementspecifyingtheURIthatisusedinExample5-11staglibdirective.ThetaglibelementinthedeploymentdescriptoralsospecifiesthelocationoftheTLDfile(WEB-INF/tlds/xml_gen.tld):

<taglib>

<taglib-uri>/toxml_view</taglib-uri>

<taglib-location>/WEB-INF/tlds/xml_gen.tld</taglib-location>

</taglib>

Example5-14showstheTLDfileforthistaglibrary,whichspecifiesthevalidatorclassandthesimplecustomtag(amarker)usedinExample5-11.Iamnotgoingtoshowthecodeforthetoxmltag,sinceitdoesnotcontainanycodeofinterest,beyondthefactthatithasoneStringmembervariablecalledfilename.Thesolepurposeofthetag'suseistoputthevalidatorclasstowork.TheJSPcontainercreatesonevalidatorinstanceforeachtaglibrarythatincludesavalidatorclass.

Example5-14.TheTLDfilefortheXMLviewcustomtag


<!DOCTYPEtaglib

PUBLIC"-//SunMicrosystems,Inc.//DTDJSPTagLibrary1.2//EN"

"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">

<taglib>

<tlib-version>1.0</tlib-version>

<jsp-version>1.2</jsp-version>

<short-name>Validatortest</short-name>

<description>Validatortest</description>

<validator>

<validator-class>

com.jspservletcookbook.ToXmlValidator

</validator-class>

<description>

SavesXMLviewsofJSPpagestothespecified

directory.

</description>

</validator>

<tag>

<name>toxml</name>

<tag-class>com.jspservletcookbook.ToXml</tag-class>

<body-content>EMPTY</body-content>

<description>

ThistagdemonstratestheproductionofJSPXMLviewfiles.

</description>

<attribute>

<name>filename</name>

<required>true</required>

<rtexprvalue>false</rtexprvalue>

<description>

Thisattributeprovidesthefilename.</description>

</attribute>

</tag>

</taglib>

Thecom.jspservletcookbook.ToXmlValidatorclass,thelibrary'svalidator,executesitsvalidatemethodwhenaJSPpageusingthetoxmltagisloaded.HowdoesthevalidatorclassknowwheretosavethefilesrepresentingtheJSP'sXMLview?Thecom.jspservletcookbook.ToXmlValidatorclassderivesthedirectorypathforsavingitsgeneratedfilesfromthepropertiesfileshownbelow.ThisallowsanydeployerofthecustomtagtochangethedirectoryforthesavedXMLviews,withouttouchingthevalidatorclass'ssourcecode.Thepropertiesfileislocatedinthesamedirectoryasthevalidatorclass.ThepathtothispropertiesfileisWEB-INF/classes/com/jspservletcookbook/validator.properties:

directory=h:/home/xmlviews

Thefilenameisprovidedbythetagitself,asin:

<t:toxmlfilename="my_xmlview"/>

TheentirefilepathfortheXMLviewlookslike:h:/home/xmlviews/my_xmlview.xml.

Thevalidatorclassaddsthe.xmlextensionwhenitcreatestheXMLviewfile.ThevalidatorfirstextractsthefilenamefromthetoxmltagbyusingaSAXparsertoparsetheinputstreamfromthejavax.servlet.jsp.tagext.PageDataobject.

Younowhaveallofthepiecestogetherexceptfortheall-importantvalidatorclass,whichisshowninExample5-15.Thevalidatemethodreadsthedirectorypropertyvalueusingajava.util.ResourceBundleobject.ThevalidatemethodgetsthefilenamebyusingthehelperclassthatExample5-16shows.ThevalidatemethodthengeneratestheXMLviewoftheJSPpagebyusingthejava.io.InputStreamreturnedfromPageData.getInputStream().

Example5-15.AvalidatorclassforgeneratingXMLviewfiles


importjavax.servlet.jsp.tagext.TagLibraryValidator;

importjavax.servlet.jsp.tagext.ValidationMessage;

importjavax.servlet.jsp.tagext.PageData;

importjava.io.*;

importjava.util.ResourceBundle;

importjava.util.MissingResourceException;

importjava.util.Date;

publicclassToXmlValidatorextendsTagLibraryValidator{

/**CreatesnewToXmlValidator*/

publicToXmlValidator(){

}

publicValidationMessage[]validate(java.lang.Stringprefix,

java.lang.Stringuri,PageDatapage){

ValidationMessage[]vam=null;

try{

ResourceBundlebundle=

ResourceBundle.getBundle("com.jspservletcookbook.validator");

Stringdirectory=bundle.getString("directory");

StringfileName=getFilename(page);

//throwanExceptionifthedirectoryisinvalid

if(directory==null)

thrownewException(

"ReceivedanulldirectoryfortheXMLviewfile.");

//throwanExceptionifthefilenameisinvalid

if(fileName==null)

thrownewIOException(

"ReceivedanullfilenamefortheXMLviewfile.");

Filefile=newFile(directory+"/"+fileName+".xml");

FileWriterwriter=newFileWriter(file);

BufferedReaderin=newBufferedReader(

newInputStreamReader(page.getInputStream()));

Stringline="";

//writetheXMLviewtothespecifiedfile

while((line=in.readLine())!=null){

writer.write(line);

}

in.close();

writer.close();

}catch(IOExceptionio){

//returnavalidationmessage

ValidationMessagevmsg=new

ValidationMessage(null,io.getMessage());

vam=newValidationMessage[1];

vam[0]=vmsg;

returnvam;

}catch(MissingResourceExceptionmre){



ValidationMessage(null,mre.getMessage());


vam[0]=vmsg;

returnvam;

}catch(Exceptione){



ValidationMessage(null,e.getMessage());


vam[0]=vmsg;

returnvam;

}

//returnemptyarray


returnvam;

}

privateStringgetFilename(PageDatapage)throwsException{

try{

ValidateHandlerhandler=newValidateHandler();

returnhandler.getFilename(page);

}catch(Exceptione){

throwe;}

}

}

Example5-16showstheValidateHandlerhelperclassthatourvalidatorusestogetthefilenamefromthecustomtag.TheValidateHandlermakesafirstpassthroughtheXMLview(beforeitiswrittentoafile)toextractthefilenamethattheuserhasaddedwiththetoxmlelement'sfilenameattribute.TheValidateHandlerdoesalltheworkbehindthescenestoparsetheXMLsothatthevalidatorclasscangetthefilenamewithasimplemethodcall:

ValidateHandlerhandler=newValidateHandler();

returnhandler.getFilename(page);

TheValidateHandlerusestheJavaAPIforXMLprocessing(JAXP)andtheSimpleAPIforXML(SAX)toparsetheXMLprovidedbyjavax.servlet.jsp.tagext.PageData.getInputStream().YouhavetoplacetheValidateHandlerclassinsideoftheWEB-INF/classesdirectory(orinsideofaJARfileinWEB-INF/lib)sothatyourwebapplication(theToXmlValidatorclass)canfindit.YoucanuseanycomponentyouwanttoprovidetheSAXfunctionalitythatawebapplicationneeds.IfyouchoosetouseJAXP,andyourwebcontainerisnotyetbundledwiththenecessaryJAXPcomponents,thenaddthefollowingJARfilestoyourWEB-INF/libdirectoryforacompleteJAXPinstallation:jaxp-api.jar,dom.jar,sax.jar,xalan.jar,xercesImpl.jar,andxsltc.jar.YoucandownloadthesecomponentsaspartoftheJavaWebServicesDeveloperPack(http://java.sun.com/webservices/webservicespack.html),andtheJAXPlibrariesareincludedaspartofJava1.4.x.

Example5-16.ADefaultHandlerthatgrabsthefilenamefromthecustomtagattribute

importorg.xml.sax.Attributes;

http://java.sun.com/webservices/webservicespack.html

importorg.xml.sax.SAXParseException;

importorg.xml.sax.SAXException;

importorg.xml.sax.helpers.DefaultHandler;

importjavax.xml.parsers.SAXParserFactory;

importjavax.xml.parsers.FactoryConfigurationError;

importjavax.xml.parsers.ParserConfigurationException;

importjavax.xml.parsers.SAXParser;


importjavax.servlet.jsp.tagext.PageData;

publicclassValidateHandlerextendsDefaultHandler{

privateStringfileName="";

publicvoidstartElement(StringnameSpaceuri,

Stringsname,Stringqname,Attributesattrs){

for(inti=0;i<attrs.getLength();i++)

if("filename".equals(attrs.getLocalName(i)))

this.fileName=attrs.getValue(i);

}

publicStringgetFilename(PageDatapage)

throwsFactoryConfigurationError,ParserConfigurationException,

SAXException,IOException{

try{

SAXParserFactoryfactory=SAXParserFactory.newInstance();

factory.setNamespaceAware(true);

SAXParsersaxparser=factory.newSAXParser();

saxparser.parse(page.getInputStream(),this);

}catch(FactoryConfigurationErrorfe){

throwfe;

}catch(ParserConfigurationExceptionpce){

throwpce;

}catch(SAXExceptionse){

throwse;

}catch(java.io.IOExceptionio){

throwio;

}finally{

returnthis.fileName;}

}

publicvoiderror(SAXParseExceptione)

throwsSAXParseException

{

throwe;

}

}

Example5-17showstheXMLviewgeneratedfromtheJSPpageofExample5-13(withsomecarriagereturnsadded).Itmightbeugly,butnowyouknowwhatanXMLviewlookslike!TheHTMLcodeisalltreatedastemplatedata,enclosedinajsp:textelementandCDATAsections.ThetwoXMLelements,jsp:rootandt:toxml,aregivensequentialIDnumbersaspartoftheirjsp:idattributesintheXMLview.TheTagLibraryValidatorclasscanusetheseIDstoprovidefinelygrainedXML-relatedmessagesinvolvingthevalidatedJSPpage.

Example5-17.TheXMLviewofExample5-13

<jsp:rootjsp:id="0"xmlns:jsp="http://java.sun.com/JSP/Page"version="1.2"

xmlns:t="/toxml_view">

<jsp:text><![CDATA[]]></jsp:text>

<jsp:text><![CDATA[<html>]]></jsp:text>

<jsp:text><![CDATA[<head>]]></jsp:text>

<jsp:text><![CDATA[<title>Testtld]]></jsp:text>

<jsp:text><![CDATA[</title>]]></jsp:text>

<jsp:text><![CDATA[</head>]]></jsp:text>

<jsp:text><![CDATA[<bodybgcolor="#ffffff">Hello,thispageisusingthetoxmltagto

lookatitsXMLView.]]></jsp:text>

<t:toxmljsp:id="1"filename="my_xmlview"/>

<jsp:text><![CDATA[]]></jsp:text>

<jsp:text><![CDATA[</body>]]></jsp:text>

<jsp:text><![CDATA[</html>]]></jsp:text>

</jsp:root>

SeeAlso

Recipe5.5oncreatingaJSPfromscratchasaJSPdocument;ChapterJSP.6(JSPdocuments)oftheJSP2.0specification;ChapterJSP.10(XMLviews)oftheJSP2.0specification.

Chapter6.DynamicallyIncludingContentinServletsandJSPs

Introduction

Recipe6.1.IncludingaResourceEachTimeaServletHandlesaRequest

Recipe6.2.UsinganExternalConfigurationtoIncludeaResourceinaServlet

Recipe6.3.IncludingResourcesNestedatMultipleLevelsinaServlet

Recipe6.4.IncludingaResourcethatSeldomChangesintoaJSP

Recipe6.5.IncludingContentinaJSPEachTimetheJSPHandlesaRequest

Recipe6.6.UsinganExternalConfigurationFiletoIncludeaResourceinaJSP

Recipe6.7.IncludinganXMLFragmentinaJSPDocument

Recipe6.8.IncludingContentfromOutsideaContextinaJSP

Introduction

ServletsandJSPsoftenincludefragmentsofinformationthatarecommontoanorganization,suchaslogos,copyrights,trademarks,ornavigationbars.Thewebapplicationusestheincludemechanismstoimporttheinformationwhereveritisneeded,sinceitiseasiertochangecontentinoneplacethentomaintainitineverypieceofcodewhereitisused.Someofthisinformationisstaticandeitherneverorrarelychanges,suchasanorganization'slogo.Inothercases,theinformationismoredynamicandchangesoftenandunpredictably,suchasatextualgreetingthatmustbelocalizedforeachuser.Inbothcases,youwanttoensurethattheservletorJSPcanevolveindependentlyofitsincludedcontent,andthattheimplementationoftheservletorJSPproperlyupdatesitsincludedcontentasnecessary.

ThischapterrecommendsrecipesforincludingcontentinbothservletsandJSPsunderseveralconditions:

Whentheincludedinformationisrefreshedeverytimeausermakesarequest.

Whentheincludedinformationinvolvestwoormorenestedlevelsforexample,whenanincludedfileinturnincludesanotherpieceofinformation,andsoon.

Whenyouwanttousethedeploymentdescriptortoupdatetheitemthataservletincludes,whichisahandy,lesserror-pronewayofincludingcontentwhenthecontentisconfigurableandchangesratheroften.

WhenyouwanttoimportresourcesintoaJSPfromoutsidethewebapplication.

Recipe6.1describeshowtoimportaresourceeachtimetheservlet

handlesarequest.

Recipe6.1IncludingaResourceEachTimeaServletHandlesaRequest

Problem

Youwanttoincludeinformationfromanexternalfileinaservleteachtimetheservlethandlesarequest.

Solution

Usethejavax.servlet.RequestDispatcher.include(request,response)

methodinthedoGet()methodoftheservletthatincludestheexternalfile.

Discussion

Includingthecontentinthejavax.servlet.http.HttpServlet'sdoGet()methodinitiatestheincludemechanismwheneverthewebcontainerreceivesaGETrequestfortheservlet.

Whenusingthisdesign,implementtheservlet'sdoPost()methodtocalldoGet(request,response).

Example6-1showsaservletthatimportsacopyrighttemplateinthedoGet()methodusingthe

javax.servlet.RequestDispatcher.include()method.

Example6-1.IncludingcontentintheHttpServlet'sinit()method




publicclassIncludeServletextendsHttpServlet{






out.println("<html>");

out.println("<head>");

out.println("<title>IncludeServlet</title>");

out.println("</head>");

out.println("<body>");

out.println("<h1>WelcomeToOurUniverse</h1>");

out.println("Imaginetherestofthepagehere.<br><br>");

//Includethecopyrightinformation

RequestDispatcherdispatcher=request.getRequestDispatcher(

"/copyright");

dispatcher.include(request,response);

out.println("</body>");

out.println("</html>");

}//doGet

}

Example6-1getsaRequestDispatcherobjectbycallingthejavax.servlet.ServletRequest.getRequestDispatcher()

method.TheparametertothegetRequestDispatcher()methodinthiscaseistheservletpathtotheresourcethattheincludeservletimports:/copyright.Thispathismappedinweb.xmltotheCopyrightservlet,whichisshowninExample6-2.

Example6-2.TheimportedCopyrightservlet

publicclassCopyrightextendsHttpServlet{





out.println("Copyright©2003-2004EmbraceAndExtendCorp.");

}

}

TheCopyrightservletoutputsalineoftextthatincludesthecharacterentitycodeforthecopyrightsymbol(©),sothatthecopyrightsymbolisdisplayedcorrectlyintheresultingHTML.Whentheimportingservletcallstheinclude()method,thecopyrighttextisinsertedinthemethodcall'scodelocation.

AservletcanimportanHTMLpage,aswellastheoutputofaJSPpageorservlet.IfyouareimportingHTMLfragmentsinthismanner,makesurethattheimportedtextdoesnotbreakyourHTMLpage,suchasbyrepeatingHTMLtagsorfailingtoclosecertaintags.

Figure6-1showsthepagegeneratedbytheIncludeServletina

browser.

Figure6-1.TheIncludeServlet'spageinabrowser

Recipe6.2describeshowtoconfiguretheimportedresourceinanexternalconfigurationfile,suchasweb.xml.

JasonHunter,whoprovidedatechnicalreviewofthisbook,pointsoutthatmanypeopleareusinganofflinebuildprocesstopregeneratestatic(e.g.,HTML)fileswhenalotofthesite'swebcontentusesincludes,suchasimportingheadersandfootersintomostofthewebsite'spages.Inmostcases,theservercanhandletherequestsforstaticfilesmuchmoreefficientlythanrequestsfordynamicpages(suchasaJSPthatincludesotherresources).SeeChapter3,ServletBestPractices,inthebookJavaEnterpriseBestPractices(O'Reilly).

SeeAlso

Recipe6.2andRecipe6.3onincludingresourcesinservlets;Recipe6.4-Recipe6.7onusingjsp:include,theincludedirective,aswellasincludingresourcesintoJSPdocumentsorXMLfiles;ChapterSRV.14.2.5oftheServlet2.4specification;ChapterJSP.5.4onoftheJSP2.0specificationonjsp:include;ChapterJSP.1.10.3oftheJSP

2.0specificationontheincludedirective.

Recipe6.2UsinganExternalConfigurationtoIncludeaResourceinaServlet

Problem

Youwanttouseanexternalconfigurationfile(suchasweb.xml)toconfiguretheresourcethatisincludedinaservlet.

Solution

Useinitparameterswiththeincludingservlettoallowtheexternalconfigurationoftheincludemechanism,thenincludetheresourcewiththejavax.servlet.RequestDispatcher.include(request,response)

method.

Discussion

Youmaywanttoperiodicallychangetheresourcethataservletincludes,withoutchangingandrecompilingtheservletcode.Youcanmakethesechangesbyalteringtheservlet'sinitparametersinweb.xml.Usingthisstrategy,eithertheincludedresource'sfilelocationitselforthemethodofretrievingtheresource(suchasfromadatabase)canchange.Youcanensurethattheservletimportsthecorrectresourcebyalteringthecontentoftheparam-valueelement.Example6-3showsaservletthatisconfiguredtoincludeafilenamedprivacy.jspf.Thisrepresentsastandardprivacystatementforthewebapplication.

Example6-3.Specifyinganincludedresourcebyusingtheservlet'sinit-paramelement

<servlet>

<servlet-name>PrivacyServlet</servlet-name>

<servlet-class>com.jspservletcookbook.IncludeServlet</servlet-class>

<init-param>

<param-name>included-resource</param-name>

<param-value>privacy.jspf</param-value>

<init-param>

</servlet>

Example6-4showsthedoGet()methodofthePrivacyServlet.Thismethodgetsthevalueoftheincluded-resourceinitparameter(privacy.jspf),thenincludestheJSPsegment.

Example6-4.Includingaresourcespecifiedbyaninitparameter








out.println("<title>IncludeServlet</title>");



out.println("<h1>WelcomeToOurUniverse</h1>");

out.println("Imaginetherestofthepagehere.<br><br>");

//Includetheprivacyinformationbasedonaninit-paramvalue

StringincludeRes=(String)getInitParameter(

"included-resource");

//getaRequestDispatcherobjectbasedontheinit-paramvalue

RequestDispatcherdispatcher=request.

getRequestDispatcher(includeRes);




}

Example6-4getsaRequestDispatcherrepresentingtheconfiguredinit-paramvaluewiththiscode:

//theincludeResvariableholdstheinit-paramvalue"privacy.jspf"

RequestDispatcherdispatcher=request.getRequestDispatcher(includeRes);

Thenthedispatcher.include(request,response)methodisreplacedbytheoutputoftheprivacy.jspffile.Example6-5showstheJSPsegmentthatthePrivacyServletincludes.TheJSP'scontenthassomeHTMLtagsthatfitintotheHTMLrepresentedbytheincludingpage.

Example6-5.AJSPsegmentincludedinaservletwithaRequestDispatcher

<%@pageerrorPage="/error.jsp"%>

<p><strong>ParkerRiverNetSolutionsPrivacyPolicy</strong></p>

<p>AnypersonalinformationyouprovidetousregardingWeb-orsoftware-development

servicesorsharewaresoftware,suchasyourname,address,telephonenumber,ande-mail

address,willnotbereleased,sold,orrentedtoanyentitiesorindividualsoutside

ofParkerRiverNetSolutions.</p>

Includedsegmentsorpagescannotsetorchangeresponseheaders,soanyattemptstosetthecontenttypeinanincludedservletorJSPasin:

<%@pagecontentType="text/xml"%>

areignored.

AlltheincludedJSPdoesisspecifyanerrorpagecomposedofsomeformatting-relatedHTMLtagsandtext.Figure6-2showsthebrowserpageforthePrivacyServlet.

Figure6-2.AwebpagewithanincludedJSPsegment

YoumayalsowanttoaugmentExample6-4toprovideadefaultresourceforinclusionintheservlet,justincasethedeploymentdescriptor(web.xml)mistakenlyomitsaninitparameterfortheservlet.ThemethodgetInitParameterreturnsnullintheeventofthisomission.Youcouldtestforthisnullconditionandthenprovideadefaultvaluefortheincludedstatement.

SeeAlso

Recipe6.3onincludingresourcesthathavenestedincludes;Recipe6.4-Recipe6.8onincludingresourcesinJSPs;ChapterSRV.14.2.5oftheServletRecipe2.4specification;ChapterJSP.1.10.3oftheJSP2.0specificationonincludingfilesinJSPs.

Recipe6.3IncludingResourcesNestedatMultipleLevelsinaServlet

Problem

Youwanttoincluderesourcesinaservletthatalreadyincludeservlets,JSPs,orHTML.

Solution


methodtoincludethetop-levelfile.Makesurethaterrorpagesareproperlyconfiguredinweb.xml,justincaseanexceptionisthrowninadeep-nested,importedfile.

Discussion

Eventhoughitdoesnotrepresentthebestarchitecturaldecision,itispossibleforaservlettoincludearesourcethatitselfincludesanotherresource,resultinginanumberofinclusionstakingplacebeneaththesurface.ImaginetheRussiandollsthatfitinsideeachother.Youunscrewthetophalfofthedolls,onlytofindsmallerreplicasofthedollsnestedinsidetheouterones.ItisnotoutlandishtothinkofverycomplexwebpagesusingHTMLframeandtabletags,containingheadersandfooters,withthesesegmentsofthepagecontainingotherspecializedcontentusinganincludemechanism.Oneoftheincludedfilesnestedseverallevelsdeepcouldthrowanexceptionorcorruptthechainofinclusionsinsomemanner.Althoughthereisnofoolproofwaytodefendagainstthisoccurrence,forthepurposesofdebugging,makesurethatthewebapplicationhasanerrorpageconfiguredsothatitcandisplayinformation

abouttheresourcethatranintoincludeproblems.

Thisrecipeprovidesanexampleofaservletthathasthreelevelsofincludedresources.TheouterservletincludesanotherservletnamedLevel2,whichincludesaJSPlevel3.jsp,whichcompletesthepicturebyincludingtheinnerservlet,Level4.Figure6-3showsthebrowserdisplaywhenauserrequeststhecom.jspservletcookbook.MultipleIncservlet.

Figure6-3.Threeincludedfilesinonewebpage

Example6-6showstheservletcode.Thisservletisresponsibleforthefirstleveloftext("HellofromLevel1"),theneachoftheincludedresourcescontributescontenttotheresponse.

Example6-6.Theouterincludedservlet




publicclassMultipleIncextendsHttpServlet{








out.println("<title>MultipleIncludes</title>");



out.println("<h1>HellofromLevel1</h1>");

out.println("ThistextisdisplayedatLevel1.");


getRequestDispatcher("/level2");




}

}

Thecode:

RequestDispatcherdispatcher=request.getRequestDispatcher("/level2");


includestheoutputoftheservletthatismappedtotheservletpath/level2,whichExample6-7shows(justthedoGetmethod).

Example6-7.Thefirstinnerincludedservlet

publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throws

ServletException,IOException{


out.println("<h2>HellofromLevel2</h2>");

out.println("ThistextisincludedatLevel2.");

//IncludetheJSPfilenamed"level3.jsp"

try{


"/level3.jsp");


}catch(Exceptionse){

Stringcontext_path=(String)request.getAttribute(

"javax.servlet.include.context_path");

Stringservlet_path=(String)request.getAttribute(

"javax.servlet.include.servlet_path");

StringerrMessage=newStringBuffer(

"ExceptionraisedduringLevel2servletinclude:<br>").

append("Contextpath:"+context_path+"<br>").

append("Servletpath:"+servlet_path).toString();

thrownewServletException(errMessage);

}

}

Example6-7writesmoretexttotheresponse,thenincludesalevel3.jsp,liketheouterservlet,usingajavax.servlet.RequestDispatcherobjecttoinitiateincludingtheJSP.TheLevel2servletdoessomeotherstuffwithatry/catchblockandrequestattributes,inordertodemonstratethehandlingofexceptionsthatmaybethrownduringincludeoperations.

AccordingtotheJSPAPIspecification,includedresourceshaveaccesstofiverequestattributes:

javax.servlet.include.request_uri

javax.servlet.include.context_path

javax.servlet.include.servlet_path

javax.servlet.include.path_info

javax.servlet.include.query_string

Inthecatchblock,theLevel2servletgetsthevalueoftwooftheserequestattributeswith:

Stringcontext_path=

(String)request.getAttribute("javax.servlet.include.context_path");

Stringservlet_path=

(String)request.getAttribute("javax.servlet.include.servlet_path");

Inthecatchblock,theLevel2servletthenthrowsanewServletExceptionwiththeattributevaluesaspartoftheexceptionmessage.Anerrorpageconfiguredforthewebapplicationdisplaysinformationabouttheexceptionthatwasgeneratedbytheincludeoperation.

Theerror-pageconfigurationinweb.xmllookslike:

<error-page>

<exception-type>

javax.servlet.ServletException

</exception-type>

<location>/error</location>

</error-page>

where"/error"ismappedtoaservletthatdisplaysexception-relatedinformation.

InExample6-7,thecontextpathwasemptyandtheservletpathwas

/level2.Figure6-4showsabrowserdisplayingtheerrorpage.Theservletgeneratingtheexceptionisspecifiedasthetop-levelservlet(MultipleInc)becausethiswasthecodethatoriginatedtheincludemechanismwhichresultedintheServletException.

Figure6-4.Displayingexceptioninformationcausedduringanincludeoperation

Example6-8showstheJSPfile(level3.jsp)thatthefirstinnerservletimports.Thelevel3.jspfilerepresentsthesecondlevelofincludedcontent.

Theincludedservletsdonotcallthejava.io.PrintWriter.close()method,becausethatactionwouldpreventtheresponsethatfollowstheouterservlet'sincludecodefrombeingsenttotheclient.Theouterservlet(MultipleIncinExample6-6)finallycallsPrintWriter.close()whenitisfinishedincludingthenestedresources.

Example6-8.Theincludedlevel3.jspJSPfile

<%@pageerrorPage="/error"%>

<h3>HellofromLevel3</h3>

ThistextisincludedatLevel3.

<jsp:includepage="/level4"/>

Finally,theJSPfileusesthejsp:includestandardactiontoimportthetextreturnedfromaservletthatismappedtothe/level4path.TheLevel4servletdoesthesamethingastheotheroftherecipe'sservletsitwritescharacterdatatothePrintWriterobjectsoIhavenotshownitssourcecode.ThereasonIincludedwastodemonstratehowseveraldifferentresourcetypescanbenestedinachainofincludedfiles.Theouterservletincludesservlettwo,whichincludesaJSPfile,whichinturnincludesthetextreturnedfromathirdservlet.ThefirstincludedservletencloseditsownincludecodeinatryblocktocatchanyexceptionsraisedbyincludingaJSPfile.

SeeAlso

Recipe6.1onusingtheRequestDispatcherincludemechanism;Recipe6.2ondetermininganincludedresourcewithanconfigurationfile;Recipe6.4-Recipe6.8onincludingresourcesinJSPs;ChapterSRV.14.2.5oftheServletRecipe2.4proposedfinalspecification;ChapterJSP.1.10.3oftheJSP2.0specificationonincludingfilesinJSPs;Chapter9onspecifyingerrorspagesinwebapplications.

Recipe6.4IncludingaResourcethatSeldomChangesintoaJSP

Problem

Youwanttoincludearesourcethatdoesnotchangeverymuch(suchasapagefragmentthatrepresentsaheaderorfooter)inaJSP.

Solution

UsetheincludedirectiveintheincludingJSPpage,andgivetheincludedJSPsegmenta.jspfextension.

Discussion

JSPpagesareoftencompositesofpagefragmentsthatrepresentnavigationbars,headers(pageelementsthatappearatthetopofawebpage),footers(elementsthatappearatthebottomofawebpage),andthemainbodycontent.Sincepagesinawebapplicationorasitemayallusethesamenavigationbar,thisfileismaintainedinoneplaceandusedbyallofthewebcomponentsthatrequireit.IfyouaregoingtoimportaJSPsegmentthatisastaticorunchangingresource,usetheincludedirectiveintheJSP,asin:

<%@includefile="/WEB-INF/jspf/navbar.jspf"%>

IfyouareusingaJSPdocument(seeChapter5)orXMLsyntaxfortheJSP,usethisformoftheincludedirective:

<jsp:directive.includefile="/WEB-INF/jspf/navbar.jspf"/>

Ifthevalueofthefileattributebeginswitha"/"character,thenitisacontext-relativepath,meaningthatitisrelativetothewebapplicationcontainingtheJSPthatusesthisdirective.IftheJSPincludesthelatterdirective,thenthisfilepathmeans"beginatthewebapplicationrootandincludethe/WEB-INF/jspf/navbar.jspffile."

Afileattributevalueinincludethatdoesnotbeginwitha"/"characterisapage-relativepath,whichisrelativetotheJSPpagethatisusingtheincludedirective.Thefollowingincludedirectiveattemptstoincludeafileinsideofthesegmentsdirectory,whichhasthesameparentdirectoryastheincludingJSP:

<%@includefile="segments/navbar.jspf"%>

Theincludedirectiveincludesthetextorcodeoftheincludedsegmentduringthetranslationphase,whentheJSPisconvertedintoaservlet.TheincludemechanismisamoreefficientwayofimportingthetextorcodethatyouwouldotherwisetypeintoaJSPpriortoitsconversiontoaservlet,suchasHTMLtagsortaglibdirectives.Example6-9showshowtousetheincludedirectivetoimportasegmentoftaglibdirectivesintoaJSP.

Thedifferencebetweentheincludedirectiveandthejsp:includestandardactionisthattheincludedirectiveimportstheactualtextorbytesoftheincludedsegment,whereasthejsp:includestandardactionsendsarequesttotheincludedpageandthenincludesthedynamicresponsetothatrequest.SeeRecipe6.5.

Example6-9.IncludingaJSPsegmentintoaJSPpageattranslationtime


<%@includefile="/WEB-INF/jspf/taglib-inc.jspf"%>

<html>

<head>

<title>MainContent</title>

</head>

<body>

<h1>Hereisthemaincontent</h1>

ThiswebapplicationisusingthefollowingServletAPI:

<c:outvalue="${pageContext.servletContext.majorVersion}"/>.<c:outvalue=

"${pageContext.servletContext.minorVersion}"/><br><br>

<jsp:useBeanid="timeValues"class="java.util.Date"/>

<c:settarget="${timeValues}"value=

"${pageContext.session.creationTime}"property="time"/>

Thesessioncreationtime:

<fmt:formatDatevalue="${timeValues}"type="both"dateStyle=

"medium"/><br><br>

ThetoXmltagwillcreateanXMLviewofthispage.

<t:toXmlfilename="include-xmlview"/>

</body>

</html>

ThesecondlineofExample6-9includesaJSPsegmentnamedtaglib-inc.jspf.ThissegmentincludesthetaglibdirectivesresponsibleformakingavailabletheJSTLandcustomtagusedinthepage.Example6-10showsthetaglib-inc.jspfpage.

Example6-10.AJSPsegmentcontainingtaglibdirectives


<%@tagliburi="http://java.sun.com/jstl/fmt"prefix="fmt"%>

<%@tagliburi="/toxml_view"prefix="t"%>

Theincludedirectiveincludesthesethreetaglibdirectivesjustasifyouhadtypedtheminyourself,thentheJSPcontainerconvertsthe

enclosingJSPintoaservlet.ThethreetaglibdirectivesenabletheuseofthefollowingtagsinExample6-9:

c:out

c:set

fmt:formatDate

t:toXml

TheJSP2.0specificationrecommendsthatyougiveincompleteJSPcodethatisdesignedtobeincludedinotherfilesa.jspfextension,whichusedtomean"JSPfragment."The2.0specification,however,nowreferstothesefragmentsas"JSPsegments"inordertoavoidconfusingthesefileswiththejavax.servlet.jsp.tagext.JspFragmentinterface.ThisinterfaceispartofthetagextensionAPI.

Figure6-5showswhattheJSPlookslikeinabrowserwindow.

Figure6-5.AJSPwithanincludedJSPsegmentoftaglibdirectives

ThispagedisplaystheServletAPIusedbythewebcontainer,thejavax.servlet.http.HttpSessioncreationtime(formattedusingthefmt:formatDateJSTLtag),andthecustomtagthatisdescribedinRecipe5.6.ThistaggeneratesanXMLviewofthecontainingpageandsavesanewXMLfilenamedaccordingtoitsfilenameattribute.Itwasincludedtoshowamethodofincludingafewdifferenttypesoftaglibs.

SeeAlso

Recipe6.5onusingthejsp:includestandardaction;Recipe6.7onincludingJSPsegmentsinXMLfiles;Recipe6.8onincludingcontentfromoutsideofaJSP'scontext;ChapterJSP.1.10.3oftheJSP2.0specificationonincludingfilesinJSPs;Chapter23ontheJSTLtags.

Recipe6.5IncludingContentinaJSPEachTimetheJSPHandlesaRequest

Problem

YouwanttoincludecontentinaJSPeachtimeitreceivesarequest,ratherthanwhentheJSPisconvertedtoaservlet.

Solution

Usethejsp:includestandardaction.

Discussion

Thejsp:includeactionincludesaresourceinaJSPeachtimeitreceivesarequest,whichmakesjsp:includemoreofadynamicincludemechanismthantheincludedirective(seeRecipe6.4).Usingjsp:include,theincludedJSPsegmentshaveaccesstotheincludingpage'srequest,session,andapplicationimplicitobjects,andtoanyattributestheseobjectscontain.Usethejsp:includeactionineachlocationofthefilewhereyouneedtoimportresourcessuchasJSPsegmentsfromthesamewebapplication.

Theimportcustomaction,whichispartofthecoreJSTL,canimportresourcesfromotherwebapplicationsorfromotherlocationsontheInternet.SeeRecipe6.8.

Example6-10showsaJSPpagethatreceivessubmittedforminformationfromanotherpageinthewebapplication.Thereceivingpageusesjsp:includetoincludeheaderandfooterpagesegmentsatthetopandbottomofthepage.

Justtoshowthattheincludedsegmentshaveaccesstothesamerequestandsessioninformationastheirparentpage,theheadersegmentdisplaystheperson'ssubmittedname,whichisstoredinfnameandlnamerequestparameters,intheformofagreeting-relatedtitleHTMLtag.ThefooterpageelementdisplaysthesessionIDalongwiththeuser'ssubmittedfirstandlastname.First,Figure6-6showsanHTMLpagewithasimplesubmissionformfortheuser'sfirstname,lastname,andemailaddress.

Figure6-6.AnHTMLform

AssumethatthisformpageincludesembeddedJavaScripttocheckthevalidityoftheenteredinformation.WhentheuserclickstheSubmitbutton,theforminformationissubmittedwiththefollowingHTMLtagto/solutions.jsp:

<formmethod=postaction="/solutions.jsp">

Example6-11showsthesolutions.jsppage,whichincludestwoJSPsegments:header.jspfandfooter.jspf.Theheader.jspfcontainsthecontentsofaheadHTMLtag,andplacestheuser'ssubmittednameinitsnestedtitletag.Thefooter.jspfpageforthesakeofdemonstrationechoestheuser'snameandshowshissessionID,whichitobtainsfromtheimplicitsessionJSPobject.TheJSP2.0specificationrecommendsthatyoukeepthesefilesinWEB-INF/jspf.

Example6-11.Includingtwopagesegmentsanddisplayingsubmittedformvalues


<html>

<jsp:includepage="/WEB-INF/jspf/header.jspf"/>

<bodybgcolor="white">

<tablewidth="660"border="0"summary="Atwo-columntableinwhichresidesalogoand

navigationbar">

<tr><tdvalign="top">

Organizationimagegoeshere...<p>

<u>Main</u>

</td>

<tdalign="right"valign="top">

Navbargoeshere...

</td></tr><tr><tdvalign="top"align="center"colspan="2">

<tableborder="0"summary=

"Anestedtableforaligningbodycontent">

<tr><td><h2>Thanksforregisteringatthissite</h2></td></tr>

<tr><td>Hereistheinfoyousubmitted:</td></tr>

<tr><td>Name:

<%=request.getParameter("fname")%>

<%=request.getParameter("lname")%></td></tr>

<tr><td>Email:

<%=request.getParameter("eaddress")%>

</td></tr></table>

</td></tr><tr><td></td></tr>

</table>

<tablewidth="660"border="0"summary=

"Atablecontainingafooternavigationbar.">

<tr><tdvalign="top"align="center">

<jsp:includepage="/WEB-INF/jspf/footer.jsp"/>

</td></tr>

</table>

</body>

</html>

Example6-12showstheheader.jspfJSPsegment.

Example6-12.AJSPheadersegmentincludedwithjsp:include

<HEAD>

<METAname="author"content=

"BruceW.Perry,[email protected]">

<METAname="keywords"content=

"Java,JSP,servlets,databases,MySQL,Oracle,webdevelopment">

<TITLE>ParkerRiver:ThanksForVisiting


<%=request.getParameter("lname")%>

</TITLE>

</HEAD>

Allthissegmentdoesisincludetheuser'snameinthetitletag.Example6-13showstheimportedfooter.jspfsegment.Thissegmentalsowritestheuser'snametothedisplayedoutputandaddsthesessionID,aftercheckingwhetherthejavax.servlet.http.HttpSessionobjectisnull,andbeforeitcallstheHttpSession.getId()method.

Example6-13.AJSPfootersegmentincludedwithjsp:include

Thanksforvisiting


<%=request.getParameter("lname")%><br>

SessionID:

<%if(request.getSession()!=null){%>

<%=request.getSession().getId()%>

<%}else{%>

Unknown

<%}%><br><br>

<ahref="/index.html">Main</a>|<ahref="/service.html">Services</a>|

<ahref="/sitemap.html">SiteMap</a>|

<ahref="/resources.html">Resources</a>|

<ahref="/contacts.html">ContactUs</a>|

<ahref="/prns_privacy.html">Privacy</a>

Figure6-7showsthesolutions.jsppageinawebbrowser.

Figure6-7.Theincludedheaderandfootersegmentsdisplayedinawebbrowser

Usingjsp:include,changestoincludedfilesarereflectedimmediatelyintheincludingpages.Ontheotherhand,ifyoumakechangestoapagethatisincludedusingtheincludedirective,thosechangesarenotreflectedintheincludingpageuntilyoumodifythatpageandforcetheJSPcontainertorecompileit.

SeeAlso

Recipe6.4ontheincludedirective;Recipe6.7onincludingJSPsegmentsinXMLfiles;Recipe6.8onincludingcontentfromoutsideofaJSP'scontext;ChapterJSP.1.10.3oftheJSP2.0specificationonincludingfilesinJSPs;Chapter23ontheJSTLtags.

Recipe6.6UsinganExternalConfigurationFiletoIncludeaResourceinaJSP

Problem

YouwanttoincludeafiledynamicallyinaJSP,basedonavaluederivedfromaconfigurationfile.

Solution

Usethejsp:includestandardaction.Providethevalueinanexternalpropertiesfileorasaconfigurationparameterinthedeploymentdescriptor.

Discussion

UsinganexternalconfigurationtospecifyanincludefileforaJSPallowsyoutochangethenameand/orpathtotheincludedfilewithouttouchingtheJSP'scode.Inaddition,whenusingjsp:includetheJSPdoesnothavetoberecompiledtoreflectanychangesintheincludedfilethewebresourceisincludedbytheJSPeachtimeithandlesarequest.Ifyouchangethefilepointedtobytheconfigurationfile,theresponsefromtheincludedresourceisaddedtotheincludingJSP'sresponseduringthenextrequest.

Thedifferencebetweenajsp:includestandardactionandincludedirectiveisthattheincludedirectiveincludesthebytesorcontentsoftheimportedfilebeforetheJSPiscompiled(duringthetranslationphasefortheJSP).Iftheincludedsegmentchanges,theupdateswillnotbereflectedintheJSPuntiltheJSPitselfismodified,whichcausesaJSPcontainer(suchasTomcat'sJasperJSPcontainer)torecompiletheJSP.

Example6-14showsaJSPthatusesanexternalpropertiesfiletospecifythefiletoinclude.

Example6-14.Usingjava.util.ResourceBundle.getBundle()tofetchanexternallyconfiguredfile



<html>

<%java.util.ResourceBundlebundle=

java.util.ResourceBundle.getBundle("com.jspservletcookbook.include");

Stringsegment=bundle.getString("external-include");%>

<jsp:includepage="<%=segment%>"/>

<body>

<h2>WelcometoourPortalHome<c:outvalue="${param.fname}"/><c:outvalue="${param.

lname}"/></h2>


Thetimeis<c:outvalue="${dateString}"/>.<br><br>

</body>

</html>

Example6-14includesaJSPsegmentthatisfoundatthepathspecifiedbytheexternal-includeproperty.Thispropertyiswritteninasimpletextfilecalledinclude.properties,withcontentthatlookslikethis:

external-include=WEB-INF/jspf/header_tag.jsp

Theinclude.propertiesfileisstoredinWEB-INF/classes/com/jspservletcookbook.Whenyour

servletorJSPattemptstoaccessalistofpropertyvaluesbycallingthestaticmethodjava.util.ReseourceBundle.getBundle("com.jspservletcookbook.include"),getBundleautomaticallyreplacestheperiod"."characterswith"/"andappends".properties"totheendoftheString(makingthesearchlooklike"com/jspservletcookbook/include.properties"inourexample).

TheexamplecodesavesthepropertyvalueinaStringvariablesegmentwiththefollowingcode:

Stringsegment=bundle.getString("external-include");

Thenthevalueofthesegmentvariable,whichisafilepath,specifiesthefilefortheJSPtoinclude:WEB-INF/jspf/header_tag.jsp.ThisisaccomplishedwiththeJSPexpression<%=segment%>inthepageattributevalueforjsp:include:

<jsp:includepage="<%=segment%>"/>

WhentheJSPpageisexecuted,theincludedfile'sresponseisincludedinthepartofthepagewherethejsp:includestandardactionoccurs.Example6-15showsthecontentoftheincludedfile,header_tag.jsp.

Example6-15.Thecontentoftheheader_tag.jspsegment


<HEAD>






<c:outvalue="${param.fname}"/>

<c:outvalue="${param.lname}"/>

</TITLE>

</HEAD>

ThisisacompleteHEADHTMLtag,includingtwonestedMETAtagsandaTITLEtag.IfyourequestedtheincludingJSPpageathttp://localhost:8080/home/externalInclude.jsp?fname=Mister&lname=Bean,thereturnedcontentfromthisJSPsegmenttheactualtextthattheJSPcontainersubstitutesforthejsp:includetagintheoutputlookslikeExample6-16.

Example6-16.Theoutputwhenjsp:includeisused

<HEAD>






Mister

Bean

</TITLE>

</HEAD>

Theincludedsegmentprocessestherequestparametersfnameandlnamefromthequerystring:

fname=Mister&lname=Bean

andincludestheirvaluesintheTITLEtag.Figure6-8showswhattheexternalInclude.jsppagelookslikeinabrowser.

Figure6-8.BrowserviewofJSPthatusesjsp:includetoincludeanotherJSPsegment

Inthisexample,theincludedsegmentusesthepropertaglibdirectivesothatthec:outJSTL1.0tagscanbeused.IfyouareusingJSTL1.1,thentheuriattributevalueishttp://java.sun.com/jsp/jstl/core:

<%@taglib

uri="http://java.sun.com/jstl/core"

prefix="c"%>

Youcanalsopassparametersfortheincludedsegmenttoprocess,inthemannerof:

<jsp:includepage="<%=segment%>">

<jsp:paramname="role"value="comedian"/>

</jsp:include>

Ifyouwanttouseacontextparameterinthewebapplication'sdeploymentdescriptorinsteadtoprovideapathfortheincludedfile,addacontext-paramelementtoweb.xml(asshowninExample6-17).

Example6-17.Acontext-paramelementprovidesanincludedfilepath

<context-param>

<param-name>external-include</param-name>

<param-value>WEB-INF/jspf/header_tag.jsp</param-value>

</context-param>

ThengetthevalueofthecontextparameterintheincludingJSP:

<jsp:includepage="<%=application.getInitParameter("external-include")%>"/>

TheJSPtheninsertsthefilepathWEB-INF/jspf/header_tag.jspasthevalueforthejsp:includepageattribute.

SeeAlso

Recipe6.4ontheincludedirective;Recipe6.7onincludingJSPsegmentsinXMLfiles;Recipe6.8onincludingcontentfromoutsideofaJSP'scontext;ChapterJSP.1.10.3oftheJSP2.0specificationonincludingfilesinJSPs;Chapter23ontheJSTLtags;thiswebpageforhowthegetBundlemethodreturnscertaintypesofResourceBundles:http://java.sun.com/j2se/1.4.1/docs/api/java/util/ResourceBundle.html#getBundlejava.util.Locale,java.lang.ClassLoader).

http://java.sun.com/j2se/1.4.1/docs/api/java/util/ResourceBundle.html#getBundle

Recipe6.7IncludinganXMLFragmentinaJSPDocument

Problem

YouwanttoincludeafragmentofanXMLfileinsideofaJSPdocument,orincludeaJSPpageinXMLsyntax.

Solution

Usethejsp:includestandardactionfortheincludesthatyouwanttooccurwitheachrequestoftheJSP.Usethejsp:directive.includeelementiftheincludeactionshouldoccurduringthetranslationphase.

Discussion

BecauseaJSPdocumentisawell-formedXMLfile,bothofthemechanismsthatyoucanusetoincludeJSPsegmentsareXMLelements:jsp:includeandjsp:directive.include.AJSPdocumentisaJSPpageinXMLsyntax,inwhichallofthecodeiswell-formedXML;inotherwords,theentirepageconsistsofXMLelements,attributes,andthebodycontentofsomeXMLelements.YouthentaketheJSPdocumentandplaceitintherootofyourwebapplication(orwhereveryoumakeyourJSPpagesavailable;therootistheusualplace),andtheJSPcontainertranslatestheXMLfileintoaservlet.OnereasonforusingJSPdocumentsistointegratetheJSPswithotherXMLtechnologies,suchasXHTML,SVG,orSOAP.Recipe5.5describesJSPdocumentsinmoredetail.Example6-18showsaJSPdocumentversionofExample6-14,usingjsp:includetoincludeafilethatislocatedatthepathWEB-INF/jspf/header_tag.jspf.

Example6-18.AJSPdocumentusingjsp:includetoincludeafile


xmlns:c="http://java.sun.com/jstl/core"

xmlns="http://www.w3.org/1999/xhtml"version="2.0">


<html>

<jsp:includepage="WEB-INF/jspf/header_tag.jspf"/>

<body>

<h2>WelcometoourPortal<c:outvalue="

${param.fname}"/><jsp:text></jsp:text>

<c:outvalue="${param.lname}"/></h2>


<jsp:text>Thetimeis</jsp:text><c:outvalue="${dateString}"/>.

<br/><br/>

</body>

</html>

</jsp:root>

InExample6-18,theJSPpageincludesthetextthatisreturnedbyheader_tag.jspf.Usingjsp:include,theincludedfiledoesnothavetobewell-formedXMLitself,aslongasitreturnstextthatiswell-formedXMLandfitscorrectlyintotheJSPdocument.

TheJSP2.0specificationrecommendsthatJSPsegmentsthatyouincludeinJSPpagesorJSPdocumentsbegivena.jspfextension.Inaddition,onewaytodifferentiateJSPdocumentsfromconventionalJSPpagesistogivetheJSPdocumentsa.jspxextension(whenusingtheServlet2.4versionofweb.xml).Tomcat4.1.xwillcompileandexecuteasJSPpagesthefileswiththeseextensionsifyouaddtheseservlet-mappingelementstoconf/web.xml:

<servlet-mapping>

<servlet-name>jsp</servlet-name>

<url-pattern>*.jspf</url-pattern>

</servlet-mapping>

<servlet-mapping>

<servlet-name>jsp</servlet-name>

<url-pattern>*.jspx</url-pattern>

</servlet-mapping>

Example6-19showstheincludedfileheader_tag.jspf.IthasitsowntaglibdirectivesothattheJSTL-relatedtagsinsidetheTITLEtagsproducetheproperoutputfromtherequestparametersfnameandlname.ThecommentatthebottomofExample6-18showsthetextthatisreturnedfromthisJSPsegment,usingjsp:include,whentheenclosingJSPpageisrequestedfromhttp://localhost:8080/home/x617.jspx?fname=Bruce&lname=Perry.

Example6-19.Theincludedfileheader_tag.jspf


<HEAD>


"BruceW.Perry,[email protected]"/>


"Java,JSP,servlets,databases,MySQL,Oracle,webdevelopment"/>


<c:outvalue="${param.fname}"/><c:outvalue="${param.lname}"/>

</TITLE>

</HEAD>

Figure6-9showswhatthecompletedocumentlookslikeinabrowser.

Figure6-9.AJSPdocumentdisplayedinabrowser

Youcanalsousethejsp:directive.includeelement,whichincludesthecontentbeforetheJSPdocumentisconvertedintoaservlet,ratherthanatruntimeaswithjsp:include.ToconvertExample6-17touseanincludedirective,replacethejsp:includeelementwith:

<jsp:directive.includefile="WEB-INF/jspf/header_tag.jspf"/>

Theincludedcontentcannothaveanynon-XMLsyntaxforms,suchasaJSPtaglibdirective,becausetheincludedcodeisincludedverbatimintotheJSPdocumentwhenitisconvertedintoaservlet.

AnalternativeapproachistouseCDATAsectionsintheXMLtoattempttopreservethewordsandsymbolsthatwouldotherwisecausetheXMLfiletofailthewell-formedtest.TheCDATAsectionslooklike<![CDATA[...]]>.

Youwouldhavetoremovethetag-libdirectivefromthetopofExample6-19fortheJSPtocompilecorrectlyusingjsp:directive.include.Inaddition,thec:outtagsinsideofthe

includedsegmentwouldthenbedependentontheinclusionintheenclosingJSPdocumentofanxmlnsattributetomakethecoreJSTLelementsavailable,asinthetopofExample6-18.

AruleofthumbtousewiththetwoincludemechanismsisthatiftheincludedsegmentwillchangefrequentlyandtheenclosingJSPpagemustimmediatelyreflectthosechanges,usejsp:include.Iftheincludedsegmentisrelativelystaticandunchanging,usejsp:directive.include.

SeeAlso

Recipe6.4ontheincludedirective;Recipe6.5onthejsp:includestandardaction;Recipe6.8onincludingcontentfromoutsideofaJSP'scontext;ChapterJSP.1.10.3oftheJSP2.0specificationonincludingfilesinJSPs;Chapter23ontheJSTLtags.

Recipe6.8IncludingContentfromOutsideaContextinaJSP

Problem

YouwanttoincludeaJSPsegmentfromoutsidetheincludingfile'scontext.

Solution

Usethec:importJSTLcoretag.

Discussion

Thec:importtaggivesJSPpageauthorsmuchflexibilityinpullinginresourcesfrominsideandoutsidetheirwebapplication.Thec:importtagallowsapagetoimportwebresources:

FromoutsideJSP'swebcontainer,usinganabsoluteURL(suchashttp://java.sun.com/api).

Fromanothercontextinthesamewebcontainer.Forexample,yourdomainmayincludeacentralrepositoryofincludedcontentathttp://www.mydomain.com/warehouse.AJSPpagethatisinstalledinacontextnamed/customercouldimportaresourcefromthe/warehousecontextbyusing:<c:importurl="/catalog_header.jspf"context="/warehouse"/>

Fromthesamecontext,similartousingjsp:include.

ThisrecipeincludesexamplesofimportingresourcesfromoutsidetheimportingJSP'scontext.Example6-19importsaJSPsegmentheader_tag.jspfromthe/dbprojcontext.Theurlattributespecifiestheresourcetoinclude;thecontextattributedeclaresthecontextfromwhichtheJSPimportstheresource.Tousethec:importtag,theJSPhastoincludeataglibdirectivesuchas:


Example6-20includesagroupoftaglibsbyinsertingthetaglib-inc.jspfJSPsegmentinthesecondline.

Example6-20.Usingthec:importtagtoimportanexternalURL


<%@includefile="/WEB-INF/jspf/taglib-inc.jspf"%>

<html>

<c:importurl="/header_tag.jspf"context="/dbproj"/>

<body>

<h2>WelcometoourPortal<c:outvalue="

${param.fname}"/><c:outvalue="${param.lname}"/>

</h2>


Thetimeis<c:outvalue="${dateString}"/>.

<br/><br/>

</body>

</html>

Thec:importtaginsertsthetextgeneratedby/dbproj/header_tag.jspinthepartofthecodewherethec:importtagislocated.The/dbprojcontextpathrepresentsadifferentwebapplicationorcontextthantheimportingJSP.Thetopoftheimportingpagenowlookslikethefollowingtext,sincethisistheHTMLthattheimportedfileproduces:

<html>

<HEAD>






MisterBean

</TITLE>

</HEAD>

<body>



UsingTomcat,thecontextelementinconf/server.xmlhastoincludethisattribute/valuepairortheJSPthatusesc:importwillraiseanexceptionifitattemptstoimportresourcesfromanothercontext:

crossContext="true"

Example6-21importsadescriptionoftheHTTP/1.1protocol,RequestForComments(RFC)2068.

Theexampledeclaresitscontenttypeas"text/plain,"sothatthebrowserdoesnottrytodisplaythetextfileasHTML,whichcanbeunreadablewithplaintextfiles.ThenExample6-21usesataglibdirectivesothattheJSPcanusethec:importtag.Thec:importtagspecifiesthelocationoftheimportedtextfileasanabsoluteURL:http://www.ietf.org/rfc/rfc2068.txt.

Example6-21.Usingc:importtoimportatextresourcewhoseaddressisanabsoluteURL

<%@pagecontentType="text/plain"%>


<c:importurl="http://www.ietf.org/rfc/rfc2068.txt"/>

http://www.ietf.org/rfc/rfc2068.txt

IfaJSPusesc:importtoaccessaforbiddenresource(whichwillcausethereceivingservertorespondwithaHTTPstatuscode403),thec:importtagthrowansexceptionandtheJSPcompilationwillfail.

Youcanalsoincludeparameterswithc:importusingnestedc:paramtags.Example6-22importsafileheader_tag.jspf,andmakesavailabletworequestparametersforthatfiletoprocess:fnameandlname.ThetaglibdirectiveatthetopofExample6-22allowstheuseofthec:importandc:paramtagslateroninthecode.

Example6-22.Includingparametervaluesusingc:param


<html>

<c:importurl="WEB-INF/jspf/header_tag.jspf">

<c:paramname="fname"value="Mister"/>

<c:paramname="lname"value="Bean"/>

</c:import>

<body>

<h2>Therestofthepagegoeshere...</h2>

</body>

</html>

Theheader_tag.jspffiletakesthevaluesofthetwoparametersandaddsthemtotheTITLEtag'sgreeting.Example6-23showstheHTMLthatresultsfromthisimportaction.

Example6-23.RequestparametervaluesarereflectedintheHTMLoutput

<html>

<HEAD>






MisterBean

</TITLE>

</HEAD>

<body>

<h2>Therestofthepagegoeshere...</h2>

</body>

</html>

SeeAlso

Recipe6.1-Recipe6.3onincludingresourcesinservlets;Recipe6.4-Recipe6.7onusingjsp:include,theincludedirective,andincludingresourcesinJSPdocumentsorXMLfiles;Chapter23onUsingtheJSTL1.0;ChapterJSP.5.4oftheJSP2.0specificationonjsp:include;ChapterJSP.1.10.3oftheJSP2.0specificationontheincludedirective.

Chapter7.HandlingWebFormDatainServletsandJSPs

Introduction

Recipe7.1.HandlingaPOSTHTTPRequestinaServlet

Recipe7.2.HandlingaPOSTHTTPRequestinaJSP

Recipe7.3.SettingthePropertiesofaJavaBeaninaJSP

Recipe7.4.SettingaScopedAttributeinaJSPtotheValueofaFormParameter

Recipe7.5.PostingDatafromaServlet

Recipe7.6.PostingDatafromaJSP

Recipe7.7.UsingaServlettoAddaParametertoaQueryString

Recipe7.8.UsingaJSPtoAddaParametertoaQueryString

Recipe7.9.UsingaFiltertoReadParameterValues

Introduction

EverywebdeveloperisfamiliarwiththescenarioinwhichaclientfillsoutanHTMLformandthensubmitstheinsertedinformationtoaserver-sideprogramforprocessing.SomeoftheseprogramsusetheHTTPrequestmethodPOSTtodeliverthedatatotheserver-sideprogram.ThePOSTmethodsendsthedatatotheserverinthebodyoftherequest,ratherthanasaquerystringappendedtoaURL(asintheGETmethod).Forexample,considertheHTMLformtaginExample7-1.

Example7-1.HTMLformtagsetupforpostingdata

<formmethod=POSTaction="/project/controller">

<b>UserName:</b><inputtype="text"name="username"

size="20"><br><br>

<b>Department:</b><inputtype="text"name="department"

size="15"><br><br>

<b>Email:</b><inputtype="text"name="email"

size="15"><br><br>

<inputtype="submit"value="Submit">

</form>

Whentheclientsubmitsthisforminformation,thetopoftheclient'srequesttextlookslikethis:

POST/project/controllerHTTP/1.1

Accept:image/gif,image/x-xbitmap,image/jpeg,image/pjpeg,application/msword,

application/vnd.ms-powerpoint,application/vnd.ms-excel,application/pdf,*/*

Referer:http://localhost:8080/project/login.jsp

Accept-Language:en-us

Content-Type:application/x-www-form-urlencoded

Beneaththistext,afterafewmoreheaders,thebodyoftherequestcarriesthesubmitteddata:

username=Bruce+W+Perry&password=bw_p1968

JSPsandservletsmakeparsingthePOSTdataquitetransparentforthedeveloper.Thisisthetopicofthenextfewrecipes.WethendiscusshowtouseservletsandJSPstopostdatasothattheyessentiallyplaytheroleofclient,insteadofactingasaserver-sideprogram.

Recipe7.1HandlingaPOSTHTTPRequestinaServlet

Problem

YouwanttoprocessdatathatispartofaPOSTrequest.

Solution

UsetheServletRequest.getParameter(Stringname),getParameterMap(),getParameterNames(),orgetParameterValues(Stringname)methodsintheservlet'sdoPostmethod.

Discussion

Theservicemethodofaservletcallstheservlet'sdoPostmethodwhenaclientsendsaPOSTHTTPrequest.Theservletdeveloperthenhasfourdifferentmethodsshecancalltogainaccesstotheposteddata,whichmakesitprettyeasytoprocesstheserequests.JustincaseaclientapplicationusesaGETmethodtosendtheservletitsdataasaquerystring,theservletshouldalsocall:

doPost(request,response);

intheservlet'sdoGet()method.Example7-2demonstrateshandlingPOSTdatawiththeoft-usedgetParameter(Stringname)method,aswellaswiththegetParameterMap()method,whichreturnsajava.util.Map.Themapcontainsparameterkeysandvalues.ThegetParameterNames()methodreturnsa

java.util.Enumerationoftheparameternames.YoucaniteratethroughthisEnumerationandpassthevaluestogetParameter(Stringname).AnotherServletRequestmethod,getParameterValues(Stringname),returnsaStringarrayofallthepostedvaluesforthatparametername(ifthereisonlyonevalue,thereturnedarraycontainsoneString).Figure7-1showsthebrowserdisplayofthePostHandlerservletafterauserhassubmittedtheforminExample7-1.

Figure7-1.Servletdisplaysname/valuepairsfrompostedforminput

Example7-2.UsingtheServletRequest.getParameterandgetParameterMapmethodstohandleposteddata



importjava.util.Map;

importjava.util.Iterator;

importjava.util.Map.Entry;

publicclassPostHandlerextendsHttpServlet{

publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throws

ServletException,java.io.IOException{

/*UsetheServletRequest.getParameter(Stringname),getParameterMap(),

getParameterNames(),orgetParameterValues()methodsintheservlet'sdoPostmethod*/

Stringname=request.getParameter("username");

Stringdepart=request.getParameter("department");

Stringemail=request.getParameter("email");





out.println("<title>Welcome</title>");



out.println("<h1>YourIdentity</h1>");

out.println(

"Yournameis:"+((name==null||name.equals(""))?

"Unknown":name));

out.println("<br><br>");

out.println(

"Yourdepartmentis:"+((depart==null||depart.equals(""))?

"Unknown":depart));


out.println(

"Youremailaddressis:"+((email==null||

email.equals(""))?"Unknown":email));

out.println("<h2>UsingServletRequest.getParameterMap</h2>");

Mapparam_map=request.getParameterMap();

if(param_map==null)


"getParameterMapreturnednullin:"+

getClass().getName());

//iteratethroughthejava.util.Mapanddisplaypostedparameter

//values

//thekeysoftheMap.EntryobjectsaretypeString;thevaluesare

//typeString[],

//orStringarray

Iteratoriterator=param_map.entrySet().iterator();

while(iterator.hasNext()){

Map.Entryme=(Map.Entry)iterator.next();

out.println(me.getKey()+":");

String[]arr=(String[])me.getValue();

for(inti=0;i<arr.length;i++){

out.println(arr[i]);

//printcommasaftermultiplevalues,

//exceptforthelastone

if(i>0&&i!=arr.length-1)

out.println(",");

}//endfor


}//endwhile



}




}

}

Gettingthevalueofaparameterisassimpleasusingrequest.getParameter(parametername).ThenyoucantestforthefailuretoreturnavalidvaluewithcodefromExample7-2:

out.println("Yournameis:"+

((name==null||name.equals(""))?"Unknown":name));

IfthenamevariableisanemptyStringornull,thentheservletprints"Unknown";otherwise,itprintsthenamevalue.Thereareseveraldesignpatternsyoucanuseforvalidatingforminput,includingclient-sideJavaScriptandspecialvalidationJavaBeans.

Handlingthejava.util.Maptypeismoreinvolvedandentailsmorecode.TheservletgetstheparametermapbycallingtheServletRequestmethod:

Mapparam_map=request.getParameterMap()

Thenthecodegetsajava.util.Iteratorfromthejava.util.SetreturnedfromMap.entrySet().TheSetcontainsMap.Entryobjects,whicharekey/valuepairsrepresentingtheparameternameandvalue.Theservletusestheiteratortocyclethroughtheparameternamesandvalues:

Iteratoriterator=param_map.entrySet().iterator();

while(iterator.hasNext()){

Map.Entryme=(Map.Entry)iterator.next();

out.println(me.getKey()+":");

//ThereturnedvalueisaStringarray

String[]arr=(String[])me.getValue();

for(inti=0;i<arr.length;i++){

out.println(arr[i]);

//printcommasaftermultiplevalues,

//exceptforthelastone

if(i>0&&i!=arr.length-1)

out.println(",");

}//endfor


}//endwhile

Ifthislookstooelaborateforprocessingposteddata,thenreservegetParameterMap()forapplicationsthataredesignedtodealwiththem,suchasavalidatorbeanthattakesaMapasaconstructorormethodparameter.Inaddition,Recipe7.2showsaJSPthatusesJSTLtoconvenientlyprocessaparametermap.

SeeAlso

Recipe7.2onhandlingaPOSTrequestinaJSP;Recipe7.5onpostingdatafromaservlet;Recipe7.7onusingaservlettoaddaparametertoaquerystring;theServletRequestAPIdocsathttp://java.sun.com/j2ee/1.4/docs/api/index.html.

http://java.sun.com/j2ee/1.4/docs/api/index.html

Recipe7.2HandlingaPOSTHTTPRequestinaJSP

Problem

YouwanttohaveaJSPhandlethedatapostedfromaformorclientapplication.

Solution

UsetheJSTLc:forEachtagtoiterateovertheparameternamesandvalues.

Discussion

TheJSTLmakesitveryeasytoprocessinputdatafromaPOSTmethod.TheJSPinExample7-3usesonlytemplatetextandJSTLtagstodisplaypostedinformation.Thec:forEachtagiteratesovertheposteddatausingtheimplicitJSTLobjectparam.Theparamobjectcontainsjava.util.Map.Entrytypes,whicheachholdakey/valuepair.Thekeyandvaluecorrespondtothenameofasubmittedparameteranditsvalue,suchas"department=Development."UsingtheExpressionLanguage(EL),thesyntax"${map_entry.key}"or"${map_entry.value}"istheequivalentofcallingtheMap.Entry.getKey()andgetValue()methods.Thereturnvaluesofthesemethodcallsarefedtothec:outJSTLtagfordisplayintheHTMLpage.Figure7-2showswhatthebrowserpagelookslikeiftheformsubmittedtotheJSPistheonedetailedinExample7-1.Withyourtaglib,useaurivalueofhttp://java.sun.com/jsp/jstl/coreforJSTL1.1.

Example7-3.IteratingposteddatawiththeJSTL



<html>

<head><title>PostDataViewer</title></head>

<body>

<h2>Hereisyourposteddata</h2>

<c:forEachvar="map_entry"items="${param}">

<strong><c:outvalue="${map_entry.key}"/></strong>:

<c:outvalue="${map_entry.value}"/><br><br>

</c:forEach>

</body>

</html>

MakesuretoincludethetaglibdirectivewhenyouareusingtheJSTLtags.ThetaglibinExample7-3takescareofanyofthecustomtagswiththe"c"prefix,asinc:forEach.

Chapter23explainshowtoinstalltheJSTLinyourwebapplication,makedifferentcustomtags,andusetheEL.

Figure7-2.AJSPdisplayingpostedname/valuepairs

Ifyouwanttogetthevaluesofparameterswithoutusingac:forEachtag,thenusethecodefragmentinExample7-4.Thiscodedisplaysthevaluesofparameterswhentheparameternamesareknownbythedeveloper(whichisusuallythecase).

Example7-4.Displayingindividualparametervaluesusingc:out


<strong>Username:</strong>:<c:outvalue="${param.username}"/>

<br><br>

<strong>Department:</strong>:<c:outvalue="${param.department}"/>

<strong>Email:</strong>:<c:outvalue="${param.email}"/>

SubstitutingthiscodeintotheJSPproducesthesameresultsasthoseshownFigure7-2.

TheJSP2.0specificationisdesignedtoallowtheuseoftheELintemplatetextinotherwords,withoutthec:outJSTLtag.

SeeAlso

Recipe7.2onhandlingaPOSTrequestinaJSP;Recipe7.3onsettingthepropertiesofaJavaBeantoforminput;Recipe7.4onsettingascopedattributetothevalueofaparameter;Recipe7.6onpostingdatafromaJSP;Chapter23onusingtheJSTL.

Recipe7.3SettingthePropertiesofaJavaBeaninaJSP

Problem

YouwanttosetaJavaBean'spropertiestothevaluesenteredinaform.

Solution

Usethejsp:setPropertystandardaction,withitspropertyattributesetto"*"anditsclassattributesettothefullyqualifiedclassnameoftheJavaBean.

Discussion

Thejsp:setPropertystandardactionhasabuilt-inmethodforautomaticallymappingthevaluessubmittedinaformtoaJavaBean'sfieldsorvariables.ThenamesofthesubmittedparametershavetocorrespondtothenamesoftheJavaBean'ssettermethods.Example7-5showsasetBean.jsppagethatreceivesdatafromanHTMLform:

<formmethod=postaction="http://localhost:8080/home/setBean.jsp">

TheJSPfirstinstantiatesanobjectofthetypecom.jspservletcookbook.UserBeanusingjsp:useBean.Thenitsetsthepropertiesofthebeanusingjsp:setProperty.Thenameattributeofjsp:setPropertymatchestheidattributeofjsp:useBean.Thepropertyattributeofjsp:setPropertyissimplysetto"*".

Example7-5.beanSet.jspJSPthatsetstheUserBean'spropertieswithforminput



<jsp:useBeanid="userB"class="com.jspservletcookbook.UserBean">

<jsp:setPropertyname="userB"property="*"/>

</jsp:useBean>

<html>

<head><title>PostDataViewer</title></head>

<body>


<strong>Username</strong>:

<c:outvalue="${userB.username}"/><br><br>

<strong>Department</strong>:

<c:outvalue="${userB.department}"/><br><br>

<strong>Email</strong>:

<c:outvalue="${userB.email}"/>

</body>

</html>

Example7-5usesthec:outelementoftheJSTLtodisplaythebean'svariousvaluesinabrowserpage.Thevalueattributeofc:outusestheELtoacquireapropertyvalue,asin"${userB.email}".ThissyntaxistheequivalentofcallingtheUserBean'sgetEmail()method.Example7-6showstheUserBean,whichusestheJavaBeannamingconventionstoensurethatitspropertiescanbeproperlysetandaccessed.Figure7-3showsthebrowserdisplayofthevalues.

Figure7-3.DisplayingforminputviaaJavaBean

Thejsp:setPropertyaction,asusedinthisrecipe,setstheJavaBean'spropertiesbyusingintrospectiontolineupparameternameswiththebean'ssettermethods.Ifthebeanhasafieldnamed"Username,"thentheparameternamemustbeexactly"Username"andthesettermethodmustbeexactly"setUsername(Stringname)"(ifthebean'sfieldisaString).Watchout,it'scase-sensitive!

Example7-6.EncapsulatingtheposteddatainaJavaBean


publicclassUserBeanimplementsjava.io.Serializable{

Stringusername;

Stringemail;

Stringdepartment;

publicUserBean(){}

publicvoidsetUsername(String_username){

if(_username!=null&&_username.length()>0)

username=_username;

else

username="Unknown";

}

publicStringgetUsername(){

if(username!=null)

returnusername;

else

return"Unknown";}

publicvoidsetEmail(String_email){

if(_email!=null&&_email.length()>0)

email=_email;

else

email="Unknown";

}

publicStringgetEmail(){

if(_email!=null)

returnemail;

else

return"Unknown";}

publicvoidsetDepartment(String_department){

if(_department!=null&&_department.length()>0)

department=_department;

else

department="Unknown";

}

publicStringgetDepartment(){

if(department!=null)

returndepartment;

else

return"Unknown";}

}

Recipe7.4showshowtouseabeantovalidateforminput,thensetascopedattributetotheinput.

SeeAlso

Recipe7.2onhandlingaPOSTrequestinaJSP;Recipe7.4onsettingascopedattributetothevalueofaparameter;Recipe7.6onpostingdatafromaJSP;Chapter23onusingtheJSTL.

Recipe7.4SettingaScopedAttributeinaJSPtotheValueofaFormParameter

Problem

Youwanttosetarequest-,session-,orapplication-scopedattributetoavaluethataclienthassubmittedaspartofforminput.

Solution

Usethejsp:useBeanandjsp:setPropertystandardactionstosetaJavaBean'spropertytothesubmittedvalue.Thenusethec:setJSTLcustomtagtosettheattributetothevalidatedvalue.

Discussion

Somewebapplicationsmayvalidateforminputsuchasanemail/passwordcombination,thensetarequest-,session-,orapplication-scopedattributetothevalidatedvalue.AnefficientwaytohandleimportantdatathatausersubmitsistouseaJavaBeanwhosepurposeistovalidatethesubmissionagainstsomebusinessruleorexternalresource,suchasadatabase.Ifthesubmissionisvalid,thentheapplicationcreatesasessionattribute,forinstance,withthevalue.Ifthesubmissionisinvalid,thenabooleanvariableintheJavaBeanissettofalse.TheJSPtowhichtheforminputissentcancheckthisvaluebeforeithandlesthedataasvalid.

Example7-7showsaClientValidatorbeanthathasthreefields:email,password,andvalid.ThisbeanisusedbyaJSPtovalidateforminputbeforetheJSPsetsrequest-scopedattributestothesubmitted

values.

Example7-7.TheClientValidatorbean


publicclassClientValidatorimplementsjava.io.Serializable{

Stringemail;

Stringpassword;

booleanvalid;

publicClientValidator(){

this.valid=false;}

publicbooleanisValid(){

/*UseaDataAccessObjecttovalidatetheemailandpassword.

Ifthevalidationdoesnotfail,thensetthis.validtotrue*/

this.valid=true;

returnvalid;

}

publicvoidsetEmail(String_email){

if(_email!=null&&_email.length()>0)

email=_email;

else

email="Unknown";

}

publicStringgetEmail(){

returnemail;

}

publicvoidsetPassword(String_password){

if(_password!=null&&_password.length()>0)

password=_password;

else

password="Unknown";

}

publicStringgetPassword(){

returnpassword;}

}

Example7-8istheJSPthatusesClientValidator.TheJSPfirstusesjsp:useBeantocreateaninstanceofthebean.ThenitsetsthefieldsorpropertiesofthebeantothevaluesthathavebeenpostedtotheJSP,whichare"email"and"password".IftheisValidbeanpropertyistrue,whichistestedwiththisJSTLcode:

<c:iftest="${isValid}">

thentheJSPsetstworequest-scopedattributes.Theattributesarenowavailabletoapagethatisforwardedthisrequest.SessionattributesareaccessiblefromservletsandJSPsthatareassociatedwiththesamesession(seeChapter11).Theapplicationscopeencompassesthecontextorwebapplication.

Ifyouwanttosetsession-orapplication-scopedattributes,changethecodeinExample7-8to:

<c:setvar="email"value="${chk.email}"

scope="session"/>

<c:setvar="password"value="${chk.password}"

scope="session"/>

or:

<c:setvar="email"value="${chk.email}"

scope="application"/>

<c:setvar="password"value="${chk.password}"

scope="application"/>

Example7-8.validChk.jsppagethatusesavalidatorbeantocheckforminputdata



<jsp:useBeanid="chk"class="com.jspservletcookbook.ClientValidator">

<jsp:setPropertyname="chk"property="*"/>

</jsp:useBean>

<%--getvalidpropertyfromClientValidatorbean--%>

<c:setvar="isValid"value="${chk.valid}"/>

<c:iftest="${isValid}">

<c:setvar="email"value="${chk.email}"scope="request"/>

<c:setvar="password"value="${chk.password}"scope="request"/>

</c:if>

<html>

<head><title>ClientChecker</title></head>

<body>

<h2>Welcome</h2>

<strong>Email</strong>:

<c:outvalue="${email}"/><br><br>

<strong>Password</strong>:

<c:outvalue="${password}"/>

</body>

</html>

SeeAlso

Recipe7.2onhandlingaPOSTrequestinaJSP;Recipe7.3onsettingthepropertiesofaJavaBeantoforminput;Recipe7.6onpostingdatafromaJSP;Chapter23onusingtheJSTL.

Recipe7.5PostingDatafromaServlet

Problem

YouwanttosendparametersandtheirvaluesasaPOSTrequestfromaservlet.

Solution

UsetheJakartaCommonsHttpClientcomponentanditsPostMethodclasstoautomatethepostingofdatatootherprograms.

Discussion

TheJakartaCommonsHttpClientisacomponentthatallowsthedevelopertomimicthefeaturesofawebbrowserinhisJavacode,suchassendingGETandPOSTHTTPrequests,aswellasusingHTTPSforsecuresockets.Asthehomepagedescribesthisusefulcomponent,HttpClient"providesanefficient,up-to-date,andfeature-richpackageimplementingtheclientsideofthemostrecentHTTPstandardsandrecommendations"(http://jakarta.apache.org/commons/httpclient/).HttpClientisofferedundertheApacheSoftwareLicense.

ThisrecipedescribesusingHttpClienttopostdatatoanotherserver-sideprogramusingthePOSTHTTPmethod.First,downloadtheHttpClientdistributionfromtheJakartasite(http://jakarta.apache.org/commons/httpclient/downloads.html).ThenunpackthedistributionandplacetheJARfilethatitcontainsintheWEB-INF/libdirectoryofyourwebapplication.Atthiswriting,theJARforRelease2.0Alpha3wascommons-httpclient-2.0-alpha2.jar.Onceyou

http://jakarta.apache.org/commons/httpclient/default.htm

http://jakarta.apache.org/commons/httpclient/downloads.html

havetakencareofthisinstallation,yourservletsandbeanscanusetheHttpClientclasses.

Example7-9isaservletthatpostsdatatoaJSP:http://localhost:8080/home/viewPost.jsp.Example7-3showstheviewPost.jspfile.Notetheclassesfromtheorg.apache.commons.httpclientpackagethattheservlethastoimportatthetopofthecode.

Example7-9.AservletthatpostsdatatoaJSPusingHttpClient




importorg.apache.commons.httpclient.HttpClient;

importorg.apache.commons.httpclient.HttpStatus;

importorg.apache.commons.httpclient.methods.PostMethod;

importorg.apache.commons.httpclient.NameValuePair;

publicclassClientPostextendsHttpServlet{

publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)


HttpClienthttpClient=newHttpClient();

PostMethodpostMethod=newPostMethod(

"http://localhost:8080/home/viewPost.jsp");

NameValuePair[]postData={

newNameValuePair("username","devgal"),

newNameValuePair("department","development"),

newNameValuePair("email","[email protected]")

};

//the2.0beta1versionhasa

//PostMethod.setRequestBody(NameValuePair[])

//method,asaddParametersisdeprecated

postMethod.addParameters(postData);

httpClient.executeMethod(postMethod);

//displaytheresponsetothePOSTmethod



//A"200OK"HTTPStatusCode

if(postMethod.getStatusCode()==HttpStatus.SC_OK){

out.println(postMethod.getResponseBodyAsString());

}else{

out.println("ThePOSTactionraisedanerror:"+postMethod.getStatusLine());

}

//releasetheconnectionusedbythemethod

postMethod.releaseConnection();

}




}

}

Thecodesendsthreename/valuepairstotheJSP(namedusername,

department,andemail),whichwillhandletheposteddata.HttpClienthandlesthereturnedtextfromthePOSTmethodsothatyoucandisplayitinthesameservlet.IfyouexpecttoreceivelargeamountsoftextasreturnvaluesfromthePOST,thenconsiderusingtheHttpMethodBase.getResponseBodyAsStream()methodinsteadofgetResponseBodyAsString().ThegetResponseBodyAsStream()methodreturnsajava.io.InputStream.Example7-9isderivedfromsamplecodeprovidedattheHttpClientwebsite.

Figure7-4showsthewebbrowserdisplayafterrequestingtheClientPostservlet.

Figure7-4.Displayingthereturnedtextafterpostingdatafromaservlet

SeeAlso

Recipe7.1onhandlingaPOSTrequestinaservlet;Recipe7.7onusingaservlettoaddaparametertoaquerystring;theJakartaCommonsHttpClientpage:http://jakarta.apache.org/commons/httpclient.

http://jakarta.apache.org/commons/httpclient

Recipe7.6PostingDatafromaJSP

Problem

YouwanttosendparametersandtheirvaluesasanHTTPPOSTrequestfromaJSP.

Solution

TheeasiestwaytopostdatafromaJSPistodoittheoldfashionedway:usetheHTMLformtagandaSubmitbutton.Ifyouhavetosendthedatadynamically(asinnotrelyingonausertopressaformbutton),useaJavaBeanthatencapsulatestheHttpClientcodediscussedinRecipe7.5.

Discussion

ThesimplestwaytoinitiateaPOSTmethodinaJSPistosetuptheHTMLtemplatetextasshowninExample7-1:provideanHTMLformtagthattheuserfillsoutandsubmits.SinceExample7-1alreadyshowsatypicalHTMLform,I'lusethisspacetoshowaJavaBeanthatallowsaJSPtodynamicallypostdatatoanotherserver-sideprocess.

Example7-10showsajspPost.jsppagethatusesaPostBeanutilityclasstosendasetofparameters/valuestoanotherJSP.ThereceivingJSP,viewPost.jsp,processestheparametersthatthePostBeanobjectsendsit,thenreturnssometextfortheJSPinExample7-10todisplay.TheJSPpassestheparametersthatitwantstopostasajava.util.MaptothePostBeanclass.ThePostBeanurlpropertyisthedestinationfortheposteddata(theaddressthatyouwould

otherwiseplaceintheactionattributeofaformHTMLtag).Thecode:

<jsp:setPropertyname="postBean"property="parameters"value="<%=request.

getParameterMap()%>"/>

getsaMapoftheparametersthatwerepassedtothejspPost.jsppagewiththeHttpServletRequest.getParameterMap()method,thenpassesthatMaptothePostBeanclasstobereposted.

Example7-10.AJSPthatpostsparametersandvaluesdynamically


<%--createaninstanceofthePostBeanclassifoncedoesnotexist--%>

<jsp:useBeanid="postBean"class="com.jspservletcookbook.PostBean"/>

<%--setthePostBeanparameterspropertytoaMaptype--%>

<jsp:setPropertyname="postBean"property="parameters"value="<%=request.

getParameterMap()%>"/>

<jsp:setPropertyname="postBean"property="url"value="http://localhost:8080/home/

viewPost.jsp"/>

<%--Posttheparametersanddisplaythereturnedtext--%>

<jsp:getPropertyname="postBean"property="post"/>

Example7-11showsthePostBeanclassthattheJSPpageusestopostdata.ThisbeanusestheJakartaCommonsHttpClientcomponenttosendanHTTPPOSTrequest.ThesendingactionhappensinthePostBean.getPost()method,whichsendsofftheparametersandreturnsthetextresultfromthereceivingservlet(inthisexample,it'sviewPost.jsp).BecausethebeanmethodiscalledgetPost(),usingtheJavaBeannamingconventionsformethodsthatreturnpropertyvalues,wecancallthemethodintheJSPwith:

<jsp:getPropertyname="postBean"property="post"/>

ThelattercodeisthenreplacedwiththeStringreturnvalue.

Example7-11.Adata-postingJavaBeanforusebyaJSPorservlet





importorg.apache.commons.httpclient.HttpClient;

importorg.apache.commons.httpclient.HttpStatus;

importorg.apache.commons.httpclient.methods.PostMethod;

importorg.apache.commons.httpclient.NameValuePair;

importorg.apache.commons.httpclient.HttpException;

publicclassPostBeanimplementsjava.io.Serializable{

privateMapparameters;

privateStringurl;

publicPostBean(){

}

publicvoidsetParameters(Mapparam){

if(param!=null)

parameters=param;

}

publicMapgetParameters(){

returnparameters;

}

publicvoidsetUrl(Stringurl){

if(url!=null&&!(url.equals("")))

this.url=url;

}

publicStringgetUrl(){

returnurl;

}

publicStringgetPost()throwsjava.io.IOException,HttpException{

if(url==null||url.equals("")||parameters==null)

thrownewIllegalStateException(

"InvalidurlorparametersinPostBean.getPostmethod.");

StringreturnData="";

HttpClienthttpClient=newHttpClient();

PostMethodpostMethod=newPostMethod(url);

//converttheMappassedintothebeantoaNameValuePair[]type

NameValuePair[]postData=getParams(parameters);

//the2.0beta1versionhasa

//PostMethod.setRequestBody(NameValuePair[])

//method,asaddParametersisdeprecated

postMethod.addParameters(postData);

httpClient.executeMethod(postMethod);

//A"200OK"HTTPStatusCode

if(postMethod.getStatusCode()==HttpStatus.SC_OK){

returnData=postMethod.getResponseBodyAsString();

}else{

returnData="ThePOSTactionraisedanerror:"+

postMethod.getStatusLine();

}

//releasetheconnectionusedbythemethod

postMethod.releaseConnection();

returnreturnData;

}//endgetPost

privateNameValuePair[]getParams(Mapmap){

NameValuePair[]pairs=newNameValuePair[map.size()];

//UseanIteratortoputname/valuepairsfromtheMap

//intothearray

Iteratoriter=map.entrySet().iterator();

inti=0;

while(iter.hasNext()){

Map.Entryme=(Map.Entry)iter.next();

//Map.Entry.getValue()returnsaString[]arraytype

pairs[i]=newNameValuePair(

(String)me.getKey(),((String[])me.getValue())[0]);

i++;

}

returnpairs;

}//endgetParams

}

ThedisplayedresultslooksexactlylikeFigure7-5,whichalsousesviewPost.jsptoshowthename/valuepairsthatwerefedtotheJSP.Again,ifyouhavetouseaJSPtodynamicallymimicanHTMLform,itisagoodideatodelegatethemechanicsofpostingdatatoaJavaBeansothattheJSPremainsapresentationcomponentandthebeancanbereusedelsewhere.

Figure7-5.DisplayingparametersaddedfromaforwardingJSP

SeeAlso

Recipe7.2onhandlingaPOSTrequestinaJSP;Recipe7.3onsettingthepropertiesofaJavaBeantoforminput;Recipe7.8onusingaJSPto

addaparametertoaquerystring.

Recipe7.7UsingaServlettoAddaParametertoaQueryString

Problem

Youwanttouseaservlettoaddoneormoreparameterstoaquerystring,thenforwardtherequesttoitsfinaldestination.

Solution

UsetheHttpServletRequestAPItogettheexistingquerystring.Thenappendanynewparameterstothequerystringanduseajavax.servlet.RequestDispatchertoforwardtherequest.

Discussion

TheservletinExample7-12simplytakesanyexistingquerystringandappendstheparametersthatithastoaddtothisString.Thenitsendsthenowextended(ornew)querystringonitsmerrywaywithacalltoRequestDispatcher.forward.

Example7-12.Addingaparametertoaquerystringwithaservlet




publicclassQueryModifierextendsHttpServlet{



//returnsnulliftheURLdoesnotcontainaquerystring

Stringquerystr=request.getQueryString();

if(querystr!=null){

querystr=querystr+

"&inspector-name=Jen&[email protected]";

}else{

querystr="inspector-name=Jen&[email protected]";}

RequestDispatcherdispatcher=

request.getRequestDispatcher("/viewPost.jsp?"+querystr);


}

publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)


doGet(request,response);

}

}

TheHttpServletRequest.getQueryString()methodreturnsthequerystringwithouttheopening"?",asin:

first=Bruce&last=Perry&zipcode=01922

IfyouwanttogettherequestURLrightuptothequerystringbutnotincludethe

"?",useHttpServletRequest.getRequestURL(),whichreturnsajava.lang.StringBuffertype.

SeeAlso

Recipe7.1onhandlingaPOSTrequestinaservlet;Recipe7.5onpostingdatafromaservlet.

Recipe7.8UsingaJSPtoAddaParametertoaQueryString

Problem

YouwanttouseaJSPtoaddoneormoreparameterstoaquerystring,thenforwardtherequesttoitsdestination.

Solution

Usethejsp:forwardandjsp:paramstandardactions.

Discussion

AddingoneormoreparametersandforwardingtoanothercomponentisaseasyasfourlinesinaJSP.Thejsp:forwardactionaddsanyjsp:paramstoexistingparameterswhenitforwardsthistexttotheprocessingcomponent,asshowninExample7-13.

Example7-13.AddingparametersandforwardinginaJSP

<jsp:forwardpage="/viewPost.jsp">

<jsp:paramname="inspector-name"value="Jen"/>

<jsp:paramname="inspector-email"value="[email protected]"/>

</jsp:forward>

IfthisJSPisrequestedwiththefollowingURL:

http://localhost:8080/home/addParam.jsp?first=Bruce&last=Perry&zip=01922

thenthethreeoriginalparameters(first,last,andzip)arepreservedwhenthejsp:forwardactionaddstwoadditionalparameters(inspector-name,inspector-email)andforwardsthepage.Intheexample,thepageisprocessedbytheviewPost.jsppageshowninExample7-3.RequestingaddParam.jspinabrowserforwardstherequest,andatotaloffiveparameterstotheviewPost.jsppage.Figure7-5showstheresultinabrowser.

SeeAlso

Recipe7.2onhandlingaPOSTrequestinaJSP;Recipe7.3onsettingthepropertiesofaJavaBeantoforminput;Recipe7.6onpostingdatafromaJSP.

Recipe7.9UsingaFiltertoReadParameterValues

Problem

Youwanttouseafiltertointerceptforminputandreadit.

Solution

UsethevariousgetParametermethodsoftheServletRequestAPItotakealookatparametervaluesinafilter.

Discussion

Whenyoudevelopafilterforaservlet,yourfilterclasshastoimplementthejavax.servlet.Filterinterface.ThismeansthatyourFilterclasshastoimplementthedoFilter(request,response)anddestroy()methodsofthatinterface.ThedoFiltermethodcontainsthehooktothefilteredservlet'sparametervalues.ThedoFilter'sServletRequestparameterhasthegetParameter,getParameterMap,getParameterNames,andgetParameterValuesmethodswhichallowthefiltertopeekataservlet'sparametersandvalues.

First,youhavetomaptheFilteryouhavedesignedtotheservlet.Thischunkofweb.xmlmapsaFilterobjecttoaservletnamedViewer.



<filter>

<filter-name>ParamSnoop</filter-name>

<filter-class>com.jspservletcookbook.ParamSnoop</filter-class>

</filter>

<filter-mapping>

<filter-name>ParamSnoop</filter-name>

<servlet-name>Viewer</servlet-name>

</filter-mapping>



PlacethefilterclassintheWEB-INF/classesdirectoryofyourwebapplication,orinsideaJARfilethatisplacedinWEB-INF/lib.Theservletcontainercreatesaninstancewhenthecontainerstartsupofeachfilterthatisdeclaredinweb.xml.Thecontainerthenexecutesthefilter(callsitsdoFiltermethod)whenauserrequestsanyoftheservletsthefilterismappedto.SotheParamSnoopfiltercaninspectarequestmadetotheViewerservletbeforetheservletprocessestherequest.

"OnlyoneinstanceperfilterdeclarationinthedeploymentdescriptorisinstantiatedperJavavirtualmachineofthecontainer,"accordingtotheServletv2.4specification,ChapterSRV.6.2.1.

Example7-14getsaccesstotheparametersintheinterceptedrequestbycallingServletRequest.getParameterMap().However,youarefreetouseotherServletRequestAPImethodstolookatparameters,suchasgetParameterStringName.ThegetParameterMap()methodreturnsajava.util.Mapofparameternamesandvalues,whichyouextractfromtheMapusingajava.util.Iteratoranditsnext()method.

ThecallMap.entrySet()returnsajava.util.Set,fromwhichyouobtainanIteratorbycallingSet.iterator().TheobjectsreturnedfromtheIterator.next()methodinthiscaseareMap.Entryobjectsthathold

key/valuepairs,relatingtotheparameternamesandvalues.

Example7-14alsoshowshowtopullthekey/valuepairsoutofthemapandlogthevaluesusingtheServletContext.log()method.

Example7-14.Snoopingonparametervalueswithaservlet







publicclassParamSnoopimplementsFilter{

privateFilterConfigconfig;

/**CreatesnewParamSnoop*/

publicParamSnoop(){

}

publicvoidinit(FilterConfigfilterConfig)throwsServletException{

this.config=filterConfig;

}

publicvoiddoFilter(

ServletRequestrequest,ServletResponseresponse,FilterChainchain)

throwsjava.io.IOException,ServletException{

MapparamMap=request.getParameterMap();

ServletContextcontext=config.getServletContext();

/*usetheServletContext.logmethodtolog

paramnames/values*/

context.log("doFiltercalledin:"+config.getFilterName()+

"on"+(newjava.util.Date()));

context.log("Snoopingtheparametersinrequest:"+

((HttpServletRequest)request).getRequestURI());

Iteratoriter=paramMap.entrySet().iterator();

while(iter.hasNext()){

Map.Entryme=(Map.Entry)iter.next();

context.log((String)me.getKey()+":"+

((String[])me.getValue())[0]);

}

//continuetherequest,responsetonextfilterorservlet

//destination

chain.doFilter(request,response);

}

publicvoiddestroy(){

/*calledbeforetheFilterinstanceisremoved

fromservicebythewebcontainer*/

}

}

TheonlyreasonweusedtheServletContext.log()methodwastodisplaytheinspectionofparametersbythefilter.HereisanexampleoftheTomcatlogin<Tomcat-installation-directory>/logsshowingthetwoparametersthatwerestoredintheservletrequest(last,first).Inotherwords,thewebbrowserrequestwashttp://localhost:8080/home/viewer?first=Bruce&last=Perry.

2003-04-1317:13:33doFiltercalledin:ParamSnooponSunApr1317:13:33EDT2003

2003-04-1317:13:33Snoopingtheparametersinrequest:/home/viewer

2003-04-1317:13:33last:Perry

2003-04-1317:13:33first:Bruce

SeeAlso

Recipe7.1onhandlingaPOSTrequestinaservlet;Recipe7.7onusingaservlettoaddaparametertoaquerystring;Chapter19onfilteringrequestsandresponses;ChapterSRV.6onFiltersintheServlet2.4specification.

Chapter8.UploadingFilesIntroduction

Recipe8.1.PreparingtheHTMLPageforFileUploads

Recipe8.2.Usingthecom.oreilly.servletLibrary

Recipe8.3.UploadingOneFileataTime

Recipe8.4.UploadingMultipleFiles

Recipe8.5.RenamingFiles

Recipe8.6.UsingaJSPtoHandleaFileUpload

Introduction

WebsitesusetheHTMLformtagtoallowuserstosubmitfilesfromtheirownfilesystemforprocessingontheserver.Theformtagenablestheuploadingactionwithanestedinputelementthathasatypeattributesetto"file".TheformandinputtagisspecifiedusingthesyntaxdescribedinRecipe8.1.

TheHTTPrequestforfileuploadingusesacontenttypeof"multipart/form-data".TheHTTPmessagethattheusersendstotheserverbyclickingthewebpage'sSubmitbuttoncontainsdescriptiveheadersandthebodyofeachuploadedfile.Eachoftheuploadedfilesisseparatedbyaspecifiedboundarypattern(seetheContent-TypeheadervalueinExample8-1).Example8-1showsanabbreviatedviewofa"multipart/form-data"typerequestincludingtheuploadingofthreeverysmallfiles.Tomakethisexamplemorecompact,IhaveremovedsomeofthevaluesfromtheAcceptrequestheader.

Example8-1.AnHTTPrequestmessagewiththreeuploadedfiles

POST/home/upload.jspHTTP/1.1

Accept:image/gif,image/x-xbitmap,image/jpeg,image/pjpeg...

Referer:http://localhost:8080/home/interact.html


Content-Type:multipart/form-data;boundary=---------------------------7d33c11c6018e

Accept-Encoding:gzip,deflate

User-Agent:Mozilla/4.0(compatible;MSIE5.5;WindowsNT4.0)

Host:localhost:9000

Content-Length:541

Connection:Keep-Alive

Cache-Control:no-cache

Cookie:JSESSIONID=7F6154184FFF3D1AE345E1F2FFF1A22E

-----------------------------7d33c11c6018e

Content-Disposition:form-data;name="file1";filename="H:\home\file1.txt"

Content-Type:text/plain

Thisisfile1.

-----------------------------7d33c11c6018e



Thisisfile2.

-----------------------------7d33c11c6018e



Thisisfile3.

-----------------------------7d33c11c6018e--

TheHTTPrequestdelineateseachuploadedfilewithaboundarypattern:

-----------------------------7d33c11c6018e.

EachofthefileshasaContent-DispositionandContent-Typeheader.ThesimpletextfilesthatExample8-1uploadstotheserverhaveonlyonelineeachtogiveyouaclearsnapshotofwhatthistypeofHTTPrequestlookslike.Formoredetailsonthefile-uploadingmechanismitself,seeRFC1867:http://www.ietf.org/rfc/rfc1867.txt.


Recipe8.1PreparingtheHTMLPageforFileUploads

Problem

YouwanttosetupanHTMLpagetoallowtheusertospecifyafilefromhisfilesystemtouploadtotheserver.

Solution

UsetheHTMLformtagwithitsenctypeattributesetto"multipart/form-data".Useaninputtagnestedintheformtagwithatypeattributeof"file".

Discussion

TheHTMLforfileuploadinginvolvesafew"musthaves."Theformtagspecifiestheservlet(orotherserver-sidecomponent)thatishandlingthefileuploadinitsactionattribute.ThemethodattributemustbePOST(notGET)forthefileuploadactiontowork.Theformtag'senctypeattributemustbe"multipart/form-data".

Thewidgetwithwhichtheuserentersthefiletouploadisaninputtagwithatypeof"file",andlookslikeatextfield.Thenameattributeuniquelynamestheparticularinputtag,whichbecomesimportantwhentheHTMLspecifiestheuploadingofmorethanonefile(seethenoteattheendofthisrecipe).Withoutanyadditionalintervention,theserversavestheuploadedfilewithitsoriginalfilename.Theacceptattributeisdesignedtolimitthefiletypesthattheusercanchooseforuploading,suchastothe"application/pdf"MIMEtype,butthisattribute

haspoorsupportamongbrowsers.

WhendisplayingtheHTMLinExample8-2,browsersautomaticallyshowaBrowsebutton.Whentheformclientselectsthebutton,thebrowserdisplaysatypicalfilesystemnavigationwindowwithwhichtheusercanselectthefile.

Example8-2.SimpleHTMLforfileuploading

<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.0Transitional//EN">

<html>

<head>

<title>PleaseChooseTheFile</title>

</head>


<tableborder="0"><tr>

<formaction="/home/servlet/com.jspservletcookbook.UploadServlet"method="post"

enctype="multipart/form-data">

<tdvalign="top"><strong>Pleasechooseyourdocument:</strong><br></td>

<td><inputtype="file"name="file1">

<br><br>

</td></tr>

<tr><td><inputtype="submit"value="UploadFile"></td></tr>

</form>

</table>

</body>

</html>

Afterselection,thetextfielddisplaysthefullpathtotheselectedfile.Figure8-1showsthisHTMLpageinawebbrowser.

Figure8-1.HTMLpageforuploadingafiletoaservlet

Figure8-1showstheinputfieldaftertheuserhasalreadychosenthefile.Thebrowserthenautomaticallyfillsinthetextfieldwiththecompletefilepath.

Toallowtheuploadingofmultiplefiles,includemorethanoneinputtagwithdifferentvaluesforthenameattribute.ThebrowserassociatesaBrowsebuttonwitheachofthem.

SeeAlso

Recipe8.4onusingthecom.oreilly.servletlibraryforfileuploading;Recipe8.5onhandlingasinglefileupload;Recipe8.6onhandlingmultiplefileuploads;Recipe8.5oncontrollingfilenaming;Recipe8.6onusingaJSPtohandlefileuploads;thehomepageforcom.oreilly.servlet:http://www.servlets.com/cos/index.html;theRFC1867documentonform-basedfileuploads:http://www.ietf.org/rfc/rfc1867.txt.

http://www.servlets.com/cos/index.html


Recipe8.2Usingthecom.oreilly.servletLibrary

Problem

Youwanttousethecom.oreilly.servletclassesthatO'ReillyauthorJasonHunterhasdevelopedtohandlefileuploads.

Ofcourse,thisisn'tmuchofaproblem,asJason'slibrarytakesmostoftheworkoutofuploadingandacceptingfiles.IuseJason'slibraryhere(withhispermission,ofcourse)becauseithandlesfileuploadsnicely,andthere'snogoodreasontoreinventaperfectlygoodwheel.

Solution

DownloadthedistributionZIPfilefromhttp://www.servlets.com/cos/index.html.Addthecos.jarfile,whichispartofthedistributiontotheWEB-INF/libdirectoryofyourwebapplication.Makesurethatyouadheretothesoftwarelicensewhenusingthelibrary.

Discussion

AJARfilenamedcos.jarincludesthecom.oreilly.servletandcom.oreilly.servlet.multipartpackages.Thesepackagesincludeseveralclasses,suchasalloftheJavaclassesthatbeginwith"Multipart,"whichcanbeusedtohandlefileuploadinginaservlet.

Thecos.jararchivealsocontainsmanyotherinterestingandusefulclassestouse


withservlets,butthefollowingrecipesfocusonfileuploads.

DownloadthelatestZIPfilecontainingthedistributionfromhttp://www.servlets.com/cos/index.html.ThecontentsoftheZIPfileincludecos.jar,whichyouneedtoaddtotheWEB-INF/libdirectoryofyourwebapplication.Inyourservlet,youthenimporttheclassesthatyouwanttouse:

importcom.oreilly.servlet.MultipartRequest;

importcom.oreilly.servlet.multipart.FileRenamePolicy;

Beforeyouhaveintegratedtheseclassesintoyourcode,makesurethatyouhavereadtheaccompanyingsoftwarelicenseforthiscode:http://www.servlets.com/cos/license.html.

Therestoftherecipesinthischapterassumethatyouhavecos.jarandtheclassesitcontainsavailableinyourwebapplication.Ifyoudon'ttakestepstomaketheseclassesavailable,noneoftheexamplesinthischapterwillfunctionproperly.

SeeAlso

Recipe8.1onpreparingtheHTMLforafileupload;Recipe8.5onhandlingasinglefileupload;Recipe8.6onhandlingmultiplefileuploadsinaservlet;Recipe8.5oncontrollingfilenaming;Recipe8.6onusingaJSPtohandlefileuploads;thehomepageforcom.oreilly.servlet:http://www.servlets.com/cos/index.html;theRFC1867documentonform-basedfileuploads:http://www.ietf.org/rfc/rfc1867.txt.


http://www.servlets.com/cos/license.html



Recipe8.3UploadingOneFileataTime

Problem

Youwanttocreateacomponentthatcanreceiveaclientfileuploadandstorethefileinalocaldirectory.

Solution

Createaservletthatusesthecom.oreilly.servlet.MultipartRequestclassfromJasonHunter'scos.jararchive.

Discussion

TheMultipartRequestclassincludesseveraloverloadedconstructors.TheoneusedinExample8-3takesthejavax.servlet.http.HttpServletRequestobject,thepathtothedirectorywhereyouwanttosaveuploadedfiles,andthesizelimitforthefileasparameters.InExample8-3,iftheclientuploadsafilethatexceeds5MB,thentheUploadServletthrowsajava.io.IOException.Youcanallowthisexceptiontobemanagedbyanerror-pageelementinweb.xmlforIOExceptions,asExample8-3does,oruseatry/catchblockintheuploadservlettodealwitherrors.

SeeChapter9forhowtodeclareerrorpagesforthewebapplication.

WithMultipartRequest,assoonasthecodeinstantiatestheobject,theobjectishandlingthefileupload;inotherwords,youdonothavetocallamethodtocommencemanagingtheupload.

TheservletinExample8-3initiatesthefileuploadandthendisplaysthenameoftheuploadedfile(s).

Example8-3.AservletthatusestheMultipartRequestclass






publicclassUploadServletextendsHttpServlet{

privateStringwebTempPath;

publicvoidinit()

webTempPath=getServletContext().getRealPath("/")+"data";

}




//filelimitsizeof5MB

MultipartRequestmpr=newMultipartRequest(

request,webTempPath,5*1024*1024);

Enumerationenum=mpr.getFileNames();





out.println("<title>Servletupload</title>");



for(inti=1;enum.hasMoreElements();i++)

out.println("Thenameofuploadedfile"+i+

"is:"+mpr.getFilesystemName((String)enum.nextElement())

+"<br><br>");



}




thrownewServletException("GETmethodusedwith"+

getClass().getName()+":POSTmethodrequired.");

}

}

Thecodegeneratesthepathtothesavedirectorybycallingjavax.servlet.ServletContext.getRealPath("/")togetanabsolutepathnametotherootofthewebapplication(asinh:\home\).Thenthecodeaddsthenameofthedirectorywherethefilewillbesaved(data).

Thisdirectorynamecouldalsobeaddedusinganexternalconfigurationsuchasacontext-paramelementinweb.xml.SeeRecipe8.6fordetails.

ThemethodMultipartRequest.getFilesystemName(StringName)returnsthefilenamefromtheclient'sfilesystem.Thefilecanbesavedontheserverendwithitsoriginalfilename,oryoucanuseadifferentMultipartRequestconstructorthattakesasaparameteraFileRenamePolicyobject.Thisconstructorlookslike:

MultipartRequest(javax.servlet.http.HttpServletRequestrequest,

java.lang.StringsaveDirectory,intmaxPostSize,

FileRenamePolicypolicy)

ThereareafewversionsoftheMultipartRequestconstructorwiththeFileRenamePolicyparameter,whichisusedtorenameuploadedfiles(seeRecipe8.5).Example8-3alsothrowsaServletExceptioniftheUploadServletisrequestedwithaGETmethod,whichisnotallowedwithfileuploads.

SeeAlso

Recipe8.1onpreparingtheHTMLforafileupload;Recipe8.4ondownloadingandusingthecom.oreilly.servletlibrary;Recipe8.6onhandlingmultiplefileuploadsinaservlet;Recipe8.5oncontrollingfilenamingduringfileuploads;Recipe8.6onusingaJSPtohandlefileuploads;thehomepageforcom.oreilly.servlet:http://www.servlets.com/cos/index.html;theRFC1867documentonform-basedfileuploads:http://www.ietf.org/rfc/rfc1867.txt.



Recipe8.4UploadingMultipleFiles

Problem

Youwanttouploadmorethanonefileatatimefromaclient,andhandleeachfileasitisuploaded.

Solution

UsetheMultipartParserfromJasonHunter'scos.jararchive.

Discussion

TheMultipartParserclassallowstheservlettohandleeachfilepartsequentiallyastheserverreceivesamultipartHTTPrequest.

YoucanalsousetheMultipartRequestclasstohandlemultiplefiles.However,theMultipartParserallowsyoutohandleeachpart(suchasbysavingittoadatabase)duringtheparsingofamultiple-fileupload.

Inaddition,thefile'scontenttype,size,andnamecanbereadastheservlethandlestherequest.Theservletcanalsomakebasicchecksusingthisclass,suchascountinghowmanyfileswereuploadedandverifyingwhethertheuseruploadedafileforeachoftheavailableforminputfields.

TheHTMLfilefromRecipe8.5hasbeenalteredtoallowtheuploadofthreedifferentfilesfromtheuser'sfilesystem,asshowninFigure8-2.

Figure8-2.AnHTMLformforuploadingthreefiles

ThisHTMLformiscreatedbyincludingthreeinputtagswithtype="file",asin:

<inputtype="file"name="file1"><br><br>

<inputtype="file"name="file2"><br><br>

<inputtype="file"name="file3">

Example8-4handlesthemultiplefileuploadsbyimportingthreeclassesfromthecos.jararchive.TheMultipartParserclassrestrictsthesizeoffileuploadsto5MBinExample8-4;however,youcansetthisconstructorparametertoanothervaluetoallowsmallerorlargerfilesizes,orleavetheacceptedfilesizeatthe1MBdefault.

YoucanviewtheJavadocforthisclassathttp://www.servlets.com/cos/javadoc/com/oreilly/servlet/multipart/MultipartParser.html.

TheMultipartParserobjectthrowsajava.io.IOExceptionifanyofthefileuploadsexceedthesizelimit.Callingthe

http://www.servlets.com/cos/javadoc/com/oreilly/servlet/multipart/MultipartParser.html

MultipartParser.readNextPart()methodreturnsaParttype,ornulliftheincomingstreamdoesnotcontainanymoreparts.APartcanbeeitheraFilePartoraParamPart,dependingonthecontentitincludes.TheParamPartcoverstheotherparametersthatanHTMLformmightinclude,suchas"username".TheFileParthasseveralmethodsthatprovideinformationabouttheuploadedfile,suchasitscontenttypeandthefilename.TheFilePart.writeTo(java.io.Filedir)methodsavesthefiletothespecifieddirectoryandreturnsthefilesizeasalongtype.TheFilePartcanalsowritetoanOutputStream,asinwriteTo(java.io.OutputStreamout).

Example8-4.Aservlethandlingmultiplefileuploads




importcom.oreilly.servlet.multipart.MultipartParser;

importcom.oreilly.servlet.multipart.Part;

importcom.oreilly.servlet.multipart.FilePart;

publicclassParserServletextendsHttpServlet{

privateStringfileSavePath;

publicvoidinit(){

//saveuploadedfilestoa'data'directoryinthewebapp

fileSavePath=getServletContext().getRealPath("/")+"data";

}








out.println("<title>Fileuploads</title>");



out.println("<h2>Hereisinformationaboutanyuploadedfiles</h2>");

try{


MultipartParserparser=newMultipartParser(

request,5*1024*1024);

Part_part=null;

while((_part=parser.readNextPart())!=null){

if(_part.isFile()){

//getsomeinfoaboutthefile

FilePartfPart=(FilePart)_part;

Stringname=fPart.getFileName();

if(name!=null){

longfileSize=fPart.writeTo(

newjava.io.File(fileSavePath));

out.println("Theuser'sfilepathforthefile:"+

fPart.getFilePath()+"<br>");

out.println("Thecontenttypeofthefile:"+

fPart.getContentType()+"<br>");

out.println("Thefilesize:"+fileSize+"bytes<br><br>");

//commencewithanotherfile,ifthereisone

}else{

out.println(

"Theuserdidnotuploadafileforthispart.");

}

}elseif(_part.isParam()){

//dosomethingelseifitisanon-file-typeparameter,

//suchasausername

}

}//endwhile



}catch(java.io.IOExceptionioe){

//anerror-pageinthedeploymentdescriptoris

//mappedtothejava.io.IOException

thrownewjava.io.IOException(

"IOExceptionoccurredin:"+getClass().getName());

}

}//doPost





"GETmethodusedwith"+getClass().getName()+

":POSTmethodrequired.");

}

}

Figure8-3showsthedescriptivepagethattheservletdisplaysabouteachuploadedfile.

Figure8-3.Aservletdisplaysinformationaboutuploadedfiles

SeeAlso

Recipe8.1onpreparingtheHTMLforafileupload;Recipe8.4ondownloadingandusingthecom.oreilly.servletlibrary;Recipe8.5onhandlingasinglefileuploadinaservlet;Recipe8.5oncontrollingfilenaming;Recipe8.6onusingaJSPtohandlefileuploads;thehomepageforcom.oreilly.servlet:http://www.servlets.com/cos/index.html;theRFC1867documentonform-basedfileuploads:http://www.ietf.org/rfc/rfc1867.txt.



Recipe8.5RenamingFiles

Problem

Youwanttorenametheuploadedfilesaccordingtoastandardpolicyortoavoidconflictswithexistingfilesthathavethesamename.

Solution

Createaclassthatimplementsthecom.oreilly.servlet.multipart.FileRenamePolicyinterface,orusetheDefaultFileRenamePolicyclass.Thenusethatclassasaparameterintheconstructorforthecom.oreilly.servlet.MultipartRequestclass.

Discussion

Thecom.oreilly.servlet.multipartpackagecontainsaFileRenamePolicyinterfacethatcanbeusedwhenyouwanttoimplementaparticularfile-renamingpolicywithfileuploads.

TheDefaultFileRenamePolicyclassrenamesanuploadedfilewhosenameconflictswithanexistingfilebyaddinganumbertotheuploadedfilename.Forexample,ifindex.txtalreadyexists,thentheDefaultFileRenamePolicyclassrenamestheuploadedfileindex1.txt;andifasecondfileisuploadedwiththesamenameitwillberenamedindex2.txt,andsoon.

Ifyouwanttoimplementyourownrenamingpolicy,thencreateyourownclassthatimplementstheFileRenamePolicyinterface,then

implementtheclass'srename(java.io.Filefile)methodtoinitiatetherenamingaction.

ThiscodesampleshowsaMultipartRequestconstructorfromExample8-3.Thistime,theconstructoraddsaDefaultFileRenamePolicyobjectasaconstructorparameter:


request,webTempPath,(5*1024*1024),newDefaultFileRenamePolicy());

Makesuretoincludethefollowingimportstatementsintheservletclass:


importcom.oreilly.servlet.multipart.DefaultFileRenamePolicy;

Asmentionedbefore,youcanimplementtheFileRenamePolicyinterfaceyourselfandcreateacustomfile-renamingmechanism.Example8-5showsaMyFileRenamePolicyclassthatrenameseachuploadedfilebyappendingatimestamptotheendofitsname.Thesimpletimestampiscalculatedas:

//secondssinceJan1,1970,00:00:00

newjava.util.Date().getTime()/1000

ThecoderenamesthefilebyappendingtheString(representingaseriesofnumbers)tothefilenameminusitsextension,andthenappendingtheextensionattheend(ifthefilenameoriginallyhadanextension).

Example8-5.RenaminguploadedfileswithyourownJavaclass


importjava.io.File;


importcom.oreilly.servlet.multipart.FileRenamePolicy;

publicclassMyFileRenamePolicyimplementsFileRenamePolicy{

//implementtherename(Filef)methodtosatisfythe

//FileRenamePolicyinterfacecontract

publicFilerename(Filef){

//Gettheparentdirectorypathasinh:/home/useror/home/user

StringparentDir=f.getParent();

//Getfilenamewithoutitspathlocation,suchas'index.txt'

Stringfname=f.getName();

//Gettheextensionifthefilehasone

StringfileExt="";

inti=-1;

if((i=fname.indexOf("."))!=-1){

fileExt=fname.substring(i);

fname=fname.substring(0,i);

}

//addthetimestamp

fname=fname+(""+(newDate().getTime()/1000));

//piecetogetherthefilename

fname=parentDir+System.getProperty(

"file.separator")+fname+fileExt;

Filetemp=newFile(fname);

returntemp;

}

}

Giventhatyournewclassiscalledcom.jspservletcookbook.MyFileRenamePolicyandimplementstheFileRenamePolicyinterface,theconstructorfortheMultipartRequestwouldnowlooklikethis:


request,webTempPath,(5*1024*1024),

newcom.jspservletcookbook.MyFileRenamePolicy());

StoreyournewclassintheWEB-INF/classesdirectoryofthewebapplicationusingthesamedirectorystructureastheclass'spackagename(asinWEB-INF/classes/com/jspservletcookbook/MyFileRenamePolicy.class).

Ingeneral,thecom.oreilly.servletpackagealsoincludestheMultipartFilterclass.AccordingtoanarticlethatJasonhaswritten(http://www.servlets.com/soapbox/filters.html),"TheMultipartFilterworksbywatchingincomingrequestsandwhenitdetectsafileuploadrequest(withthecontenttypemultipart/form-data),thefilterwrapstherequestobjectwithaspecialrequestwrapperthatknowshowtoparsethespecialcontenttypeformat."

SeeAlso

Recipe8.1onpreparingHTMLforafileupload;Recipe8.4ondownloadingandusingthecom.oreilly.servletlibrary;Recipe8.3andRecipe8.6onhandlingsingle-andmultiple-fileuploadsinaservlet;Recipe8.6onusingaJSPtohandlefileuploads;thehomepageforcom.oreilly.servlet:http://www.servlets.com/cos/index.html;theRFC1867documentonform-basedfileuploads:http://www.ietf.org/rfc/rfc1867.txt.

http://www.servlets.com/soapbox/filters.html



Recipe8.6UsingaJSPtoHandleaFileUpload

Problem

YouwanttouseaJSPtohandleafileupload.

Solution

CreateaJavaBeanthatwrapsthefunctionalityofthecom.oreilly.servlet.MultipartRequestclassfromJasonHunter'scos.jarlibrary.Thenusethejsp:useBeanstandardactioninaJSPtocreateaninstanceofthisbeanforhandlingthefileuploads.

Discussion

ThisrecipedescribesaJavaBeanthatusesthecom.oreilly.servlet.MultipartRequestclasstomanagefileuploads.First,I'llshowthebeanthatwrapsthefunctionalityoftheMultipartRequestclass,thentheJSPthatusesthebeantouploadafile.

Example8-6showstheUploadBeanusedbytheJSPinExample8-7.

Example8-6.Afile-uploadingJavaBean




importjavax.servlet.ServletRequest;


importcom.oreilly.servlet.multipart.DefaultFileRenamePolicy;

publicclassUploadBean{

privateStringwebTempPath;

privateHttpServletRequestreq;

privateStringdir;

publicUploadBean(){}

publicvoidsetDir(StringdirName){

if(dirName==null||dirName.equals(""))

thrownewIllegalArgumentException(

"invalidvaluepassedto"+getClass().getName()+".setDir");

webTempPath=dirName;

}

publicvoidsetReq(ServletRequestrequest){

if(request!=null&&requestinstanceofHttpServletRequest){

req=(HttpServletRequest)request;

}else{


"Invalidvaluepassedto"+getClass().getName()+".setReq");

}

}

publicStringgetUploadedFiles()throwsjava.io.IOException{



req,webTempPath,5*1024*1024,newDefaultFileRenamePolicy());

Enumerationenum=mpr.getFileNames();

StringBufferbuff=newStringBuffer("");

for(inti=1;enum.hasMoreElements();i++){

buff.append("Thenameofuploadedfile").append(i).

append("is:").

append(mpr.getFilesystemName((String)enum.nextElement())).

append("<br><br>");

}//for

//returntheString

returnbuff.toString();

}//getUploadedFiles

}

ThiscodeimportstheclassesitneedstohandletheuploadedfileswiththeMultipartRequestclass.TheDefaultFileRenamePolicyclassisusedintheMultipartRequestconstructortohandleconflictsbetweenthenamesofuploadedfilesandanyexistingfileswiththesamename.Whenthesenamingconflictsoccur,theDefaultFileRenamePolicyclassautomaticallyaddsanumbertotheendoftheuploadedfile,asinindex1.txtiftheuploadedfilewasnamedindex.txt.

Example8-6usestheJavaBeannamingconventionsforitsmethods,asinsetDir()andgetUploadedFiles(),whichallowthemethods

tobecalledusingthejsp:getPropertyandjsp:setPropertystandardactions.Example8-7showstheuseofbothoftheseactionsandtheJSPthathandlesthefileuploadanddisplayinformationabouttheuploadedfiles.

TheJSPusestheUploadBean,theclassIjustdefined.TheJSPinstantiatesthebeanusingthejsp:useBeanstandardaction,setsthedirectorynamewheretheuploadedfilewillbesavedwithjsp:setProperty,thenusesjsp:getPropertytosavethefile(s)tothespecifieddirectory.

Example8-7.AJSPthatuploadsfilesanddisplaysinformationaboutthem

<jsp:useBeanid="uploader"class="com.jspservletcookbook.UploadBean"/>

<jsp:setPropertyname="uploader"property="dir"

value="<%=application.getInitParameter(\"save-dir\")%>"/>

<jsp:setPropertyname="uploader"property="req"value="<%=request%>"/>

<html>

<head><title>fileuploads</title></head>

<body>

<h2>Hereisinformationabouttheuploadedfiles</h2>

<jsp:getPropertyname="uploader"property="uploadedFiles"/>

</body>

</html>

TheJSPinExample8-7createsaninstanceoftheUploadBeanwiththiscode:

<jsp:useBeanid="uploader"class="com.jspservletcookbook.UploadBean"/>

Thecom.jspservletcookbook.UploadBeanclassmustbeplacedinthewebapplication'sWEB-INF/classesdirectory(insideofWEB-INF/classes/com/jspservlet/cookbook),orinaJARfileinsideofWEB-INF/lib.

TheJSPthenpassestheHttpServletRequestobjecttothebeanwiththiscode:

<jsp:setPropertyname="uploader"property="req"value="<%=request%>"/>

UnderJSP2.0,youcanpassalongtherequestvaluewiththiscode:

<jsp:setPropertyname="uploader"property="req"value="${pageContext.request}"/>

TheJSP2.0specificationallowstheuseofELsyntaxinthejsp:setPropertyvalueattribute.

ThebeanneedstherequestobjecttopassintotheMultipartRequestconstructor,whichdoesallthefile-uploadingwork.TheJSPalsospecifiesthedirectorywhereuploadedfilesaresaved:

<jsp:setPropertyname="uploader"property="dir"

value="<%=application.getInitParameter(\"save-dir\")%>"/>

Theexpressionapplication.getInitParameter(\"save-dir\")returnsthevalueofthecontextparametersave-dir,whichisthepathtothedirectorywheretheuploadedfilesaresaved.Hereiswhatthisweb.xmlelementlookslike:



<context-param>

<param-name>save-dir</param-name>

<param-value>h:\home\data</param-value>

</context-param>



Thefinalstepistocallthebean'sgetUploadedFiles()method.TheJSPaccomplishesthistaskusingthejsp:getPropertystandardaction,asin:

<jsp:getPropertyname="uploader"property="uploadedFiles"/>

TheJSPcancallthebean'smethodinthismanner,asthoughtheJSPwasfetchingabeanproperty,becauseInamedthemethodwiththestandard"get"prefix:getUploadedFiles().Tricky!

Figure8-4showstheresultingwebpageaftertheuserhassubmittedtheHTMLform.

Figure8-4.AJSPthathandlesfileuploads

TousethisJSPtohandleafileupload,youhavetospecifyitinanHTMLformtag'sactionattribute,asin:

<formaction="http://localhost:9000/home/upload.jsp"method="post"

enctype="multipart/form-data">

SeeAlso

Recipe8.1onpreparingtheHTMLforafileupload;Recipe8.4ondownloadingandusingthecom.oreilly.servletlibrary;Recipe8.3andRecipe8.6onhandlingsingle-andmultiple-fileuploadsinaservlet;Recipe8.5oncontrollingfilerenamingasfilesareuploaded;thehomepageforcom.oreilly.servlet:http://www.servlets.com/cos/index.html;theRFC1867documentonform-basedfileuploads:http://www.ietf.org/rfc/rfc1867.txt.



Chapter9.HandlingExceptionsinWebApplications

Introduction

Recipe9.1.DeclaringExceptionHandlersinweb.xml

Recipe9.2.CreatinganException-HandlingServlet

Recipe9.3.SendinganErrorfromaServlet

Recipe9.4.SendinganErrorfromaJSP

Recipe9.5.CreatinganError-HandlingJSP

Recipe9.6.DeclaringaSpecialException-HandlingJSPforOtherJSPs

Introduction

Webapplicationscansometimesshowanumberoferrorsthatyoudon'twantuserstosee.Ifauserwhoexpectstobeservedaninformation-richpageisinsteadgreetedwithanuglyandincomprehensibleannouncementofan"HTTPStatus500"inherwebbrowser,youcanbetthisvisittothesitewillbeherlast!AllwebsiteshandleunexpectedHTTPstatuscodes(suchasthe"404NotFound"or"403Forbidden")withafriendlyandinformativeerrormessage,butyou'llwanttohidethesemessagesfromyourusers.ToolstohandlebothJavaruntimeexceptionsandtheseunanticipatedHTTPstatuscodesareavailabletodevelopers,andtherecipesinthischaptershowyouhowtousethemeffectively.

Recipe9.1DeclaringExceptionHandlersinweb.xml

Problem

YouwanttodisplaycertainservletsorJSPswhenawebcomponentthrowsaJavaexceptionorgeneratesunexpectedserverresponsecodes.

Solution

Usetheerror-pageelementinweb.xmltospecifytheinvocationofservletsorJSPsinresponsetocertainexceptionsorHTTPstatuscodes.

Discussion

AJavawebdevelopershouldhandlethesetypesofunexpectedoccurrenceswithinhiswebapplication:

The"404NotFound"serverresponsecode,whichindicatesthattheuserhasmadeamistakewhentypingintheURL,orrequestedapagethatnolongerexists.

The"500InternalServerError"thatcanberaisedbyaservletwhenitcallssendError(500)ontheHttpServletResponseobject.

Runtimeexceptionsthatarethrownbythewebapplicationandnotcaughtbythefilter,servlet,orJSP.

Youconfigurethehandlingofexceptionsandserverresponsecodeswiththeerror-pageelementinthedeploymentdescriptor.Theerror-pageelementinweb.xmlcomesafteranyservlet,servlet-mapping,session-config,mime-mapping,andwelcome-file-listelements,aswellasbeforeanytaglib,resource-env-ref,resource-ref,orsecurity-constraintelements.Theerror-pageelementincludesamappingbetweenthestatuscodeorexceptiontype,aswellasthepathtoawebresource.Thisresource,whichshouldbeaservlet,JSP,orHTMLfile,shouldinformtheuseraboutwhathappenedandprovidelinkstootherpartsofthewebsite,dependingonthenatureoftheerror.

Example9-1showsadeploymentdescriptorforservletAPI2.3thatconfigureserrorpages.

Example9-1.Configuringerrorpagesinweb.xml


<!DOCTYPEweb-app



>

<web-app>



<servlet>

<servlet-name>Error404</servlet-name>

<servlet-class>com.jspservletcookbook.Error404</servlet-class>

</servlet>

<servlet>


<servlet-class>com.jspservletcookbook.Error403</servlet-class>

</servlet>

<servlet>

<servlet-name>ErrorIo</servlet-name>

<servlet-class>com.jspservletcookbook.ErrorIo</servlet-class>

</servlet>

<servlet>

<servlet-name>ErrorServlet</servlet-name>

<servlet-class>com.jspservletcookbook.ErrorServlet</servlet-class>

</servlet>

<servlet>

<servlet-name>ErrorGen</servlet-name>

<servlet-class>com.jspservletcookbook.ErrorGen</servlet-class>

</servlet>



<servlet-mapping>


<url-pattern>/err404</url-pattern>

</servlet-mapping>

<servlet-mapping>


<url-pattern>/err403</url-pattern>

</servlet-mapping>

<servlet-mapping>

<servlet-name>ErrorIo</servlet-name>

<url-pattern>/errIo</url-pattern>

</servlet-mapping>

<servlet-mapping>

<servlet-name>ErrorServlet</servlet-name>

<url-pattern>/errServ</url-pattern>

</servlet-mapping>

<servlet-mapping>

<servlet-name>ErrorGen</servlet-name>

<url-pattern>/errGen</url-pattern>

</servlet-mapping>





<error-page>


<location>/err404</location>

</error-page>



<error-page>


<location>/err403</location>

</error-page>



<error-page>

<exception-type>javax.servlet.ServletException</exception-type>

<location>/errServ</location>

</error-page>

<error-page>

<exception-type>java.io.IOException</exception-type>

<location>/errIo</location>

</error-page>



<error-page>

<exception-type>java.lang.Throwable</exception-type>

<location>/errGen</location>

</error-page>

</web-app>

Whenaservletthrowsanexception,thewebcontainersearchestheconfigurationsinweb.xmlthatusetheexception-typeelementforamatchwiththethrownexceptiontype.InExample9-1,ifthewebapplicationthrowsaServletException,thenthewebcontainerinvokesthe/errServservlet.Thewebcontainerinvokestheclosestmatchintheclasshierarchy.Forexample,ifaservletthrowsanIOException,thecontainerinvokesthe/errIoservletthatismappedtothethrownexceptiontype,notthecomponentmappedtojava.lang.ThrowableeventhoughIOExceptionisinthesameclasshierarchyasThrowable.IfthisapplicationthrowsanIllegalStateException,thecontainerinvokesthe/errGenservlet(whichismappedtoThrowable),becausethereisnospecificerrorpagemappingforIllegalStateException.

IntheeventofanHTTPresponsecodeof403or404,thecontainerinvokesthewebcomponentsorHTMLpagesmappedwiththelocationelementtothoseexactnumbers.

Thewebcontainermustreturnaresponsecodeof500ifanexceptionoccursthatisnothandledbythiserror-pagemechanism,accordingtotheservletAPIspecification.

SeeAlso

Recipe9.2oncreatingaservleterrorhandler;Recipe9.3onsendinganerrorfromaservlet;Recipe9.4onsendinganerrorfromaJSP;Recipe9.5onusingJSPstohandleerrors;Recipe9.6ondeclaringinaJSPthatanotherJSPwillhandleitsexceptions;Chapter1onthedeployment

descriptor;theJavaservletspecification,whichcoverserrorhandlinginChapterSRV.9.9:http://java.sun.com/products/servlet/index.html.

http://java.sun.com/products/servlet/index.html

Recipe9.2CreatinganException-HandlingServlet

Problem

Youwanttocreateaservletthatgeneratesanerrorpage.

Solution

Createaservletthatdisplayssomeinformationabouttheerror,thenmapexceptiontypesand/orerrorcodestotheservletinthedeploymentdescriptor.

Discussion

Anerror-handlingservlethasaccesstoseveralrequestattributesthatitcanusetodescribetheerror.Theerrorpagealsohasaccesstotherequestandresponseobjectsassociatedwiththepagethatgeneratedtheerror.Forexample,thejava.lang.Throwableobjectassociatedwithanyexceptionscanbeaccessedwiththefollowingcode:

Throwablethrowable=(Throwable)

request.getAttribute("javax.servlet.error.exception");

Youcanaccesstheserverresponsecodewiththiscode:

Stringstatus_code=((Integer)

request.getAttribute("javax.servlet.error.status_code")).toString();

Table9-1showstherequestattributesthatanerror-handlingservlethas

accessto.

Table9-1.Requestattributesavailabletoservleterrorpages

Requestattribute Javatype

javax.servlet.error.status_code java.lang.Integer

javax.servlet.error.exception_type java.lang.Class

javax.servlet.error.message java.lang.String

javax.servlet.error.exception java.lang.Throwable

javax.servlet.error.request_uri java.lang.String

javax.servlet.error.servlet_name java.lang.String

Example9-2showstheErrorGenservlet.ThewebcontainerinvokesthisservletwhenanotherservletorJSPthrowsanunhandledThrowable,accordingtotheconfigurationinExample9-1.

Example9-2.Anerror-handlingservlet




publicclassErrorGenextendsHttpServlet{




//checktheservletexception

Throwablethrowable=(Throwable)

request.getAttribute("javax.servlet.error.exception");

StringservletName=(String)

request.getAttribute("javax.servlet.error.servlet_name");

if(servletName==null)

servletName="Unknown";

StringrequestUri=(String)

request.getAttribute("javax.servlet.error.request_uri");

if(requestUri==null)

requestUri="Unknown";





out.println("<title>Errorpage</title>");



if(throwable==null){

out.println("<h2>Theerrorinformationisnotavailable</h2>");

out.println("Pleasereturntothe<ahref=\""+

response.encodeURL("http://localhost:8080/home")+

"\">homepage</a>.");

}else{

out.println("<h2>Hereistheerrorinformation</h2>");

out.println(

"Theservletnameassociatedwiththrowingtheexception:"+

servletName+"<br><br>");

out.println("Thetypeofexception:"+

throwable.getClass().getName()+"<br><br>");

out.println("TherequestURI:"+requestUri+"<br><br>");

out.println("Theexceptionmessage:"+throwable.getMessage());

}



}





}

}

Theservletgetsareferencetothethrownexception,thendisplaysinformationsuchastheexception'sclassnameandtheexceptionmessage.TherequestURIrepresentsapartialpath(suchas/home/errGen.jsp)tothecomponentthatthrewtheexception,whichcanbeveryhelpfulfordebuggingandinformationpurposes.Figure9-1showswhatthebrowserdisplayswhenaservletthrowsanexceptionusingTomcat'swebcontainer.

Figure9-1.ErrorpageHTMLdisplayedbyanerror-handlingservlet

Figure9-2showstheerrorpagedisplayedbyourexampleservletwhenaJSPinthesamewebapplicationthrowsajava.lang.ArithmeticException.

Figure9-2.TheerrorpagedisplayedbyExample9-1whenaJSPthrowsanexception

SeeAlso

Recipe9.1ondeclaringexceptionhandlersinthedeploymentdescriptor;Recipe9.3onsendinganerrorfromaservlet;Recipe9.4onsendinganerrorfromaJSP;Recipe9.5onusingJSPstohandleerrors;Recipe9.6ondeclaringinaJSPthatanotherJSPwillhandleitsexceptions;Chapter1onthedeploymentdescriptor;theJavaservletspecification,whichcoverserrorhandlinginChapterSRV.9.9:http://java.sun.com/products/servlet/index.html.


Recipe9.3SendinganErrorfromaServlet

Problem

Youwanttouseaservlettomanuallysendaresponseerrortotheclient.

Solution

Usethejavax.servlet.HttpServletResponse.sendError()method.

Discussion

Thejavax.servlet.http.HttpServletResponseclasshastwoversionsofthesendError()method:onethattakesanintparameterrepresentingtheHTTPresponsecode(suchas500),andtheothertakinganintparameterandaStringerrormessage.TheStringparameterisusedtodisplayamessagetotheclientifanerrorpageisnotconfiguredforthatparticularresponsecode.Example9-3showstheskeletonofaservletwhosecommentedsectionsdescribevariousscenariosforsendingresponsecodes.

Usethetwo-parametermethodversion,sothatameaningfulmessageisdisplayedintheeventthattheapplicationhasnotconfiguredanerrorpageforaparticularerrorcode.

Example9-3.Sendingaresponsecodefromaservlet




publicclassSenderextendsHttpServlet{




/*iftheservlettriestoaccessaresourceandfindsoutthattheclientisnot

authorizedtoaccessit-"401Unauthorized"*/

//response.sendError(401,

//"Youarenotauthorizedtoviewtherequestedcomponent");

/*iftheservlettriestoaccessaresourcethatisforbiddenforthisclientandthere

isnofurtherinformationonit-"403Forbidden"*/


//"Youareforbiddenfromviewingtherequestedcomponent;no

//furtherinformation");

/*iftheservlettriestoaccessaresourcethatisnotfoundgiventheclient'sprovided

URL-"404NotFound"*/


//"Theservercouldnotfindtherequestedcomponent");

}




}

}

IfanerrorpageisconfiguredfortheerrorcodethatyouspecifiedinthesendError()method,thewebcontainerinvokestheerrorpagemappedtothaterrorcode.Iftheerrorcodedoesnothaveanerrorpageconfiguredforitinweb.xml,thewebcontainergeneratesadefaultHTMLpagecontainingthemessageyouincludedastheStringparametertothesendError()method,asinFigure9-3.TheserverleavescookiesandotherresponseheadersunmodifiedwhenitreturnsthisHTMLtotheclient.

IfyoucallsendError()afteralreadycommittingtheresponsetotheclient(suchaswhentheresponsebuffer,atemporarystoragelocationfortheresponsedata,isfulland"auto-flushed"),sendError()throwsajava.lang.IllegalStateException.Youcansetthebuffersizewiththejavax.servlet.ServletResponse.setBufferSize()method.

Figure9-3.ServerresponsetoHttpServletResponse.sendErrorwhenthereisnoerror

pageisconfiguredfortheerrorcode

SeeAlso

Recipe9.1ondeclaringexceptionhandlersinthedeploymentdescriptor;Recipe9.2ondevelopingaservleterrorhandler;Recipe9.4onsendinganerrorfromaJSP;Recipe9.5onusingJSPstohandleerrors;Recipe9.6ondeclaringinaJSPthatanotherJSPwillhandleitsexceptions;Chapter1onthedeploymentdescriptor;theJavaservletspecification,whichcoverserrorhandlinginChapterSRV.9.9:http://java.sun.com/products/servlet/index.html.


Recipe9.4SendinganErrorfromaJSP

Problem

YouwanttouseaJSPtomanuallysendaresponseerrortoaclient.

Solution

UsetheresponseimplicitobjectandthesendErrormethodinsideaJSPscriptlet.

Discussion

IfyouwanttosendaresponseerrorfromaJSP,thensimplygrabtheresponseimplicitobjectinsideascriptletandcallsendError()onit.MakesurenottocallsendError()afteralreadyflushingorcommittingtheresponsetotheclient,orthemethodwillthrowajava.lang.IllegalStateException.TheJSPcodeinExample9-4,whichcouldbeastandaloneJSPorafragmentofalargerpage,resultsinthedisplayofFigure9-3whenrequestedwiththefollowingquerystring:"?client-unauthorized=true".

Example9-4.UsingtheresponseimplicitobjecttosendaresponseerrorfromaJSP

<%@tagliburi=

"http://java.sun.com/jstl/core"prefix="c"%>

<c:iftest="${param.client-unauthorized}">

<%response.sendError(401,

"Youarenotauthorizedtoviewtherequestedcomponent");

%>

</c:if>

SeeAlso

Recipe9.1ondeclaringexceptionhandlersinthedeploymentdescriptor;Recipe9.2ondevelopingaservleterrorhandler;Recipe9.3onsendinganerrorfromaservlet;Recipe9.5onusingJSPstohandleerrors;Recipe9.6ondeclaringinaJSPthatanotherJSPwillhandleitsexceptions;Chapter1onthedeploymentdescriptor;theJavaservletspecification,whichcoverserrorhandlinginChapterSRV.9.9:http://java.sun.com/products/servlet/index.html.


Recipe9.5CreatinganError-HandlingJSP

Problem

YouwanttouseaJSPasyourerrorpageforbothservletsandJSPs.

Solution

CreateaJSPthatdisplaysinformationaboutthejava.lang.Throwablereportedbyusingthespecifiedrequestattributes,suchasjavax.servlet.error.exception.Usetheerror-pageattributeinweb.xmltomapcertainexceptiontypestotheJSP.

Discussion

AJSPcandisplayerrorinformationinthesamemannerastheservletusedinRecipe9.2.Example9-5canbeusedastheerrorpageforbothJSPsandservlets.ThissampleJSPusestheJSTLandtheELtodisplaythethrownexception'svariouscharacteristics,suchasitsfullyqualifiedclassname.

Example9-5.UsingaJSPasanerrorpage

<%@pageisErrorPage="true"%>


<html>

<head><title>Sorryabouttheerror</title></head>

<body>

<h2>Sorry,WeErredHandlingYourRequest</h2>

<strong>Hereisinformationabouttheerror:</strong><br><br>

Theservletnameassociatedwiththrowingtheexception:

<c:outvalue="${requestScope[\"javax.servlet.error.servlet_name\"]}"/>

<br><br>

Thetypeofexception:

<c:outvalue=

"${requestScope[\"javax.servlet.error.exception\"].class.name}"/>

<br><br>

TherequestURI:

<c:outvalue="${requestScope[\"javax.servlet.error.request_uri\"]}"/>

<br><br>

Theexceptionmessage:

<c:outvalue=

"${requestScope[\"javax.servlet.error.exception\"].message}"/>

</body>

</html>

TheerrorpagegrabstherequestUniformResourceIndicator(URI),whichistheservletpathbeginningwiththecontextpathandnotincludinganyquerystring,withthiscode:

<c:outvalue="${requestScope[\"javax.servlet.error.request_uri\"]}"/>

Thispassesthevalueofarequestattributenamedjavax.servlet.error.request_uritothec:outJSTLtag,whichresultsintheattributevaluedisplayedintheHTML.MakesuretoescapethedoublequotesinsidetheELphrase,asin:

"${requestScope[\"javax.servlet.error.request_uri\"]"

Thecodegetsinformationabouttheexceptionfromtherequestattributesthatareautomaticallycreatedbythewebcontainerwhenthe

servletorJSPthrowsanexception.Forexample,ifyouwanttoaddtheresponsestatuscodetothisinformation,thenthisnumberisavailablefromtherequestattributejavax.servlet.error.status_code.

SeeTable9-1forthecompletelistoftheseattributes.

Inaddition,thepartofExample9-5thatgetstheclassnameoftheexceptioncallsgetClass().getName()ontheThrowableobject.Figure9-4showsthebrowserdisplayofthiserrorpageafteraJSPnamederrGen.jspgeneratesanerror.

Figure9-4.AJSPerrorpagedisplaysinformationaboutathrownexception

Theweb.xmldeploymentdescriptorusesthefollowingelementtospecifythattheerrorpageofExample9-5shouldhandleany

java.io.IOExceptions:

<error-page>

<exception-type>java.io.IOException</exception-type>

<location>/errHandler.jsp</location>

</error-page>

Example9-6showstheJSPthatthrowstheexception.

Example9-6.AJSPthatthrowsajava.io.IOException

<html>

<head><title>ExceptionThrower</title></head>

<body>

<h2>ThrowanIOException</h2>

<%java.io.Filefile=newjava.io.File(

"z:"+System.getProperty("file.separator")+"temp");

file.createNewFile();%>

</body>

</html>

SeeAlso

Recipe9.1ondeclaringerrorpagesinweb.xml;Recipe9.2oncreatingaspecialexception-handlingservlet;Recipe9.3onsendinganerrorfromaservlet;Recipe9.4onsendinganerrorfromaJSP;Recipe9.6ondeclaringinaJSPthatanotherJSPwillhandleitsexceptions;Chapter23onusingtheJSTL;theJSP2.0specificationanditsChapterJSP.1.4onerrorhandling:http://java.sun.com/products/jsp/.

http://java.sun.com/products/jsp/default.htm

Recipe9.6DeclaringaSpecialException-HandlingJSPforOtherJSPs

Problem

YouwanttodeclareinsideofaJSPthatanotherorexternalJSPwillhandleanythrownerrors.

Solution

SetthepagedirectiveattributeerrorPagetothespecialJSPerrorpage'spathinthewebapplication.TheJSPerrorpageitselfhasitspagedirectiveattributeisErrorPagesetto"true".

Discussion

TheJSPspecificationallowsaJSPauthortodeclareatthetopofthepagethataspecialerror-handlingJSPwillhandleanyexceptionsthrownbythepagethattheyareauthoring.ThisdesignallowstheencapsulationoferrorhandlinginsideaspeciallydesignedJSP.

IfyouwanttospecificallytargetaJSPerrorpagewithinJSPcode,setthepagedirective'serrorPageattributetothetargeterrorpage'slocationinthewebapplication.Example9-7showsaJSPwithapagedirectivedeclaringerrHandler.jspasitserrorpage.

Thispagedirectivedeclarationoverridesanymatchingerror-pageconfigurationsinweb.xml.IfthisJSPthrowsanjava.io.IOExceptionandweb.xmlhasanexception-typeattributeforthatexception,thewebcontainerinvokestheerrorpagespecifiedbythepagedirectiveinsteadofanyURIspecifiedintheweb.xmlconfiguration.

Example9-7.AJSPthatspecifiesanotherJSPasitserrorpage

<%@pageerrorPage="/errHandler.jsp"%>

<html>

<head><title>ExceptionThrower</title></head>

<body>

<h2>ThrowanIOException</h2>

<%

java.io.Filefile=newjava.io.File("z:"+System.getProperty("file.separator")+

"temp");

file.createNewFile();%>

</body>

</html>

Theerrorpagehasaccesstoanexceptionimplicitobjectthatrepresentsthejava.lang.Throwableobjectassociatedwiththeerror.

Example9-8usestheJSTLandtheELtoshowinformationabouttheexception.SeeChapter23ifyouhavenotyetbeenintroducedtotheJSTLortheEL.

Example9-8.AJSPerrorpagenamederrHandler.jsp

<%@pageisErrorPage="true"%>


<html>

<head><title>Sorryabouttheerror</title></head>

<body>

<h2>Sorry,WeErredHandlingYourRequest</h2>

<strong>Hereisinformationabouttheerror:</strong><br><br>

Theservletnameassociatedwiththrowingtheexception:

<%--JSP2.0usageonly!

<c:outvalue="${pageContext.errorData.servletName}"/>--%>

<br><br>

Thetypeofexception:

<c:outvalue="${pageContext.exception.class.name}"/>

<br><br>

TherequestURI:

<%--JSP2.0usageonly!

<c:outvalue="${pageContext.errorData.requestURI}"/>--%>

<br><br>

Theexceptionmessage:

<c:outvalue="${pageContext.exception.message}"/>

</body>

</html>

Figure9-5showstheerrHandler.jsppagedisplayedinabrowser,aftertheJSPinExample9-7hasthrownajava.io.IOExceptionwhiletryingtocreateafileonaphantomdisk.Thecommented-outsectionsofExample9-8showtheuseofthejavax.servlet.jsp.ErrorDataclass,whichallowsyoutousetheELtogetmoreinformationabouttheerror.Forexample,youcangettherequestURI(asin/home/errGen.jsp)oftheoffendingJSPwiththissyntax:

${pageContext.errorData.requestURI}

However,thisusagefailsinaJSP1.2containersuchasTomcat4.1.12,becauseitwasintroducedinJSP2.0.Thisiswhythereisanemptyspaceinthebrowserpageafter"TherequestURI:."

Figure9-5.AJSPerrorpageusingthepagedirectiveattributeserrorPageandisErrorPage

Youcanalsousethissyntaxtogetaccesstothejava.lang.Throwableobjectintheerrorpage:

<c:outvalue="${requestScope[

\"javax.servlet.jsp.jspException\"]}"/>

SeeAlso

Recipe9.1ondeclaringerrorpagesinweb.xml;Recipe9.2oncreatingaspecialexception-handlingservlet;Recipe9.3onsendinganerrorfromaservlet;Recipe9.4onsendinganerrorfromaJSP;Recipe9.5onusingJSPstohandleerrors;Chapter23onusingtheJSTL;ChapterJSP.1.4oftheJSP2.0specificationonerrorhandling:http://java.sun.com/products/jsp/.

http://java.sun.com/products/jsp/default.htm

Chapter10.ReadingandSettingCookiesIntroduction

Recipe10.1.SettingaCookiewithaServlet

Recipe10.2.CreatinganArrayfromAlloftheRequest'sCookies

Recipe10.3.SettingaCookiewithaJSP

Recipe10.4.ReadingCookieValueswithaServlet

Recipe10.5.ReadingCookieValueswithaJSP

Recipe10.6.AlteringorRemovingaCookieThatHasAlreadyBeenSet

Introduction

Inatypicalvisittoawebsite,ausersendsmultiplerequestsforresourcestoawebserver.Ifawebpagecontainsmanyimages(andmostdo!),thenrequestingthesinglewebpageinvolvesoneHTTPrequestfortheHTMLcodeandothertemplatetext(suchasheadlinesandphrases),followedbyseparaterequestsforeachimagethewebpagecontains.Futurerequestsforthesamepageoftenreturnversionsofthesetextandimagesthatarecachedontheclient'scomputerforthesakeofefficiency,dependingonwhetherthefetchedresourcespermitcaching.Atanyrate,theserverviewseachHTTPrequestforthesewebresourcesasseparateanddiscretefromtheotherrequests.Withouttheuseofadditionalprotocols,theserverdoesnothaveamechanismformanagingclientstate,suchastheprogressofawebuserthroughaquestionnaireorstorefront.Beingabletologicallyrelateoneormorewebrequestsasasingleusersessioniswherecookiescomein.

Acookieisasmallpieceofinformationonauser'scomputerthatawebservercanusetoidentifythatuserthenexttimehevisitsthesite.Whenauserinitiallyvisitsthecookie-enabledsite,theserverrespondswithanextraresponseheaderthatlookslike:

Set-Cookie:mycookie=1051565332678;Domain=.myorg.com;

Expires=Tue,29-Apr-200307:42:12GMT

Consequently,whentheuservisitsthesamesite,hisbrowsersendsanextrarequestheaderthatcontainsthecookieassociatedwiththatweblocation.Hereiswhattherequestheaderslooklikewhentheclientreturnstothesitethatpreviouslysetthecookie;sincetheservletcontainerisTomcat4.1.12,theCookierequestheaderalsoincludesaname/valuepairforthesession-relatedcookie(JSESSIONID):

GET/home/cookieHTTP/1.1

Accept:image/gif,image/x-xbitmap,image/jpeg,image/pjpeg,application/msword,

application/vnd.ms-powerpoint,application/vnd.ms-excel,application/pdf,*/*


Accept-Encoding:gzip,deflate

User-Agent:Mozilla/4.0(compatible;MSIE5.5;WindowsNT4.0)

Host:localhost:9000


Cookie:JSESSIONID=F80F0F571FDE4873CFF3FF0B842D4938;mycookie=1051610231064

Acookiecontainsanameandavalue;thecookiecanalsohaveseveralotheroptionalattribute/valuepairs,whichareseparatedbysemicolons:

Domain

Specifiesthedomaintowhichthiscookiewillbesentinfuturerequests,asinDomain=.jspservletcookbook.com.ThedefaultvalueofthisoptionalattributeisthehostnameofthedomainthathassenttheSet-Cookieheader.

Path

Furtherdelineatesthepartofthewebsitethat,whenrequested,issentthecookiebytheclient.Mostcookiesgivethisattributeavalueof/.Forexample,ifonlythecustomercontextpathshouldreceivethecookie,thentheSet-Cookieheaderwouldincludethepath=/customerattribute/valuepair.Theclientwouldnotsendthecookievaluewhenmakinganyrequeststothedomainthatdonotincludethe/customercontextpath.

Expires

Specifiesthemaximumamountoftimetheuser'sbrowsershouldkeepthecookie.Thisattributeisadatestringrepresentingafuturedate.IfExpiresspecifiesapastdate,thenthecookieisdeleted.TheJavaCookieAPImanagesthisattributebycallingtheCookie

object'ssetMaxAge()method(seeRecipe10.1).

Version

Anoptionalvalueof0forNetscape'spreliminaryspecificationand1fortheRFC2109document.

Secure

TrueifthecookiecanbesentonlyoverasecureconnectionsuchasHTTPS.

Comment

Mayhaveasavalueadescriptionofthecookie'spurpose.

Abrowserisexpectedtosupport20cookiesforeachwebserver,300cookiestotal,andmaylimitcookiesizeto4KBeach,accordingtothejavax.servlet.http.CookieAPIdocumentation.Thecookienameandvaluecombinetorepresentthe4-KBlimit,accordingtotheNetscapepreliminaryspecification.Atypicalcookieisfarlessthan4KBinsize.

Theusercanalsodisablecookies,sothathisbrowserdoesnotsaveanyofthecookiesinaweb-serverresponse.Forexample,inNetscape7.1,themenucombinationEdit Preferences Privacy&SecurityCookiesallowsyoutopreventtheacceptanceofcookiesbychoosingthe"Disablecookies"radiobutton.Inthiscase,thewebdeveloperuses"URLrewriting"foranyclientsthathavedisabledcookies(seeRecipe11.7andRecipe11.8).

TheJavaservletAPIabstractsacookieasanobjectoftypejavax.servlet.http.Cookie.Therecipesinthischaptershowhowtocreatenewcookies,aswellasreadoralterexistingcookies,withbothservletsandJSPs.

Recipe10.1SettingaCookiewithaServlet

Problem

Youwanttosetacookieusingaservlet.

Solution

Createthejavax.servlet.http.Cookieobjectinaservlet,thensetthecookieonauser'smachinewiththejavax.servlet.http.HttpServletResponse.addCookie(Cookie

cookie)method.

Discussion

Insidetheservlet,createtheCookiebyinstantiatinganewCookieandcallingitssetter(ormutator)methods.TheCookieconstructorincludesthenameandvalueforthecookie:

Cookiecookie=newCookie("mycookie","the1cookie");

Example10-1createsacookieandsetsitspathattribute(asin:cookie.setPath(Stringpath))tothenameofthecontextpath(asin/home).Withthispathsetting,theclientwillnotsendthecookietotheserverunlesstheclientrequestsresourceswithinthespecifiedcontextpath.ThecodeusesHttpServletRequest.getContextPath()toprovidethevalueforthecookie'spathattribute.

Example10-1.Aservletthatsetsacookieanddisplayssomecookieinformation




publicclassCookieServletextendsHttpServlet{




Cookiecookie=null;

//GetanarrayofCookiesassociatedwiththisdomain

Cookie[]cookies=request.getCookies();

booleannewCookie=false;

//Getthe'mycookie'Cookieifitexists

if(cookies!=null){

for(inti=0;i<cookies.length;i++){

if(cookies[i].getName().equals("mycookie")){

cookie=cookies[i];

}

}//endfor

}//endif

if(cookie==null){

newCookie=true;

//Getthecookie'sMax-Agefromacontext-paramelement

//Ifthe'cookie-age'paramisnotsetproperly

//thensetthecookietoadefaultof-1,'neverexpires'

intmaxAge;

try{

maxAge=newInteger(

getServletContext().getInitParameter(

"cookie-age")).intValue();

}catch(Exceptione){

maxAge=-1;

}//try

//CreatetheCookieobject

cookie=newCookie("mycookie",""+getNextCookieValue());

cookie.setPath(request.getContextPath());

cookie.setMaxAge(maxAge);

response.addCookie(cookie);

}//endif

//getsomeinfoaboutthecookie





out.println("<title>Cookieinfo</title>");



out.println(

"<h2>Informationaboutthecookienamed\"mycookie\"</h2>");

out.println("Cookievalue:"+cookie.getValue()+"<br>");

if(newCookie){

out.println("CookieMax-Age:"+cookie.getMaxAge()+"<br>");

out.println("CookiePath:"+cookie.getPath()+"<br>");

}



}

privatelonggetNextCookieValue(){

//returnsthenumberofmillesecondssinceJan1,1970

returnnewjava.util.Date().getTime();

}





}

}

Example10-1usesCookie.setMaxAge(intage)tospecifywhenthecookiewillexpireorbedeletedbythebrowser.Themethodparameterrepresentsthemaximumnumberofsecondsthatthecookiewillliveontheuser'smachineafteritiscreated.Theexamplecodegetsthevalueforthismethodfromacontext-paramelementinweb.xml,whichallowsawebdevelopertoconfigureoroptionallychangethisvalueinthedeploymentdescriptor.Hereisanexampleofacontext-paramelementthatprovidesavalueforacookie'sage:

<context-param>

<param-name>cookie-age</param-name>


</context-param>

Forexample,ifyouwantedthecookietolingerforoneyear(365x24x60x60seconds),youcouldusethiscode:

cookie.setMaxAge(31536000);

Userscandeleteacookiefromtheirmachine,regardlessofthemaximumagethatyouhavecreatedforit.Somebrowsersprovideawindowintoauser'scookies,withfeaturesthatallowtheusertoremoveoneormorecookies.Don'tassumethatbecauseyousetamaximumage,thecookiewillalwaysbeavailableonusers'machines.

Example10-1alsochecksfortheexistenceofacookieofthesamenamethatthecodeplanstogivethenewcookie(mycookie).Iftheuserhasnotalreadysentthemycookiecookie,thentheservletsetsanewcookieanddisplayssomeofthecookie'svaluesafterward.

Figure10-1showstheservletoutput.

Figure10-1.Aservletshowsinformationaboutanewcookie

ThecookievalueisarbitrarilysettoaStringshowingalargenumber,justtodemonstratehowtoprovidethevalueforacookie.Asmanycookiesneeduniquevalues,youcoulduseamethodwherebytheuser'semailaddressoruniquedatabaseIDisencodedandthenusedasthecookievalue.

SeeAlso

Recipe10.3onsettingacookiewithaJSP;Recipe10.4onusingaservlettoreadcookies;Recipe10.5onreadingcookievalueswithaJSP;Recipe10.6onalteringorremovinganexistingcookie;theRFC2109

documentdealingwithcookies:ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt;Netscape'spreliminaryspecificationforcookies:http://wp.netscape.com/newsref/std/cookie_spec.html;theJavaCookieAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html.

http://wp.netscape.com/newsref/std/cookie_spec.html

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html

Recipe10.2CreatinganArrayfromAlloftheRequest'sCookies

Problem

Youwanttostoreallofthecookiescontainedbyaclient'srequestinaCookiearray.

Solution

UsetheHttpServletRequest.getCookies()method,whichreturnsanarrayofjavax.servlet.http.Cookieobjects.

Discussion

TocreateanarrayofCookiesrepresentingallofthecookiesincludedinarequest,usetheHttpServletRequest.getCookies()method.YoucanthenaccessthenameandvalueofacookiebycallingtheCookieclass'sgetName()andgetValue()methods.

ThecodeforaccessinganarrayofCookieslookslikeExample10-2.

Example10-2.CreatingaCookiearray

//servlet'sdoGetmethod




Cookiecookie=null;



//Checkforanullvalue,thendosomethingwithanyCookies

if(cookies!=null){//readeachCookievalue

}

//restoftheservlet

Onceacookiehasalreadybeencreated,thenexttimetheusersendsthecookieasarequestheader,theonlyinformationyoucanextractfromtheCookieobjectisitsnameandvalue.Youwillnotbeabletoderivethecookie'smaximumagefromtherequestheader,becausealltheheaderwillcontainistheCookieobject:headername,thenthenameandvalueofthecookie.

SeeAlso

Recipe10.1onsettingacookiewithaservlet;Recipe10.3onsettingacookiewithaJSP;Recipe10.4onusingaservlettoreadcookies;Recipe10.5onreadingcookievalueswithaJSP;Recipe10.6onalteringorremovinganexistingcookie;theRFC2109documentdealingwithcookies:ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt;Netscape'spreliminaryspecificationforcookies:http://wp.netscape.com/newsref/std/cookie_spec.html;theJavaCookieAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html.

ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt



Recipe10.3SettingaCookiewithaJSP

Problem

YouwanttouseaJSPtosetacookieonaclient.

Solution

WrapaJavaBeanaroundtheservletAPIforcreatingcookies.ThenusethebeanintheJSPwiththejsp:useBeanstandardaction.

Discussion

AJSPcanuseaJavaBeantocreatethecookieandsetthecookieontheclient.Example10-3createsaninstanceofaJavaBeanoftypecom.jspservletcookbook.CookieBeanusingthejsp:useBeanstandardaction.ThentheJSPsetsafewbeanproperties.ThebeanwillpassthroughthepropertyvaluestothecookiethatitisgeneratingfortheJSP.TheJSPusesjsp:setPropertytosetthefollowingcookieproperties:

Thecookiename(bakedcookieinthecode).

Themaximumnumberofsecondsthebrowserwillholdontothecookie(roughlyoneyearinExample10-2).Thisnumberisconvertedtoareadablefuturedateforthecookie'sExpiresattribute.

Thepathontheserverassociatedwiththiscookie.OncetheJSPhassentthiscookietotheclient,theclientwillreturntheassociated

cookieonlyintherequestheadersforrequeststhatcontainthespecifiedcontextpath(suchas/home).Forexample,ifthecookieissetbytheJSPfileto/home/cookieSet.jsp,onlyrequestsforresourcesin/homewillincludeaCookieheader.

Example10-3.AJSPthatsendsacookietoaclient

<jsp:useBeanid="cookieBean"class="com.jspservletcookbook.CookieBean"/>

<jsp:setPropertyname="cookieBean"property="name"value="bakedcookie"/>

<%--set'Expires'attributetoaboutoneyearfromnow--%>

<jsp:setPropertyname="cookieBean"property="maxAge"value=

"<%=(365*24*60*60)%>"/>

<jsp:setPropertyname="cookieBean"property="path"value="<%=request.getContextPath()

%>"/>

<jsp:setPropertyname="cookieBean"property="cookieHeader"value="<%=response%>"/>

<html>

<head><title>CookieMaker</title></head>

<body>

<h2>Hereisinformationaboutthenewcookie</h2>

Name:<jsp:getPropertyname="cookieBean"property="name"/><br>

Value:<jsp:getPropertyname="cookieBean"property="value"/><br>

Path:<jsp:getPropertyname="cookieBean"property="path"/>

</body>

</html>

TheJSPpassesalongtheHttpServletResponseobjecttoitswrapperbean,sothatthebeancancallresponse.addCookie(Cookiecookie)tosendtheclientthenewcookie.Theresponseobjectispassedtothebeanusingthiscode(seethesetCookieHeader()methodinExample10-4):

<jsp:setPropertyname="cookieBean"property="cookieHeader"value=

"<%=response%>"/>

ThebottomoftheJSPdisplayssomeofthenewcookie'svalues.Figure10-2showstheJSP'soutputinawebbrowser.Repeatedlyrequesting

theJSPwilloverwritetheexistingcookiewithanewone.

Figure10-2.AJSPshowsinformationaboutanewcookie

Example10-4showsthecodefortheCookieBeanitself,whichisratherlengthyduetoallthegetterandsettermethods.

ThisJavaBeanclassmustbeplacedintheWEB-INF/classesdirectoryofthewebapplication(includingadirectorystructurethatmatchesthebean'spackagename)sothatthewebcontainercanloadtheclass.ThebeancouldalsobearchivedinaJARfilethatisplacedinWEB-INF/lib;however,theJARwouldstillhavetocontainadirectorystructurethatmatchesthebean'spackagename.

YoucansetthecookievalueintheJSP(whichisnotdoneinExample10-3)bycallingthebean'ssetValue(Stringvalue)methodviajsp:setProperty:

<jsp:setPropertyname="cookieBean"property="value"value="newvalue"/>

ThebeanhastoimporttheCookieandHttpServletResponseclasses,becauseitusesthemtomakethenewcookie,thensendthecookietotheclient.Example10-4wrapsitsownmethodsaroundsome

oftheCookieclassmethods,suchassetValue()andsetMaxAge().

Example10-4.AJavaBeanformakingcookies



importjavax.servlet.http.Cookie;

publicclassCookieBean{

privateCookiecookie=null;

publicCookieBean(){}

//setthecookiename

publicvoidsetName(Stringname){

if(name==null||(name.equals("")))


"Invalidcookienamesetin:"+getClass().getName());

cookie=newCookie(name,""+newjava.util.Date().getTime());

}

//setthecookievalue

publicvoidsetValue(Stringvalue){

if(value==null||(value.equals("")))


"Invalidcookievaluesetin:"+getClass().getName());

if(cookie!=null)

cookie.setValue(value);

}

publicvoidsetMaxAge(intmaxAge){

if(cookie!=null)

cookie.setMaxAge(maxAge);

}

publicvoidsetPath(Stringpath){

if(path==null||(path.equals("")))


"Invalidcookiepathsetin:"+getClass().getName());

if(cookie!=null)

cookie.setPath(path);

}

publicvoidsetCookieHeader(HttpServletResponseresponse){

if(response==null)


"InvalidHttpServletResponsesetin:"+getClass().getName());

if(cookie!=null)

response.addCookie(cookie);

}

publicStringgetName(){

if(cookie!=null)

returncookie.getName();

else

return"unavailable";

}

publicStringgetValue(){

if(cookie!=null)

returncookie.getValue();

else


}

publicStringgetPath(){

if(cookie!=null)

returncookie.getPath();

else


}

}

IftheJSPfailstousejsp:setPropertytocallthebean'ssetCookieHeader(HttpServletResponseresponse)method,thenthecookieiscreatedbutneverincludedintheresponseheaderssenttotheclient.Inthisdesign,youallowtheusertosetsomeoptionalcookieattributes(suchasPath)beforesheexplicitlysendsthecookieaspartoftheresponse.

SeeAlso

Recipe10.1onsettingacookiewithaservlet;Recipe10.2oncreatinganarrayfromalloftherequest'scookies;Recipe10.4onusingaservlettoreadcookies;Recipe10.5onreadingcookievalueswithaJSP;Recipe10.6onalteringorremovinganexistingcookie;theRFC2109documentdealingwithcookies:ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt;Netscape'spreliminaryspecificationforcookies:http://wp.netscape.com/newsref/std/cookie_spec.html;theJavaCookieAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html.




Recipe10.4ReadingCookieValueswithaServlet

Problem

Youwanttoreadcookievaluesfromaclientusingaservlet.

Solution

CreateaJavaarrayofjavax.servlet.http.CookieobjectsbycallingtheHttpServletRequest.getCookies()method.Thencyclethroughthearray,accessingeachcookieandvalueasneeded.

Discussion

ThewebuserwillsendcookiestoawebsiteonlyiftheuseroriginallyreceivedSet-Cookieheadersfromthatdomain.Inaddition,ifthecookiewassetwithaPathattributespecifyingacontextpath,thentheservletcanaccessthecookieonlyiftheservletisalsoassociatedwiththecontextpath.Asaresult,alwaystestthereturnvalueoftherequest.getCookies()method(whichreturnsanarrayofCookieobjects)toseeifitisnull,indicatingthattheuserhasnotsentanycookies,beforeoperatinguponit.

Example10-5displaysthevalueofanyfoundcookiesinawebbrowser.TheCookieReaderclassusesthejavax.servlet.http.Cookie.getName()andgetValue()methodsinordertodisplaythisinformation.

Example10-5.Acookie-readingservlet




publicclassCookieReaderextendsHttpServlet{




Cookiecookie=null;



booleanhasCookies=false;

//ifcookiescontainsanarrayandnotanullvalue,

//thenwecandisplayinformationaboutthecookies.

if(cookies!=null)

hasCookies=true;

//displaythename/valueofeachcookie





out.println("<title>Cookieinformation</title>");



if(hasCookies){

out.println(

"<h2>Thenameandvalueofeachfoundcookie</h2>");

for(inti=0;i<cookies.length;i++){

cookie=cookies[i];

out.println(

"Nameofcookie#"+(i+1)+":"+cookie.getName()+"<br>");

out.println(

"Valueofcookie#"+(i+1)+":"+

cookie.getValue()+"<br><br>");

}//for

}else{

out.println(

"<h2>Thisrequestdidnotincludeanycookies</h2>");

}


out.println("</html>");}





}

}

Thejavax.servlet.http.Cookieclassisanabstractionofacookiethathasgetterandsettermethodsforacookie'sattributes,suchasitsname,value,path,andsecureattributes.However,whenyouretrieveacookie,youcanonlygetitsnameandvalue,becausethisistheonlyinformationthattheclientincludesintherequestheader.TheCookierequestheaderlookslike:

Cookie:JSESSIONID=F80F0F571FDE4873CFF3FF0B842D4938;mycookie=1051610231064

Forexample,callingCookie.getPath()onaretrievedcookiewillreturnnull,evenifthecookiewasoriginallysetwithavalidpathattribute,suchas/mypath.YoucanonlyaccessthesevaluesintheservletorJSPthatcreatesthecookieobjectinthefirstplace(seeRecipe

10.1andRecipe10.3).

Figure10-3showshowawebbrowserdisplaysthisservlet'soutput.

Figure10-3.Aservletdisplayscookieinformation

SeeAlso

Recipe10.1onsettingacookiewithaservlet;Recipe10.2oncreatinganarrayfromalloftherequest'scookies;Recipe10.3onsettingacookiewithaJSP;Recipe10.5onreadingcookievalueswithaJSP;Recipe10.6onalteringorremovinganexistingcookie;theRFC2109documentdealingwithcookies:ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt;Netscape'spreliminaryspecificationforcookies:http://wp.netscape.com/newsref/std/cookie_spec.html;theJavaCookieAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html.




Recipe10.5ReadingCookieValueswithaJSP

Problem

YouwanttoreadcookievalueswithaJSP.

Solution

UsetheJSTLanditscookieimplicitobjecttodisplaythenameandvalueofanycookiesfoundintherequest.

Discussion

TheJSTLanditsELhaveacookieimplicitobject(avariablethatisautomaticallyavailabletoJSPorELcode)thatyoucanuseinJSPstodisplayanycookienamesandvalues.FormoreinformationontheJSTLandEL,seeChapter23.

YoucanaccessthecookieimplicitobjectinJSPcodethisway:

${cookie}

Thisimplicitobjectevaluatestoajava.util.Maptypewhosevaluesyoucaniterateoverwiththec:forEachJSTLtag.Eachiterationofc:forEachreturnsajava.util.Map.Entry,whichencapsulatesakey/valuepair.Thekeyisthenameofthecookie;thevalueisajavax.servlet.http.Cookieobject.

Example10-6usesthiscodetoretrieveaCookieobjectfromtheMapofavailablecookies:

<c:forEachvar="cookieVal"items="${cookie}">

Thevarattributeofc:forEachcontainsaMap.Entryobjectwhosekeyisthecookiename;thevalueistheCookieobject.Thecodeusesc:outtagstodisplaythecookienamesandvaluesintheJSP.Thisoddsyntaxdisplaysthevalueofeachcookie:

<c:outvalue="${cookieVal.value.value}"/>

ThecodecookieVal.valueevaluatestothejavax.servlet.http.Cookieobject.Thefullphrase${cookieVal.value.value}istheequivalentofcallingCookie.getValue().

Example10-6.AJSPthatreadscookienamesandvalues


<html>

<body>

<%--checkwhethertherequestcontainsanycookies--%>

<c:choose>

<c:whentest="${emptycookie}">

<h2>Wedidnotfindanycookiesintherequest</h2>

</c:when>

<c:otherwise>

<h2>Thenameandvalueofeachfoundcookie</h2>

<c:forEachvar="cookieVal"items="${cookie}">

<strong>Cookiename:</strong><c:outvalue="${cookieVal.key}"/><br>

<strong>Cookievalue:</strong><c:outvalue=

"${cookieVal.value.value}"/><br><br>

</c:forEach>

</c:otherwise>

</c:choose>

</body>

</html>

Figure10-4showstheJSPdisplayingtheavailablecookieinformation.

Figure10-4.OutputofthecookieReader.jsppage

MakesuretoincludethetaglibdirectivefortheJSTLcorelibraryatthetopofyourJSP,sothatyoucanusetheJSTLtagstoviewanycookievalues:

<%@tagliburi=

"http://java.sun.com/jstl/core"prefix="c"%>

Useuri=http://java.sun.com/jsp/jstl/corewhenusingJSTL1.1

SeeAlso

Recipe10.1onsettingacookiewithaservlet;Recipe10.2oncreatinganarrayfromalloftherequest'scookies;Recipe10.3onsettingacookiewithaJSP;Recipe10.4onusingaservlettoreadcookies;Recipe10.6onalteringorremovinganexistingcookie;theRFC2109

documentdealingwithcookies:ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt;Netscape'spreliminaryspecificationforcookies:http://wp.netscape.com/newsref/std/cookie_spec.html;TheJavaCookieAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html.




Recipe10.6AlteringorRemovingaCookieThatHasAlreadyBeenSet

Problem

Youwanttooverwriteorremoveanexistingcookie.

Solution

Sendacookiewiththesamenameandpathasanexistingcookietooverwritetheexistingcookie.Todeleteacookie,sendacookiewiththesamenameandpathbutsettheExpiresattributetoadateinthepast.

Discussion

Youcanoverwriteacookieandoptionallyprovidedifferentvaluesforitsattributes(suchasthecookievalue)byincludingacookieinaresponseheaderthathasthesamenameandpathasanexistingcookie.Forexample,imagineaservlethassetacookieontheclientwiththefollowingresponseheader:

Set-Cookie:newcookie=1051642031398;Expires=Wed,28-Apr-200418:47:11GMT;Path=/home

Thiscookiecanbeoverwrittenontheclientbychangingitscookievalue,butnotthenameandpath:

Set-Cookie:newcookie=A1lnew;Expires=Wed,28-Apr-200418:52:50GMT;Path=/home

Thisresponseheaderwillreplacenewcookiewithacookieofthesamename.Thenewversionhasanewvalue(A1lnew)andanExpiresattributevalue.

DeletingaCookie

YoucandeleteacookiebysendingaresponseheadertotheclientwiththesamecookienameandPathvalue,butwithanExpiresattributevaluethatrepresentsadateinthepast.WithJava'sCookieAPI,yousimplycallthejavax.servlet.http.Cookie.setMaxAge()methodwithanargumentvalueof0.Example10-7istheJSPofRecipe10.2.ThistimetheJSPisdeletingmycookiebysettingthemaxAgepropertyto0usingjsp:setProperty.

Example10-7.Deletinganexistingcookie

<jsp:useBeanid="cookieBean"class="com.jspservletcookbook.CookieBean"/>

<jsp:setPropertyname="cookieBean"property="name"value="mycookie"/>

<%--deletethecookiebycallingCookie.setMaxAge(0)--%>

<jsp:setPropertyname="cookieBean"property="maxAge"value="0"/>

<jsp:setPropertyname="cookieBean"property="value"value="finished"/>

<jsp:setPropertyname="cookieBean"property="path"value=

"<%=request.getContextPath()%>"/>

<jsp:setPropertyname="cookieBean"property="cookieHeader"value=

"<%=response%>"/>

<%--restofJSPcontinues--%>

CookiescanbedeletedonlybyaSet-Cookieresponseheaderemanatingfromthesamedomainthatcreatedthecookie,withthesamecookienameandPathattribute.HereiswhattheresponseheaderfromthedeletingJSPlookslike:

HTTP/1.1200OK

Content-Type:text/html;charset=ISO-8859-1

Set-Cookie:mycookie=finished;Expires=Thu,01-Jan-197000:00:10GMT;Path=/home

Transfer-Encoding:chunked

Date:Tue,29Apr200319:18:59GMT

Server:ApacheCoyote/1.0

NotethattheExpiresattributevalueisadateinthepast.Asaresult,theclientwillnolongersendthemycookiecookieinitsrequestheaderswhenitmakesarequesttothesamedomainatthe/homecontextpath.However,itmaysendothercookies(withdifferentnames)thatwerecreatedduringpriorvisitstothesamedomainandcontextpath.

Thebrowserusercandeleteacookiefromhismachineanytimehewants,soalwaysplanaccordingly.

SeeAlso

Recipe10.1onsettingacookiewithaservlet;Recipe10.2oncreatinganarrayfromalloftherequest'scookies;Recipe10.3onsettingacookiewithaJSP;Recipe10.4onusingaservlettoreadcookies;Recipe10.5onreadingcookievalueswithaJSP;theRFC2109documentdealingwithcookies:ftp://ftp.rfc-editor.org/in-notes/rfc2109.txt;Netscape'spreliminaryspecificationforcookies:http://wp.netscape.com/newsref/std/cookie_spec.html;theJavaCookieAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/Cookie.html.




Chapter11.SessionTracking

Introduction

Recipe11.1.SettingtheSessionTimeoutinweb.xml

Recipe11.2.SettingtheSessionTimeoutinAllTomcatWebApplications

Recipe11.3.SettingtheSessionTimeoutProgrammatically

Recipe11.4.CheckingifaSessionExistsinanHttpServletRequest

Recipe11.5.TrackingSessionActivityinServlets

Recipe11.6.TrackingSessionActivityinJSPs

Recipe11.7.UsingURLRewritinginaJSP

Recipe11.8.UsingURLRewritinginaServlet

Recipe11.9.UsingaListenertoTracktheSessionLifecycle

Recipe11.10.UsingaListenertoMonitorSessionAttributes

Recipe11.11.UsingaFiltertoMonitorSessionAttributes

Introduction

ThischapterdescribeshowtomonitorsessionsinservletsandJSPs.Asessionrepresentsaninteractionbetweenawebuserandawebapplication.TheHypertextTransferProtocol(HTTP)isastatelessprotocol,meaningthatitisnotdesignedtomaintainstate,ortheprogressofasingleuserassheinteractswithawebserverbyexchangingHTTPrequestsandresponses.EachrequestforaJSPorservlet,atleastfromtheHTTPserver'spointofview,isconsideredseparatefromotherrequestsandnotassociatedwiththesameuser.Manywebapplications,however,needtofollowauser'sprogressstepbystepthroughouttheapplication,tokeeptrackofherpurchaseditemsand/orpreferences.

Forexample,whenauserbuysbooksatAmazon.com,thewebsitemonitorswhatisaddedtoorremovedfromthecustomer'sshoppingcartandusesthisinformationduringthecheckoutandpaymentprocess.Inaddition,Amazon.comshowsuserswhichbookstheyhavelookedatduringtheircurrentsession.Sequentialvisitsbyasingleusertoane-commercesitelikethisareconsideredpartsofonesession.

Webapplicationscommonlyusecookiesinordertoimplementsessions.Allservletcontainershavetosupporttheuseofcookiestotracksessions,accordingtotheServletv2.3and2.4specifications.Acookieisasmallpieceofinformationthatisstoredbytheclientwebbrowserinresponsetoaresponseheaderissuedbythewebserver.CookiesaredescribedinmoredetailinChapter10,butsincetheyarecentraltothesessionconcept,Iincludeabriefoverviewoftheiruseinsessiontrackinghere.

Whenauserrequestsapagefromawebserver,theserverrespondswithacollectionofname/valuepairscalledresponseheaders,alongwiththeHTMLresponse.TheseheadersmayincludeonelabeledSet-Cookie,whichrequeststhattheclientstoresomestateinformationlocally.TheonlyrequiredelementoftheSet-CookieHTTPresponseheaderisthecookienameandvalue.Thecookiemayincludeother

piecesofinformationseparatedbysemicolons.ThecookiethatJavawebcontainerssetinordertoimplementsessiontrackinglookslikejsessionid=cookie-value,wherecookie-valueisusuallyalongnumericstringofbytesusinghexadecimalnotation.Accordingtotheservletspecificationv2.3,thiscookie'snamemustbeJSESSIONID.Somewebcontainersgeneratethenameinlowercase,however,likeTomcat.Atypicalsession-relatedcookielookslikethefollowing:

jsessionid=3CAF7CD0A0BFF5076B390CCD24FD8F0D

ThecookievaluerepresentsthesessionID.ThisIDuniquelyidentifiestheuserfortheperiodwhenheismakingrequeststothewebserver.Forexample,if10usersareinteractingwiththewebapplicationatthesametime,thewebserverassignsthem10uniquesessionIDs.Additionally,ifapersonsitsdownathisPCandconnectswiththewebapplicationusingInternetExplorer,thenmovesovertoaconnectedlaptopandopensupSafaritothesamewebapplication,thosebrowserswillbeassociatedwithtwodifferentsessionIDs.Thewebserverdoesnothaveanywayofknowingthatthesamepersonisinteractingwiththewebapplicationfromtwodifferentbrowsersatthesametime,particularlyifheisconnectingfrombehindaproxyserver.However,aslongastheuserworkswithasinglebrowserandthatuser'ssessionhasnotyettimedout,awebservercantrackthatuser'sactions,andassociatethemasonesession.

DisabledCookies

Whatiftheuserblockscookies?Webbrowserstypicallyallowthedisablingofcookiesintheuserpreferences.ServersmayalsousetheSecureSocketsLayer(SSL),whichhasabuilt-insession-trackingmechanism.Inaddition,URLrewritingisacommonfallbackmethodofsessiontracking.URLrewritinginvolvesaddingthesessionIDasapathparametertotheURLwhenlinkingfromonepagetothenext,sothatthenextpagehasaccess(withoutcookies)tothesessionID.TheseURLslooklikethis:

/home/default.jsp;jsessionid=3CAF7CD0A0BFF5076B390CCD24FD8F0D

AsmostpagerequestsineverydaywebusearenotmadeusingSSL,youshouldcodeyoursessiontracking-relatedwebcomponentstoaccommodateURLrewriting.

Recipe11.1SettingtheSessionTimeoutinweb.xml

Problem

Youwanttoconfigureatimeoutperiodforthewebapplicationinthedeploymentdescriptor.

Solution

Createasession-configelementinweb.xml.

Discussion

Thelengthoftimethatasessionlastsbeforetheserverinvalidatesthesessionandunbindsanyofitsobjectsisanimportantcomponentofyourwebapplication.InTomcat4.1.x,thedefaulttimeoutperiodforasessionis30minutes.Ifanyrequeststhatareassociatedwiththesessionhavebeeninactiveforthatperiod,thesessiontimesout.Iftheuserdecidestoreturntothewebapplicationafter30minutes,usingthesamebrowser,thenanewsessioniscreatedforhim.Example11-1showshowtosetyourowntimeoutperiodforsessions.

Example11-1.Configuringthesessiontimeout


<!DOCTYPEweb-app



>

<web-app>



<session-config>


</session-config>

</web-app>

Placeonenestedsession-timeoutelementwithinthesession-config.Thetimeoutisexpressedasminutes,andoverridesthedefaulttimeout(whichis30minutesinTomcat,forexample).However,theHttpSession.getMaxInactiveInterval()methodinaservletreturnsthetimeoutperiodforthatsessioninseconds;ifyoursessionisconfiguredinweb.xmlfor15minutes,getMaxInactiveInterval()returns900.

Anotherwaytoconfigureatimeoutvalueforaservletistousetheinit-paramelementinweb.xml,asshowninExample11-2.

Example11-2.Addinganinit-paramtoaservlettosetasessiontimeoutinterval

<servlet>

<servlet-name>Cart</servlet-name>

<servlet-class>com.jspservletcookbook.TimeoutSession</servlet-class>

<init-param>

<param-name>timeout</param-name>


</init-param>

</servlet>

Theservletelementinthiswebapplication'sweb.xmlfilehasanested

init-param,whichcreatesaparametercalledtimeout.TheCartservlettakestheparametervalue(600seconds,equivalentto10minutes)andpassesittothesession.setMaxInactiveInterval(intseconds)method.Example11-3showsthedoGet()methodoftheservlet,whichsetsthesessiontimeoutvariabletotheconfiguredparametervalue.

Example11-3.Usinginitparameterstosetaservlet'ssessiontimeout






HttpSessionsession=request.getSession();

//initiallysettodefaulttimeoutinterval

int_default=session.getMaxInactiveInterval();

inttimeout=_default;

try{

timeout=newInteger(getInitParameter("timeout")).intValue();

}catch(NumberFormatExceptionnfe){

//reportanyproblemswiththeconfiguredvalueinweb.xml

log("Problemwithconfiguringsessiontimeoutin:"+


}//try

//nowsetthesessiontotheconfiguredtimeoutperiod

if(timeout!=_default&&timeout>-2)

session.setMaxInactiveInterval(timeout);



out.println("<title>CartServlet</title>");



out.println("Thetimeoutintervalis:"+

session.getMaxInactiveInterval());



}

Figure11-1showstheresultofrunningthisservletinabrowserwindow.

Figure11-1.Dynamicallychangingthesessiontimeout

Thesessiontimeoutischangedonlyiftheconfiguredvalueisdifferentthantheinitialvalue,andifthevalueisgreaterthan-2:

if(timeout!=_default&&timeout>-2)

session.setMaxInactiveInterval(timeout);

Atimeoutintervalcanbesetto-1,whichisdefinedbytheServletv2.4specificationasasessionthatneverexpires.

Thisbehaviormaynotbeimplementedconsistentlyfromservertoserver.

Asmentionedbefore,sessionsareimplementedthemajorityofthetimeascookies.Chapter10includesrecipesdescribingthehandlingofcookiesinJSPsandservlets.

SeeAlso

Recipe11.2andRecipe11.3onconfiguringthesessiontimeoutinTomcatwebapplications;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).

Recipe11.2SettingtheSessionTimeoutinAllTomcatWebApplications

Problem

YouwanttoconfigureasessiontimeoutperiodforallofthewebapplicationsthatarerunningwithinaninstanceofTomcat.

Solution

Setthesessiontimeoutwithinthesession-configelementin<Tomcat-installation-directory>/conf/web.xml.

Discussion

YoucansetthesessiontimeoutforallwebapplicationsbyconfiguringTomcat'sdefaultconf/web.xmlfile.Ifthedeploymentdescriptorforaparticularwebapplicationdoesnothaveasession-configelement,thentheapplicationusesthevaluesetinconf/web.xmlasthedefaultsessiontimeout.Thecontentofthesession-timeoutelement(nestedwithinsession-config)representsthetimeinminutesuntilaninactivesessionexpires.

Example11-4showsthesession-configelementinthedefaultweb.xmlfileforTomcat4.1.x,withtheaccompanyingXMLcomment.

Example11-4.Thesession-configelementinsideofthedefaultTomcatweb.xmlfile

<session-config>


</session-config>

Onapplicationdeployment,Tomcatprocessesitsdefaultweb.xmlfile,followedbythedeploymentdescriptorsforeachwebapplication.Yourownsession-configelementoverridestheonespecifiedinconf/web.xml.Itisusuallyabetterideatoconfiguresessionsforeachwebapplicationindividually,particularlyiftheyaredesignedtobeportable.

SeeAlso

Recipe11.1onconfiguringthesessiontimeout;Recipe11.3onsettingthesessiontimeoutprogrammatically;Recipe11.4oncheckingthevalidityofasession;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).

Recipe11.3SettingtheSessionTimeoutProgrammatically

Problem

Youwanttosetasessiontimeoutinyourservletcode.

Solution

UsetheHttpServletRequestobject'sgetSession()methodtogetareferencetotheHttpSessionobject.ThenchangethetimeoutperiodprogrammaticallybyusingtheHttpSession.setMaxInactiveInterval(intseconds)method.

Discussion

TheHttpSession.setMaxInactiveInterval(intseconds)methodsetsthetimeoutforasessionindividually,sothatonlytheparticularsessionobjectbeingoperateduponisaffected.Otherservletsthatdosessiontrackinginthewebapplicationstillusethesession-timeoutvalueinweb.xmlor,intheabsenceofthiselement,theserver'sdefaultsession-timeoutvalue.Example11-5checksthetimeoutperiodforasession,thenresetsthattimeoutperiodto20minutes.

Example11-5.Resettingadefaulttimeoutperiod



importjava.text.DateFormat;



publicclassSimpleSessionextendsHttpServlet{









out.println("<title>SimpleSessionTracker</title>");



out.println("<h2>SessionInfo</h2>");

out.println("sessionID:"+session.getId()+"<br><br>");

out.println("TheSESSIONTIMEOUTperiodis"+

session.getMaxInactiveInterval()+"seconds.<br><br>");

out.println("Nowchangingitto20minutes.<br><br>");

session.setMaxInactiveInterval(20*60);

out.println("TheSESSIONTIMEOUTperiodisnow"+

session.getMaxInactiveInterval()+"seconds.");



}

}

Figure11-2showstheresultofrequestingthisservletinawebbrowser.

Figure11-2.Gettingsession-timeoutinfo

ThisservletgetstheHttpSessionobjectwiththeHttpServletRequestclass'sgetSession()method.

Whatevertheservlet'sdefaulttimeoutperiodis,say,30minutes,Example11-5changestheaccessedsession'stimeoutto20minutes:

session.setMaxInactiveInterval(20*60);

Remember,thismethodaltersthedefaultsession-timeoutintervalonlyforthesessionassociatedwiththeuserswhorequestthisservlet.Whywouldsomeusersgetadifferenttimeoutintervalthanothers?Perhapsweb-usertestingatyourorganizationhasindicatedthatasessiontimeoutoffiveminutesismoreappropriateforyourshoppingcart-relatedservlets,whereassomechart-ormap-creationservletsrequirethedefaulttimeoutof30minutesormore,sincetheirusersmightlingeroverthecompleximagesintheirbrowsersforalongperiod.

Inmostwebapplications,thesessiontimeoutisset(oraltered)inthe

deploymentdescriptor,andyouwillnothavetodynamicallychangethetimeoutintheservletcode.

SeeAlso

Recipe11.1onconfiguringthesessiontimeout;Recipe11.2onsettingthesessiontimeoutinallTomcatapplications;Recipe11.4oncheckingthevalidityofasession;Chapter1onweb.xml;Chapter7oftheServletv2.3andv2.4specificationsonsessions;thesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).

Recipe11.4CheckingifaSessionExistsinanHttpServletRequest

Problem

Youwanttocheckifawebapplicationuserhasavalidsession.

Solution

UsetheHttpServletRequestobject'sgetSession(false)methodtofindoutwhethertheHttpSessionobjectisnull.

Discussion

Somewebcomponentsaredesignedtomonitorifasessionisvalid,thenoptionallyredirectorforwardtheusertoanotherwebcomponentbasedonthevalidityofthesession.Forexample,imaginethatausermakesarequesttoacomponentthatexpectstofindacustomobjectstoredinthesessionobject,suchasa"shoppingcart."Youwanttocheckifthesessionisvalid;however,youdonotwanttocreateanewsessionfortherequestifthesessionisnotvalid,becauseanotherwebcomponentfartherbackinthechainofapplicationcomponentsisresponsibleforcreatingnewsessionsandpopulatingthemwithshoppingcartitems.TheusermayhaveenteredthewebapplicationatStep3insteadofStep1.Inthiscase,ifthesessionisinvalid,therequestisforwardedtoanotheraccesspointintheapplication(suchasaloginscreen).

IfyoucalltheHttpServletRequestobject'sgetSession(false)methodandthemethodreturnsfalse,thentheuserdoesnothaveavalidsessionandtherequestobjecthasnotcreatedanewsessionfor

her.

EitherHttpServletRequest.getSession(true)orgetSession()willattempttocreateanewsession.

Example11-6isaservletthatchecksauser'ssession,thenredirectstheusertoanotherwebcomponentifthesessionobjectisnull.

Example11-6.Checkingifasessionisvalidornot



publicclassSessionCheckextendsHttpServlet{



HttpSessionsession=request.getSession(false);

if(session==null){

response.sendRedirect("/myproj/login.jsp");

}else{

response.sendRedirect("/myproj/menu.jsp");

}

}

}

IfthesessioninExample11-6isnull,theservletredirectstherequesttothelogin.jsppageatthecontextpath/myproj.Ifthesessionobjectisvalid,therequestisredirectedtothe/myproj/menu.jspcomponent.

TheHttpServletResponse.sendRedirect(Stringlocation)methodsendstheclientanHTTPresponsethatlookslikethis:

HTTP/1.1302MovedTemporarily

Location:

http://localhost:9000/dbproj/login.jsp

Content-Type:text/html;charset=ISO-8859-1

...

TheclientthensendsanotherrequestfortheURLspecifiedinthelocationheaderoftheHTTPresponse.

SeeAlso

Recipe11.1andRecipe11.3onconfiguringthesessiontimeout;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).

Recipe11.5TrackingSessionActivityinServlets

Problem

Youwanttouseaservlettotrackthecreationtimeandlast-accessedtimeforasession.

Solution

UsetheHttpServletRequestobject'sgetSession()methodtogetareferencetotheHttpSessionobject.ThencalltheHttpSession.getCreationTime()andHttpSession.getLastAccessedTime()methodsonthatobject.

Discussion

ThisrecipedescribeshowtousetheHttpSessionAPItofindoutthecreationtimeandthelast-accessedtimeforasession.Howwouldawebapplicationusethisinformation?Forone,youmightwanttomonitorthepatternofrequestactivityinawebapplicationbycomparingthesessioncreationtime,thelast-accessedtime,andthecurrenttime.Forexample,thedifferencebetweenthecreationtimeandthecurrenttime(measuredinseconds)wouldindicatehowlongthewebapplicationhadbeentrackingaparticularuser'ssession.

ThemethodHttpSession.getLastAccessedTime()returnsthetime(asalongdatatype)ofthelasttimetheusermadearequestassociatedwithaparticularsession.

AservletthatcallsgetLastAccessedTime()representsthemostcurrent

requestassociatedwiththesession.Inotherwords,thetimeatwhichtheuserrequeststheservletthatcallsgetLastAccessedTime()becomesthelastaccessedtime.

Example11-7displaysthecurrenttime,aswellasthesession'screationandlast-accessedtimes.

TheHttpServletRequest.getSession()methodassociatesanewsessionwiththerequestifonedoesnotalreadyexist.TheHttpServletRequest.getSession(false)methodreturnsnullifasessionisnotassociatedwiththerequestanditwillnotcreateanewHttpSessionfortheuser.SeeRecipe11.4.

Example11-7.CallingHttpSessionmethodsinaservlet







publicclassSessionDisplayextendsHttpServlet{







DatecreationTime=newDate(session.getCreationTime());

DatelastAccessed=newDate(session.getLastAccessedTime());

Datenow=newDate();

DateFormatformatter=

DateFormat.getDateTimeInstance(DateFormat.MEDIUM,

DateFormat.MEDIUM);



out.println(

"<title>DisplayingtheSessionCreationand"+

"Last-AccessedTime</title>");



out.println("<h2>SessionCreationandLast-AccessedTime</h2>");

out.println(

"Thetimeanddatenowis:"+formatter.format(now)+

"<br><br>");

out.println("Thesessioncreationtime:"+

"HttpSession.getCreationTime():"+

formatter.format(creationTime)+"<br><br>");

out.println("Thelasttimethesessionwasaccessed:"+

HttpSession.getLastAccessedTime():"+

formatter.format(lastAccessed));



}//doGet





}//doPost

}

AnexampleofabrowserdisplayforthisservletisshowninFigure11-3.

Figure11-3.Findingoutasession'screationandlast-accessedtimes

Asinthepriorrecipe,thisexampleusesajava.text.DateFormatobjecttoformatDateStringsforbrowserdisplay.Thedate-relatedHttpSessionmethodsgetCreationTime()andgetLastAccessedTime()returnlongdatatypes,fromwhichjava.util.Dateobjectscanbecreated:

DatecreationTime=newDate(session.getCreationTime());

Thesession'screationtimecanthenbedisplayedusingtheDateFormat'sformat(Date_date)method.

ThenextrecipeshowshowaJSPcantracksessionactivity.

SeeAlso

Recipe11.5andRecipe11.8;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thejavax.servlet.http.HttpSessionAPIathttp://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.htmlthesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).

http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.html

Recipe11.6TrackingSessionActivityinJSPs

Problem

Youwanttofindoutasession'screationtimeandlast-accessedtimeusingJSPs.

Solution

UsetheJSTLtogetaccesstotheJSP'sassociatedHttpSessionobject.ThencalltheHttpSession.getCreationTime()andHttpSession.getLastAccessedTime()methodsonthatobject.

Discussion

ItisveryeasytokeeptrackofsessionactivityinaJSP;youjustuseslightlydifferentmethodsandtoolscomparedtothoseusedwithaservlet.Example11-8usestheoutcustomactionfromtheJSTL1.0todisplayinformationaboutthecurrentsession.Chapter24describestheJSTLanditsassociatedELinmoredetail.

Example11-8.TrackingsessionsusingtheJSTL



<html>

<head><title>ViewSessionJSP</title></head>

<body>

<h2>SessionInfoFromAJSP</h2>

Thesessionid:<c:outvalue="${pageContext.session.id}"/><br><br>

Thesessioncreationtimeasalongvalue:

<c:outvalue="${pageContext.session.creationTime}"/><br><br>

Thelastaccessedtimeasalongvalue:

<c:outvalue="${pageContext.session.lastAccessedTime}"/><br><br>

</body>

</html>

ThisJSPusesataglibdirectivetomakethecustomactionsthatarepartofthecoretaglibraryavailable.Byconvention,theuriattributeforthecoretagsishttp://java.sun.com/jstl/core,andtheprefixisc(youcancreateyourownprefixinthetaglibdirective).WithJSTL1.1,theurivalueishttp://java.sun.com/jsp/jstl/core.TheJSPthenusestheouttagfromtheJSTL'scoretaglibrarytodisplaythecurrentsessionID(thereturnvalueofHttpSession.getId()),thesession'screationtimeasalongtype,andthesession'slast-accessedtime.Figure11-4showsabrowserdisplayofthesevalues.

Figure11-4.ShowingsessioninfoinaJSP

TheoutelementwritesthevalueofitsvalueattributetotheJSP'sresponsestream.However,itistheELthatdoesthefetchingofthevalue.Forexample,thefollowingELexpressiongetsthevalueofthesession'screationtime:

${pageContext.session.creationTime}

ThepageContextreferenceisoneoftheimplicitobjectsthatcanbeaccessedfromtheEL.ThisisequivalenttotheimplicitJSPscriptingobjectofthesamename.

Thewaythecreationtimeisaccessedisdifferentthanamethodcall;youusethedot(.)operatortogetthepageContext'ssessionproperty,theninturnusethedotoperatortoaccessthesessionobject'screationTimeproperty.Sothewholephraselookslikethis:

pageContext.session.creationTime.

Finally,intheEL,allvariableandpropertyvaluesaredereferenced(togettheirvalues)bybracketingthemin${}characters.

TheJSPgetstheothersessionvaluesinthesameway.Forexample,thesession'slast-accessedtime(thelongtypereturnvaluefromthemethodHttpSession.getLastAccessedTime())isreturnedusingthissyntax:

${pageContext.session.lastAccessedTime}

Example11-8displaysthelast-accessedtimeforasessionasalarge,unfriendlynumber.Naturally,thisvalueismoreunderstandabledisplayedasadate.Example11-9showshowtousetheJSTL'scustomformattingactionstoformatadatestring.

Example11-9.Formattingthesessioncreationtimeandlast-accessedtimewiththeJSTL




<html>

<head><title>ViewSessionJSP</title></head>

<body>

<h2>SessionInfoFromAJSP</h2>

ThesessionID:<c:outvalue="${pageContext.session.id}"/>

<h3>SessiondatevaluesformattedasDates</h3>



"${pageContext.session.creationTime}"property="time"/>

Thecreationtime:<fmt:formatDatevalue="${timeValues}"type="both"

dateStyle="medium"/><br><br>


"${pageContext.session.lastAccessedTime}"property="time"/>

Thelastaccessedtime:<fmt:formatDatevalue="${timeValues}"type=

"both"dateStyle="short"/>

</body>

</html>

Figure11-5showsthebrowserdisplayforthisJSP.

Figure11-5.Sessiondate/timesformattedusingtheJSTL

ThisJSPtakestwodate-relatedsessionvalues:thedate/timewhenthesessionwascreatedandthelastdate/timewhenarequestassociatedwiththissessionwasmadetothewebapplication.Itdisplaystheirvaluesinthebrowser.Asmentionedpreviously,thesevaluesarereturnedfromtheHttpSessionobjectaslongJavatypes.YouhavetocreateaDateobjectwithitstimepropertysettotheselongvalues.ThenusetheJSTLformattingcustomactionstocreatereadableStringsfromthedates.First,maketheformattingtaglibraryavailabletotheJSPwiththistaglibdirective:


Thejava.util.DateobjectthatwillbeusedtocreatedatesoutoflongvaluesisgeneratedusingaJSPstandardactioncalledjsp:useBean.Hereistheexample'ssyntax:


ThislinecreatesanewDateobjectandstorestheobjectinavariablecalledtimeValues,makingitavailablethroughtheELwiththesyntax${timeValues}.TheJSPthenusesthesetcustomactiontosetatimepropertyintheDateobject:

<c:settarget="${timeValues}"value="${pageContext.session.creationTime}"

property="time"/>

Thevalueofset'stargetattributeistheJavaBeanwhosepropertyyouaresetting.Thepropertynameisspecifiedbythesetelement'spropertyattribute.ThevaluethisexpressionsetsthetimepropertytoisthelongtypereturnedfromthisJSTLexpression:

${pageContext.session.creationTime}

Inotherwords,usingthecustomactionthiswayistheequivalentofcallingthejava.util.Date.setTime(longsecs)methodonthetimeValuesDateobject.Thistimevalueisactuallysetanddisplayedtwice,torepresentthecreationtimeandlast-accessedtimeofthesession.Example11-10isthecodechunkthatdoesthesettinganddisplaying,includingthefmt:formatDatecustomaction.

Example11-10.Displayingasession'screationtimeandlast-accessedtime

<c:settarget="${timeValues}"value="${pageContext.session.creationTime}"

property="time"/>

Thecreationtime:<fmt:formatDatevalue="${timeValues}"type="both"

dateStyle="medium"/><br><br>


"${pageContext.session.lastAccessedTime}"property="time"/>

Thelastaccessedtime:<fmt:formatDatevalue="${timeValues}"type="both"

dateStyle="short"/>

TheformatDateelementisoneoftheJSTL'sformattingactions,whicharedescribedinChapter24.ThewaytheformatDateactionworksinthisexampleisthatthefollowingcodeisreplacedbytheformatteddatevalue,asin"Jan21,20031:57:39PM":

<fmt:formatDatevalue="${timeValues}"type="both"dateStyle="short"/>

Inordertodisplaytheirdifferences,Example11-10givestwodifferentvalues(mediumandshort)forthedateStyleattribute.

SeeAlso

Recipe11.4oncheckingthevalidityofasession;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thejavax.servlet.http.HttpSessionAPIathttp://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.htmlthesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).


Recipe11.7UsingURLRewritinginaJSP

Problem

YouwanttomakesurethatURLrewritingisusedinaJSP,incaseanyusersdisablecookiesintheirbrowsers.

Solution

UsetheurlcustomactionintheJSTLtocreateURLsthatautomaticallyincludethesessionIDasaparameter.

Discussion

Itispossiblethatsomeusersofawebapplicationwillconfiguretheirbrowserstodisablecookies.SincecookiesarethedefaultbasisforsessiontrackingwithJSPs,howwilldisablingcookiesaffecttheseusers'experiencewiththewebapplication?Irecommenddesigningallsession-trackingJSPstoaccommodateURLrewriting,sothatthecookie-averseusersdonotcrashandburninyourwebapplication.

OnesolutiontothisproblemistousetheurlcustomactionthatispartoftheJSTL.

TheurlelementautomaticallyinsertsthesessionIDasaparameterwithURLsthatwillbeusedinhref,form,andframesettags,forinstance.Thisallowsthepagesthattheselinkspointto,suchasservletsorJSPs,totracksessionswithoutusingcookies.

OneofthenicethingsaboutusingtheurlelementlikethisisthatitaddsthesessionIDasaparametertotheURLwhennecessary,without

theJSPauthor'sintervention.Example11-11showshowtouseurl.

Example11-11.UsingtheurlcoretagtorewriteURLs



<html>

<head><title>URLRewriter</title></head>

<body>

<h1>ThispagewilluseURLrewritingifnecessary</h2>

<c:urlvalue="/default.jsp"var="goToDefault"escapeXml="false"/>

Gotothedefault.jsppage<ahref="<c:outvalue="${goToDefault}"/>">here</a>.

</body>

</html>

ThisexampleusesataglibdirectivetomaketheJSTL'scoretaglibraryavailable.Thisdirectivelookslikethis:


TheurlelementofthistaglibrarycreatesaURLrepresentingthewebcomponentdefault.jsplocatedonthetoplevelofthewebapplication.TheURLisstoredinagoToDefaultvariableusingtheurlelement'svarattribute.TheescapeXmlattributeissettofalse(itistruebydefault)topreventcharacterssuchasampersandsandanglebracketsfrombeingconvertedtotheircharacterentitycodesintheURL.Theurlelementlookslikethis:


TheURLcreatedbythecustomactionisthenusedasthevalueforanhrefattributeinthefollowingmanner:

<ahref="<c:outvalue="${goToDefault}"/>">here</a>

ThiscodeusestheoutcustomactionandanELexpression(${goToDefault})tocreatethehyperlink.Afterthepageisrequested,thereturnedHTMLlookslikethisifcookiesaredisabledinthebrowser:

<ahref="/home/default.jsp;jsessionid=3CAF7CD0A0BFF5076B390CCD24FD8F0D">here</a>

YoumaynoticetwodifferencesbetweentheURLthatwascreatedhere:


andtheURLthatwasgeneratedfromtheoutcustomaction:

/home/default.jsp;jsessionid=3CAF7CD0A0BFF5076B390CCD24FD8F0D

First,theurlcustomactionhasautomaticallyaddedthecontextpath(/homeintheexample)asaprefixto/default.jsp.Second,thesessionIDwasaddedtotheURLasapathparameternamedjsessionid,sothatthelinkdestinationcanaccessthesessionIDassociatedwiththisuserandundertakesessiontracking.

Apathparameterbeginswithasemicolonandaname/valuepair,asin;jsessionid=3CAF7CD0A0B.

TheURLthattheJSPcreatesbyusingtheoutelementmayalsohaveadditionalparameters.Example11-12isthesameasthefirstrecipeexample,exceptthatparametershavebeenaddedtotheURLinsidetheurlcustomaction.

Example11-12.Addingparametersusingtheurlcustomaction



<html>

<head><title>JSPPage</title></head>

<body>

<h1>ThispagewilluseURLrewritingifnecessary</h2>

<c:urlvalue="/default.jsp?n=${param.first}&l=${param.last}"

var="goToDefault"/>

Gotothedefault.jsppage<ahref="<c:outvalue="${goToDefault}"

escapeXml="false"/>">here</a>.

</body>

</html>

TheURLnowlookslikethis:

/default.jsp?n=${param.first}&l=${param.last}

ThisURLusesembeddedELsyntaxtoaccesstworequestparameters,calledfirstandlast.IfcodeusestheELtoaccessaparameternamedfirst,forinstance,thenitusestheparamELimplicitobject,followedbythedotoperator,andthenameoftheparameter,asin${param.first}.SupposetheexampleJSPisrequestedinthefollowingmanner:

http://localhost:8080/home/url_rewrite.jsp?first=Bruce&last=Perry

Theurlelement'svalueattributeresolvestothiscode:

<c:urlvalue="/default.jsp?n=Bruce&l=Perry"var="goToDefault"/>

TheoutcustomactionfurtheralongintheexampleJSPhasitsescapeXmlattributesettofalse.IfescapeXmlisleftwithitsdefaultvalue(true)andtheampersandcharacter(&)isreplacedwithitscharacterentitycode(&),thequerystringintheURLlookslikethis

whentheJSPisexecuted:

<ahref="/home/default.jsp;jsessionid=D37AF592DACABD?n=Bruce&l=Perry">

here</a>

TopreventthisoutcomewhengeneratinglinkedURLswiththeoutelement,makesuretosetout'sescapeXmlattributetofalse.

Table11-1.Specialcharactersandentitycodes

Character Entitycode

< <

> >

& &

' '

" "

MakesuretouserelativeURLsoftheform/default.jspwhenusingURLrewritingwiththeurlelement.URLrewritingwillnottakeplaceifanabsoluteURLisusedinurl'svalueattribute,asinhttp://www.mysite.com/home/default.jsp.

SeeAlso

Recipe11.6ontrackingsessionactivityinJSPs;Recipe11.8onusingURLrewritinginaservlet;theJSPConfigurationsectionoftheJSPv2.0specification;Chapter23ontheJSTL;thesession-trackingsectionsofJavaServerPagesbyHansBergsten(O'Reilly).

Recipe11.8UsingURLRewritinginaServlet

Problem

YouwanttocreateaservletthatusesURLrewritingiftheuserhasdisabledcookiesinhisbrowser.

Solution

UsetheHttpServletResponse.encodeURL(Stringurl)methodtoencodeallURLsthatareusedtolinkwithotherpages.

Discussion

Thejavax.servlet.HttpServletResponseclassincludesaniftymethodthatwillencodeaURLwiththecurrentsessionID,intheeventthattheusermakingtheservletrequesthasdisabledcookies.

Infact,ifyouusetheHttpServletResponse.encodeURL(Stringurl)methodtoencodetheURLsthatareusedinaservlet,thismethodtakescareofURLrewritingifnecessary,andyouwon'thavetoworryaboutwhethercookiesareenabledinusers'browsers.YoumustconscientiouslyencodeeveryURLlinkinvolvedwiththeservletwhenusingthismethod.Example11-13isaservletversionoftheexampleusedinRecipe11.6.

Example11-13.UsingURLrewritinginaservlet



publicclassUrlRewriteextendsHttpServlet{






StringcontextPath=request.getContextPath();

StringencodedUrl=response.encodeURL(contextPath+

"/default.jsp");



out.println("<title>URLRewriter</title>");



out.println(

"<h1>ThispagewilluseURLrewritingifnecessary</h2>");

out.println("Gotothedefault.jsppage<ahref=\""+encodedUrl+

"\">here</a>.");



}





}

}

Inthepagethatissenttothebrowserwithcookiesdisabled,theURLlookslike:/home/default.jsp;jsessionid=3CAF7CD0A0BFF5076B390CCD24FD8F0D

OneofthedifferencesbetweenusingencodeURLandtheJSPsolutioninRecipe11.7(whichusedtheurlcustomactionfromtheJSTL)isthatthecustomactioninJSTL1.0willautomaticallyprependthecontextpathtotheURL.Ifthecontextpathwas/home,andtheURLwas/default.jsp,thentherewrittenURLwouldlooklike/home/default.jsp;jsessionid=3CAF7CD0A0BFF5076B390CCD24FD8F0D.AutomaticallyaddingthecontextpathinthismannertotheURLisaseparateoperationcomparedwithURLrewriting;itisnotperformedbytheencodeURLmethod.Ifyouwanttoduplicatethisoperationwithaservlet,addthecontextpathtotheURLbeforecallingtheencodeURLmethod,asin:


StringencodedUrl=response.encodeURL(contextPath+"/default.jsp")

YoucanalsousetherelatedHttpServletResponse.encodeRedirectURL(Stringurl)methodtoinitiateURLrewritingwithcallstoHttpServletResponse.sendRedirect(Stringurl).TheservletdoGet()methodinExample11-14usesencodeRedirectURLtoensurethatthedestinationURLshaveaccesstothesessionIDoftheredirecteduser.

Example11-14.UsingencodeRedirectURLinaservletdoGetmethod



//redirecttheuserdependingonthevalueofthegoparam

Stringdestination=request.getParameter("go");


if(destination==null||destination.equals(""))


"Missingorinvalid'go'parameterin"+


if(destination.equals("weather")){

//ensureURLrewriting

response.sendRedirect(

response.encodeRedirectURL(

contextPath+"/weather"));}

if(destination.equals("maps")){

//ensureURLrewriting

response.sendRedirect(

response.encodeRedirectURL(

contextPath+"/maps"));}

}

Theresponse.sendRedirect(Stringurl)methodredirectstherequesttothedestinationrepresentedbyitsurlparameter.TheserversendsanHTTPstatusmessagetotheclient:

HTTP/1.1302MovedTemporarily

Additionally,aLocationresponseheaderissentalongthatprovidestheclientwiththenewURLfortherequestedfile.Ifnecessary,theresponse.encodeRedirectURL(Stringurl)methodaddsthesessionIDtotheredirectdestinationofthisURL.Theexamplegetsthenameofaservletfromthevalueoftherequest'sgoparameter:

Stringdestination=request.getParameter("go");

TheservletthrowsaServletExceptioniftheparameteriseithermissingorisanemptyString.Ifthegoparameterisvalid,theservletredirectstherequesttooneoftwoservlets,withpathsof/weatheror/maps(thecontextpathintheexampleis/home).Ifimplemented

properlyontheserver,thefollowingcodeaddsthesessionIDtotheURLiftherequester'scookiesaredisabled,sothedestinationservletcaninitiatesessiontracking:

response.sendRedirect(response.encodeRedirectURL(contextPath+"/weather"));

SeeAlso

Recipe11.4oncheckingthevalidityofasession;Recipe11.7onusingURLrewritinginaJSP;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thejavax.servlet.http.HttpSessionAPIathttp://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.htmlthesession-trackingsectionsofJavaServletProgrammingbyJasonHunter(O'Reilly)andJavaServerPagesbyHansBergsten(O'Reilly).


Recipe11.9UsingaListenertoTracktheSessionLifecycle

Problem

YouwantanobjectthatimplementstheHttpSessionListenerinterfacetorespondwhenasessioniscreatedordestroyed.

Solution

CreatealistenerclassthatimplementstheHttpSessionListenerinterface,andregistertheclassinyourdeploymentdescriptor.

Discussion

TheservletAPIprovidesthejavax.servlet.http.HttpSessionListenerinterfaceforuseinrespondingtosessioncreationordestruction.Aclassthatimplementsthisinterfacecanperformcustombehavioroneither(orboth)ofthesetwoevents.Hereistheprocessforcreatinganddeclaringasessionlistenerforyourwebapplication:

1. CreateaclassthatimplementstheHttpSessionListenerinterface.Thisinterfacedefinestwomethods:sessionCreated()andsessionDestroyed(),eachofwhichacceptasingleHttpSessionEventparameter.

Makesuretheimplementingclasshasazero-argumentconstructor.

PlacethecompiledclassintheWEB-INF/classesdirectoryofyour

webapplication(includinganyofitspackage-relateddirectories);orstoretheclassinaJARlocatedintheWEB-INF/libdirectory.

Declarethelistenerintheweb.xmldeploymentdescriptor.

Restartthewebcontainer(ifnecessary),whichwillinstantiateyourlistenerclassandregisteritasalistenerforallnewsessionsandsessioninvalidationsinthewebapplication.

ObjectsthatareboundtosessionsshouldimplementtheHttpSessionBindingListenerinterface.Thislistenerdoesnothavetobeconfiguredinthedeploymentdescriptor,buttheboundobjectsmustimplementHttpSessionBindingListener,aswellasthevalueBound(),valueUnbound(),andinit()methods.TheHttpSessionActivationListenerisdesignedforsessionsthatmigratebetweenJavaVirtualMachines(JVMs).ObjectsthatareboundtothesesessionsmustimplementHttpSessionActivationListeneranditstwomethods:sessionDidActivate()andsessionWillActivate().

Hereistheweb.xmlentryforourexamplelistenerclass:

<listener>

<listener-class>com.jspservletcookbook.SessionListen</listener-class>

</listener>

TheHttpSessionListenerclassinExample11-15keepsacountoflivesessionsinthewebapplicationandwritesamessagetotheconsolewheneverasessioniscreatedordestroyed.Itwouldbebettertologmessagesusingacomponentsuchaslog4j,whichI'lldiscussinChapter14.

Example11-15.Keepingtrackofsessionactivitywithalistenerclass





publicclassSessionListenimplementsHttpSessionListener{

privateintsessionCount;

publicSessionListen(){

this.sessionCount=0;

}

publicvoidsessionCreated(HttpSessionEventse){

HttpSessionsession=se.getSession();

session.setMaxInactiveInterval(60);

//incrementthesessioncount

sessionCount++;

Stringid=session.getId();

Datenow=newDate();

Stringmessage=newStringBuffer(

"NewSessioncreatedon").

append(now.toString()).append("\nID:").

append(id).append("\n").append("Therearenow").

append(""+sessionCount).append(

"livesessionsintheapplication.").toString();

System.out.println(message);

}

publicvoidsessionDestroyed(HttpSessionEventse){



--sessionCount;//decrementthesessioncountvariable

Stringmessage=newStringBuffer("Sessiondestroyed"+

"\nValueofdestroyedsessionIDis").

append(""+id).append("\n").append(

"Therearenow").append(""+sessionCount).append(

"livesessionsintheapplication.").toString();


}

}

Eachlistenermusthaveazero-argumentconstructor.TheSessionListenclasshasoneinstancevariable,anintthatkeepstrackofthenumberofsessions.InthesessionCreated()method,thecodegetsaccesstothenewsessionbycallingtheHttpSessionEvent.getSession()method.Thesession'stimeoutisthenresetto60seconds,sothecreatinganddestroyingcanbeobservedintheconsolewithoutalotofdelay.

AnHttpSessionListenerclassisnotifiedonlyofrequeststopagesthatcreatenewsessions,suchaswiththerequest.getSession()method.ThislistenerisalsonotifiedifaservletorJSPinvalidatesanexistingsession,aneventthatwilltriggertheclass'ssessionDestroyed()method.IfaservletorJSPisaccessed,butdoesnotdosessiontracking,thenthelistenerisnotnotifiedofthoseactivities;thesameistruewhenthesessionisfurtheraccessedthroughthewebapplicationafteritiscreated,unlessitisexplicitlyinvalidated.

SimilarmessagingandaccesstotheHttpSessionobjecttakesplaceinthesessionDestroyed()method.TheresultingconsoleinFigure11-6showsthatyoucangetinformationabouttheHttpSessionobjectinbothofthelistener'smethods.

Figure11-6.Notificationsofsessioncreationandinvalidation

UsingtheHttpSessionListenerinterface,itispossibletocreateclassesthatmonitorhowmanysessionsarecreatedduringacertainperiodoftime,andhowlongittakesbeforetheyareleftidleandtimeout.

SeeAlso

Chapter14onusinglistenerstologmessages;Recipe11.4oncheckingthevalidityofasession;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thejavax.servlet.http.HttpSessionAPIathttp://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.html


Recipe11.10UsingaListenertoMonitorSessionAttributes

Problem

Youwantalistenerclasstobenotifiedwhenasessionattributeisadded,removed,orreplaced.

Solution

CreateaJavaclassthatimplementstheHttpSessionAttributeListenerinterface.Registerthisclassusingthewebapplication'sdeploymentdescriptor.

Discussion

TheHttpSessionAttributeListenerinterfacehasthreemethods:attributeAdded(),attributeRemoved(),andattributeReplaced();allhaveaparameterofthetypeHttpSessionBindingEvent.Thislistenerisnotifiedwhenthesessionsets,removes,orchangesanattribute.Therefore,themethodcallsinthewebapplicationthatcauseanHttpSessionAttributeListenernotificationare:

HttpSession.setAttribute(Stringname,Objectvalue).

HttpSession.removeAttribute(Stringname).

AcalltoHttpSession.setAttribute()whenanattributeof

thesamenameisalreadyboundtothesession.Theoriginalattributeisreplaced,triggeringacalltotheattributeReplaced(HttpSessionBindingEventevent)

method.

Example11-16displaysamessagetotheconsolewhenasessionobjectisbound,includingthevalueoftheobject(whichisaStringinthissimpleexample).Messagesarealsodisplayedwhentheattributeisremovedorreplaced.Tomakethislisteneravailabletotheapplication:

1. Givetheclassazero-argumentconstructor.

Addtheclasstothewebapplication'sWEB-INF/classesorlibdirectory(whenit'sinaJAR).

Declarethelistenerinthedeploymentdescriptor.

Restartthewebcontainer(ifnecessary)soitcaninstantiatethelistener.

Example11-16.Listeningforsessionobjectbindingorunbinding




publicclassSessionAttribListenimplementsHttpSessionAttributeListener{

//CreatesnewSessionAttribListen

publicSessionAttribListen(){

System.out.println(getClass().getName());

}

publicvoidattributeAdded(HttpSessionBindingEventse){



Stringname=se.getName();

Stringvalue=(String)se.getValue();

Stringsource=se.getSource().getClass().getName();


"Attributeboundtosessionin").append(source).

append("\nTheattributename:").append(name).

append("\n").append("Theattributevalue:").

append(value).append("\n").

append("ThesessionID:").

append(id).toString();


}

publicvoidattributeRemoved(HttpSessionBindingEventse){



Stringname=se.getName();

if(name==null)

name="Unknown";

Stringvalue=(String)se.getValue();



"Attributeunboundfromsessionin").append(source).

append("\nTheattributename:").append(name).

append("\n").append("Theattributevalue:").

append(value).append("\n").append(

"ThesessionID:").append(id).toString();


}

publicvoidattributeReplaced(HttpSessionBindingEventse){



"Attributereplacedinsession").

append(source).toString();


}

}

Whenattributesareadded,replaced,andremovedfromasessioninthewebapplication,thisclassprintsinformationabouttheattributeandthesessiontothewebcontainer'sconsole.TheHttpSessiontypethatbindstheattributecanbeaccessedbycallingtheHttpSessionBindingEventclass'sgetSession()method.Inallthreeofthelistener'smethods,youcangettheIDofthesessionassociatedwiththeattribute,aswellastheattribute'snameandvalue.Insidethelistenerclass'sconstructorisalineofcodethatprintsthelistenerclassnametotheconsolewhenitisinstantiated:

System.out.println(getClass().getName());

Thismessageindicatestothedeveloperthatthelistenerisproperly

referencedinweb.xml,andthatthewebcontainerhascreatedaninstanceofthelistener.Finally,thislistenerclassprintsamessagetotheconsoleaboutthesessionclassthatisthesourceoftheevent.Thelistenerusesthejava.util.EventObject.getSource()method(whichisinheritedbytheHttpSessionBindingEventobject)togetareferencetothesourceofthesession-bindingevent:


ThesevariableistheHttpSessionBindingEventobject.HereistheinformationthatisprintedtotheTomcatconsole:

Attributeboundtosessioninorg.apache.catalina.session.StandardSession

Theattributename:session-attribute

Theattributevalue:Hello

ThesessionID:9ED2C34964778265A34F7AB0DEA4B884

Attributereplacedinsessionorg.apache.catalina.session.StandardSession

Attributeunboundfromsessioninorg.apache.catalina.session.StandardSession

Theattributename:session-attribute

Theattributevalue:Hellothere.

ThesessionID:9ED2C34964778265A34F7AB0DEA4B884

ThelistenerallowsyoutogetthesessionID,aswellasthenameandvalueofthesessionattribute,duringtheattribute'sremovalfromthesession.TheHttpSessionBindingEvent.getValue()methodreturnsthevalueoftheattributeasajava.lang.Object.Therefore,ifyouwantaccesstotheattributeinthelistener,thenyouwouldhavetocasttheObjecttypetoitsappropriatetypeduringitsaddition,removal,orreplacement.Forexample,imaginethatyouhavestoredajava.util.Mapinasession.YouwanttochecktheMapcontentsinthelistener'sattributeRemovedmethod.IfthevariablebeisoftypeHttpSessionBindingEvent,thenthiscodechecksthereturntypeofbe.getValue():

java.util.Mapmap=null;

Objectvalue=null;

if((value=be.getValue())instanceofjava.util.Map){

map=(java.util.Map)value;

System.out.println("HashMapvalue:"+map.get("key"));

}

Thismethodreturnsthevalueofthesession-boundobjectthat'sbeingremoved.IfthereturntypeisaMap,thelocalvariablevalueiscasttoajava.util.Map,thentheget()methodiscalledonthatMap(giventhattheMapinstancecontainsakeycalled"key").

SeeAlso

Chapter14onusinglistenerstologmessages;Recipe11.4oncheckingthevalidityofasession;Recipe11.9onusingalistenertotracksessionlifecycle;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thejavax.servlet.http.HttpSessionAPIathttp://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.html


Recipe11.11UsingaFiltertoMonitorSessionAttributes

Problem

Youwanttouseafiltertocheckasessionattributepriortotherequestreachingaservlet.

Solution

CreateaJavaclassthatimplementsjavax.servlet.Filter,writesession-relatedcodeintheclass'sdoFilter()method,thenconfigurethefilterinyourdeploymentdescriptor.

Discussion

Filters,astheirnamesuggests,aresemipermeablebarriersthroughwhichrequeststoyourwebapplicationmustpassbeforetheyreachservlets,JSPs,orevenstaticcontent.FiltersaretechnicallyJavaclassesthatimplementthejavax.servlet.Filterinterface.AfiltercanhavealookattheServletRequestandServletResponseobjectsbeforetheseobjectsfindtheirwaytoaservlet'sservicemethods(whichincludeservice(),doGet(),anddoPost()).Filterscaninitiateauthentication,logging,encryption,databaseactions,caching,andjustaboutanyothertaskthatpassesthroughrequestandresponseobjects.

Filtersareconfiguredinweb.xml.InExample11-18,afilterchecksalogged-inHttpSessionattribute,andlogsitsactivitiesbycallingtheServletContextobject'slog()method.Thisfilterismappedtoaservletregisteredinweb.xmlasMyServlet.Anyrequeststothe

MyServletservletcausetheSessionFilter.doFilter()methodtobecalled.Example11-17showstherelevantentriesinweb.xml.

Example11-17.Configuringafilterinweb.xml



<filter>

<filter-name>SessionFilter</filter-name>

<filter-class>com.jspservletcookbook.SessionFilter</filter-class>

</filter>

<filter-mapping>



</filter-mapping>



<servlet>


<servlet-class>com.jspservletcookbook.MyServlet</servlet-class>

</servlet>



Thefilterelementspecifiesthefilter'sregisterednameanditsfullyqualifiedJavaclass.YoupackagethefilterclasswiththerestofthewebapplicationbyplacingtheclassinWEB-INF/classesorinaJARfileinWEB-INF/lib.Thefilter-mappingelementmapsthefiltertotheservletregisteredinthedeploymentdescriptorasMyServlet.FilterscanalsobemappedtoURLpatterns(Chapter20explainsthissyntaxindetail).Example11-18isthesourcecodeforcom.jspservletcookbook.SessionFilter.

Example11-18.Afilterthatsnoopsonsessioninformation




publicclassSessionFilterimplementsFilter{


//CreatesnewSessionFilter

publicSessionFilter(){}


System.out.println("Instancecreatedof"+getClass().getName());


}

publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,

FilterChainchain)throwsjava.io.IOException,ServletException{

HttpSessionsession=((HttpServletRequest)request).getSession();

ServletContextcontext=config.getServletContext();

/*usetheServletContext.logmethodtolog

filtermessages*/

context.log("doFiltercalledin:"+config.getFilterName()+

"on"+(newjava.util.Date()));

//logthesessionID

context.log("sessionID:"+session.getId());

//Findoutwhetherthelogged-insessionattributeisset

Stringlogged=(String)session.getAttribute("logged-in");

if(logged==null)

session.setAttribute("logged-in","no");

//logamessageaboutthelog-instatus

context.log("log-instatus:"+

(String)session.getAttribute("logged-in"));

context.log("");


}




}

}

Everyfilterhastohaveazero-argumentconstructor,justlikelistenerclasses.

Theinit()methoddisplaysaconsolemessagewhenitsinstanceiscreatedbythewebcontainer.Thejavax.servlet.FilterConfigobjectisusedtogettheServletContextobjectforthisfilter(bycallingFilterConfig.getServletContext()).TheServletContext.log()methodisusedtologmessagesfromthefilter.Thesemessagescanthenbereadintheserverlogs.InTomcat,lookinthe<Tomcat-install-directory>/logsdirectoryforlogfileswithnamessuchaslocalhost_home_log.2003-01-24.txt.Hereisanexampleofthelogentriesforthisfilter:

2003-01-2411:56:09doFiltercalledin:SessionFilteronFriJan2411:56:09EST2003

2003-01-2411:56:09sessionID:E04DE93D9B88A974ED2350BCF7945F34

2003-01-2411:56:09log-instatus:no

Thefiltergetsaccesstothesessionwiththiscode:

HttpSessionsession=((HttpServletRequest)request).getSession();

SincethedoFilter()methodhasaServletRequestparametertype,andnotaHttpServletRequesttype,therequestparameterhastobecasttothelattertypesothatthecodecancalltherequest.getSession()method.

BewareofdoingthisblindlyinenvironmentswhereyouarenotpositivethatallservletsareHttpServlets.Ifyouaren'tsure,asimpleclasscheckbeforecastingcansolvethisproblem.

Oncethefilterhasaccesstothesessionobject,itlooksforacertainsessionattribute(logged-in).Ifsession.getAttribute("logged-in")returnsnull,thisattributeisaddedtothesessionwiththevalue"no".Thecodethencallschain.doFilter(request,response)insideofthefilter'sdoFilter()method.

ThismethodcallontheFilterChainobjectensuresthattherequestandresponsearepassedalongtothenextfilteronthechain,or,intheabsenceofanymoremappedfilters,tothetargetedwebresource.Example11-19showsthedoGet()methodoftheMyServletservletthatthefilterinExample11-18ismappedto.

Example11-19.doGetmethodofaservlettowhichafilterismapped







Stringlogged=(String)session.getAttribute("logged-in");



out.println("<title>FilterServlet</title>");



out.println("<h2>SessionLoggedinInfo</h2>");

out.println("loggedin:"+logged+"<br><br>");



}

Thisservletchecksthelogged-insessionattributeanddisplaysitsvalue,asshowninFigure11-7.

Afilterismappedtoaservlet'sregisterednamelikethis:

<filter-mapping>



</filter-mapping>

Therequestsforthisservletwillnotpassthroughthemappedfilterfirst,however,iftheservletisrequestedwithan"invoker"-styleURLoftheformhttp://localhost:8080/servlet/com.jspservletcookbook.MyServlet.Ifthiscausesproblemsforthewebapplication,considerdisablingoroverridingtheURLmappingof/servlet/*inyourwebapplication.Recipe3.6describeshowtodothis.

Figure11-7.Checkingasessionobjectafterafilterhasalteredit

AfiltercantakeanumberofactionswithasessionobjectbeforeitreachesaservletorJSPthatdoessessiontracking,suchasadd,remove,orchangesessionattributes.Itcanalsoalterthesession'stimeoutperiod(withtheHttpSession.setMaxInactiveInterval(intseconds)method)basedonanattributeofthesessionorrequest.

SeeAlso

Chapter19onusingfilters;Recipe11.4oncheckingthevalidityofasession;Chapter1onweb.xml;Chapter7oftheServletv2.3and2.4specificationsonsessions;thejavax.servlet.http.HttpSessionAPIathttp://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpSession.htmlChapter1onweb.xml;Chapter6oftheServletv2.3and2.4specificationsonfiltering.


Chapter12.IntegratingJavaScriptwithServletsandJSPs

Introduction

Recipe12.1.IncludingJavaScriptModulesinaServlet

Recipe12.2.IncludingJavaScriptModulesinaJSP

Recipe12.3.CreatingaNewWindowwithJavaScriptinaServlet

Recipe12.4.CreatingaNewWindowwithJavaScriptinaJSP

Recipe12.5.UsingJavaScripttoValidateFormValuesinaServlet

Recipe12.6.UsingJavaScripttoValidateFormValuesinaJSP

Introduction

JavaScriptisascriptingsystemforwebpages,standaloneapplications,andservers.NetscapeCorporationinventedJavaScript,whichhasbecomesuchapopularandusefulprogrammingtoolthatallmajorbrowsersnowsupportit.UnliketheJavacodeshowninthisbook,JavaScriptismainlyexecutedinthewebbrowserasaclient-sidescriptingsystem,ratherthanontheserver.

MostbusywebsitesuseJavaScriptfordynamicbehavior,suchasvalidatingforminputorcreatingnewbrowserwindows(muchtothechagrinofusers,whoareoftenoverwhelmedbyirresponsibleanddynamicallygeneratedpopups!).Justchoose"ViewSource"fromthebrowsermenubarforatypicalwebpage,andoftenthefirsttextitemsyou'llseedisplayedareendlesslinesofJavaScript.JavaScriptisusedforadvancedtaskssuchascontrollingoranimatingbrowsershapes(dynamicHTML),creatingflyingobjects,andinitializingthebehaviorofembeddedvideos.

DevelopersconvertingstaticwebpagestoJSPsorservletsmayhavetointegrateexistingJavaScriptcodeintotheirJavasourcecode.Thisiswhattheupcomingrecipesareallabout.

JavaScriptguidesareavailablefromhttp://devedge.netscape.com/.

http://devedge.netscape.com/default.htm

Recipe12.1IncludingJavaScriptModulesinaServlet

Problem

YouwanttoimportamoduleorfilecontainingJavaScriptcodesothattheJavaScriptcanbeincludedintheservlet'sHTMLoutput.

Solution

Usethejavax.servlet.RequestDispatch.include()methodtoimporttheneededJavaScriptintoyourpage.

Discussion

AnefficientmethodforhandlingJavaScriptthroughoutawebprojectistostoretheJavaScriptcodeinseparatefilesormodules.ServletsthatrequiretheJavaScriptfunctionscanthenimporttheJavaScriptmodules.YouwouldnotstoreyourJavaclassfileswilly-nillyalloverthecomputer'sfilesystemwithoutanorganizationthatmirrorsthecode'spurpose.NorshouldyouorganizeyourJavaScriptinanythingbutwell-definedmodules.

TheJavaScriptisincludedintheservlet'sHTMLoutputwithscripttagsandexecutedinthebrowserwhenneeded.Example12-1showsamoduleofJavaScriptcodenamedfunctions.js.Thismoduleisstoredinthewebapplication'sWEB-INF/javascriptdirectory.

AsensibleplacetostoreJavaScriptmodulesisintheirowndirectory,sothattheyareeasytolocateanddonotclutterupthetop-leveldirectoryofthewebapplication.TheJavaScriptdirectorycanbeasub-directoryofWEB-INF,asin

thisrecipe.

Example12-1.AJavaScriptmodule

<scriptlanguage="JavaScript">

functionCheckEmail(email)

{

varfirstchunk,indx,secondchunk

if(email==""){

alert("Pleasemakesureyouhaveenteredavalid"+

"emailbeforesubmittingtheinfo.")

returnfalse

}

//getthezero-basedindexofthe"@"character

indx=email.indexOf("@")

//ifthestringdoesnotcontainan@,thenreturnfalse

if(indx==-1){



returnfalse

}

//ifthefirstpartofemailis<twocharsandthyesecondpartis<sevenchars

//(arbitrarybutworkablecriteria),rejecttheinputaddress

firstchunk=email.substr(0,indx)//uptobutnotincludingthe"@"

//startatcharfollowingthe"@"andincludeuptoendofemailaddr

secondchunk=email.substr(indx+1)

//ifthepartfollowingthe"@"doesnotincludeaperiod"."then

//alsoreturnfalse

if((firstchunk.length<2)||(secondchunk.length<7)||

(secondchunk.indexOf(".")==-1)){



returnfalse

}

//theemailwasokay;atleastithada@,morethanoneusernamechars,

//morethansixcharsafterthe"@",andthesubstringafterthe"@"

//containeda"."char

returntrue

}//CheckEmail

functionCreateWindow(uri){

varnewWin=

window.open(uri,'newwin1',

'width=500,height=400,resizable,'+

'scrollable,scrollbars=yes');

newWin.focus();

}

</script>

ThemoduleinExample12-1containsascriptblockwithtwo

JavaScriptfunctiondefinitions.ThefunctionCheckEmailensuresthattheemailaddressauserhastypedintoanHTMLformcontainsatleastan@character,twocharactersprecedingthe@andsevencharactersafterthatcharacter,andthatthecharactersafterthe@containaperiodcharacter(.).TheCreateWindowfunctioncreatesanewbrowserwindowwiththesuppliedURI.

Example12-2showsaservletthatimportsthisJavaScriptfileusingthejavax.servlet.RequestDispatcher.include()method.

Example12-2.AservletincludesaJavaScriptfile




publicclassModuleServletextendsHttpServlet{







"/WEB-INF/javascript/functions.js");


out.println("<title>ClientForms</title></head><body>");

out.println("<h2>EnterYourNameandEmail</h2>");

out.println("<formaction=

\"/home/displayHeaders.jsp\"name=\"entryForm\"onSubmit=

\"returnCheckEmail(this.email.value)\">");


out.println(

"Firstandlastname:</td><tdvalign=\"top\"><inputtype=

\"text\"name=\"name\"size=\"20\"></td></tr>");

out.println("<tr><tdvalign=\"top\">");

out.println("Email:</td>

<tdvalign=\"top\"><inputtype=\"text\"name=

\"email\"size=\"20\"></td>");

out.println("<tr><tdvalign=\"top\"><inputtype=

\"submit\"value=\"Submit\"></td>");

out.println("</tr></table></form>");


}//doGet

}

TheservletinExample12-2usesaRequestDispatchertoincludethecodecontainedinfunctions.jswithintheHTMLheadtaggeneratedbytheservlet.ThegeneratedpageincludesanHTMLformtag.WhenthepageuserclickstheSubmitbutton,theformtag'sonSubmiteventhandlercheckstheemailaddressthattheusertypedintotheformusingtheimportedJavaScriptCheckEmailfunction.Thisfunctionreturnsfalse,whichcancelstheformsubmissioniftheemailaddressdoesnotmeetthesimplecriteriaspecifiedbythefunction.

Figure12-1showswhatthewebpagelookslikewhentheuserhasenteredanemailaddressintotheform.

Figure12-1.AservletgeneratesawebpagecontainingJavaScript

Userscanalsousethebuilt-insrcattributeoftheHTMLscripttagtoimportaJavaScriptmodule,asin:

<scriptsrc="functions.js">

SeeAlso

TheNetscapeDevEdgesiteathttp://devedge.netscape.com/;Recipe12.2,Recipe12.4,andRecipe12.6onusingJavaScriptwithJSPs;Recipe12.3onusingJavaScriptwithservletsforcreatingnewbrowserwindows;Recipe12.5onvalidatingformvalueswithaservletandJavaScript;Recipe18.3onusingafilterwithHTTPrequests.


Recipe12.2IncludingJavaScriptModulesinaJSP

Problem

YouwanttoincludeamoduleorfilecontainingJavaScriptcodewithinaJSPpage'soutput.

Solution

Usethec:importJSTLcoretag.

Discussion

ThepreviousrecipedescribedhowtoincludeafilecontainingJavaScript(Example12-1)intoaservlet'sHTMLinput.ItisveryeasytoaccomplishthesametaskinaJSP,suchasbyusingtheimportMod.jspfileshowninExample12-3.ThisJSPusestheJSTLcoretagc:importtoincludeafilenamedfunctions.js.Thefunctions.jsmodulecontainsascripttagwithtwoJavaScriptfunctiondefinitions(Example12-1inRecipe12.1).TheHTMLgeneratedbytheJSPshowsthatthec:importactionpositionedthescripttagwithintheJSP'sheadtag.TheJSPgeneratestheHTMLformshownpreviouslyinFigure12-1.

Example12-3.UsingtheJSTLc:importtagtoimportJavaScript


<html>

<head>

<c:importurl="/WEB-INF/javascript/functions.js"/>

<title>ClientForms</title></head><body>

<h2>EnterYourNameandEmail</h2>

<formaction="/home/displayHeaders.jsp"name="entryForm"

onSubmit="returnCheckEmail(this.email.value)">

<tableborder="0"><tr><tdvalign="top">

Firstandlastname:</td><tdvalign="top"><inputtype="text"name="name"size="20"></

td></tr>


Email:</td><tdvalign="top"><inputtype="text"name="email"size="20"></td></tr>

<tr><tdvalign="top"><inputtype="submit"value="Submit"></td>

</tr></table>

</form>

</body></html>

WhentheusersubmitstheHTMLform,heractionisinterceptedbytheformtag'sonSubmiteventhandler,whichdoesabasicsyntaxcheckontheemailaddresstheusertypedintotheform.Theformsubmit,targetedtoa/home/displayHeaders.jsppage,iscancelledifthesubmittedemailaddresshasthewrongsyntax.

TheJavaScriptcodethis.email.valuereturnstheStringthattheusertypedintothetextfieldnamedemail.Thekeywordthisreferstotheformobject,whichcontainstheeventhandleronSubmit.TheJavaScriptcodeisaparameterofthiseventhandler.

SeeAlso

TheNetscapeDevEdgesiteathttp://devedge.netscape.com/;Recipe12.4onusingJavaScripttocreateanewwindowinaJSP;Recipe12.6onusingJavaScripttovalidateforminputinaJSP;Recipe12.3onusingJavaScriptwithservletsforcreatingnewbrowserwindows;Recipe12.5onvalidatingformvalueswithaservletandJavaScript;Recipe18.3onusingafilterwithHTTPrequests.


Recipe12.3CreatingaNewWindowwithJavaScriptinaServlet

Problem

YouwantaservlettocontainJavaScriptthatcangenerateanewbrowserwindow.

Solution

Useajavax.servlet.RequestDispatchertoincludetheJavaScriptfunctionintheservlet.TheJavaScriptfunctioncallstheJavaScriptwindowobject'sopenmethod.

Discussion

Thisrecipeusesthesameimportedmoduleasthefirsttworecipes,butthistimetheservletusesthesecondfunctiondefinition(CreateWindow)ratherthanthefirst.Example12-4generatesanHTMLbuttonwidget.Whentheuserclicksthebutton,JavaScriptgeneratesasmallwindow(sometimesreferredtoasawindoid,orpopup).TheservletdynamicallyretrievestheURLforloadingintothenewwindowfromaservletinitparameter,whichissomethingyoucannotdowithastaticHTMLpage.

Example12-4.AservletthatloadsJavaScriptforcreatingawindow




publicclassWindowServletextendsHttpServlet{



//URLforthepop-upwindowisconfigured

Stringurl=getInitParameter("popup-url");

//justincasetheinitParameterismisconfigured

if(url==null||url.equals(""))

url="/displayHeaders.jsp";

//addthecontextpathasaprefixtotheURL,asin/home

url=request.getContextPath()+url;








out.println("<h2>CookieInfo</h2>");

out.println("<formaction=\"\"onSubmit=\"returnfalse\">");


out.println(

"Clickonthebuttontogetmoreinfooncookies:</td>");

out.println("<tdvalign=\"top\">");

out.println("<inputtype=\"button\"name=\"button1\""+

"value=\"MoreInfo\"onClick=\"CreateWindow('"+url+

"')\"></td></tr>");



}//enddoGet

}

Thisservletassumessomeconfigurationstepshavebeentakenintheapplication'sdeploymentdescriptor.Thisconfigurationincludesaninit-paramthatspecifiestheURLforloadingintothenewwindow.TheurlvariableistheCreateWindowfunction'sparameter(seeExample12-1foradefinitionoftheJavaScriptfunctions).TheservletgeneratestheHTMLanddynamicallyprovidestheURLforloadingintothenewwindow.HereistheHTMLbuttondefinitionintheservlet'soutput:

<inputtype="button"name="button1"value="MoreInfo"

onClick="CreateWindow('home/cookieReader.jsp')">

Iftheapplicationisdynamicallyreloadable(thewebcontainermonitorsthedeploymentdescriptorforanychangesandreloadsthecontextifthefileisaltered),thenthedevelopercanchangethevalueoftheservletinit-paraminthedeploymentdescriptor.Theservletpop-upwindowthenloadsthenewURLwithoutrecompilingtheservletorstoppingtheserver.

Hereistheconfigurationforthisservletinweb.xml:

<servlet>

<servlet-name>windowservlet</servlet-name>

<servlet-class>com.jspservletcookbook.WindowServlet</servlet-class>

<init-param>

<param-name>popup-url</param-name>

<param-value>/cookieReader.jsp</param-value>

</init-param>

</servlet>

TheservletloadsthedefinitionfortheJavaScriptfunctionCreateWindowwiththiscode:



IntheHTMLcodetheservletgenerates,thescripttagcontainingtheJavaScriptcodeappearswithintheHTMLheadtag.Whentheuserclickstheformbuttonontheservlet-generatedwebpage,anewwindowiscreatedandtheURLspecifiedbytheinit-paramelementinweb.xml(cookieReader.jsp)isloaded.Figure12-2showstheservletoutput.Figure12-3showsthepop-upwindow.

Figure12-2.Aservletthatcreatesapop-upwindow

Figure12-3.ThenewwindowloadsaURLvaluefromaservletinit-param

SeeAlso

TheNetscapeDevEdgesiteathttp://devedge.netscape.com/;Recipe12.2,Recipe12.4,andRecipe12.6onusingJavaScriptwithJSPs;Recipe12.5onvalidatingformvalueswithaservletandJavaScript;Recipe18.3onusingafilterwithHTTPrequests.


Recipe12.4CreatingaNewWindowwithJavaScriptinaJSP

Problem

YouwanttouseJavaScriptinaJSPtocreateanewbrowserwindow.

Solution

Usethec:importJSTLtagtoimporttheJavaScriptcodeintotheJSP.ThenusetheinitParamJSTLimplicitobjecttodynamicallyprovidetheURLforaJavaScript-generatedwindow.

Discussion

TheJSPinExample12-5(windowJ.jsp)usestheJSTL'sc:importcoretagtoimporttheJavaScriptfunctiondefinitionforcreatinganewwindow.TheJSPthencallstheJavaScriptfunction(CreateWindow)intheonClickeventhandlerforawebpagebutton.TheCreateWindowfunctionloadstheURLspecifiedinitsparameterintothenewbrowserwindow.Example12-5usesthec:outcoretagandELsyntaxtodynamicallyacquiretheURLfortheJavaScriptwindowfromacontextparameter.Thec:outtaglookslikethis:

<c:outvalue=

"${pageContext.request.contextPath}${initParam[\"jsp-url\"]}"/>

ThevalueattributespecifiestwoELexpressions.ThefirstoneprovidestheJSP'scontextpath,whilethesecondgivesthevalueofthecontext-paramelementjsp-url.ThefullURLspecifiedbythese

concatenatedELexpressionsis/home/cookieReader.jsp.

Example12-5.UsingtheJSTLtoimportJavaScriptintoaJSP


<html>

<head>

<c:importurl="/WEB-INF/javascript/functions.js"/>

<title>HelpPage</title></head><body>

<h2>CookieInfo</h2>

<formaction=""onSubmit="returnfalse">


Clickonthebuttontogetmoreinfooncookies:</td>

<tdvalign="top">

<inputtype="button"name="button1"value=

"MoreInfo"onClick=

"CreateWindow('<c:outvalue=

"${pageContext.request.contextPath}${initParam[\"jsp-url\"]}"/>')">

</td></tr>

</table></form>

</body></html>

ThisJSPusesthefollowingcontext-paramelementinweb.xml:

<context-param>

<param-name>jsp-url</param-name>

<param-value>/cookieReader.jsp</param-value>

</context-param>

TheELimplicitobjectinitParamevaluatestoajava.util.Map

containingthenamesandvaluesofanycontext-paramelementsconfiguredforthewebapplication.AnimplicitobjectisavariablethattheJSTLautomaticallymakesavailabletoyourJSPcode.

Example12-5usestheELsyntaxinitParam[\"jsp-url\"],asopposedtoinitParam.jsp-url,inordertoreturntheintendedvalueinTomcat5(alphaversionasofthiswriting).Thecode'spurposeistoescapethehyphencharacter(-)in"jsp-url."

SeeAlso

TheNetscapeDevEdgesiteathttp://devedge.netscape.com/;Recipe12.2andRecipe12.6onusingJavaScriptwithJSPstoimportJavaScriptandvalidateforminput;Recipe12.3oncreatingnewbrowserwindowswithservletsandJavaScript;Recipe12.5onvalidatingformvalueswithaservletandJavaScript;Recipe18.3onusingafilterwithHTTPrequests.


Recipe12.5UsingJavaScripttoValidateFormValuesinaServlet

Problem

YouwanttovalidateforminputvaluesusingJavaScriptinaJSP.

Solution

Useajavax.servlet.RequestDispatchertoincludethevalidatingJavaScriptintheservlet.ThencallthevalidatingJavaScriptfunctionintheform'sonSubmiteventhandler.

Discussion

Example12-6isaJavaScriptmodulenamedvalidate.js.ThisfileshouldbelocatedinWEB-INF/javascript/validate.js.Thefilecontainsascripttagthatcontainsonefunctiondefinition:validate.ThisJavaScriptfunctioniteratesthroughtheformelements(suchasinputtagswhosetypeattributeistextinotherwords,textformfields)todetermineifanyofthemhavebeenleftblank.Theparameterforthevalidatefunctionisaformobject.

Iftheuserhasleftthefieldsempty,thisfunctiondisplaysanalertwindowandthencancelstheformsubmit.Amorerealisticvalidationfunctionmightinvolveagreaterdegreeofcomplexbusinesslogic,butIamkeepingthisexamplesimpleinordertodemonstratethemechanicsofincludingthefunctioninaservlet.

Example12-6.AJavaScriptmodulenamedvalidate.jsforvalidatingforminput

<scriptlanguage="JavaScript">

functionvalidate(form1)

{

for(i=0;i<form1.length;i++){

if((form1.elements[i].value=="")){

alert("Youmustprovideavalueforthefieldnamed:"+

form1.elements[i].name)

returnfalse

}

}

returntrue

}

</script>

TheservletinExample12-7includesthevalidate.jsfileusingaRequestDispatcher.TheRequestDispatcherpositionstheJavaScriptscripttagwithinanHTMLheadtagintheservlet'soutput.Theservletpage'sformtaghasanattributethatiscomposedofthecontextpath(thereturnvalueofrequest.getContextPath())concatenatedwiththe/displayHeaders.jspJSPfile.Iftheformfieldsarefilledoutproperly,thebrowsersubmitstheformtotheJSPpage(/home/displayHeaders.jsp).

Finally,theform'sonSubmiteventhandlercallstheincludedJavaScriptfunctionvalidate,passinginthethisJavaScriptkeyword.Thethisparameterevaluatestotheformobject.Iftheuserfailstofilloutthenameandemailfields,thevalidatefunctioncancelsthebrowser'ssubmissionoftheformbyreturningfalse.

Example12-7.ImportingJavaScriptinaservlettovalidateformvalues




publicclassFormServletextendsHttpServlet{








"/WEB-INF/javascript/validate.js");



out.println("<h2>Pleasesubmityourinformation</h2>");

out.println(

"<formaction=\""+request.getContextPath()+

"/displayHeaders.jsp\"onSubmit=\"returnvalidate(this)\">");


out.println("Yourname:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"username\"size=\"20\">");


out.println("Youremail:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"email\"size=\"20\">");


out.println(

"<inputtype=\"submit\"value=\"SubmitInfo\"></td></tr>");



}//doGet

}

Figure12-4showsthebrowserpagecontainingtheform.Figure12-5showsthealertwindowgeneratedbytheJavaScriptfunction.

Figure12-4.TheservletoutputforanHTMLform

Figure12-5.TheincludedJavaScriptvalidatefunctionproducesanalertwindow

Anotheroptionforvalidatingforminputistouseafiltertocheck

parametervalues,andthenreturntheusertotheformpageoranewpageiftheinputcontainsanerror.DevelopersmightpreferthisoptionbecauseafilterallowsyoutouseJavacodetoparsetheparametervaluesandgivesyouagreatdealofcontroloverthecustomizationoftheresponsepage,inthecaseofaforminputerror.Recipe18.3describeshowtouseafilterwithaservlettodealwithclientrequests.

SeeAlso

TheNetscapeDevEdgesiteathttp://devedge.netscape.com/;Recipe12.2andRecipe12.6onusingJavaScriptwithJSPstoimportJavaScriptandvalidateforminput;Recipe12.3oncreatingnewbrowserwindowswithservletsandJavaScript;Recipe12.5onvalidatingformvalueswithaservletandJavaScript;Recipe18.3onusingafilterwithHTTPrequests.


Recipe12.6UsingJavaScripttoValidateFormValuesinaJSP

Problem

YouwanttoimportJavaScriptintoaJSPtovalidateHTMLformvalues.

Solution

Usethec:importJSTLcoretagtoimporttheJavaScriptfunctiondefinitions.ThenvalidatetheHTMLforminputbyusingtheformtag'sonSubmiteventhandler.

Discussion

TheJSPinExample12-8usestheJSTLcoretagc:importtoincludethecontentsofthe/WEB-INF/javascript/validate.jsfile.SeeExample12-6forthecontentsofvalidate.js,whichisadefinitionforthefunctionvalidate.Thisfunctiondetermineswhethertheuserhasleftanyformfieldsblank.

TherestoftheJSPisstraightforward:theonSubmiteventhandlercallsthevalidatefunctionandpassesintheformobject(representedbytheJavaScriptkeywordthis)asaparameter.Byreturningfalse,thevalidatefunctioncancelstheformsubmitifitfindsanyblankfields.

Example12-8.AJSPusesJavaScripttovalidateHTMLforminput


<html>

<head>

<c:importurl="/WEB-INF/javascript/validate.js"/>

<title>HelpPage</title></head><body>

<h2>Pleasesubmityourinformation</h2>

<formaction="/home/displayHeaders.jsp"onSubmit="returnvalidate(this)">


Yourname:</td><tdvalign="top">

<inputtype="text"name="username"size="20">

</td></tr><tr><tdvalign="top">

Youremail:</td><tdvalign="top">

<inputtype="text"name="email"size="20">

</td></tr>


<inputtype="submit"value="SubmitInfo"></td></tr>

</table></form>

</body></html>

Figure12-4showsthewebpagecontainingtheform.Figure12-5depictsthealertwindowthatwouldbedisplayediftheuserleavesoneormoretextfieldsblankwhensubmittingtheform.

SeeAlso

TheNetscapeDevEdgesiteathttp://devedge.netscape.com/;Recipe12.2andRecipe12.4onusingJavaScriptwithJSPstoimportJavaScriptfunctiondefinitionsandcreatenewbrowserwindows;Recipe12.3on


creatingnewbrowserwindowswithservletsandJavaScript;Recipe12.5onvalidatingformvalueswithaservletandJavaScript;Recipe18.3onusingafilterwithHTTPrequests.

Chapter13.SendingNon-HTMLContentIntroduction

Recipe13.1.SendingaPDFFile

Recipe13.2.SendingaWordProcessingFile

Recipe13.3.SendinganXMLfile

Recipe13.4.SendinganAudioFile

Recipe13.5.ViewingInternalResourcesinaServlet

Introduction

Mostwebsitesofferasmorgasbordofmediatypestotheirusers.TypicalwebcontentthesedaysincludesPortableDocumentFormat(PDF)files,word-processingdocuments,audiofiles,movies,andExtensibleMarkupLanguage(XML).Insomecases,thesealternativefiletypesarestoredindatabasesasbinarydata,orstreamsofunencodedbytes.Webdeveloperscannotalwaysprovidetheiruserswithstraightforwardhyperlinkstothesefilesfordownloading.TheuserchoosesalinkorentersaURLinthebrowser'slocationfield,andaservletorsomeotherwebcomponentdownloadsthebinarydatatotheclient.Theclientinmostcasessavesthedataasafile,foruselaterindocumentviewersandotherapplications.

Thefollowingrecipesdescribehowtoinitiatethisdownloadmethod.Inatypicalscenario,theservletsetsupadownloadwherebythebrowserpromptstheuserwitha"SaveAs"dialogallowinghimtosavethefilesonhisownfilesystem.Thesestrategies,however,donotguarantee100-percentconsistentbehavioramongwebbrowsers.Somebrowsersallowtheusertopreciselyconfigurehowhewantstohandlehandlecertainfiletypes(suchasaPDFdocument).Forexample,Opera5givestheuserallkindsofoptionsfordealingwithdownloads,suchasopeningupanexternalhelperapplication,displayingafileusingaplug-in,orimmediatelydownloadingafiletoaspecifiedfolderwithoutfirstopeningupa"SaveAs"window.

Testhowyourwebapplicationworksinvariousbrowsers,inresponsetodifferentbrowserconfigurations,aswellasondifferentplatforms,sothatyouareawareofthedifferentbrowserresponseselicitedbytheservlet.

ThealternativetothesestrategiesissimplyprovidingalinktoaPDFfileforinstanceifthedataexistsasafile.Thismethod,however,also

placesagreatdealoftheresponsibilityontheclientbrowser,andtheuserwhoconfiguresthebrowser,formanagingthemediatype.Whileadvancedusersmaylikethisapproach,itisrarelysufficientforless-experiencedusers.

Recipe13.1SendingaPDFFile

Problem

YouwanttosendbinarydatarepresentingaPDFfiletoauser.

Solution

Useaservletandajava.io.BufferedInputStreamtoreadthebytesfromthefile.Sendthefilecontenttotheuserwithajavax.servlet.ServletOutputStreamretrievedfromthejavax.servlet.http.HttpServletResponseobject.

Discussion

PDFfilesareubiquitousontheWeb,asmostusersareequippedwiththeAdobeReaderapplicationthatreadsthem.Example13-1takesafilenamefromaquerystringthatispartoftherequesttotheservlet,andrespondswithbinarydatathatrepresentsthePDFfile.TheservletidentifiesthefilethatitsendstotheclientastheMIMEtypeapplication/pdfbyusingtheContent-Typeresponseheader.

MultipurposeInternetMailExtensions(MIME)designatethemediatypesofvariousdatathataresentasemailoraspartofHTTPresponsesontheWeb.AMIMEtypehasatop-leveltypeandasub-typeseparatedbyaforward-slashcharacter,asintext/html,application/pdf,oraudio/mpeg.TheContent-Typeresponseheaderisthemethodtheserverresponseusestoconveytheintendedtypeandformatofthedatathattheserversendstoanetworkclientsuchasawebbrowser.SeethefollowingRequestForComments(RFC)technicaldocumentsonMIMEformoreinformation:ftp://ftp.rfc-editor.org/in-notes/rfc2045.txtandftp://ftp.rfc-editor.org/in-notes/rfc2046.txt.



Table13-1showsseveralMIMEtypesthatwebdevelopersmayencounter.

Table13-1.SomecommonMIMEtypes

File MIMEtype Extension

XML text/xml .xml

HTML text/html .html

Plaintextfile text/plain .txt

PDF application/pdf .pdf

GraphicsInterchangeFormat(GIF)image image/gif .gif

JPEGimage image/jpeg .jpeg

PNGimage image/x-png .png

MP3musicfile audio/mpeg .mp3

ShockwaveFlashanimation application/futuresplashorapplication/x-shockwave-flash .swf

MicrosoftWorddocument application/msword .doc

Excelworksheet application/vnd.ms-excel .xls

PowerPointdocument application/vnd.ms-powerpoint .ppt

Therequesttotheservletlookslikethis:

http://localhost:8080/home/sendpdf?file=chapter5

Example13-1checkstoseeiftherequestparameterfileisvalidandthenaddsthefileextension.pdftothefilenameifitdoesnotalreadyhavethatsuffix.ThisisthefilenametheHTTPresponserecommendstothebrowser(itwillappearasthedefaultfilenameinanydisplayed"SaveAs"windows).

JasonHunterinJavaEnterpriseBestPractices(O'Reilly)pointsoutthatitisoftenusefultoincludetheintendedfilename(forthe"SaveAs"dialogboxthebrowserproduces)directlyintheURLasextrapathinfo.Thebrowserdetectsthatnameastherequestedresourceandmayspecifythenameinthe"SaveAs"dialogwindow.AnexampleURLinthiscaselookslike:

http://localhost:8080/home/chapter5.pdf?file=ch5

Example13-1.SendingaPDFfileasbinarydata


importjava.io.FileInputStream;

importjava.io.BufferedInputStream;

importjava.io.File;




publicclassSendPdfextendsHttpServlet{



IOException{

//getthefilenamefromthe"file"parameter

StringfileName=(String)request.getParameter("file");

if(fileName==null||fileName.equals(""))


"Invalidornon-existentfileparameterinSendPdfservlet.");

//addthe.pdfsuffixifitdoesn'talreadyexist

if(fileName.indexOf(".pdf")==-1)

fileName=fileName+".pdf";

//wherearePDFskept?

StringpdfDir=getServletContext().getInitParameter("pdf-dir");

if(pdfDir==null||pdfDir.equals(""))


"Invalidornon-existent'pdfDir'context-param.");

ServletOutputStreamstream=null;

BufferedInputStreambuf=null;

try{

stream=response.getOutputStream();

Filepdf=newFile(pdfDir+"/"+fileName);

//setresponseheaders

response.setContentType("application/pdf");

response.addHeader(

"Content-Disposition","attachment;filename="+fileName);

response.setContentLength((int)pdf.length());

FileInputStreaminput=newFileInputStream(pdf);

buf=newBufferedInputStream(input);

intreadBytes=0;

//readfromthefile;writetotheServletOutputStream

while((readBytes=buf.read())!=-1)

stream.write(readBytes);

}catch(IOExceptionioe){

thrownewServletException(ioe.getMessage());

}finally{

//closetheinput/outputstreams

if(stream!=null)

stream.close();

if(buf!=null)

buf.close();

}

}//enddoGet



throwsServletException,IOException{


}

}

Example13-1getsthedirectorywherethePDFfilesarestoredfromacontext-paramelementinthedeploymentdescriptor:

<context-param>

<param-name>pdf-dir</param-name>

<param-value>h:/book/distribute</param-value>

</context-param>

Rememberthatthecontext-paramelementsappearbeforethefilter,filter-mapping,listener,andservletelementsintheweb.xmlversionforservletAPI2.3.

ThecodethengetstheServletOutputStreamfromthe

HttpServletResponseobject.ThebinarydatarepresentingthePDFiswrittentothisstream:


Theservletdoesnotuseajava.io.PrintWriterasinresponse.getWriter(),becauseaPrintWriterisdesignedforreturningcharacterdata,suchasHTML,thatthebrowserdisplaysonthecomputerscreen.Example13-1addstheresponseheadersthathelppreventthebrowsersfromtryingtodisplaythebytesascontentinthebrowserwindow:

response.setContentType("application/pdf");

response.addHeader(


response.setContentLength((int)pdf.length());

TheContent-Dispositionheaderfieldsignalstheclienttotreatthereceivedcontentasanattachment,notascharacterstobedisplayedinthebrowser.Thisoptionalresponseheaderalsoprovidesarecommendedfilename,whichthebrowsermayincludeasthedefaultfilenameinany"SaveAs"windows.

SeeRFC2183atftp://ftp.rfc-editor.org/in-notes/rfc2183.txtforbackgroundinformationontheContent-Dispositionheader.

TheclientbrowsercanusetheContent-Lengthheadervalue(providedwithresponse.setContentLength())toindicatetotheuserthedownloadprogresswithawidgetthatshowsahorizontalbarsteadilyfillingwithcolor.Theservletalsousesajava.io.BufferedInputStreamtobuffertheinputfromthefileinabyte[]array,whichspeedsupthetransferofdatafromtheservertotheclient.


SeeRecipe13.5foranexampleofusingajava.net.URLConnection(asopposedtoaFileInputStream)togetaninputstreamassociatedwithawebresource.AURLConnectionisusefulwhenyouwanttoobtainbinarydatafromaPDFfilethatisavailableonlyasawebaddressbeginningwith"http://".

ThecodeclosestheServletOutputStreamandtheBufferedInputStreaminafinallyblocktoreleaseanysystemresourcesusedbytheseobjects.Thecodewithinthefinallyblockexecutesregardlessofwhetherthecodethrowsanexception.

InternetExplorer5.5usuallyraisesanexceptionthatisdisplayedintheTomcatlogfilewhenarequestismadetothisrecipe'sservlet.Theloggedexceptiondoesnotdisrupttheapplication,nordoesitappearwhentheservletisrequestedbyOpera5,orbyInternetExplorer5.2andtheSafariMacintoshbrowsers.Theexceptionmessageincludesthetext"Connectionresetbypeer:socketwriteerror."Thismessagehasraisedspeculationonvariousservlet-relatedmailingliststhattheIEclientbrowseronWindowshascausedtheexceptionbyseveringtheconnectionwithTomcatafterthedatatransfer.Nobodyhasyetdevisedadefinitivesolutiontothisapparentlyharmlessexception,beyondsuggestingthattheservletcontainer'sloggingmechanismbeconfiguredtoignoreexceptionsofthistype.

SeeAlso

Recipe13.2-Recipe13.4onsendingWord,XML,andMP3filesasbinarydata;Recipe13.5ongettinganinputstreamrepresentingawebresourcesuchasweb.xml;RFCtechnicaldocumentsonMIME:ftp://ftp.rfc-editor.org/in-notes/rfc2045.txtandftp://ftp.rfc-editor.org/in-notes/rfc2046.txt.;RFC2183atftp://ftp.rfc-editor.org/in-notes/rfc2183.txtforbackgroundinformationontheContent-Dispositionheader;theMediaTypessectionoftheHTTPPocketReferencebyClintonLong(O'Reilly).




Recipe13.2SendingaWordProcessingFile

Problem

YouwanttosendaMicrosoftWordfileasbinarydata.

Solution

UsethesameservletsetupasdescribedinRecipe13.1,butincludeadifferentfileextensionandaContent-Typeofapplication/msword.

Discussion

YoumighthavesomeMicrosoftWorddocumentsthatyouwanttodistributeasbinarydatafromaservlet.Example13-2usesthesamebasicstructureasExample13-1,withafewchangestoadapttheservletforsendingMicrosoftWorddocuments.Theseincludeaccessingadifferentcontext-paramelement(youcouldkeepallfilesfordownloadinthesamedirectory,however),andusingadifferentMIMEtypeastheparameterforthesetContentType()method,asinresponse.setContentType("application/msword").

Example13-2.SendingaWordfileasbinarydata




importjava.io.File;




publicclassSendWordextendsHttpServlet{



IOException{





"Invalidornon-existentfileparameterinSendWord.");

//addthe.docsuffixifitdoesn'talreadyexist

if(fileName.indexOf(".doc")==-1)

fileName=fileName+".doc";

//whereareWordfileskept?

StringwordDir=getServletContext().getInitParameter("word-dir");

if(wordDir==null||wordDir.equals(""))


"Invalidornon-existentwordDircontext-param.");



try{


Filedoc=newFile(wordDir+"/"+fileName);


response.setContentType("application/msword");

response.addHeader(


response.setContentLength((int)doc.length());

FileInputStreaminput=newFileInputStream(doc);


intreadBytes=0;






}finally{


if(stream!=null)

stream.close();

if(buf!=null)

buf.close();

}

}//enddoGet



IOException{


}

}

TheServletOutputStream(theinformationsentastheservlet

response)andtheBufferedInputStream(fromwhichtheservletgetsthefiletosend)arebothclosedinthefinallyblocktomakesureanysystemresourcestheyusearereleased.SeetheendofthediscussioninRecipe13.1forafurtherdescriptionofthiscode,includingthewarningattheendofthatrecipeabouttheInternetExplorer-relatedexception.

SeeAlso

Recipe13.1onsendingaPDFfile;Recipe13.3andRecipe13.4onsendingXMLandMP3filesasbinarydata;Recipe13.5ongettinganinputstreamrepresentingawebresourcesuchasweb.xml;RFCtechnicaldocumentsonMIME:ftp://ftp.rfc-editor.org/in-notes/rfc2045.txtandftp://ftp.rfc-editor.org/in-notes/rfc2046.txt;RFC2183atftp://ftp.rfc-editor.org/in-notes/rfc2183.txtforbackgroundinformationontheContent-Dispositionheader;theMediaTypessectionoftheHTTPPocketReferencebyClintonWong(O'Reilly);Chapter1introducingthedevelopmentofaservlet.




Recipe13.3SendinganXMLfile

Problem

YouwanttosendanXMLfileasbinarydatafromaservlet.

Solution

Usethejavax.servlet.ServletOutputStreamobtainedfromthejavax.servlet.http.HttpServletResponseobjecttosendtheXMLfileasbinarydatatotheclient.

Discussion

ThisrecipedescribeshowtosendanXMLfileasbinarydatafromaServletOutputStream,sothattheusercanhandlethefileasdownloadedXML.Example13-3obtainsthebytesthatrepresenttheXMLasaBufferedInputStreamwrappedaroundaFileInputStream.ThecodeisverysimilartoExample13-1inRecipe13.1,exceptthatitusesaMIMEtypeoftext/XML.

InapopularformofconvertingXMLintoareadableformat,youcouldconverttheXMLcontenttoHTMLoranotherformusingExtensibleStylesheetLanguageTransformations(XSLT).IftheintentistouseXSLTforgeneratingthecontentinabrowser,leaveouttheContent-Dispositionresponseheader,becausethisheaderisdesignedtohandletheXMLasadownloadedfilethatwillbesavedintheuser'sfilesystem.SeeChapter23onusingthex:transformJSTLtag.

Example13-3.SendinganXMLfilewithaservlet




importjava.io.File;




publicclassSendXmlextendsHttpServlet{



IOException{





"Invalidornon-existentfileparameterinSendXmlservlet.");

//addthe.xmlsuffixifitdoesn'talreadyexist

if(fileName.indexOf(".xml")==-1)

fileName=fileName+".xml";

//whereareXMLfileskept?

StringxmlDir=getServletContext().getInitParameter("xml-dir");

if(xmlDir==null||xmlDir.equals(""))


"Invalidornon-existentxmlDircontext-param.");



try{


Filexml=newFile(xmlDir+"/"+fileName);


response.setContentType("text/xml");

response.addHeader(


response.setContentLength((int)xml.length());

FileInputStreaminput=newFileInputStream(xml);


intreadBytes=0;






}finally{


if(stream!=null)

stream.close();

if(buf!=null)

buf.close();

}//finally

}//enddoGet





}

}

Forthecontext-paramtoworkcorrectlyinthiscode,youhavetoincludeinweb.xmlanelementthatlookslike:

<context-param>

<param-name>xml-dir</param-name>

<param-value>h:/home/xml</param-value>

</context-param>

SeeChapter1ifyouneedanintroductionorrefresherforthedeploymentdescriptorweb.xml.

ThediscussioninRecipe13.1describesthebasicmechanicsofthiscode,soIdon'trepeatthatinformationhere.SeethenoteattheendofRecipe13.1abouttheInternetExplorer-relatedexceptionthatyoumayexperiencewithservletsofthistype.

SeeAlso

Recipe13.1onsendingaPDFfile;Recipe13.2onsendingaMicrosoftWordfileasbinarydata;Recipe13.4onsendingMP3filesasbinarydata;Recipe13.5ongettinganinputstreamrepresentingawebresourcesuchasweb.xml;theRFCtechnicaldocumentsonMIME:

ftp://ftp.rfc-editor.org/in-notes/rfc2045.txtandftp://ftp.rfc-editor.org/in-notes/rfc2046.txt;RFC2183atftp://ftp.rfc-editor.org/in-notes/rfc2183.txtforbackgroundinformationontheContent-Dispositionheader;theMediaTypessectionoftheHTTPPocketReferencebyClintonWong(O'Reilly);Chapter1introducingthedevelopmentofaservlet;atutorialonjava.sun.comonXSLT:http://java.sun.com/webservices/docs/1.1/tutorial/doc/JAXPXSLT.html#wp68287




http://java.sun.com/webservices/docs/1.1/tutorial/doc/JAXPXSLT.html#wp68287

Recipe13.4SendinganAudioFile

Problem

YouwanttosendanaudiofilesuchasanMPEGlayer3(MP3)mediatype.

Solution

Useajava.io.BufferedInputStreamtofetchtheaudiodata,andthejavax.servlet.ServletOutputStreamfromthejavax.servlet.http.HttpServletResponseobjecttosendthedatatotheclient.

Discussion

ThecodeinExample13-4usesthesameapproachasthepriorrecipes,exceptfortheMIMEtype,whichisspecifiedasaudio/mpeg.

WebbrowsersassociateanumberofotherMIMEtypesforMP3files,includingaudio/x-mpeg,audio/mp3,andaudio/x-mp3.

TheuserrequestsafilenameintheURL,asin:

http://localhost:8080/home/sendmp3?file=song_name

Thedeploymentdescriptor(web.xml)mapstheservletpath/sendmp3to

theservletclassofExample13-4:com.jspservletcookbook.SendMp3.Iftherequestedfiledoesnotalreadyhavethe.mp3suffix,thenthecodeaddsthatfileextension.Acontext-paramelementinthedeploymentdescriptorspecifiesthedirectorywheretheaudiofilesarekept:

<context-param>

<param-name>mp3-dir</param-name>

<param-value>h:/home/mp3s</param-value>

</context-param>

Example13-4usesthisdirectoryname,plusthefilename,astheconstructorparametertocreateanewjava.io.Fileobject,whichisthesourceforajava.io.FileInputStream.ABufferedInputStreambuffersthebytesfromthesongfile,whichtheServletOutputStreamresponsereads.

Example13-4.SendinganMP3file




importjava.io.File;




publicclassSendMp3extendsHttpServlet{


HttpServletResponseresponse)throwsServletException,IOException{





"Invalidornon-existentfileparameterinSendMp3servlet.");

//addthe.mp3suffixifitdoesn'talreadyexist

if(fileName.indexOf(".mp3")==-1)

fileName=fileName+".mp3";

//whereareMP3fileskept?

Stringmp3Dir=getServletContext().getInitParameter("mp3-dir");

if(mp3Dir==null||mp3Dir.equals(""))


"Invalidornon-existentmp3-Dircontext-param.");



try{


Filemp3=newFile(mp3Dir+"/"+fileName);


response.setContentType("audio/mpeg");

response.addHeader(


response.setContentLength((int)mp3.length());

FileInputStreaminput=newFileInputStream(mp3);


intreadBytes=0;






}finally{


if(stream!=null)

stream.close();

if(buf!=null)

buf.close();

}

}//doGet


HttpServletResponseresponse)throwsServletException,IOException{


}

}

ReviewRecipe13.1forafurtherexplanationofthiscode,includingthewarningattheendofthe"Discussion"sectionaboutloggedexceptionsthatmayoccurwithInternetExplorer.

SeeAlso

Recipe13.1onMIMEtypesandsendingaPDFfileasbinarydata;Recipe13.2andRecipe13.3onsendingWordandXMLfiles,respectively,asbinarydata;Recipe13.5onreceivinganinputstreamrepresentingawebresourcesuchasweb.xml;theRFCtechnicaldocumentsonMIME:ftp://ftp.rfc-editor.org/in-notes/rfc2045.txtand


ftp://ftp.rfc-editor.org/in-notes/rfc2046.txt;RFC2183atftp://ftp.rfc-editor.org/in-notes/rfc2183.txtforbackgroundinformationontheContent-Dispositionheader;theMediaTypessectionoftheHTTPPocketReferencebyClintonWong(O'Reilly);Chapter1introducingthedevelopmentofaservlet.



Recipe13.5ViewingInternalResourcesinaServlet

Problem

Youwanttouseaservlettofetchinternalresourcesfromawebapplicationforviewingbyauthenticatedusers.

Solution

Usethejavax.servlet.ServletContext.getResource(Stringpath)methodtogeneratetheinputstreamfromthewebresource.

Discussion

Aservletcouldbeusedwhileawebapplicationisindevelopmenttoprovideaviewofthedeploymentdescriptor.Webdevelopersoftenhavetodouble-checkweb.xmlforthevaluesofcontext-paramelements,aservlet'sregisteredname,andotherinformation.Wouldn'titbenicetojustrequestaservletinthebrowsertoviewweb.xml?

Example13-5opensupweb.xmlusingtheServletContext.getResource()method,whichreturnsajava.net.URLobjectrepresentingthedeploymentdescriptoratthepathWEB-INF/web.xml.

ThecodeopensaconnectiontotheXMLfilebycallingtheURLobject'sopenConnection()method,whichreturnsajava.net.URLConnectionobject.ThenthecodebufferstheinputstreamtotheresourcebywrappingitinaBufferedInputStream:

buf=newBufferedInputStream(urlConn.getInputStream());

TheurlConnvariablereferstoaURLConnection.

IfthebrowserisnotsavvyaboutdisplayingXMLfilesinareadablefashion(Netscape7.1andInternetExplorercandisplaythesefilesproperly),youcanuseXSLTtoconverttheXMLintoHTMLbeforeitissenttothebrowser.

Example13-5.Displayingthedeploymentdescriptorviaaservlet





importjava.net.URL;

importjava.net.URLConnection;

importjava.net.MalformedURLException;



publicclassResourceServletextendsHttpServlet{



IOException{

//getweb.xmlfordisplaybyaservlet

Stringfile="/WEB-INF/web.xml";

URLurl=null;

URLConnectionurlConn=null;

PrintWriterout=null;


try{

out=response.getWriter();

//accessawebresourcewithinthesamewebapplication

//asaURLobject

url=getServletContext().getResource(file);

//setresponseheader

response.setContentType("text/xml");

urlConn=url.openConnection();

//establishconnectionwithURLrepresentingweb.xml

urlConn.connect();

buf=newBufferedInputStream(urlConn.getInputStream());

intreadBytes=0;

//readfromthefile;writetothePrintWriter


out.write(readBytes);

}catch(MalformedURLExceptionmue){

thrownewServletException(mue.getMessage());



}finally{


if(out!=null)

out.close();

if(buf!=null)

buf.close();

}

}//doGet





}

}

Thisservletisdesignedfordevelopers;ifjustanyonehasachancetostudythedeploymentdescriptor,itwillcompromisethewebapplication'ssecurity.Therefore,youshouldremovetheservletfromproductionversionsofthewebapplication,oruseauthenticationtoallowonlyauthorizeduserstoviewtheservlet'soutput(seeChapter15fordetails).

ThecodeusesaPrintWritertowritethebytesreceivedfromtheinputstream,becausetheservletintendstodisplaytheresponseascharacters(insteadofofferingtheresponsetotheclientasadownloadedresource).TheServletContext.getResource(Stringpath)methodtakesapaththatbeingswiththe/character.Thepathisinterpretedasbeginningatthecontextroot,ortop-leveldirectory,ofthewebapplication.Therefore,theservletobtainsweb.xmlwiththefollowing

code:

Stringfile="/WEB-INF/web.xml";

...

url=getServletContext().getResource(file);

TheServletContext.getResouce()methodreturnsnullifitisunabletoreturnavalidresourcerepresentingthepathparameter.

SeeAlso

Recipe13.1-Recipe13.4onsendingPDF,Word,XML,andaudiofiles,respectively,asbinarydata;theRFCtechnicaldocumentsonMIME:ftp://ftp.rfc-editor.org/in-notes/rfc2045.txtandftp://ftp.rfc-editor.org/in-notes/rfc2046.txt;RFC2183atftp://ftp.rfc-editor.org/in-notes/rfc2183.txtforbackgroundinformationontheContent-Dispositionheader;theMediaTypessectionoftheHTTPPocketReferencebyClintonWong(O'Reilly);Chapter1introducingthedevelopmentofaservlet.




Chapter14.LoggingMessagesfromServletsandJSPs

Introduction

Recipe14.1.LoggingWithoutLog4j

Recipe14.2.SettingUpLog4j

Recipe14.3.UsingaLoggerWithoutaConfigurationFile

Recipe14.4.AddinganAppendertotheRootLogger

Recipe14.5.UsingaPatternwithaLogger'sAppender

Recipe14.6.Usinglog4jinaJSP

Recipe14.7.LoggingMessagesUsingaServletContextEventListener

Recipe14.8.LoggingMessagesUsingaSessionEventListener

Introduction

Logginginvolvessendingmessagesfromyourapplicationanddisplayingthisinformationinavarietyofwaysforwebdevelopersandadministrators.Themessagescanbedeliveredtoaconsole,ortheycanbestoredpersistentlyinfilesordatabases.Loggingmaybeusedonlyforsendingdebug-relatedinformationwhileawebapplicationisbeingdeveloped,orthesemessagesmayprovideinformationfromanapplicationinproduction,includingdataaboutwarningsandfatalerrors.

Thischapterdescribesaverypowerfulopensourceloggingtoolcalledlog4j.ThisisaJavaARchive(JAR)file(log4j-1.2.8.jar)thatyoucanaddtoyourwebapplicationbyplacingitinyourWEB-INF/libdirectory.Thismakesitavailableforuseinanyservletsorbeansthatyouwanttosendloggingmessagesfrom.Thissectionprovidesonlyabriefintroductiontolog4j,becauseitspowerdoesentailsomecomplexity.

log4jinvolvesthreemainconcepts:loggers,appenders,andlayouts.log4jusesanexternalconfigurationfile,similartoadeploymentdescriptor,toconfigurethesethreeloggingelements.Theupcomingrecipesprovidesomeexamplesoftheseconfigurationfiles,whicharemostlysimpletextfilesinvolvingalistofname/valuepairs.Thepowerofusingexternalfilesisthatyoucanchangethepropertiesinthesetextfilestoalteralogger(forinstance,modifytheformatofitsmessages)insteadofrecompilingtheservletcode.

Forthechangestotakeeffect,youmayrequireareloadoftheservletorothercomponentthatinitializestheloggingsystemfortheapplication.

Loggers

Aloggeristheentitythataservletusestologmessages.Touseone,importthelog4jclassesintotheservlet,createaninstanceofalogger(specificallyanorg.apache.log4j.Logger),thencallthelogger'smethods.Themethodsarenamedafterthelogginglevelofthemessage.Forexample,tologaninformationalmessage(anINFOlevel)youwouldcall:

logger.info("HttpServletinitmethodcalled.");

log4jhasfivedifferentlevelsoflogcategories:DEBUG,INFO,WARN,ERROR,andFATAL.ThelogcategoriesareorganizedinascendingorderbeginningwithDEBUGaloggerconfiguredforINFO-levellogginglogsonlyINFO,WARN,ERROR,andFATALmessages(butnotDEBUG-levelmessages,becauseinthishierarchyDEBUGisbeneathINFOandtheotherlevels).Hereisabriefdescriptionofthepurposeofeachlevel:

DEBUGinvolvesloggingmessageswhileinitiallydevelopinganddebugginganapplication.

INFOhelpsyoumonitortheprogressofanapplication.

WARNdesignatespotentiallyharmfulsituations.

ERRORrepresentsanerrorthattheapplicationcanlikelyrecoverfrom.

FATALsuggestserrorsthatwillcauseanapplicationtoabort.

Everyloggerisconfiguredwithalevel(suchasDEBUG)inthelog4jpropertiesorconfigurationfile(seeRecipe14.4).log4jalsoassociatesthemessagesthatyoulogwithaspecifiedlevel,whichmakesiteasytousebecausethemethodnamesarethesameasthelevelnames.Theloggerdoesnotsendthesemessagesunlessthelogger'slevelisequaltoorgreaterthanthelevelrepresentedbythemethodcall(asinlogger.debug(Objectmessage)).

Forexample,let'ssayyouconfiguretheloggerwithalevelofDEBUG,thendevelopaservletwithanumberoflogger.debug(Objectmessage)calls.

Later,youcanchangetheconfigurationfileandgivetheloggeranINFOlevel.Changingtheconfigurationinthismanner"turnsoff"DEBUG-levellogginginthatservlet,sothattheseloggingmessagesnolongershowupinthelogfiles,database,orotherloggingrepository.ThisisbecauseDEBUGisnotequaltoorgreaterthanINFOinthehierarchyofloggingcategories.

Similarly,youcanturnbackonDEBUG-levellogginginthepriorexamplebysimplyswitchingthelogger'sconfigurationbackfromINFOtoDEBUG.Asaresult,thedebug-levelmessageswillnolongerbefilteredout.

ProgrammerswritingsoftwarewithseveralDEBUG-levelmethodcallscaneasilyswitchintoWARN-orERROR-leveldebuggingoncetheapplicationmovesintoitsnextstageofdevelopment,orgoesintoproduction.

Appenders

log4jisalsoverypowerfulintermsofthedifferentwaysyoucanlogmessages.Youcanuselog4jtologmessagestoaconsole,afile,arollingfile(whichautomaticallycreatesabackupfilewhenalogfilereachesaspecifiedsize),adatabase,anemailserver,andseveralothertypesoflogrepositories.log4jcallseachoftheseloggingmechanismsanappender.Recipe14.4introducestheconfigurationfileinwhichyoucandescribeappenders.

Layouts

Whatdoestheactualloggedmessagelooklike?Whatinformationdoesitinclude?log4jshinesinthisareatoo.Youcanspecifynumerousdifferentlayoutsforthemessagesusingthelog4jconfigurationfile.log4jletsyou

specifyverycomplex(orsimple)layoutsusingconversionpatterns,whicharesomewhatsimilartoregularexpressions.Toachievethemostbasiclayout,youcanspecifyanorg.apache.log4j.SimpleLayout.Withthisformat,thelogcontainsthelevelname,followedbyadash(-)andtheactualmessage:

INFO-HttpServletinitmethodcalled.

Usinganorg.apache.log4j.PatternLayoutismorepowerful,andRecipe14.5providessomeexamplesofdifferentlayoutsforloggingmessages.

Recipe14.1LoggingWithoutLog4j

Problem

Youwanttoputamessageintheserverlogs.

Solution

CalltheServletContext.log()methodinsidetheservlet.

Discussion

Ifyoujustwanttologamessageintheservletcontainer'slogfileanddonotneedthepoweroflog4j,usetheServletContext.log()method.Example14-1showsthetwoversionsofthelog()method.OnetakestheStringmessageasaparameter,andtheotherhastwoparameters:aStringmessageandaThrowable.TheservletlogwillcontainthestacktraceoftheThrowableifyouusethislog()form.

Example14-1.AservletusestheServletContext.log()method




publicclassContextLogextendsHttpServlet{




StringyourMessage=request.getParameter("mine");

//CallthetwoServletContext.logmethods

ServletContextcontext=getServletContext();

if(yourMessage==null||yourMessage.equals(""))

//logversionwithThrowableparameter

context.log("Nomessagereceived:",

newIllegalStateException("Missingparameter"));

else

context.log("Hereisthevisitor'smessage:"+yourMessage);



//loggingservletsprobablywanttodisplaymoreHTML

out.println(

"<html><head><title>ServletContextlogging</title></head><body>");

out.println("<h2>Messagessent</h2>");


}//doGet

}

TheServletContextlogsitstextmessagestotheservletcontainer'slogfile.WithTomcattheselogsarefoundin<Tomcat-installation-directory>/logs.BelowistheoutputofExample14-1andthesecondformofServletContext.log(),whichprintsthemessageandtheThrowable'sstacktrace(onlythefirsttwolevelsofthemethodstackareshown).Youcanseethatthelogincludesthedateandtimeoftheloggingactivity,andthemessagetext:

2003-05-0814:42:43Nomessagereceived:

java.lang.IllegalStateException:Missingparameter

atcom.jspservletcookbook.ContextLog.doGet(UnknownSource)

atjavax.servlet.http.HttpServlet.service(HttpServlet.java:740)

...

Thesingle-parameterformofthelog()methodsimplydisplaysthedate,time,andtextofthemessage,asinthefirstlineofthepriorlogsample.Eachlog()methodcallplacesthemessageonanewlineintheserverlogfile.

SeeAlso

Recipe14.2-Recipe14.8onusinglog4jtodesignyourowncustomloggingmechanism;ChapterSRV.3oftheservletAPIontheservletcontext;linkstothelatestservletspecification:http://java.sun.com/products/servlet/index.html.


Recipe14.2SettingUpLog4j

Problem

Youwanttosetuplog4jforuseinyourwebapplication.

Solution

Downloadthelog4jdistributionfromtheApacheJakartaprojectandplacetheaccompanyinglog4j-1.2.8.jarfile(thenamewillbedifferentfordifferentlog4jversions)intheWEB-INF/libdirectoryofyourwebapplication.

Discussion

Thelog4jpackageisavailableforuseundertheApacheSoftwareLicense,whichisincludedwiththedistribution.Herearethestepsforsettinguplog4jforyourwebapplication:

1. Gotothelog4jwebsiteanddownloadthedistributioninZIP(Windows)orgzipped(Unix-basedsystems)format:http://jakarta.apache.org/log4j/docs/download.html.Thedownloadedfilewillbenamedsomethinglikejakarta-log4j-1.2.8.ziporjakarta-log4j-1.2.8.tar.gz.

Unpackthedistribution,whichcreatesadirectoryjakarta-log4j-1.2.8(forVersion1.2.8oflog4j).Insidethedistdirectoryofthistop-leveldirectoryisthelog4j-1.2.8.jarfile.CopythisJARfileintotheWEB-INF/libdirectoryofyourwebapplication(s).

Createalog4jpropertiesfileandplaceitinthewebapplication's

http://jakarta.apache.org/log4j/docs/download.html

WEB-INF/classesdirectory.Thisistypicallyatextfilewithname/valuepairsforconfiguringlog4jelementssuchasloggers,appenders,andlayouts.Recipe14.4includesanexampleofthisfile.

Intheservletsorbeanswhereyouwillusealogger,includetheproperimportstatements.Example14-2isaskeletalservletshowingtheclassesthatyoumighttypicallyuse.

Example14-2.Importinglog4j-relatedpackages

importorg.apache.log4j.Logger;

importorg.apache.log4j.PropertyConfigurator;



publicclassLoggerSkelextendsHttpServlet{

privateLoggerlog;

publicvoidinit(){

//log4jwillfindthelog4j.propertiesfile

//inWEB-INF/classes

log=Logger.getLogger(LoggerSkel.class);

//Justanexampleofusingthelogger

log.debug("Instancecreatedof:"+getClass().getName());

}




//dologginghereifnecessary

}//doGet

}

Aslongaslog4j-1.2.8.jarislocatedinWEB-INF/lib,yourservletcanusethenecessaryclassesfromtheorg.apache.log4j.*packages.

SeeAlso

Recipe14.3-Recipe14.8onusinglog4jtodesignyourowncustomloggingmechanism;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.


http://jakarta.apache.org/log4j/docs/documentation.html

Recipe14.3UsingaLoggerWithoutaConfigurationFile

Problem

Youwanttousealoggerinaservletwithoutsettingupyourownconfigurationfile.

Solution

Createtheloggerintheservletandusetheorg.apache.log4j.BasicConfiguratorclasstoconfigurethelogger.

Discussion

log4jallowstheconfigurationofaloggerwithoutaprovidedconfigurationorpropertiesfile.Example14-3isaservletthatinstantiatesaloggerinitsinit()method,whichtheservletcontainercallswhentheservletinstanceiscreated.ThestaticBasicConfigurator.configure()methodcreatesaConsoleAppender;inotherwords,theloggerwilllogitsmessagestotheconsoleusingadefaultformat.

Example14-3.AservletusesBasicConfiguratortoconfigurealogger



importorg.apache.log4j.BasicConfigurator;



publicclassLoggerNconfigextendsHttpServlet{

privateLoggerlog=null;

publicvoidinit(){

//usetherootlogger

log=Logger.getRootLogger();

//thisloggerwilllogtotheconsolewithadefaultmessageformat

BasicConfigurator.configure();

}




//displayaDEBUGlevelmessage

log.debug("SendingaDEBUGmessage");

//displayanINFOlevelmessage

log.info("SendinganINFOmessage");

//betterdisplaysomeHTML



out.println(

"<html><head><title>Servletlogging</title></head><body>");

out.println("<h2>HellofromaLoggerwithnoConfigfile</h2>");

//Thislogger'sparentistherootlogger

out.println(

"Yourloggernameis:"+log.getName()+"<br>");

out.println(

"Yourloggerparentis:"+log.getParent().getName()+"<br>");


}//doGet





}

}

Example14-4showsanexamplemessagefromtheservlet.Themessageisbasedonadefaultformatthatincludesthethreadname(Thread-5),thelevelname(DEBUG),theloggername(com.jspservletcookbook.LoggerNconfig),andtheactualmessage("SendingaDEBUGmessage").Recipe14.5showshowtocreateaformatpatternforloggingmessages,sothatyoucancustomizethetypeofinformationthattheloggersends.

Example14-4.ExampleofaloggedmessageusingBasicConfigurator

4061660[Thread-5]DEBUGcom.jspservletcookbook.LoggerNconfig-SendingaDEBUGmessage

4061660[Thread-5]INFOcom.jspservletcookbook.LoggerNconfig-SendinganINFOmessage

HereisthepatternusedforthelayoutassociatedwithBasicConfigurator:

%-4r[%t]%-5p%c%x-%m%n

SeeRecipe14.5fordetailsontheorg.apache.log4j.PatternLayoutclass.

SeeAlso

Recipe14.2ondownloadingandsettinguplog4j;Recipe14.4-Recipe14.8onusinglog4jtodesignyourowncustomloggingmechanism;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jJavadocpage:http://jakarta.apache.org/log4j/docs/api/index.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.


http://jakarta.apache.org/log4j/docs/api/index.html


Recipe14.4AddinganAppendertotheRootLogger

Problem

Youwanttoconfigureanappenderorloggingdestinationfortherootlogger.

Solution

Createaconfigurationfilecalledlog4j.propertiesandplaceitintheWEB-INF/classesdirectoryofyourwebapplication.

Discussion

Nowourdiscussionmovesontothelog4jconfigurationfile,wheredeveloperscancustomizeloggers,appenders,andlayouts.Herearethestepsforusingthisrecipe'sexamples:

1. Createapropertiesfilenamedlog4j.properties(itscontentslooklikeExample14-5).

PlacethepropertiesfileintheWEB-INF/classesdirectoryofthewebapplication.

Importthisclassintoyourservlet:org.apache.log4j.Logger.

Intheservlet,getareferencetotherootloggerwiththestaticLogger.getRootLogger()method,andstartlogging.

Example14-5configurestherootlogger,akindof"superlogger"foryourapplication,withaDEBUGlevel.Therootloggerusesanappendernamedcons.Thisappenderisofatypeorg.apache.log4j.ConsoleAppender,meaningthatitsendsitslogmessagestotheconsole.

Example14-5.Thelog4j.propertiesfileforcreatingarootloggerappender

log4j.rootLogger=DEBUG,cons

log4j.appender.cons=org.apache.log4j.ConsoleAppender

log4j.appender.cons.layout=org.apache.log4j.SimpleLayout

Thethirdlineofthelog4j.propertiesfilestatesthattheloggerwilluseaSimpleLayout,whichlogsthelevelname(DEBUG),adash(-),andthemessageitself.Example14-6showstheservletthatisusingthelogger.log4jwillfindthelog4j.propertiesfileautomaticallyinWEB-INF/classesbecausetheservlethasnototherwiseconfiguredtheloggerwithacalltoBasicConfigurator.configure(),asshowninRecipe14.3.

Example14-6.Usingtherootloggerconfiguredwiththelog4j.propertiesfile





publicclassLoggerWconfigextendsHttpServlet{


publicvoidinit(){

//Therootloggerwillgetitsconfigurationfrom

//WEB-INF/classes/log4j.properties

log=Logger.getRootLogger();

log.info("LoggerWconfigstarted.");

}




//displayaDEBUG-levelmessage


//displayanINFO-levelmessage





out.println(


out.println(

"<h2>HellofromaLoggerwithalog4j.propertiesfile</h2>");

out.println("Yourloggernameis:"+log.getName()+"<br>");


}//enddoGet

}

Example14-6logsanINFOmessageintheservlet'sinit()method,thenlogstwomessagesintheservlet'sdoGet()servicemethod.Theloggerlogsallofthesemessagestotheconsolebecausethisishowthelog4j.propertiesfileconfigurestherootlogger'sappender.Thisiswhattheconsoleoutputlookslike:

INFO-LoggerWconfigstarted.

DEBUG-SendingaDEBUGmessage

INFO-SendinganINFOmessage

Figure14-1showstheservlet'soutputinawebbrowser.

Figure14-1.Theloggerdisplaysitsnameinaservlet

SeeAlso

Recipe14.2ondownloadingandsettinguplog4j;Recipe14.3onusingalog4jloggerwithoutapropertiesfile;Recipe14.5-Recipe14.8onusinglog4jtodesignyourowncustomloggingmechanism;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jJavadocpage:http://jakarta.apache.org/log4j/docs/api/index.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.




Recipe14.5UsingaPatternwithaLogger'sAppender

Problem

Youwanttocreateyourownloggerforaservletandgivetheloggeranappender.

Solution

Includetheappenderconfigurationinthelog4j.propertiesfile.

Discussion

Thisrecipecreatesanewlogger,whichbringsustothediscussionoflog4j'sinheritancestructure.Therootloggeristhe"superlogger"thatalllogger'sinheritfrom,similartojava.lang.ObjectinJava'sobjectorientedprogrammingsetup.Example14-7createsanewloggernamedcom.jspservletcookbook,whichinheritstherootlogger'slevel(DEBUG)andconsoleappender(namedcons).Example14-7alsocreatesanappenderforthecom.jspservletcookbooklogger.Placethislog4j.propertiesfileintheWEB-INF/classesdirectory.

Example14-7.Theconfigurationforaloggernamedcom.jspservletcookbook


log4j.logger.com.jspservletcookbook=,myAppender

#therootlogger'sappender


#thecom.jspservletcookbooklogger'sappender

log4j.appender.myAppender=org.apache.log4j.RollingFileAppender

log4j.appender.myAppender.File=h:/home/example.log

log4j.appender.myAppender.MaxBackupIndex=1

log4j.appender.myAppender.MaxFileSize=1MB

#therootlogger'slayout


#thecom.jspservletcookbooklogger'slayout

log4j.appender.myAppender.layout=org.apache.log4j.PatternLayout

log4j.appender.myAppender.layout.ConversionPattern=%-5pLogger:%c{1}

Date:%d{ISO8601}-%m%n

YouprobablynoticedthesimilaritybetweenpackagenamesandthenameofthenewloggerinExample14-7:com.jspservletcookbook.log4jusesanamingschemebasedonJava's.Here'sthebasicrundownonthisscheme:

Allloggersinheritfromtherootlogger.

Allloggerswhosenamecontainsaprefixthatmatchesaconfiguredlogger'sname(suchascom.jspservletcookbook)alsoinheritfromthatconfiguredlogger.Therefore,aloggernamedcom.jspservletcookbook.LoggerWconfigderivesitscharacteristicsfromthecom.jspservletcookbooklogger.

InExample14-7,thecom.jspservletcookbookloggerspecifiesthatitwilluseanappendernamedmyAppender.ThemyAppender

appenderisarollingfileappender,whichisalogfilethatautomaticallycreatesabackupfilewhentheoriginallogreachesacertainsize.TheappenderisbasedontheJavaclassorg.apache.log4j.RollingFileAppender,whichisamongthesetofclassesthatlog4juses.

IfyoulookattheJavadocforthatclass,thenyouseethatithasabunchofmethodsthatlooklikegetXXX(),whereXXXisoneofthelogger'sproperties.Yousetthesepropertiesoftheappenderintheconfigurationfilebygivingeachpropertyavalue.TosetthemyAppenderappender'sFileproperty,thesyntaxis:


Thisconfigurationelementspecifiesthefilelocationwheretheappenderwilllogitsmessages.WhenthisfilereachesitsMaxFileSizeof1MB,log4jrenamesthefileexample.log.1andcreatesanewexample.logtoreceivelogmessages.TheMaxBackupIndexmeansthatlog4jwillcreateonlyonebackupfile.

TheJavadocforRollingFileAppendercanbefoundat:http://jakarta.apache.org/log4j/docs/api/org/apache/log4j/RollingFileAppender.html.

Example14-7alsospecifiesalayoutforthecom.jspservletcookbooklogger,andaratherelaborateoneatthat:


log4j.appender.myAppender.layout.ConversionPattern=%-5pLogger:%c{1}Date:

%d{ISO8601}-%m%n

ThefirstlinespecifiesthatthemyAppenderlayoutwilluseanorg.apache.log4j.PatternLayout,whichisbasedonthe

http://jakarta.apache.org/log4j/docs/api/org/apache/log4j/RollingFileAppender.html

conversionpatternoftheprintffunctioninC,accordingtothePatternLayoutJavadoc.Thispatternlanguagecombinesliteraltextandconversionspecifierstogenerateaformattedlogmessage.Theconversionspecifiersareletters(likec)thathavespecialmeaningsasplaceholders.Forexample,thelettersmayrepresentdatesorloggernames.

The%characterprecedestheconversionpatternsymbols.Forexample,considerthefollowingpattern:

Logger:%c{1}

Thistranslatesto"theliteraltext`Logger:'followedbythelogger'sname."Thenumber1incurlybraces({1})followingthe%ccharactersisaprecisionspecifier,whichmeans"displayjustonesegmentofthenamebeginningfromtherighthandside."Iftheloggeriscom.jspservletcookbook.LoggerServlet,thenthe%c{1}patterndisplays"LoggerServlet"inthelogtext.Thisisbecausethecconversionspecifierisaplaceholderfortheloggername.

Thelettermdisplaysthelogmessageitself,theletternproducestheplatform-specificlineseparator,andtheletterdrepresentsthedate.Theentirestring%d{ISO8601}isalog4jdateformatter,whichdisplaysthedateindetailedform.Seehttp://jakarta.apache.org/log4j/docs/api/org/apache/log4j/helpers/ISO8601DateFormat.html

Example14.8showsaservletthatusesaloggerthatinheritsitscharacteristicsfromtwoconfiguredloggers:therootloggerandthecom.jspservletcookbooklogger.

Example14-8.Aservletusesadescendantlogger



http://jakarta.apache.org/log4j/docs/api/org/apache/log4j/helpers/ISO8601DateFormat.html



publicclassLoggerNewConfigextendsHttpServlet{


publicvoidinit(){

//thelogger'snameisthesameastheclassname:

//com.jspservletcookbook.LoggerNewConfig

log=Logger.getLogger(LoggerNewConfig.class);

log.info("LoggerNewConfigstarted.");

}




//displayaDEBUG-levelmessage


//displayanINFO-levelmessage





out.println(


out.println(

"<h2>HellofromaLoggerwithitsownconfigurationinthe"+

log4j.propertiesfile</h2>");

out.println("Yourloggernameis:"+log.getName()+"<br>");

out.println(

"Yourloggerparentis:"+log.getParent().getName()+"<br>");


}//enddoGet

}

Thestaticorg.apache.log4j.Logger.getLogger(ClassclassName)methodcreatesaloggernamedaftertheclassinExample14.8(com.jspservletcookbook.LoggerNewConfig).Therefore,thisnewloggerinheritstheappenderthatthepropertiesfileinExample14-7setupfortheloggercom.jspservletcookbook,becausethenewlogger'snamehascom.jspservletcookbookasaprefix.Infact,anyotherloggercreatedinclassesthatarepartofthecom.jspservletcookbookpackageinheritstheseproperties,aslongasthedeveloperkeepsnamingherloggersaftertheJavaclassinwhichtheyarecreated.

HereisanexampleofwhattheentirepatterntheconfigurationfileofExample14-7createdgeneratesinthelogfile:

INFOLogger:LoggerNewConfigDate:2003-07-1017:16:22,713-LoggerNewConfigstarted

DEBUGLogger:LoggerNewConfigDate:2003-07-1017:16:34,530-SendingaDEBUGmessage

INFOLogger:LoggerNewConfigDate:2003-07-1017:16:34,530-SendinganINFOmessage

Visithttp://jakarta.apache.org/log4j/docs/api/org/apache/log4j/PatternLayout.htmlformoredetailsonpatternlayouts.

Becauseoftheinheritancestructureestablishedbythelog4jconfigurationfile,theservletinExample14-8alsologsitsmessagestotheconsole.

http://jakarta.apache.org/log4j/docs/api/org/apache/log4j/PatternLayout.html

SeeAlso

Recipe14.2ondownloadingandsettinguplog4j;Recipe14.3onusingalog4jloggerwithoutapropertiesfile;Recipe14.4onaddinganappendertotherootlogger;Recipe14.6onusingloggersinJSPs;Recipe14.7andRecipe14.8onusinglog4jwithapplicationeventlisteners;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jJavadocpage:http://jakarta.apache.org/log4j/docs/api/index.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.




Recipe14.6Usinglog4jinaJSP

Problem

YouwanttoincludeloggingstatementsinaJSP.

Solution

Designacustomtagthatuseslog4jtoinitiateloggingmessages.

Discussion

AcustomtagisanXMLelementthatyouinventordesignforuseinaJSP.Inotherwords,theJSPcontainerdoesnotprovidethecustomactions;thewebdeveloperhimselfdesignstheJavaclassesthatprovidethetagfunctionality.Acustomtagoractioncanbeusedtoimplementlog4jloggingfunctionalityinJSPs.

Inthisrecipe,Ishow:

AJavaclassthatprovidesthetaghandlerforacustomtagnamedcbck:log.

ATagLibraryDescriptor(TLD)thatprovidesthewebapplicationwithinformationaboutthetag.

AJSPpagethatusesthecbck:logtag.

Example14-9showstheJavaclassLoggerTagonwhichthecbck:logtagisbased.Eachcustomactionisactuallydrivenbehindthe

scenesbyoneormoreJavaclasses.Inthiscase,LoggerTagislikeaJavaBeanthatwrapsthelog4jclasses,whichweimportatthetopofthetagclass.

CustomJSPactionsareacomplextopic,soIexplainthistagbyfocusingmainlyonitslog4jfeatures.SeeChapter22tohelpfillinthemissingspacesinyourownknowledgeaboutcustomtagdevelopment.

Example14-9.Acustomtagthatuseslog4j




importjava.lang.reflect.Method;

importjavax.servlet.jsp.*;

importjavax.servlet.jsp.tagext.*;

publicclassLoggerTagextendsBodyTagSupport{


privateStringconfigFile=null;

privateStringlevel=null;

privatestaticfinalString[]LEVELS=

{"debug","info","warn","error","fatal"};

publicvoidsetConfigFile(StringfileName){

this.configFile=fileName;

}

publicvoidsetLevel(Stringlevel){

this.level=level;

}

publicintdoEndTag()throwsJspException{

StringrealPath=pageContext.getServletContext().getRealPath("/");

StringfileSep=System.getProperty("file.separator");

if(realPath!=null&&(!realPath.endsWith(fileSep))){

realPath=realPath+fileSep;}

//configuretheloggeriftheuserprovidesthisoptionalattribute

if(configFile!=null)

PropertyConfigurator.configure(realPath+

"WEB-INF/classes/"+configFile);

//throwanexceptionifthetaguserprovidesaninvalidlevel,

//somethingotherthanDEBUG,INFO,WARN,ERROR,orFATAL

level=level.toLowerCase();

if(!contains(level))

thrownewJspException(

"Thevaluegivenforthelevelattributeisinvalid.");

//Theloggerhasthesamenameastheclass:

//com.jspservletcookbook.LoggerTag.Therefore,itinheritsits

//appendersfromaloggerdefinedintheconfigfile:

//com.jspservletcookbook

log=Logger.getLogger(LoggerTag.class);

Stringmessage=getBodyContent().getString().trim();

Methodmethod=null;

try{

method=log.getClass().

getMethod(level,newClass[]{Object.class});

method.invoke(log,newString[]{message});

}catch(Exceptione){}

returnEVAL_PAGE;

}//doEndTag

publicvoidrelease(){

//releaseresourcesusedbyinstancevariables

log=null;

configFile=null;

level=null;

}//release

privatebooleancontains(Stringstr){

for(inti=0;i<LEVELS.length;i++){

if(LEVELS[i].equals(str))

returntrue;

}

returnfalse;

}//contains

}

TheLoggerTagextendsthejavax.servlet.jsp.tagext.BodyTagSupportclass,whichisdesignedforcustomactionsthatprocessbodycontent,orthetextthatmayappearbetweenopeningandclosingtags.

Thetagattributes,arequiredattributenamedlevelandtheconfigFileoptionalattribute,arehandledlikeJavaBeanproperties:

with"setter"methods(e.g.,publicvoidsetLevel(Stringlevel)).ThedoEndTag()methoddoesmostoftheimportantworkforthetag:

1. ItattemptstoconfiguretheloggeriftheuserhasprovidedaconfigurationfilenameintheconfigFileattribute.

Itchecksifthelevelisvalid(oneofDEBUG,INFO,WARN,ERROR,orFATAL).

Itlogsthemessage.

Example14-10showstheTLD,whichconveystagspecificstotheJSPcontainer,suchaswhetheranattributeisrequiredoroptional.ThetaglibraryassociatedwiththisTLDdescribesonlythecbck:logtag.TheTLDfilesmustbelocatedinWEB-INForasubdirectorythereof,orinsideoftheMETA-INFdirectoryofaJARthatisplacedinWEB-INF/lib.

Example14-10.TheTLDforthecustomloggertag


<!DOCTYPEtaglib



<taglib>



<short-name>cbck</short-name>

<uri>jspservletcookbook.com.tags</uri>

<description>Cookbookcustomtags</description>

<tag>

<name>log</name>

<tag-class>com.jspservletcookbook.LoggerTag</tag-class>

<body-content>JSP</body-content>

<description>Thistaguseslog4jtologamessage.</description>

<attribute>

<name>configFile</name>

<required>false</required>


<description>

Thisattributeprovidesanyconfigurationfilenameforthe

logger.Thefilemustbelocatedin

WEB-INF/classes.

</description>

</attribute>

<attribute>

<name>level</name>



<description>Thisattributeprovidesthelevelforthelogrequest.

</description>

</attribute>

</tag>

</taglib>

Example14-11showsthelogger.jsppageandhowthecustomactioncanbeused.

Example14-11.AJSPusesalogcustomactiontoaccesslog4j


<%@tagliburi="jspservletcookbook.com.tags"prefix="cbck"%>

<html>

<head><title>AloggingJSP</title></head>

<body>

<h2>Hereistheloggingstatement</h2>

<cbck:loglevel="debug">

Debugmessagefromlogger.jsp

</cbck:log>

Debugmessagefromlogger.jsp

</body>

</html>

First,thepageusesthetaglibdirectivetodeclarethetaglibrarythatcontainsourcustomaction.Example14-10showstheTLDfile,anXMLfilethatdescribesthepropertiesofataglibrary'svarioustags.Chapter22describesTLDsinmoredetail.

Thecbck:logcustomactionallowsadevelopertologamessagefromtheJSPbynestingthemessagetextwithinthecbck:logtag(i.e.,thebodycontentofthetagisthelogmessage).Thecbckpartofthetagistheprefixthatthetaglibdirectivedeclared.Thelogpartisthenameofthetag.Thetagallowsthedevelopertodeclarethelogginglevelwiththecustomaction'slevelattribute.

Typically,acomponentsuchasaninitializationservletinitializesthelog4jloggingsystemwhenthewebapplicationstartsup.Thecustomactiondescribedheredoesnothavetoinitializelog4jitself.However,I'veincludedanoptionalconfigFileattributethatpermitsmetospecifythenameofalog4jconfigurationfile,whichwillconfigurethelogger'slevel,appender(s),andlayout.

Forthistag,assumethatyouwanttodecidewhichloggingleveltouse,andthuspassinavalueforthelevelattribute.ThetagclassdoesnotknowwhetherthemessagewillrequestalogginglevelofDEBUG,INFO,WARN,ERROR,orFATAL.Sincethelogger'smethodsinlog4jusethesamenameasthelevels,wecandynamicallycallthepropermethod

basedonthevalueofthelevelattribute.Thisisthepurposeofthecode:

method=log.getClass().

getMethod(level,newClass[]{Object.class});

method.invoke(log,newString[]{message});

Wegetajava.lang.reflect.MethodobjectthatisnamedeitherDEBUG,INFO,WARN,ERROR,orFATAL,andtheninvokethatmethodcallingmethod.invoke,passinginthelogmessagefromtheJSPpage.

Aconfigurationfilenameisnotrequiredforthistag,sohowdoeslog4jknowhowandwheretologthemessage?Thistagassumesthataservlethasalreadyinitializedthelog4jsystemforthewebapplication,whichistypicalfortheuseoflog4jinawebenvironment.TheconfigurationfileistheonedescribedbyRecipe14.4andshowninExample14-5.

Youcanalsouseaservletasanlog4j-initializationservlet,similartoExample14-6.

Thatconfigurationfilecreatedaloggingmechanismthatsendsmessagestotheconsoleandafile,sothatiswherethecustomtag'smessagesgo.Forexample,runninglogger.jspdisplaysamessageontheconsole:

DEBUG-Debugmessagefromlogger.jsp

Thetag'sloggerwritesthefollowingmessageinthefileexample.log:

DEBUGLogger:LoggerTagDate:2003-05-1212:53:13,750-Debugmessagefromlogger.jsp

Ifyouwanttoincludeyourownconfigurationfile,youcanincludea

configFileattributewhenusingthecustomtag.Thetagwillconfiguretheloggerusingthatfileinsteadofanypreviouslyinitializedone:

if(configFile!=null)

PropertyConfigurator.configure(

pageContext.getServletContext().getRealPath("/")+

"WEB-INF/classes/"+configFile);

ThePropertyConfigurator.configure()methodallowsyoutospecifythenameofalog4jpropertiesfilewhenyouinitializetheloggingsystem,ifthefilenameisdifferentthanlog4j.properties.ThePropertyConfigurator.configure()method(inlog4jVersion1.2.8)doesnotthrowanexceptionthatcanbecaughtinthetagclass.YoucouldcheckfortheexistenceoftheconfigFilevalue(representingthepathtoafileinthewebapplication)explicitlyinthecodeusingthejava.ioAPI,andthenthrowanexceptioniftheconfigFileattributedeclaresaninvalidfilename.

SeeAlso

Recipe14.2ondownloadingandsettinguplog4j;Recipe14.3onusingalog4jloggerwithoutapropertiesfile;Recipe14.4onaddinganappendertotherootlogger;Recipe14.5onusingapatternlayoutwithalogger'sappender;Recipe14.7andRecipe14.8onusinglog4jwithapplicationeventlisteners;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jJavadocpage:http://jakarta.apache.org/log4j/docs/api/index.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.




Recipe14.7LoggingMessagesUsingaServletContextEventListener

Problem

Youwanttologmessagesusinglog4jwhenaservletcontextiscreatedandshutdown.

Solution

Uselog4jandaservletcontexteventlistener.

Discussion

TheservletAPIincludesalistenerinterfacenamedjavax.servlet.ServletContextListenerthatyoucanusetonotifyaspecificJavaclasswhenaservletcontextiscreatedorshutdown.Thisnotifiedclassmaywanttologtheservletcontextcreationorshutdownorstoreanobjectattributeintheservletcontext,actionsthattheJavaclass(thelistener)takeswhenitreceivesitsnotification.

Theservletcontextlistenerisanapplicationeventlistener,acategorythatalsoincludessessioneventlisteners(seeChapter11orRecipe14.8)andrequesteventlisteners.Forexample,thesessioneventlistenerreceivesnotificationswhentheservletcontainercreatesnewHTTPsessionobjectsinordertotrackauser'sprogressthroughawebapplication.Theservletcontainernotifiestherequesteventlistenerwhenausermakesawebapplicationrequest,sothatalistenercantakesomekindofactionsuchasloggingtheuser'sIPaddress.

Ajavax.servlet.ServletContextisusedtostoreattributesor

accesscontextparametersthatarecommontoawebapplication,getRequestDispatcherobjectsforforwardingorincludingfiles(seeChapter6),orgetinformationsuchasanabsolutepathnameassociatedwithawebresource.Everywebapplicationhasoneassociatedservletcontext.

Thereisoneservletcontextinstanceperwebapplication(perJavaVirtualMachine(JVM),inthecaseofdistributedwebapplications)accordingtotheServletContextJavadoc:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContext.html.

log4jisagoodchoiceforgeneratingcustom-designedlogmessagesfromaclassthatimplementstheServletContextListenerinterface.Example14-12showstheContextLoggerclass,whichuseslog4jtosendmessagesinitstwomethods.

Example14-12.Aservletcontexteventlistenerthatsendslogmessages






publicclassContextLoggerimplementsServletContextListener{

privateLoggerlog;

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContext.html

publicContextLogger(){}

publicvoidcontextDestroyed(ServletContextEventsce){

Stringname=sce.getServletContext().getServletContextName();

//logrequestoftheINFOlevel

log.info("ServletContextshutdown:"+(name==null?"":name));

//doothernecessarywork,likecleanupanyleft-overresources

//usedbythewebapp

}

publicvoidcontextInitialized(ServletContextEventsce){

ServletContextcontext=sce.getServletContext();

StringrealPath=context.getRealPath("/");

StringfileSep=System.getProperty("file.separator");

//Makesuretherealpathendswithafileseparatorcharacter('/')

if(realPath!=null&&(!realPath.endsWith(fileSep))){

realPath=realPath+fileSep;}

//Initializeloggerhere;thelog4jpropertiesfilenameisspecified

//byacontextparameternamed"logger-config"

PropertyConfigurator.configure(realPath+

"WEB-INF/classes/"+context.getInitParameter("logger-config"));

log=Logger.getLogger(ContextLogger.class);

Stringname=context.getServletContextName();

//logrequestaboutservletcontextbeinginitialized

log.info("ServletContextready:"+(name==null?"":name));

}

}

Givethisclassano-argsconstructor,placeitinWEB-INF/classesorinaJARlocatedinWEB-INF/lib,andregisteritinweb.xml:

<listener>

<listener-class>

com.jspservletcookbook.ContextLogger

</listener-class>

</listener>

TheServletContextListenertracksthelifecycleofaservletcontextwithtwomethods:contextInitialized()andcontextDestroyed().Theservletcontainercallsthefirstmethodwhentheservletcontextiscreatedandthewebapplicationisreadytoreceiveitsfirstrequest.ThecontainernotifiesthelistenerclassandcallsthecontextDestroyed()methodwhentheservletcontextisabouttobeshutdown,suchaswhenawebapplicationisstoppedpriortobeingreloaded.

Tomcat4.1.24initializestheservletcontextlistenerpriortocreatingservletinstances,eveniftheapplicationconfigurestheservlettobepreloaded.Example14-12initializesthelog4jsysteminthecontextInitialized()method.

Thedeploymentdescriptorcaninstructtheservletcontainertoloadaservletinstanceandcallitsinit()methodatstartupbyincludingaload-on-startupelementnestedintheservletelement,asin:

<servlet>

<servlet-name>logger</servlet-name>

<servlet-class>

com.jspservletcookbook.LoggerServlet

</servlet-class>

<load-on-startup>1</load-on-startup>

</servlet>

Thevalueofload-on-startupisanintegerindicatingtheorderinwhichthecontainerloadstheservlet.

InthecontextInitialized()method,thelistenerconfigureslog4jusingthefilespecifiedbyacontext-paramelementinweb.xml:

<context-param>

<param-name>logger-config</param-name>

<param-value>servletLog.properties</param-value>

</context-param>

Thislog4jconfigurationfile(servletLog.properties)islocatedintheWEB-INF/classesdirectory.Thelistenerthenlogsitsmessagestotheconsoleandtoafilewhenthewebapplicationstartsuporisshutdown.Example14-13showstheconfigurationfilethelistenerusesforlog4j.

Example14-13.Log4jconfigurationfileusedbytheservletcontextlistener


log4j.logger.com.jspservletcookbook=,myAppender


#configurethe'myAppender'appender

log4j.appender.myAppender=org.apache.log4j.RollingFileAppender


log4j.appender.myAppender.MaxBackupIndex=1

log4j.appender.myAppender.MaxFileSize=1MB



log4j.appender.myAppender.layout.ConversionPattern=

%-5pLogger:%c{1}Date:%d{ISO8601}-%m%n

Thelistenergetsaloggerwiththiscode:

log=Logger.getLogger(ContextLogger.class);

Thisnamestheloggeraftertheclasscom.jspservletcookbook.ContextLogger.Therefore,inthelog4jnamingscheme,thelistener'sloggerinheritstheappenderthatExample14-13definesfortheloggercom.jspservletcokbook.Thisisbecausetheconfigurationdoesnotdefinealoggerforcom.jspservletcookbook.ContextLogger;consequently,thelistener'sloggerinheritsthenextdefinedloggeravailable:com.jspservletcookbook.Thecom.jspservletcookbookloggerhasaconsoleappenderandafileappender.

Asaresult,theservletcontextlistenersendsitslogmessagestotheconsoleandtheh:/home/example.logfile.Example14-13hasdifferentlayoutsfortheconsoleandfileappenders.Thelistener'sconsolemessageslooklikethis:

INFO-ServletContextshutdown:Thehomewebapplication

INFO-ServletContextready:Thehomewebapplication

Thelogfilemessageshaveadifferentformat:

INFOLogger:ContextLoggerDate:2003-05-1216:45:20,398-ServletContextshutdown:

Thehomewebapplication

INFOLogger:ContextLoggerDate:2003-05-1216:45:20,999-ServletContextready:The

homewebapplication

Theformatofthesemessagesconsistsofthenameofthelogginglevel(e.g.,INFO),theloggername,thedateofthelogrequest,andthemessageitself.

SeeAlso

Recipe14.2ondownloadingandsettinguplog4j;Recipe14.3onusingalog4jloggerwithoutapropertiesfile;Recipe14.4onaddinganappendertotherootlogger;Recipe14.5onusingapatternlayoutwithalogger's

appender;Recipe14.6onusingaloggerwithaJSP;Recipe14.8onusinglog4jwithsessioneventlisteners;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jJavadocpage:http://jakarta.apache.org/log4j/docs/api/index.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.




Recipe14.8LoggingMessagesUsingaSessionEventListener

Problem

Youwanttologmessagesinacustom-designedmannerfromasessioneventlistener.

Solution

Designasessioneventlistenerthatusesalog4jloggingmechanism.

Discussion

TheservletcontainernotifiesasessioneventlistenerclasswhenitcreatesanewHttpSession,aswellaswhenitisabouttoinvalidateorexpireasession.Webapplicationsusesessionstotrackauser'sprogressthroughthewebapplication,typicallybyidentifyinghimwithacookienamedJSESSIONID.SeeChapter10formoreinformationoncookies,andChapter11fordetailedcoverageofsessions.

Example14-14implementsthejavax.servlet.http.HttpSessionListenerinterfaceandtheinterface'stwomethods:sessionCreated()andsessionDestroyed().ThecodelogsmessagesrelatingtonewsessionsinsessionCreated()andrelatingtoinvalidatedsessionsinsessionDestroyed().

Example14-14.Usinglog4jinasessioneventlistener






publicclassSessionLoggerimplementsHttpSessionListener

{

privateLoggerlog;

publicSessionLogger(){

/*

Theloggersaretypicallyinitializedbyaspecialinitialization

listenerorservlet.Ifthisisnotthecase,theninitializethe

loggerhere:

java.util.ResourceBundlebundle=

java.util.ResourceBundle.getBundle(

"com.jspservletcookbook.global");

PropertyConfigurator.configure(bundle.getString(

"log-configure-path"));

*/

log=Logger.getLogger(SessionLogger.class);

}

publicvoidsessionCreated(HttpSessionEventse){

//logrequestoftheINFOlevel

log.info("HttpSessioncreated:"+se.getSession().getId());

}

publicvoidsessionDestroyed(HttpSessionEventse){

//logrequestaboutsessionsthatareinvalidated

log.info("HttpSessioninvalidated:"+se.getSession().getId());

}

}

Givethisclassano-argsconstructor,placeitinWEB-INF/classesorinaJARlocatedinWEB-INF/lib,andregisteritinweb.xml:

<listener>

<listener-class>

com.jspservletcookbook.SessionLogger

</listener-class>

</listener>

TheSessionLoggerclassgetsaloggerinitsconstructor;itdependsontheapplicationalreadyhavinginitializedthelog4jloggingmechanisminaservletorintheservletcontextlistener(asinRecipe14.4).

Awebapplicationcanconfigureitslog4jmechanismusingaspecialinitializationservletorlistener,sotheotherclassesorbeansthatdologgingdonothavetohandlethelog4jconfigurationstage.Youcaninitializethelog4jloggingmechanismusingaservletsuchastheoneshowninRecipe14.6.

Thecommented-outcodeintheconstructorshowsanotherwaythatthislistenerclasscouldconfigureitsownloggerintheeventthattheapplicationhasnotyetconfiguredtheloggingmechanism.

HereisthemessageloggedtotheTomcatconsoleafterthefirstrequesttoaservletorJSPthatparticipatesinsessiontracking:

INFO-HttpSessioncreated:A65481C53B92F869BD18961D635BBF52

Whenthesessionisinvalidated,theconsoletextis:

INFO-HttpSessioninvalidated:A65481C53B92F869BD18961D635BBF52

LikethelistenerdescribedinRecipe14.7,thesessionlistener'sloggerinheritstheloggingdestinationsorappendersfromthecom.jspservletcookbooklogger.TheconfigurationfileofExample14-13showshowthisloggerissetuptosendmessagestoboththeconsoleandanexample.logfile.Thelogfile'sappenderlayoutisspecifiedusingaPatternLayout,whichisadifferentlayoutthantheoneusedwiththeconsoleappender.Hereisexampletextfromthislogwhentheservletcontainerinvalidatesasession:

INFOLogger:SessionLoggerDate:2003-05-1220:41:05,367-HttpSessioninvalidated:

A65481C53B92F869BD18961D635BBF52

SeeAlso

Recipe14.2ondownloadingandsettinguplog4j;Recipe14.3onusingalog4jloggerwithoutapropertiesfile;Recipe14.4onaddinganappendertotherootlogger;Recipe14.5onusingapatternlayoutwithalogger'sappender;Recipe14.6onusingaloggerwithaJSP;Recipe14.8onusinglog4jwithsessioneventlisteners;thelog4jdownloadsite:http://jakarta.apache.org/log4j/docs/download.html;thelog4jJavadocpage:http://jakarta.apache.org/log4j/docs/api/index.html;thelog4jprojectdocumentationpage:http://jakarta.apache.org/log4j/docs/documentation.html.




Chapter15.AuthenticatingClientsIntroduction

Recipe15.1.CreatingUsersandPasswordswithTomcat

Recipe15.2.SettingUpSSLonTomcat

Recipe15.3.UsingBASICAuthentication

Recipe15.4.UsingForm-BasedAuthentication

Recipe15.5.LoggingOutaUser

Recipe15.6.UsingJAAStoCreateaLoginModule

Recipe15.7.CreatingtheJAASConfigurationFile

Recipe15.8.UsingJAASinaServlet

Recipe15.9.UsingJAASinaJSP

Introduction

Becauseoftheincreaseindigitalcommerceandacorrespondingriseintheneedtotransferandstoresensitivedata(suchascreditcardnumbersandfinancialaccounts),securityisofparamountimportancetoJavawebapplications.

Thischapter'srecipescovertasksthatinvolveauthentication,whichisdesignedtoanswerthequestion"areyouwhoyousayyouare?"Authenticationusuallyinvolvesaninteractionbetweenaclientoruserandserver-sidecodeforthepurposeofcheckingausernameandpassword(andsometimesadigitalcertificate,biometricdata,orotherevidence)againststoredinformation,suchasauserdatabase.

TherecipesdescribehowtosetupSecureSocketsLayer(SSL),aswellasuseBASIC-andform-basedauthenticationwithApacheTomcat.ThelaterrecipesdescribehowtouseapowerfulsecurityframeworkcalledJavaAuthenticationandAuthorizationService(JAAS)withservletsandJSPs.

Recipe15.1CreatingUsersandPasswordswithTomcat

Problem

Youwanttocreateusernamesandpasswordsforauthenticatingrequestsforcertainwebcomponents.

Solution

Addtheusernames,passwords,androlestothetomcat-users.xmlfile.

Discussion

AveryeasymethodofauthenticatinguserswithTomcatinvolvescreatingusernames,passwords,androlesinthetomcat-users.xmlfile.Thisfileisstoredin<Tomcat-installation-directory>/conf.

Everyoneisfamiliarwithusernamesandpasswords,butwhatareroles?Rolesarelogicalwaystodescribegroupsofuserswhohavesimilarresponsibilities,suchasmanagerordatabaseAdmin.Example15-1showsatomcat-users.xmlfilethatcreatestworolesandtwouserswithtwoaptlynamedXMLelements:roleanduser.

Example15-1.Thetomcat-usersXMLfile


<tomcat-users>

<rolerolename="dbadmin"/>


<userusername="BruceP"password="bwperry"roles="dbadmin,manager"/>

<userusername="JillH"password="jhayward"roles="manager"/>

</tomcat-users>

InExample15-1,theuserBrucePisassociatedwithtworoles(dbadminandmanager),whileuserJillHisassociatedonlywiththemanagerrole.TomcatusesthisfilewhenauthenticatinguserswithBASICandform-basedauthentication,asdescribedinRecipe15.3andRecipe15.4.

SeeAlso

TheTomcatdocumentationandRecipe15.2onsettingupSSLforusewithauthentication:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html;Recipe3.9onrestrictingrequestsforcertainservlets;Recipe15.3onusingBASICauthentication;Recipe15.4onusingform-basedauthentication;Recipe15.5onloggingoutauser;Recipe15.6-Recipe15.9onusingJAAS.

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html

Recipe15.2SettingUpSSLonTomcat

Problem

YouwanttosetupSSLonTomcatsothatyoucantransmitusernamesandpasswordsinencryptedform.

Solution

CreateadigitalcertificatefortheTomcatserverusingthe$JAVA_HOME\bin\keytoolutility,thenuncommenttheSSLConnectorelementinconf/server.xml.

Discussion

WhentransferringusernamesandpasswordsoverHTTP,youshouldsetupSSLonTomcatorwhicheverapplicationserveryouareusing.Thisprotocolensuresthatthenamesandpasswordsareinencryptedformastheytravelacrossthenetwork,andthusprotectedfromtheftandmalicioususebyhackersandotherintruders.

SettingupSSLonTomcat4isatwo-stepprocess:

1. Usethekeytoolutilitytocreateakeystorefileencapsulatingadigitalcertificateusedbytheserverforsecureconnections.

UncommenttheSSLConnectorelementinTomcat'sconf/server.xmlfile,andalteritsattributesifnecessary.

ThekeytoolutilityislocatedinthebinsubdirectoryofthedirectorywhereyouhaveinstalledtheJSDK.Thefollowingcommandlinecreates

asingleself-signeddigitalcertificatefortheTomcatserverwithinakeystorefilenamed.keystore.Thisfileiscreatedinthehomedirectoryoftheuserrunningthecommand.

%JAVA_HOME%\bin\keytool-genkey-aliastomcat-keyalgRSA

TheUnixversionofthiscommandis:

$JAVA_HOME\bin\keytool-genkey-aliastomcat-keyalgRSA

Forthiscommandtosucceed,theJAVA_HOMEenvironmentvariablemustbesettothedirectorywheretheJava2SDKisinstalled,suchash:\j2sdk1.4.1_01.

Example15-2showstheconsoleoutputresultingfromexecutingthekeytoolcommand.Thekeytoolwillrequestsomeinformationaboutyouandyourorganization,butyoucanacceptthedefaultvaluesbypressingEnter.Thisinformationisincorporatedintotheserver'scertificateandpresentedtotheuser(viaherwebbrowser)whensherequestsanycomponentswithaURLthatstartswithhttps://.

InsettingupSSLforTomcat,youmustusethesamepasswordforboththekeystoreandthecertificatethatisstoredinthekeystore.

ThedefaultpasswordusedinTomcatis"changeit":http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html.

Example15-2.Theconsoleoutputresultingfromusingthekeytoolutility


Enterkeystorepassword:changeit

Whatisyourfirstandlastname?

[Unknown]:BrucePerry

Whatisthenameofyourorganizationalunit?

[Unknown]:

Whatisthenameofyourorganization?

[Unknown]:

WhatisthenameofyourCityorLocality?

[Unknown]:

WhatisthenameofyourStateorProvince?

[Unknown]:

Whatisthetwo-lettercountrycodeforthisunit?

[Unknown]:

IsCN=BrucePerry,OU=Unknown,O=Unknown,L=Unknown,ST=Unknown,C=Unknowncorrect?

[no]:yes

Enterkeypasswordfor<tomcat>

(RETURNifsameaskeystorepassword):

Finally,uncommenttheSSLConnectorelementintheconf/server.xmlfile(showninFigure15-3)byremovingthecommentcharactersaroundit().ThenrestartTomcat.

Example15-3.TheConnectorelementinsideserver.xml



<ConnectorclassName=

"org.apache.coyote.tomcat4.CoyoteConnector"port=

"8443"minProcessors="5"maxProcessors="75"enableLookups=

"true"acceptCount="100"debug="0"scheme="https"secure="true"

useURIValidationHack="false"disableUploadTimeout="true">

<FactoryclassName=

"org.apache.coyote.tomcat4.CoyoteServerSocketFactory"clientAuth=

"false"protocol="TLS"/>

</Connector>

TheConnectorusesadifferentportnumber(8443)thanthatusedbyinsecureHTTPconnections(inTomcat,it'susually8080).AfteryouhaverestartedTomcat,youcannowmakeasecureconnectiontoawebcomponentinthehomeapplicationwithaURLthatlookslikethis:

https://localhost:8443/home/sqlJsp.jsp

Don'tforgetthehttps(asopposedtohttp)partinsettinguptheseweblinks!

SeeAlso

TheTomcatdocumentationonsettingupSSLforusewithauthentication:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html;Recipe15.1oncreatingusernamesandpasswordsinTomcat;Recipe15.3onusingBASICauthentication;Recipe15.4onusingform-basedauthentication;Recipe15.5onloggingoutauser;Recipe15.6-Recipe15.9onusingtheJAAS.


Recipe15.3UsingBASICAuthentication

Problem

YouwanttouseBASICauthenticationwithwebcomponentsinaTomcatwebapplication.

Solution

Usethesecurity-constraint,login-config,andsecurity-roleelementsinthedeploymentdescriptortoprotectoneormoreURLs.

Discussion

BASICauthenticationisasecuritymethodthathasbeenusedwithwebresourcesforseveralyears,andallpopularbrowserssupportit.ThismethodofauthenticationinvolvesthetransferofusernamesandpasswordsoveranetworkencodedwiththeBase64content-encodingmechanism.Base64iseasytodecodeandthereforenotverysecure.ThesolutionistocombineBASICauthenticationwithSSL,whichwillfurtherencryptthedataasitistransferredacrossthenetwork(seeRecipe15.2).

HereishowsettingupBASICauthenticationworkswithwebapplicationsthatyouhaveinstalledonTomcat:

1. Setupusernames,passwords,androlesintheconf/tomcat-users.xmlfiledescribedinRecipe15.1.

Createasecurity-constraintelementinthedeployment

descriptor(web.xml),specifyingthewebresourcesforwhichyouarerequiringauthentication.

Includealogin-configinweb.xml;thiselementhasanestedauth-methodelementthatcontainsthetext"BASIC".

Whentheuserrequestsanyoftheprotectedresources,theserversendsalongaresponseheaderthatlookslikethis:

WWW-Authenticate:BASICRealm="MyRealm"

Youareprobablyfamiliarwithwhathappensnext:thebrowserdisplaysastandarddialogwindowrequestingtheclienttoprovideausernameandpassword(Figure15-1).Iftheusernameandpasswordareincorrect,thebrowserwilleithergivetheuseranotherchancetologinbyredisplayingthedialogwindow,orsimplysendbackaserverstatuscode"401:Unauthorized"typeofresponse.

Theusernamesandpasswordsintheconf/tomcat-users.xmlfilearecase-sensitive.Theuserhastotypethemintothedialogwindowusingupper-andlowercaselettersexactlyastheyappearinconf/tomcat-users.xml.

Example15-4showstheweb.xmlelementsthataredesignedtoinitiateBASICauthenticationfortheURLpattern/sqlJsp.jsp.

Example15-4.Asecurity-constraintinitiatesauthenticationwithaJSPfile

<web-resource-name>JSPdatabasecomponent</web-resource-name>

<url-pattern>/sqlJsp.jsp</url-pattern>




<auth-constraint>

<role-name>dbadmin</role-name>

</auth-constraint>


<transport-guarantee>CONFIDENTIAL</transport-guarantee>



<login-config>


</login-config>

<security-role>


</security-role>



Thesecurity-constraintelementinExample15-4containsaweb-resource-collectionelement.Thiselementspecifiesthefollowingconstraintsthatapplytoanyrequestsfor/sqlJsp.jsp:

TheconstraintsapplytoanyGETorPOSTrequests(asspecifiedbythehttp-methodelements).

Theauth-constraintelementnestedinsidesecurity-constraintcontainstherole-namedbadmin.Therefore,therequestormustentertheproperusernameandpassword(asspecifiedinthetomcat-users.xmlfile)andbeassociatedwiththedbadminrole.Onlythosewhohavethedbadminrolecangainaccesstotheprotectedwebresource,eveniftheyenteraproperusernameandpassword.

Figure15-1showsthedialogboxthatNetscape7.1produceswhenTomcatisusingBASICauthentication.TheURLisusedishttps://localhost:8443/home/sqlJsp.jsp.

Figure15-1.Abrowserdialogwindowrequestsanameandpassword

NoticethattheURLusesasecureconnectiontorequesttheJSP:anHTTPSprotocolandport8443onTomcat.

Figure15-2showsabrowserwindowafteraclienthasfailedauthentication.

Figure15-2.Aserverstatuscode401pageasviewedinthewebbrowser

SeeAlso

TheTomcatdocumentationandRecipe15.2onsettingupSSLforusewithauthentication:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html;Recipe3.9onrestrictingrequestsforcertainservlets;Recipe15.5onloggingoutauser;Recipe15.6-Recipe15.9onusingJAAS.


Recipe15.4UsingForm-BasedAuthentication

Problem

Youwanttodesignyourownformtoreceivetheuser'snameandpasswordduringBASICauthentication.

Solution

Usethelogin-configelementinthedeploymentdescriptorandgiveitsnestedauth-methodelementavalueof"FORM".

Discussion

TheservletAPIoffersanalternativetousingplain-vanillaBASICauthentication:form-basedauthentication.Thismethodallowsyoutodesignyourownformforreceivingtheuser'snameandpassword,aswellasspecifyingtheinformativepagethattheserverssendtotheclientiftheuser'sauthenticationfails.ThisgivesyoutheabilitytoprovideamuchmorefriendlyandcustomizeduserinterfaceforapplicationsinvolvingBASICauthentication.

Theform-basedmethodshouldstillbecombinedwithSSLandtheHTTPSprotocolsothatthenamesandpasswordsareencryptedastheytravelthroughthenetwork.

Example15-5showstheform-basedsetupforthewebapplication'sdeploymentdescriptor.ItdiffersfromRecipe15.3ssetupinonearea:the

login-configelement,whichisemphasizedinthefollowingcodesample.

Example15-5.Theweb.xmlelementsdesignedforform-basedauthentication





<web-resource-name>JSPdatabasecomponent</web-resource-name>

<url-pattern>/sqlJsp.jsp</url-pattern>




<auth-constraint>


</auth-constraint>


<transport-guarantee>CONFIDENTIAL</transport-guarantee>



<login-config>

<auth-method>FORM</auth-method>

<form-login-config>

<form-login-page>/login.html</form-login-page>

<form-error-page>/loginError.jsp</form-error-page>

</form-login-config>

</login-config>

<security-role>


</security-role>



Theauth-methodelementincludesthetext"FORM".Theform-login-configelementspecifiesthelogin(/login.html)andauthenticationfailurepage(/loginError.html)thatyourapplicationuses.Theforwardslash(/)precedingthefilenamesmeanstonavigatetothepagefromthewebapplication'srootdirectory.

Almostbymagic,ifauserrequestsaprotectedresourceinyourapplication,theserversendshimthelogin.htmlpage(inthisexample)insteadofinitiatingthetypicalbehaviorinwhichthebrowserdisplaysitsowndialogwindow.Ifthenameandpasswordtheuserentersturnsouttobeincorrect,theserverrouteshisrequesttotheloginError.htmlpage.

Example15-6showsthelogin.htmlpage,forreference.

Example15-6.Theloginform


<html>

<head>

<title>Welcome</title>

</head>


<h2>PleaseLogintotheApplication</h2>

<formmethod="POST"action="j_security_check">

<tableborder="0"><tr>

<td>Entertheusername:</td><td>

<inputtype="text"name="j_username"size="15">

</td>

</tr>

<tr>

<td>Enterthepassword:</td><td>

<inputtype="password"name="j_password"size="15">

</td>

</tr>

<tr>

<td><inputtype="submit"value="Submit"></td>

</tr>

</table>

</form>

</body>

</html>

Figure15-3showswhatthisformlookslikeinawebbrowser.

Figure15-3.Aformforusewithform-basedauthentication

Withform-basedauthentication,theformtag'sactionattributemusthavethevalue"j_security_check".Theinputelementsfortheusernameandpasswordmustspecifythevalues"j_user_name"and"j_password",respectively,fortheirnameattributes.

Figure15-4showstheHTMLpagethattheserversendstheuserifherauthenticationfails.

Figure15-4.Form-basedauthenticationallowstheinclusionofyourownlogin-failurepage

Example15-7showsthesourceforthispage.Theform-basedapproachismorepredictableandfriendlierthanthevariousbrowsers'methodsfordealingwithBASICauthentication.

Example15-7.TheserverdisplaystheloginError.jsppagewhenauthenticationfails

<html>

<head>

<title>LoginError</title>

</head>


<h2>WeApologize,ALoginErrorOccurred</h2>

Pleaseclick<ahref="http://localhost:8080/home/sqlJsp.jsp">here</a>foranothertry.

<%--Or,dynamicallylisthyperlinkstoyourprotectedresourceshere,perhapsbygetting

themfromadatabaseorconfigurationfile,insteadofhard-codingalinkintotheerror

page.--%>

</body>

</html>

SeeAlso

TheTomcatdocumentationandRecipe15.2onsettingupSSLforusewithauthentication:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html;Recipe3.9onrestrictingrequestsforcertainservlets;Recipe15.5onloggingoutauser;Recipe15.6-Recipe15.9onusingJAAS.


Recipe15.5LoggingOutaUser

Problem

Youwanttologoutauserinasystemthatusesform-basedauthentication.

Solution

Callinvalidate()ontheuser'sHttpSessionobject.

Discussion

Invalidatingauser'sHttpSessionobjectwilllogtheuseroutinanapplicationthatusesform-basedauthentication.Naturally,thiscodeinvolvescallingHttpSession.invalidate().Example15-8displayssomeinformationaboutalogged-inuser,thenlogshimoutbyinvalidatinghissession.Thenexttimethisuserrequestsaprotectedresource,thewebapplicationwillsendhimtotheconfiguredloginpage,becausehehasbeenloggedoutoftheapplication.

Example15-8.Loggingoutauser




publicclassLogoutServletextendsHttpServlet{







out.println(

"<html><head><title>AuthenticatedUserInfo</title></head><body>");

out.println("<h2>Loggingoutauser</h2>");

out.println("request.getRemoteUser()returns:");

//getthelogged-inuser'sname

StringremUser=request.getRemoteUser();

//Istherequest.getRemoteUser()returnvaluenull?If

//so,thentheuserisnotauthenticated

out.println(remUser==null?"Notauthenticated.":remUser);

out.println("<br>");

out.println("request.isUserInRole(\"dbadmin\")returns:");

//Findoutwhethertheuserisinthedbadminrole

booleanisInRole=request.isUserInRole("dbadmin");

out.println(isInRole);

out.println("<br>");

//logouttheuserbyinvalidatingtheHttpSession

session.invalidate();


}//doGet





}//doPost

}//LogoutServlet

Alogged-inuserwhorequeststhisservletseestheoutputinFigure15-5.TheservletdisplaysthereturnvaluesofHttpServletRequest.getRemoteUser()(theusername)andHttpServletRequest.isUserInRole().Thelattermethodreturnsabooleanvalueindicatingwhethertheuserisassociatedwiththerolespecifiedbythemethod'sStringparameter.

Figure15-5.Aservletshowssomeuser-relatedinformationbeforeloggingouttheuser

Theservlettheninvalidatestheuser'ssessiontologherout.RerequestingtheservletproducestheoutputshowninFigure15-6.

Figure15-6.Theservlet'soutputindicatesalogged-outuser

SeeAlso

TheTomcatdocumentationandRecipe15.2onsettingupSSLforusewithauthentication:http://jakarta.apache.org/tomcat/tomcat-4.1-doc/ssl-howto.html;Recipe3.9onrestrictingrequestsforcertainservlets;Recipe15.6-Recipe15.9onusingJAAS.


Recipe15.6UsingJAAStoCreateaLoginModule

Problem

YouwanttousetheJavaAuthenticationandAuthorizationService(JAAS)tocreateanauthenticationmodulethataservletorJSPcanuse.

Solution

Createajavax.security.auth.spi.LoginModuleclassforyourapplication,thenstoretheclassunderWEB-INF/classesorWEB-INF/lib(inaJARfile).

Discussion

TheJAASisasecurityAPIthatcanbeusedtocreatestandalone,pluggableauthenticationorauthorizationtoolsforJavaapplications.PluggablemeansthattheJAASsecuritycodeisnotboundtoaparticularapplication;itisstoredinaJARfileandcanbedroppedorpluggedintowebapplicationsandothertypesofJavaprograms.

JAASisaJavaversionofaframeworknamedPluggableAuthenticationModule(PAM).Here'salinktoapaperonthatverytopic:http://java.sun.com/security/jaas/doc/pam.html.

Forthesakeofclarity,Recipe15.5-Recipe15.7describeasimple

http://java.sun.com/security/jaas/doc/pam.html

exampleofJAASauthenticationthatrequirestwoclasses,andoneservletthatusestheJAASAPI.Inourexamples,theseclassesarestoredinWEB-INF/classes.However,manyorganizationshaveacomplexsecurityarchitecturethatcallsforamoreextensiveauthenticationandauthorizationmodel,andthusmoreJavacodeandobjects.Inthesecases,you'llwanttocreateaseparatepackagenameforyourJAAScode,archiveitinaJARfile,andplaceitinWEB-INF/libforwebapplicationstouse.

TakethefollowingstepstouseJAASforauthenticatingwebclients:

1. MakesureyouhaveinstalledtheJAASpackagesforusewithawebapplication.JAAShasbeenintegratedintotheJava21.4SDK,soyoucanuseJAASifTomcatoryourapplicationserverisusingthisversionofJava.SeethefollowingwebsiteifyouareusingJava1.3,whichrequiresyoutodownloadandinstallJAASasaJavaextension:http://java.sun.com/products/jaas/index-10.html.

CreateaLoginModuleclasstohandletheauthentication.ThisclassmustbestoredinWEB-INF/classesorinaJARfileplacedinWEB-INF/lib.

CreateaCallbackHandlerclassthatdealswithinteractionwiththeclienttogetitsusernameandpassword.StorethisclasswithyourLoginModule.

CreateaJAASconfigurationfilethatspecifieswhichLoginModule(s)youareusingforauthentication.PlacetheconfigurationfileinalocationwheretheJAAS-relatedcodecanreadit(seethedescriptionoftheconfigurationfileinRecipe15.7).

IncludeaLoginContextobjectinservletcodeandcallitslogin()method.

Authenticationcheckswhetherauserorclienthasaparticularidentity,whichis

http://java.sun.com/products/jaas/index-10.html

typicallyoneofasetofusernamesandpasswords.JAAScanalsobeusedforauthorization,whichspecifiestheextentofaccesstodataauserhasoncesheissuccessfullyauthenticated.Thisrecipefocusessolelyonauthentication.

Inordertomakeclearerarathercomplexmatter,Ihavebrokenthesestepsupintothreerecipes:

Thisrecipedescribessteps1-3.

Recipe15.6showshowtocreatetheJAASconfigurationfile.

Recipe15.7usestheJAASauthenticationclassesinaservlet.

Example15-9showsaclassthatimplementsthejavax.security.auth.spi.LoginModuleinterface.Itperformsmostoftheworkinidentifyingclients,andusespackagesthatarepartoftheJAASAPI(emphasizedwithboldinthecodesample).YouhavetomakethisclassavailabletotheservletenginebyplacingitinWEB-INF/classesorinaJARfilestoredinWEB-INF/lib.

Example15-9.TheLoginModuleforwebauthentication



importjava.sql.*;

importjavax.naming.Context;

importjavax.naming.InitialContext;

importjavax.naming.NamingException;

importjavax.security.auth.spi.LoginModule;

importjavax.security.auth.*;

importjavax.security.auth.callback.*;

importjavax.security.auth.login.*;

importjavax.sql.*;

publicclassDataSourceLoginModuleimplementsLoginModule{

//Theseinstancevariableswillbeinitializedbythe

//initialize()method

CallbackHandlerhandler;

Subjectsubject;

MapsharedState;

Mapoptions;

privatebooleanloginPassed=false;

publicDataSourceLoginModule(){}//no-argumentsconstructor

publicvoidinitialize(Subjectsubject,CallbackHandlerhandler,

MapsharedState,Mapoptions){

this.subject=subject;

this.handler=handler;

this.sharedState=sharedState;

this.options=options;

}

publicbooleanlogin()throwsLoginException{

Stringname="";

Stringpass="";

Contextenv=null;

Connectionconn=null;

Statementstmt=null;

ResultSetrs=null;

DataSourcepool=null;

booleanpassed=false;

try{

//CreatetheCallBackarraytopasstothe

//CallbackHandler.handle()method

Callback[]callbacks=newCallback[2];

//Don'tusenullargumentswiththeNameCallbackconstructor!

callbacks[0]=newNameCallback("Username:");

//Don'tusenullargumentswithPasswordCallback!

callbacks[1]=newPasswordCallback("Password:",false);

handler.handle(callbacks);

//GettheusernameandpasswordfromtheCallBacks

NameCallbacknameCall=(NameCallback)callbacks[0];

name=nameCall.getName();

PasswordCallbackpassCall=(PasswordCallback)callbacks[1];

pass=newString(passCall.getPassword());

//LookupourDataSourcesothatwecanchecktheusernameand

//password

env=(Context)newInitialContext().lookup("java:comp/env");

pool=(DataSource)env.lookup("jdbc/oracle-8i-athletes");

if(pool==null)

thrownewLoginException(

"InitializingtheDataSourcefailed.");

//TheSQLforcheckinganameandpasswordinatablenamed

//athlete

Stringsql="select*fromathletewherename='"+name+"'";

Stringsqlpass="select*fromathletewherepasswrd='"+pass+"'";

//GetaConnectionfromtheconnectionpool

conn=pool.getConnection();

stmt=conn.createStatement();

//Checktheusername

rs=stmt.executeQuery(sql);

//IftheResultSethasrows,thentheusernamewas

//correctandnext()returnstrue

passed=rs.next();

rs.close();

if(!passed){

loginPassed=false;

thrownewFailedLoginException(

"Theusernamewasnotsuccessfullyauthenticated");

}

//Checkthepassword

rs=stmt.executeQuery(sqlpass);

passed=rs.next();

if(!passed){

loginPassed=false;

thrownewFailedLoginException(

"Thepasswordwasnotsuccessfullyauthenticated");

}else{

loginPassed=true;

returntrue;

}

}catch(Exceptione){

thrownewLoginException(e.getMessage());

}finally{

try{

//closetheStatement

stmt.close();

//ReturntheConnectiontothepool

conn.close();

}catch(SQLExceptionsqle){}

}//finally

}//login

publicbooleancommit()throwsLoginException{

//We'renotdoinganythingspecialhere,sincethisclass

//representsasimpleexampleofloginauthenticationwithJAAS.

//Justreturnwhatlogin()returned.

returnloginPassed;

}

publicbooleanabort()throwsLoginException{

//Resetstate

booleanbool=loginPassed;

loginPassed=false;

returnbool;

}

publicbooleanlogout()throwsLoginException{

//Resetstate

loginPassed=false;

returntrue;

}//logout

}//DataSourceLoginModule

AclassthatimplementsLoginModulehastoimplementtheinterface'sfivedeclaredmethods:initialize(),login(),commit(),abort(),andlogout().login()initiatesthemaintaskofcheckingtheusernameandpasswordanddeterminingwhethertosuccessfullyauthenticatetheclient.Sincethisisasimpleexample,theDataSourceLoginModulefocusesonthelogin()method.TheothermethodsinExample15-9simplyresettheobject'sstatesothatitcanperformanotherauthentication,althoughamorecomplexloginprocessinvolvesothertasks,suchassettingupauthorization-relatedobjectsfortheauthenticateduser.

JAASisaquitecomprehensiveframework.RefertoSunMicrosystems'documentation(http://java.sun.com/products/jaas/)forguidanceindevelopingmoreadvancedJAASprogramsthanthosedescribedinthisrecipe.

http://java.sun.com/products/jaas/default.htm

JAASseparatestheresponsibilityforinteractingwiththeclient(suchasgettingtheusernameandpassword)andperformingauthenticationintoCallbackHandlersandLoginModules,respectively.TheLoginModuleinExample15-9usesaCallbackHandlertogettheusernameandpassword,thenchecksthisinformationbyaccessingatablefromanOracle8idatabase.ThemoduleusesaJNDIlookuptogetaccesstothedatabase,whichChapter21explainsindetail.

Basically,theLoginModuleborrowsaConnectionfromadatabase-connectionpool,usesSQLSELECTstatementstochecktheclient'snameandpassword,thenreturnstheConnectiontothesharedpoolbyclosingit.

TheCallbackHandlerinExample15-10getstheclient'susernameandpasswordfromHTTPrequestparameters.Theclass'sconstructorincludesaServletRequestargument,fromwhichtheclasscanderiverequestparametersbycallingServletRequest'sgetParameter()method.Thisprocesswillbecomemuchclearerwhenyouseehowtheservlet(seeExample15-11inRecipe15.7)usestheseclassestoperformtheauthentication.

Example15-10.ACallbackHandlerforuseinwebauthentication


importjavax.security.auth.callback.*;


publicclassWebCallbackHandlerimplementsCallbackHandler{

privateStringuserName;

privateStringpassword;

publicWebCallbackHandler(ServletRequestrequest){

userName=request.getParameter("userName");

password=request.getParameter("password");

}

publicvoidhandle(Callback[]callbacks)throwsjava.io.IOException,

UnsupportedCallbackException{

//Addtheusernameandpasswordfromtherequestparametersto

//theCallbacks

for(inti=0;i<callbacks.length;i++){

if(callbacks[i]instanceofNameCallback){

NameCallbacknameCall=(NameCallback)callbacks[i];

nameCall.setName(userName);

}elseif(callbacks[i]instanceofPasswordCallback){

PasswordCallbackpassCall=(PasswordCallback)callbacks[i];

passCall.setPassword(password.toCharArray());

}else{

thrownewUnsupportedCallbackException(callbacks[i],

"TheCallBacksareunrecognizedinclass:"+getClass().

getName());

}

}//for

}//handle

}

JusttosummarizehowtheLoginModuleandCallbackHandlerfittogetherbeforeyoumoveontothenexttworecipes,oneoftheLoginContext'sconstructorstakesaCallbackHandlerasitssecondparameter,asinthefollowingcode:

WebCallbackHandlerwebcallback=newWebCallbackHandler(request);

LoginContextlcontext=null;

try{

lcontext=newLoginContext("WebLogin",webcallback);

}catch(LoginExceptionle){//respondtoexception...}

Recipe15.7showshowtocreateaJAASconfigurationfile,whichspecifiestheLoginModule(s)thatcertainapplicationswilluseduringauthentication.

SeeAlso

SunMicrosystems'JAASdeveloper'sguide:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASLMDevGuide.htmlalistofJAAStutorialsandsampleprograms:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASRefGuide.htmltheJavadocrelatingtoJAASconfigurationfiles:http://java.sun.com/j2se/1.4.1/docs/api/javax/security/auth/login/Configuration.htmlRecipe15.9onusingJAASwithaJSP.

http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASLMDevGuide.html

http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASRefGuide.html

http://java.sun.com/j2se/1.4.1/docs/api/javax/security/auth/login/Configuration.html

Recipe15.7CreatingtheJAASConfigurationFile

Problem

YouwanttocreatetheJAASconfigurationfile.

Solution

Createtheconfigurationfile,thenspecifytheconfiguration'slocationonyourfilesysteminthe${java.home}/jre/lib/security/java.securityfile.

Discussion

UsingJAASalsoinvolveswritingaconfigurationfiletoidentifytheLoginModule(s)thataparticularapplicationwilluse.TheconfigurationfileinExample15-11specifiesanapplicationnamed"WebLogin."

Example15-11.AJAASconfigurationfile

WebLogin{

com.jspservletcookbook.DataSourceLoginModulerequisite;

};

Althoughonlyonemoduleisspecifiedinthisrecipe,oneofthepowerfulfeaturesoftheJAASsecuritydesignistousemultipleLoginModulesorlayersinordertoauthenticateusers.Ausermighthavetobeauthenticatedinseveralwaysbeforeshegainsaccesstowebcomponentsanddata(e.g.,firstheririsesarescanned,thenshemust

specifyausernameandpassword).

Theconfigurationfilespecifies:

ThefullyqualifiedclassnameoftheLoginModule(s).

A"Flag"value,whichisjustaconstantexpressionsuchas"required"or"requisite."Theexampleuses"requisite."Table15-1describesthedifferentFlagvalues.

Oneormore"options"(Example15-11doesnotidentifyanyoptions).Theoptionsrepresentaspace-separatedlistofname/valuepairs,suchasdebug="true"(youcanuseanyname/valuepairingyouwant).TheoptionsallowtheconfigurationfiletopasspropertiesandvaluestotheunderlyingLoginModule.

Table15-1.FlagvaluesforJAASconfigurationfiles

Flagname Description

RequiredTheLoginModuleisrequiredtosucceed,andoverallauthenticationfailsifaLoginModulemarked"required"fails.However,ifafailureoccurs,authenticationstillcontinuesdowntheLoginModulelist.

RequisiteTheLoginModuleisrequiredtosucceed,andruntimecontrolreturnstotheapplication(ratherthancontinuingwithanyotherlistedLoginModules)ifauthenticationfailureoccurs.

Sufficient

IftheLoginModulesucceeds,controlreturnstotheapplicationanddoesnotcontinuewithanyotherlistedLoginModules.Ifanauthenticationfailureoccurs,authenticationcontinueswithanyotherLoginModule.Inotherwords,thefailureofthisLoginModuledoesnotautomaticallyleadtothefailureofoverallauthentication,asin"required"or"requisite."

OptionalSuccessisnotrequiredwiththisLoginModule.Ifauthenticationsuccessorfailureoccurs,authenticationcontinueswithanyotherlistedLoginModules.

Thebasicstructureoftheconfigurationfilelookslikethis:

ApplicationName{

ModuleNameFlagOptions;



};

AnotherApplication{



};

Again,youdonothavetousemultipleLoginModules.

SeethisJavadocpageformoredetailsonconfiguration:http://java.sun.com/j2se/1.4.1/docs/api/javax/security/auth/login/Configuration.html.

HowdoestheJAASimplementationfindtheconfigurationfile?Thedirectory${java.home}/jre/lib/securitycontainsafilenamedjava.security.Thisisa"properties"or"policy"fileinJavasecurityparlanceatextfilecontainingname/valuepairs.ThefollowinglineoftextprovidesthelocationoftheJAASconfigurationfilefortheauthenticationservletofExample15-11:

login.config.url.1=file:h:/home/.java.login.config

IfyouhaveotherJAASconfigurationfilesthatyouwanttocombinewiththisone,usesyntaxsimilartologin.config.url.2=file:h:/home/.my.config(notetheincrementednumber2),placedwithinthejava.securityfile.

Youcanuseanyfilenamingconvention;theconfigurationfilenamedoesnothavetobeginwithaperiod.


AsingleJAASconfigurationfilecanspecifytheLoginModule(s)formultipleapplicationnames.Recipe15.8showsaservletthatusestheLoginModuledescribedinRecipe15.5.

SeeAlso

SunMicrosystems'JAASdeveloper'sguide:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASLMDevGuide.htmlalistofJAAStutorialsandsampleprograms:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASRefGuide.htmltheJavadocrelatingtoJAASconfigurationfiles:http://java.sun.com/j2se/1.4.1/docs/api/javax/security/auth/login/Configuration.htmlRecipe15.8onusingJAASwithaservlet;Recipe15.9onusingJAASwithaJSP.




Recipe15.8UsingJAASinaServlet

Problem

YouwanttoauthenticateservletclientswithJAAS.

Solution

CreateaJavaBeanthatwrapsthefunctionalityoftheJAASAPIclassesthatyouhaveincludedinyourwebapplication.

Discussion

UsingJAASinaservletrequiresthatyouhaveaLoginModuleinstalledinyourwebapplication,eitherinWEB-INF/classesorstoredinaJARfileinWEB-INF/lib.

Example15-12showsaservletnamedLoginServletthatimplementsJAASauthentication.ThisservletusestheCallbackHandlerdescribedinRecipe15.5.ThisCallbackHandlermustalsobeplacedinWEB-INF/classesorincludedinaJARstoredinWEB-INF/lib.Abrowserrequestforthisservletlookslike:

http://localhost:8080/home/servlet/com.jspservletcookbookLoginServlet?userName=Bruce%20W%20Perry&password=bwp1968

UseaPOSTrequestfromanHTMLforminconjunctionwithSSL(Recipe15.2)ifyouwanttousethemuchmoresecurestrategyofkeepingusernamesandpasswordsoutofvisibleURLs.

Example15-12.Aservletforauthenticatingandlogginginclients




importjavax.security.auth.login.LoginContext;

importjavax.security.auth.login.LoginException;

importjavax.security.auth.callback.CallbackHandler;

publicclassLoginServletextendsHttpServlet{




//TheCallbackHandlergetstheusernameandpasswordfrom

//requestparametersintheURL;therefore,theServletRequestis

//passedtotheCallbackHandlerconstructor

WebCallbackHandlerwebcallback=newWebCallbackHandler(request);

LoginContextlcontext=null;

booleanloginSuccess=true;

try{

lcontext=newLoginContext("WebLogin",webcallback);

//thismethodthrowsaLoginException

//ifauthenticationisunsuccessful

lcontext.login();

}catch(LoginExceptionlge){

loginSuccess=false;

}



out.println(

"<html><head><title>Thanksforloggingin</title>"+

"</head><body>");

out.println("<h2>Yourloggedinstatus</h2>");

out.println(""+(loginSuccess?"Loggedin":

"FailedLogin"));


}//doGet





}//doPost

}//LoginServlet

Thisservlet:

1. CreatesaWebCallbackHandler(Example15-10)andpassestheServletRequestintotheconstructor(fromwherethe

CallbackHandlergetstheclient'snameandpassword).

CreatesaLoginContextobjectwithtwoconstructorparameters:thenameoftheloginapplication(fromourconfigurationfileinRecipe15.6,"WebLogin")andtheWebCallbackHandlerobject.

CallstheLoginContext'slogin()method,whichbeneaththesurfacecallstheDataSourceLoginModule'slogin()method(fromExample15-9),inordertoperformauthentication.

Figure15-7showsthewebbrowseroutputwhenanattemptedloginusingthisservletsucceeds.

Figure15-7.TheLoginServletsignalssuccess

SeeAlso

Recipe15.6oncreatingaJAASLoginModule;Recipe15.7oncreatingtheJAASconfigurationfile;Chapter21onaccessingdatabaseswithservlets;SunMicrosystems'JAASdeveloper'sguide:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASLMDevGuide.htmlalistofJAAStutorialsandsampleprograms:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASRefGuide.htmltheJavadocrelatingtoJAASconfigurationfiles:http://java.sun.com/j2se/1.4.1/docs/api/javax/security/auth/login/Configuration.html




Recipe15.9onusingJAASwithaJSP.

Recipe15.9UsingJAASinaJSP

Problem

YouwanttouseaJSPandJAAStoauthenticateclients.

Solution

CreateaJavaBeanthatwrapsthefunctionalityoftheJAASAPIclassesthatyouhaveincludedinyourwebapplication.

Discussion

Recipe15.5-Recipe15.7covertheJAASbasics,sothisrecipefocusesonadaptingaJSPtotheJAASsecurityAPI.

TheJSPinthisrecipeusesaJavaBeantoperformthelogin.

TheJavaBeaninExample15-13hastwoproperties(intheformofinstancevariables):aServletRequestandabooleanvalueindicatingwhetherthenameandpasswordhavepassedthelogintest.ThebeanpassestheServletRequesttotheWebCallbackHandlerconstructor;theWebCallbackHandlerultimatelyextractstheusernameandpasswordfromrequestparameters.

Example15-13.AJavaBeanusestheJAASAPItoperformauthentication



importjavax.security.auth.login.LoginContext;

importjavax.security.auth.login.LoginException;

publicclassLoginBean{

//privatebeaninstancevariablesorproperties

privateServletRequestreq;

booleanloginSuccess;

publicLoginBean(){}//bean'sno-argsconstructor

publicbooleangetLoginSuccess()throwsLoginException{

//theServletRequestpropertyhastobesetbeforethis

//methodiscalled,becausethat'swherewegetthe

//usernameandpasswordfrom

if(req==null)


"TheServletRequestcannotbenullingetLogin()");

WebCallbackHandlerwebcallback=newWebCallbackHandler(req);

try{

LoginContextlcontext=newLoginContext(

"WebLogin",webcallback);

//CalltheLoginContext'slogin()method;ifitdoesn't

//throwanexception,themethodreturnstrue

lcontext.login();

returntrue;

}catch(LoginExceptionlge){

//loginfailedbecausetheLoginContext.login()method

//threwaLoginException

returnfalse;

}

}//getLoginSuccess

publicvoidsetReq(ServletRequestrequest){

if(request==null)


"ServletRequestargumentwasnullin:"+


this.req=request;

}//setReq

}//LoginBean

ThebeandependsonitsServletRequestpropertybeingsetproperlybeforethegetLoginSuccess()methodiscalled.ThismethodperformstheloginbyusingthefamiliarLoginContextclassanditslogin()method(thatis,familiarifyoureadRecipe15.5!).

TheJavaobjectusingthebeanknowsthattheloginsucceededorfailedbasedonthebooleanreturnvalueofthegetLoginSuccess()method.TheobjectusingthebeaninthiscaseisaservletinstanceoriginatingfromtheJSPinExample15-14.

TheJSPincludesthejsp:useBeanstandardactiontocreateaninstanceoftheLoginBean(inavariablenamedjaasBean).ThenthecodeusesJSTLtagsto:

1. Setthebean'sServletRequestproperty(namedreq)tothecurrentrequest(usingc:set).

FindoutwhethertheloginsucceededbyusingtheELsyntaxtocallthebean'sgetLoginSuccess()method.

ThisrecipecombinesmanyJava-relatedtechnologies.SeeChapter23foradescriptionoftheJSTLanditsassociatedELsyntax.

Example15-14.AJSPthatlogsinusersusingtheJAASAPIandaJavaBean


<html>

<head><title>AuthenticatingJSP</title></head>

<body>

<h2>Hereisyourloginstatus...</h2>

<jsp:useBeanid="jaasBean"class="com.jspservletcookbook.LoginBean"/>

<%--Thebean's'req'propertyissetusingthe'request'propertyoftheExpression

Language'spageContextimplicitobject--%>

<c:settarget="${jaasBean}"value="${pageContext.request}"

property="req"/>

<c:choose>

<c:whentest="${jaasBean.loginSuccess}">

Loggedinsuccessfully.

</c:when>

<c:otherwise>

Loginfailed.

</c:otherwise>

</c:choose>

</body>

</html>

TheLoginBeanhasagetLoginSuccess()methodthatreturnsfalseiftheloginfails,andtrueifitsucceeds.WiththeEL,youcancallanyofabean'saccessormethodswiththeterminology:

beanname.beanpropertyname

Thebeanpropertynamepartrepresentstheactualpropertyname,notthenameofthemethod,eventhoughtheendresultofusingthissyntaxisthattheaccessormethodassociatedwiththatpropertygetscalled.Therefore,Example15-14getsthereturnvalueofthegetLoginSuccess()methodbyusing:

${jaasBean.loginSuccess}

Ifthisexpressionreturnstrue,theJSPdisplaysthetext"Loggedinsuccessfully."Otherwise,itshows"Loginfailed."

Figure15-8showstheJSP'sbrowserdisplaywhenaloginfails.

Figure15-8.AJSPsignalsaloginfailure

SeeAlso

Recipe15.6oncreatingaJAASLoginModule;Recipe15.7oncreatingtheJAASconfigurationfile;Recipe15.8onusingJAASwithaservlet;Chapter23ontheJSTL;SunMicrosystems'JAASdeveloper'sguide:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASLMDevGuide.htmlalistofJAAStutorialsandsampleprograms:http://java.sun.com/j2se/1.4.2/docs/guide/security/jaas/JAASRefGuide.htmltheJavadocrelatingtoJAASconfigurationfiles:http://java.sun.com/j2se/1.4.1/docs/api/javax/security/auth/login/Configuration.html




Chapter16.Binding,Accessing,andRemovingAttributesinWebApplications

Introduction

Recipe16.1.SettingServletContextAttributesinServlets

Recipe16.2.SettingServletContextAttributesinJSPs

Recipe16.3.AccessingorRemovingServletContextAttributesinServlets

Recipe16.4.AccessingorRemovingServletContextAttributesinJSPs

Recipe16.5.SettingSessionAttributesinServlets

Recipe16.6.SettingSessionAttributesinJSPs

Recipe16.7.AccessingorRemovingSessionAttributesinServlets

Recipe16.8.AccessingorRemovingSessionAttributesinJSPs

Recipe16.9.SettingRequestAttributesinServlets

Recipe16.10.SettingRequestAttributesinJSPs

Recipe16.11.AccessingorRemovingRequestAttributesinServlets

Recipe16.12.AccessingorRemovingRequestAttributesinJSPs

Introduction

AnattributeisaJavaobjectthatservletcodecanbind,orstore,inacertainscope,suchasaServletContext,asession,orarequest.Theobjectcantemporarilystoreandshareasmallpieceofdatainawaythatisnototherwiseavailabletoservletdevelopers.Then,whentheapplicationnolongerhasusefortheobject,yourcodecanremove,orunbindit,andthewebcontainermakestheobjectavailableforgarbagecollection.

Thischapterdescribeshowtoworkwithattributesinallthreescopes:ServletContext,session,andrequest.IfyouneedtomakeanobjectavailabletoalloftheservletsandJSPsinacontext,thenyoucanbindtheobjecttoaServletContext.Iftheapplicationcallsforanobjectsuchasa"shoppingcart"tobeboundtoasession(seeChapter11),youcansettheobjectasasessionattribute.Finally,iftheapplicationrequirestwoservletsthatcommunicateviaaRequestDispatchertoshareanobject,thentheservletscanuseanobjectattributeboundtoarequestscope.

Sincesessionsandrequestsareassociatedwithnumeroususersinabusywebapplication,developershavetopayattentiontothesizeandresourceuseofanyobjectsthatareboundasattributestorequestsorsessions.

Recipe16.1SettingServletContextAttributesinServlets

Problem

Youwanttomakeanobjectavailabletoallservletsinacontextorwebapplication.

Solution

BindanobjecttotheServletContextusingthejavax.servlet.ServletContext.setAttribute()method.

Discussion

AServletContextattributeisavailabletoallservletsandJSPsinacontextorwebapplication.HerearethestepstobindanobjecttoaServletContext:

1. CreatetheJavaclassthatyouwanttobindtoaServletContext.

PlacetheclassintheWEB-INF/classesdirectory,includingthenecessarypackage-relateddirectories.YoucanalsostoretheclassinaJARfileinWEB-INF/lib.

CreateaservletthatbindstheobjecttotheServletContextusingthejavax.servlet.ServletContext.setAttribute()method.

AccesstheobjectusingServletContext.getAttribute()in

(other)servletswheneveritisneeded.

I'llfirstshowtheobjectthatthisrecipebindstotheServletContext.TherecipethendemonstratesaservletthatstorestheobjectattributeintheServletContext.Example16-1showsasimpleobjectwrappedaroundajava.util.Maptype.UsetheMaptostoreacharacteristicofeachrequestmadetothewebapplication.Inthisexample,eachMapkeyistheIPaddressoftheclientmakingtherequest.EachMapvalueisthedateitrequestedtheservlet.

Example16-1.TheobjectthataservletbindstotheServletContext


importjava.util.Collections;

importjava.util.HashMap;



importjava.util.Set;

publicclassContextObject{

privateMapmap;

publicContextObject(){

map=Collections.synchronizedMap(newHashMap());

}

publicvoidput(Objectkey,Objectvalue){

if(key==null||value==null)


"InvalidparameterspassedtoContextObject.put");

map.put(key,value);

}

publicStringgetValues(){

StringBufferbuf=newStringBuffer("");

Setset=map.keySet();

//youhavetoexplicitlysynchronizewhenanIteratorisused

synchronized(map){

Iteratori=set.iterator();

while(i.hasNext())

buf.append((String)i.next()+"<br>");

}//synchronized

returnbuf.toString();

}

publicStringtoString(){

returngetClass().getName()+"["+map+"]";

}//toString

}

TheContextObjectclasshasmethodstoaddkeysandvaluestotheMap(put(Objectkey,Objectvalue))aswellastooutputtheMap'scurrentkeyvalues(getValues()).TheMapissynchronized,whichisessentiallythread-safe;itiscreatedintheContextObject'sconstructorinthefollowingmanner:


WhenyougenerateaMapusingthestaticjava.util.Collections.synchronizedMap()method,onlyonethreadatatimecancalltheMap'smethods.ThisisimportantwithServletContextattributesthatmaybeaccessedbyseveralservletsand/ormultiplethreadsatthesametime.

Example16-2showstheskeletonoftheContextBinderservletthatbindsaninstanceoftheContextObjectclassinExample16-1totheServletContext.

Example16-2.AservletbindsanobjecttotheServletContext




publicclassContextBinderextendsHttpServlet{



//bindanobjecttotheServletContext

getServletContext().setAttribute(

"com.jspservletcookbook.ContextObject",newContextObject());

//displaysomeHTML

...

}//enddoGet

}

TheservletmethodgetServletContext()returnsa

javax.servlet.ServletContextinstance.Youthencallthatinstance'ssetAttribute()methodwiththeStringattributenameandtheboundobjectasparameters.Asaconvention,youshouldconsidernamingattributesaftertheirfullyqualifiedclassnameinthiscase,"com.jspservletcookbook.ContextObject."

SeeAlso

Recipe16.2onsettingServletContextattributesinJSPs;Recipe16.3onaccessingorremovingaServletContextattribute;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.5onusingaServletContexteventlistener;theJavadocforjavax.servlet.ServletContextAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContextAttributeListener.html

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContextAttributeListener.html

Recipe16.2SettingServletContextAttributesinJSPs

Problem

YouwanttostoreanobjectattributeintheServletContextusingaJSP.

Solution

UsetheJSTLc:settagtobindanobjecttoapplicationscope.TheJSTLusestheapplicationimplicitobjecttorepresenttheServletContext,whichisalsothescopeusedfortheobjectattributesdiscussedinthepreviousrecipe.

Discussion

JSPdeveloperscanusetheJSTLcoretagsandthejsp:useBeanstandardactiontoimplementthesamefunctionalityastheservletinRecipe16.1.Liketheprograminthatrecipe,theupcomingJSPstoresintheServletContextanobjectattributethatcontainsajava.util.Maptype.TheMapstoreskey/valuepairsthatareaccessedbyotherservletsorJSPsinthesamecontext.

HerearethestepstobindanattributetotheServletContextusingaJSP:

1. CreatetheJavaclassthatyouwillinstantiateandbindtotheServletContext.

PlacetheJavaclassintheWEB-INF/classesdirectory,includinganypackage-relateddirectories(iftheclassisnamedcom.jspservletcookbook.ContextObjectthenplacetheclassinWEB-INF/classes/com/jspservletcookbook),orinWEB-INF/libiftheclassisstoredinaJARfile.

CreatetheJSPthatwillbindtheobjectattributetotheServletContext.StoretheJSPinthewebapplication'stop-leveldirectory.

IfthewebcontainerdoesnotalreadyprovidetheJSTL-relatedcomponents,includetheminWEB-INF/lib(seeChapter23)sothattheJSPcanusethesetaglibraries.

FirstIshowtheobjectattributethattheJSPbindstotheServletContext.Example16-3isthesameJavaclassasExample16-1,exceptforthegetMap()method,whichreturnstheMaptypethatthisobjectusestostoreinformation.IaddedthismethodtomaketheMapavailabletothec:setcoretag(seeExample16-4).BecausethetwocodesamplesareexactlythesameexceptforthegetMap()method,Example16-3hasbeenabbreviatedtoshowjustthecreationofthesynchronizedmapanditsgettermethod(seeExample16-1fortheotherpartsoftheclass).

Example16-3.TheobjectattributeboundtotheServletContextbyaJSP


importjava.util.Collections;




importjava.util.Set;

publicclassContextObject{

privateMapmap;

publicContextObject(){


}

publicMapgetMap(){

returnmap;

}

//seeExample16-1fortheotherpartsoftheclass

}

Example16-4doestheworkofcreatinganinstanceoftheobjectattributeandthenbindingtheattributetotheServletContext.ThecodecreatestheContextObjinstance(whichisstoredintheServletContext)withthejsp:useBeanstandardaction.Thenthec:setJSTLcoretagstoresthisobjectinapplicationscope,whichisanaliasfortheServletContext.TheContextObjclassstoresinformationwithaMaptypethatitcontains.ThiscodeinExample16-4storesdataintheServletContextattribute:

<c:settarget=

"${applicationScope[\"com.jspservletcookbook.ContextObject\"].map}"

value="${date}"property="${pageContext.request.remoteAddr}"/>

ThevalueofthetargetattributehastheeffectofcallinggetMap()ontheContextObjobject.Thecodethencreatesanewkey-valuepairintheMap,consistingoftheremoteIPaddressoftheclientmakingtherequest(thekey)andthecurrentdate(thevalue).Ichosethisinformationatrandomtodemonstratehowtostorepiecesofdataina

ServletContextattributeusingtheJSTLandJSPs.Yourowncodemaystoredataofpracticalvaluetoyourapplicationsuchasacustomer'suniqueIDandtheitemthatheispurchasing.

Example16-4.ThecontextBind.jspfile


<html>

<head><title>ContextbindingJSP</title></head>

<body>

<h2>HereistheboundContextObject</h2>

//createaninstanceofContextObject;storeitasaPagescopedattribute

<jsp:useBeanid="contextObj"class=

"com.jspservletcookbook.ContextObject"/>

//createaninstanceofDate;storeitasaPagescopedattribute


//bindtheobjecttotheServletContextrepresentedbythe

//'application'implicitobject

<c:setvar=

"com.jspservletcookbook.ContextObject"value="${contextObj}"scope=

"application"/>

//createanewkey/valuepairintheboundobject'sMap

<c:settarget=

"${applicationScope[\"com.jspservletcookbook.ContextObject\"].map}"

value="${date}"property="${pageContext.request.remoteAddr}"/>

</body>

</html>

Afterlookingatthiscode,youmaywonderwhytheContextObjectvariableiseffectivelynamedtwice,oncebyjsp:useBeanwhenit

createstheobject(givingtheobjectanidornamecontextObj)andagainbyc:setwhenitbindstheobjecttotheServletContext(andcreatingthenamecom.jspservletcookbook.ContextObject).

Byconvention,youshouldnametheattributeafteritsfullyqualifiedclassname.However,youcannotusethisformatwithjsp:useBean,becausethisactioncreatesaJavavariableintheunderlyingservlet.TheJavavariableisnamedcontextObj.

TheJSPcontainercreatesaservletbehindthescenestoimplementeachJSPpage.

Youcannotincludeperiod(.)characterswhennamingJavavariables,sothecoderenamestheobjectinc:set'svarattributewhentheobjectisboundtotheServletContext.

SeeAlso

Chapter23onusingtheJSTL;Recipe16.1onsettingServletContextattributesinservlets;Recipe16.4onaccessingorremovingaServletContextattributeinaJSP;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.5onusingaServletContexteventlistener;theJavadocforjavax.servlet.ServletContextAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContextAttributeListener.html


Recipe16.3AccessingorRemovingServletContextAttributesinServlets

Problem

YouwanttoaccessaServletContextattributetoworkwithitincode,orcompletelyremoveit.

Solution

UsetheServletContext.getAttribute(StringattributeName)methodtoaccesstheattribute.UsetheServletContext.removeAttribute(StringattributeName)

methodtoremovetheattributefromtheServletContext.

Discussion

ThecodeinExample16-5getstheServletContextattributeandstoresitinalocalvariable.Thenthecodeaddsanewkey/valuetotheattribute(whichcontainsajava.util.Maptypeforstoringthekeysandvalues).Later,theservletprintsoutalistoftheattribute'skeys,whichareIPaddressesassociatedwithrequeststotheservlet.

Example16-5.AccessingaServletContextattributeinaservlet




publicclassContextAccessorextendsHttpServlet{




//getaServletContextattribute

ContextObjectcontextObj=(ContextObject)

getServletContext().getAttribute(

"com.jspservletcookbook.ContextObject");

if(contextObj!=null)

contextObj.put(request.getRemoteAddr(),""+

newjava.util.Date());

//displaythecontextattributevalues



out.println(

"<html><head><title>ContextAttribute</title></head><body>");

if(contextObj!=null){

out.println("<h2>ServletContextAttributeValues</h2>");

out.println(contextObj.getValues());

}else{

out.println("<h2>ServletContextAttributeisNull</h2>");

}


}//enddoGet

}

Example16-1inRecipe16.1showstheContextObjectsourcecode.Here,theContextObjectput()methodpassesitskeyandvalueparameterstotheMapmethodofthesamename,exceptthattheContextObjectput()methoddoesnotallownullvaluesforeither

itskeysorvalues.

Ifyouwanttoremovethesameattributethatwasboundbythisrecipe,calltheServletContext.removeAttribute()methodwiththeattributenameasaparameter:

getServletContext().removeAttribute(


Aftertheattributeremovalcodeexecutes,anyfurthercallstoServletContext.getAttribute()usingthesameattributenamewillreturnnull.

SeeAlso

Recipe16.1andRecipe16.2onsettingServletContextattributesinservletsandJSPs;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.5onusingaServletContexteventlistener;theJavadocforjavax.servlet.ServletContextAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContextAttributeListener.html


Recipe16.4AccessingorRemovingServletContextAttributesinJSPs

Problem

YouwanttoaccessorremoveaServletContextattributeinaJSP.

Solution

Usethec:outJSTLcoretagtodisplaythevalueofanattributeandthec:removetagtoremovetheattributefromtheServletContext.

Discussion

BynowyouareprobablyfamiliarwiththeobjectattributethatthepreviousrecipesstoredintheServletContextunderthenamecom.jspservletcookbook.ContextObject.Ifyouarenot,Recipe16.1andRecipe16.2showthesourcecodeforthisclassandhowitisboundasanattributetoaservletandaJSP.ThisrecipeshowstheJSTLtagsthatyoucanuseinJSPcodetoaccessthisattributeandoptionallyremoveorunbindit.

Example16-6includesthetaglibdirectivethatisrequiredforusingJSTL1.0tagsinaJSP.Thec:outtagthenaccessestheServletContextattributeinthetag'svalueattribute.ThetaggetsthevalueoftheServletContextattributebyusingtheapplicationScopeJSTLimplicitobject,whichisajava.util.Maptype.

Example16-6.AccessinganapplicationattributeinaJSP


//HTMLorotherpresentationcodehere...

<c:outvalue=

"${applicationScope[\"com.jspservletcookbook.ContextObject\"].values}"

escapeXml="false"/>

AnimplicitobjectisanobjectthattheJSTLautomaticallymakesavailabletothedeveloper.YouusethetermapplicationScopewithin${...}characters,andthistermevaluatestoajava.util.MapofanyobjectattributesthatareboundtotheServletContext.

Thecode:

${applicationScope[\"com.jspservletcookbook.ContextObject\"].values}

usesELsyntaxtoaccesstheServletContextattributenamedcom.jspservletcookbook.ContextObjectandgetitsvaluesproperty,whicheffectivelycallsthegetValues()methodontheContextObjectobject.ThismethoddisplaysallthekeysoftheMapcontainedbyContextObject,separatedbyanHTMLlinebreak(<br>).TheattributeescapeXml="false"preventsthe<and>charactersin<br>frombeingescaped(andbeingreplacedby<and>,respectively),whichwouldpreventitsproperdisplayinawebbrowser.

IfIwantedtomaketheContextObjectmoreuniversal,IcouldincludeaJavaBeanpropertyallowingtheuseroftheclasstosetthelineseparator,sothattheoutputofthegetValues()methodcouldbeusedindifferentcontexts,notjustHTML.

Figure16-1showstheresultofaccessingaJSPthatusesthiscodeinabrowser.

Figure16-1.AccessingaServletContextboundattributeinaJSP

ToremovetheattributefromtheServletContext,usethec:removeJSTLtag.Thistagremovesthenamedvariablefromthespecifiedscope:

<c:removevar=

"com.jspservletcookbook.ContextObject"scope="application"/>

applicationisanaliasfortheServletContext.AfteraJSPthatcontainsthistagisexecuted,anyfurtherattemptstoaccessaServletContextattributeofthesamenamewillreturnnull.

SeeAlso

Chapter23onusingtheJSTL;Recipe16.1andRecipe16.2onsettingServletContextattributesinservletsandJSPs;Recipe16.3onaccessingorremovingServletContextattributesinservlets;Recipe

16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.5onusingaServletContexteventlistener;theJavadocforjavax.servlet.ServletContextAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContextAttributeListener.html


Recipe16.5SettingSessionAttributesinServlets

Problem

Youwanttostoreanobjectattributeinasession.

Solution

Usethejavax.servlet.http.HttpSessionclass'ssetAttribute()method.

Discussion

ThemechanismforplacingobjectattributesinsessionsisverysimilartostoringobjectsintheServletContext,whichRecipe16.1described.Thedifferenceliesinthescopeoftheobjects;inotherwords,whichusersandhowmanyconcurrentuserscanaccesstheboundobjects.

Asessionrepresentstheinteractionofauserwithawebsite.Thesequenceofwebpagesorcomponentsthatasingleuserrequestsfromawebsiterepresentsasinglesession(detailedinChapter11).Therefore,whenyoustoreanobjectinstanceinasessionattribute,everyuserwhoparticipatesinsessionsinteractswithhisowninstanceofthatobjectattribute.WithServletContextattributes,however,alloftheapplication'susersinteractwiththesameattributeinstance,sinceeachwebapplicationhasonlyoneServletContextandeachcontextisassociatedwithoneattributeinstance.

AdistributedwebapplicationhasoneServletContextinstanceperJavavirtual

machine(JVM).InsteadofusingtheServletContexttostoreinformationgloballyfortheapplication,theServletContextJavadocmakesbriefmentionofusingadatabaseinstead,toensurethatservletsinadistributedapplicationareaccessingthesamedata.SeetheServletContextJavadocat:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContext.html.

Ashoppingcartstoringauser'sitemchoicesisanexampleofanobjectthatwebdeveloperstypicallystoreasasessionattribute.Example16-7showsafragmentofservletcodeforstoringanobjectinasession.

Example16-7.Storinganobjectattributeinasession

<!--thiscodeappearsintheservlet'sdoGetordoPostmethod,whicheverisappropriate-

->

//Createasessionifonedoesnotexistyet


//bindanobjectattributeinthesession

if(session!=null)

session.setAttribute(

"com.jspservletcookbook.ContextObject",newContextObject());

Gainaccesstoasessioninaservletbyusingthejavax.servlet.http.HttpServletRequestobject'sgetSession()method.ThencallHttpSession.setAttribute(),passinginthenameoftheattributeandaninstanceoftheobjectattribute.ThecodeinExample16-7usesthesameContextObjectthatExample16-1showed(Recipe16.1).TheContextObjectusesasynchronizedjava.util.Maptypetohandlemultiplethreadsthatmightbeusingtheattributeconcurrently.

Payattentiontothepossibilityofmultiplethreadsaccessingasessionobject

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContext.html

attribute.Accordingtotheservletspecificationv2.4(ChapterSRV.7.7.1),"Multipleservletsexecutingrequestthreadsmayhaveactiveaccesstoasinglesessionobjectatthesametime.Thedeveloperhastheresponsibilityforsynchronizingaccesstosessionresourcesasappropriate."

SeeAlso

Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.7onaccessingorremovingsessionattributesinservlets;Recipe16.6andRecipe16.8onhandlingsessionattributesinJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.6onusingasessioneventlistener;theJavadocforjavax.servlet.http.HttpSessionAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/HttpSessionAttributeListener.html

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/HttpSessionAttributeListener.html

Recipe16.6SettingSessionAttributesinJSPs

Problem

YouwanttobindanobjecttoasessioninaJSP.

Solution

Usethejsp:useBeanandc:settagstocreateaninstanceofanobjectandassignitasanattributetothesession.

Discussion

TheJSTLcoretagsandthejsp:useBeanstandardactioncanbeusedtomanagesessionattributesinJSPs.Example16-8bindsanobjectattributetoasession,displaysavaluefromtheobject,andthenshowsthesessionIDoftheclientwhorequestedtheJSP.TheboundobjectistheContextObjectthatIhaveusedthroughoutthischapterasthestoredattribute.Itcontainsajava.util.MaptypeforstoringtheIPaddressesofuserswhorequesttheJSP(seeExample16-1andtheaccompanyingdescriptionofthecode).

Example16-8.SettingasessionattributeinaJSP


<html>

<head><title>ContextbindingJSP</title></head>

<body>

<h2>HerearethevaluesfromtheboundContextObject</h2>

<%--CreateinstancesoftheContextObjectandDateclasses--%>




<%--Bindtheobjectattributetothesessionscope--%>

<c:setvar=


"session"/>

<%--Putavalueintheobject,thendisplaythevalue--%>

<c:settarget=

"${sessionScope[\"com.jspservletcookbook.ContextObject\"].map}"value=

"${date}"property="${pageContext.request.remoteAddr}"/>

<c:outvalue="${sessionScope[\"com.jspservletcookbook.ContextObject\"].

values}"escapeXml="false"/>

<h2>HereisthesessionID</h2>

<c:outvalue="${pageContext.session.id}"/>

</body>

</html>

ThiscodefromExample16-8bindstheobjecttothesession:

<c:setvar=


"session"/>

TheonlydifferencebetweenExample16-8andtheJSPofRecipe16.2,whichbindstheobjecttotheServletContext,isthevalueofthescopeattributeinthec:settag(sessioninthiscase).Insimilarfashion,thec:settagsetsavalueinthesessionattributebyreferringtothesessionScopeimplicitvariable:

<c:settarget=

"${sessionScope[\"com.jspservletcookbook.ContextObject\"].map}"value=


TheELmechanismautomaticallymakesavailablethesessionScopeimplicitvariable,whichrepresentsajava.util.Maptypethatstoresanyobjectvariablesinsessionscope.

Ifyouhaveanattributenamethatdoesnotincludeperiodcharactersinit,youcanprovidetheattributenamewithoutanyfurthercontext,andtheELwillsearchthepage,request,session,andapplicationscopesforanattributeofthatname.Forexample,thefollowingELsyntaxreturnsasessionobjectattributenamedcontextObjwithoutusinganimplicitvariable(ornullifthatsessionattributedoesnotexist)tofurtherqualifythename:

${contextObj}

SeeAlso

Chapter23onusingtheJSTL;Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.7onaccessingorremovingsessionattributesinservlets;Recipe16.8onaccessingorremovingsessionattributesinJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.6onusingasessioneventlistener;theJavadocforjavax.servlet.http.HttpSessionAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/HttpSessionAttributeListener.html


Recipe16.7AccessingorRemovingSessionAttributesinServlets

Problem

Youwanttoaccessorremoveasessionattributeinaservlet.

Solution

Usethejavax.servlet.http.HttpSession.getAttribute(String

attributeName)methodtoaccesstheattribute.UsetheremoveAttribute(StringattributeName)methodtoremovetheattributefromthesession.

Discussion

Toaccessasessionattribute,youmustfirstbindtheattributetoasession,asinRecipe16.5.Theobjectattributeisnowavailabletotheuserassociatedwiththatsession.Example16-9accessesanattributenamedcom.jspservletcookbook.ContextObject.Theexamplejustshowsthecoderelatingtoaccessinganattributefromthesession.Example16-5inRecipe16.3showstheentireservletanddoGet()methodforaccessinganobjectattribute.

TheHttpSession.getAttribute()methodreturnsanObjecttype,sothereturnvaluehastobecasttotheappropriatetypebeforecallinganymethodsonit.

Example16-9.Gainingaccesstothesessionattributeinaservlet


...



//Createasessionifonedoesnotexistyet


//Thislocalvariablewillholdtheobjectattribute

ContextObjectcontextObj=null;

//getaccesstoanobjectattributeinthesession

if(session!=null)

contextObj=(ContextObject)session.getAttribute(


//ensurethecontextObjisnotnullbeforecallinganymethods

if(contextObj!=null)

out.println(contextObj.getValues());



Youmusttakethesestepsbeforeaccessingasessionattribute:

1. Compiletheclassoftheobjectthatwillbestoredinthesession.

PlacethisclassinWEB-INF/classesorinWEB-INF/libifit'sstoredinaJARfile.

Makesureaservlet,JSP,orotherwebcomponentsetstheattributetothesessionwiththeHttpSession.setAttribute()method.

Removingthesessionattributefromaservlet

Toremoveanattribute,callHttpSession.removeAttribute()withthenameoftheattribute.Usethefollowingcodeinaservlettoremovetheattributethischapterhasbeenworkingwith:




if(session!=null)

session.removeAttribute("com.jspservletcookbook.ContextObject");

Nowtheattributeisnolongeravailableinthesessionassociatedwiththeuserthatrequestedtheservlet.Thesessionattributeisstillavailableinothersessionswhereitmaybestored(albeitintheformofadifferentinstance).Eachuserisassociatedwithaspecificsession,andeachsessioncancarryitsowninstanceoftheobjectattribute.

WhenyouremovetheattributefromtheServletContext,ontheotherhand,itisnolongeravailabletoanyusers,becausethereisonlyoneServletContextforeachnondistributedwebapplication.

SeeAlso

Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.5onsettingsessionattributesinservlets;

Recipe16.6onsettingsessionattributesinJSPs;Recipe16.8onaccessingorremovingsessionattributesinJSPs;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.6onusingasessioneventlistener;theJavadocforjavax.servlet.http.HttpSessionAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/HttpSessionAttributeListener.html


Recipe16.8AccessingorRemovingSessionAttributesinJSPs

Problem

YouwanttoaccessorremoveasessionattributeinaJSP.

Solution

Usethec:outJSTLcoretagtodisplaythevalueofanattributeandthec:removetagtoremovetheattributefromthesession.

Discussion

Herearethestepstoaccessorremoveasession-scopedvariablewiththeJSTLandaJSP:

1. MakesurethatyourwebapplicationisabletousetheJSTL(i.e.,youhavetheproperJARfilessuchasjstl.jarandstandard.jarinyourWEB-INF/libdirectory;seeChapter23forinstructions).

Includethetaglibdirective,whichmakestheJSTLcoretagsavailabletotheJSP(seetheupcomingcode).

Makesuretheobjectattributeisboundtothesessioninthefirstplace,eitherbythesameJSPthataccessestheattribute,orbyanotherwebcomponent(suchasaservlet).

Thecodeinthisrecipeshowshowtoreferenceasession-scoped

variable,asopposedtoaServletContextattribute(showninRecipe16.4).ThiscodeusesthesessionScopeimplicitobjectoftheEL,whichisanautomaticallyavailablevariableinELformatthatcontainsanysession-scopedobjectattributes.ThiscoderepresentsaportionofaJSPthatdisplaysthevaluescontainedinanattributenamedcom.jspservletcookbook.ContextObject.

Example16-4inRecipe16.2showsacompleteJSPthataccessesobjectattributes.Recipe16.2accessesaServletContextattributeinaJSP,ratherthanasession-scopedattribute.


//HTMLorotherpresentationcodehere...

<c:outvalue=

"${sessionScope[\"com.jspservletcookbook.ContextObject\"].values}

escapeXml="false"/>

TheescapeXml="false"partofthec:outtagtellsthetagtoleavecharactersthatarepartofthetag'soutputsuchas<and>unescaped(inotherwords,donotconvertthemtocharacterentitiessuchas<and>).

ThisJSPcoderemovesasession-scopedvariableusingthec:removecoretag:

<c:removevar=

"com.jspservletcookbook.ContextObject"scope="session"/>

TheobjectattributeisnolongeravailablefortheindividualsessionassociatedwiththeuserthatrequestedthisJSP.Inotherwords,thec:removetagdoesnotremoveallsessionattributesofthespecified

name,justthesessionattribute(s)associatedwithanyuserwhorequeststheJSPcontainingthec:removetag.

SeeAlso

Chapter23onusingtheJSTL;Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.5onsettingsessionattributesinservlets;Recipe16.6onsettingsessionattributesinJSPs;Recipe16.7onaccessingorremovingsessionattributesinservlets;Recipe16.9-Recipe16.12onhandlingrequestattributesinservletsandJSPs;Recipe14.6onusingasessioneventlistener;theJavadocforjavax.servlet.http.HttpSessionAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/HttpSessionAttributeListener.html


Recipe16.9SettingRequestAttributesinServlets

Problem

Youwanttouseaservlettostoreanattributeinarequest.

Solution

Usethejavax.servlet.ServletRequest.setAttribute()method.

Discussion

TheServletRequest.setAttribute()methodisoftenusedincodethatdynamicallyforwardsrequestsorincludescontentwithajavax.servlet.RequestDispatcher.

WebapplicationsthatuseRequestDispatcherstosharerequestsbetweenwebcomponentscancommunicatebetweenthesecomponentsusingrequestattributes.BoththerecipientoftheRequestDispatcher.forward()methodandtheincludedfileorpageinvolvedwiththeRequestDispatcher.include()methodhaveaccesstotheoriginalorenclosingrequest.Therefore,thesewebcomponentscanalsoaccessanyobjectattributesthatarestoredinthoserequests.

TheservletinExample16-10createsaninstanceofaContextObject,storessomeinformationintheobjectbycallingitsput()method,andthenplacestheobjectintheHttpServletRequestunderthename

"com.jspservletcookbook.ContextObject."TheservletthenusesaRequestDispatchertoforwardtherequest(includingtheattribute)andresponsetotheservletpath/displayAttr.Thewebcomponentmappedtothatservletpathnowhasaccesstothepreviouslycreatedrequestattribute.

Example16-10.Bindinganobjecttoarequest




publicclassRequestBinderextendsHttpServlet{




//bindanobjecttotherequest

ContextObjectcontextObj=newContextObject();

contextObj.put(request.getRemoteAddr(),""+newjava.util.Date());

request.setAttribute(

"com.jspservletcookbook.ContextObject",contextObj);

//useRequestDispatchertoforwardrequesttoanotherservlet

//mappedtotheservletpath'/displayAttr'


"/displayAttr");


}//doGet

}

Example16-11showstheservletthatreceivestheforwardedrequest.TheRequestDisplayservletismappedinweb.xmltothe/displayAttrservletpath.ThisservletgetstherequestattributefromtheHttpServletRequestobjectbycallinggetAttribute()withtheattributename:com.jspservletcookbook.ContextObject.SincethereturnvalueofgetAttribute()istypedtoObject,thecodemustcasttheresulttoContextObject.

Example16-11.ThetargetofRequestDispatcher.forwardhasaccesstotherequestattribute




publicclassRequestDisplayextendsHttpServlet{



ContextObjectobj=(ContextObject)request.getAttribute(

"com.jspservletcookbook.RequestObject");



out.println(

"<html><head><title>RequestAttribute</title></head><body>");

out.println("<h2>Requestattributevalues</h2>");

//displaythekeysofthejava.util.Mapstoredintherequestobject

//attribute

if(obj!=null)

out.println(obj.getValues());


}//enddoGet

}

MakesuretocheckwhethertheServletRequest.getAttribute()returnvalueisnullbeforecallinganyoftheobjectattribute'smethods.ThegetAttribute()methodreturnsnulliftherequestdoesnotcontainanattributeofthespecifiedname.

SeeAlso

Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.10onsettingrequestattributesinJSPs;Recipe16.11andRecipe16.12onaccessingorremovingrequestattributesinservletsandJSPs;theJavadocforjavax.servlet.ServletRequestAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequestAttributeListener.html

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequestAttributeListener.html

Recipe16.10SettingRequestAttributesinJSPs

Problem

YouwanttosetarequestattributeusingaJSP.

Solution

UsetheJSTLcoretagsandthejsp:useBeanstandardactiontocreateaninstanceofanobjectandbindittotherequest.

Discussion

TheJSPinExample16-12storesacom.jspservletcookbook.ContextObjectintherequestscopebyfirstcreatinganinstanceofthatobjectwithjsp:useBean.AsinRecipe16.2andRecipe16.6,thecodeusesthec:settagtobindtheobjecttotherequest,butthistimegivesitsscopeattributeavalueofrequest.

YoushouldstoretheclassesfortheobjectsthatJSPsuseasrequestattributesinWEB-INF/classes,orinWEB-INF/libiftheclassispartofaJARfile.

TheJSPinExample16-12isexactlyliketheJSPcodeshowninRecipe16.2andRecipe16.6,exceptthistimethecodeusestherequestScopeimplicitobjecttofetchtherequestattributeandgiveitanewpropertyandvalue.TherequestScopeisusedinELsyntax(seeChapter23)toaccessrequestattributes.

Example16-12.SettingarequestattributeandforwardingtherequestinaJSP





<c:setvar="com.jspservletcookbook.ContextObject"value=

"${contextObj}"scope="request"/>

<c:settarget=

"${requestScope[\"com.jspservletcookbook.ContextObject\"].map}"value=


<jsp:forwardpage="/displayAttr"/>

Aftersettingtherequestattributeandgivingitsomevalues,theJSPforwardstherequesttotheservletpath/displayAttr.TheservletorJSPmappedtothatpathhasaccesstothenewrequestattribute.

SeeAlso

Chapter23onusingtheJSTL;Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.11andRecipe16.12onaccessingorremovingrequestattributesinservletsandJSPs;theJavadocforjavax.servlet.ServletRequestAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequestAttributeListener.html


Recipe16.11AccessingorRemovingRequestAttributesinServlets

Problem

Youwantaservlettoaccessorremovearequestattribute.

Solution

Usethejavax.servlet.ServletRequest.getAttribute()andjavax.servlet.ServletRequest.removeAttribute()

methods,includingthenameoftheattributeasthemethodparameter.

Discussion

Example16-13isderivedfromthedoGet()methodofExample16-11inRecipe16.9(refertothatclassifyouneedtoreviewthecompletecodeofaservlethandlingrequestattributes).Example16-13getsanobjectattributefromtheHttpServletRequestobject,whichisthedoGet()method'sfirstparameter.

TheservletcontainercreatesanHttpServletRequestobjectandpassesitasthefirstparametertoalloftheHttpServlet'sservicemethods,includingdoGet()anddoPost().

Example16-13callsoneoftheattribute'smethods,thenremovestherequestattribute.

Example16-13.Aservletaccessesandremovesarequestattribute



ContextObjectobj=(ContextObject)request.getAttribute(




out.println(

"<html><head><title>RequestAttribute</title></head><body>");

//displaytheattribute'sMapkeys

out.println("<h2>Requestattributevalues</h2>");

if(obj!=null)

out.println(obj.getValues());

//Thismethodcallmaynotbenecessaryasrequestattributes

//persistonlyaslongastherequestisbeinghandled,

//accordingtotheServletRequestAPIdocumentation.

request.removeAttribute("com.jspservletcookbook.ContextObject");


}//doGet

Iftheattributedoesnotexistintherequest(becauseitwasnotboundtotherequestinthefirstplace),ServletRequest.getAttribute()returnsnull.Makesuretheservletcodechecksforanullvaluebeforeitcallstheobject'smethods.Inaddition,theServletRequest.getAttribute()methodreturnsanObjecttype,soensurethattheservletcodecaststhereturnvaluetothepropertypebeforecallingtheexpectedtype'smethods.

SeeAlso

Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.12onaccessingorremovingrequestattributesinJSPs;Chapter6onincludingcontentinservletsandJSPs;theJavadocforjavax.servlet.ServletRequestAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequestAttributeListener.html


Recipe16.12AccessingorRemovingRequestAttributesinJSPs

Problem

YouwanttouseaJSPtoaccessorremovearequestattribute.

Solution

UsetheJSTLcoretagsc:outandc:removetoaccessandoptionallyremovetheattribute.

Discussion

Example16-14accessesanobjectattributethatisboundtotheHttpServletRequest.TheJSPaccessesthisattributebyusingELsyntaxinsidethec:outJSTLtag.

Example16-12inRecipe16.10forwardsarequestattributetoaservletusingthejsp:forwardstandardaction.TheJSPinthatexamplecanforwarditsrequestattributetotheJSPinExample16-14byusingthecode:

<jsp:forwardpage="/requestDisplay.jsp"/>

Thecode:

"${requestScope[\"com.jspservletcookbook.ContextObject\"].

values}"

usestherequestScopeJSTLimplicitobject.Thisvariable,whichthe

JSTLautomaticallymakesavailabletoEL-relatedcode,isajava.util.Maptypecontaininganyattributesboundtotherequestscope.Thecodethendisplaysthevaluestheattributecontainsbyaccessingtheobjectattribute'svaluesproperty(seeRecipe16.1foradiscussionoftheobjectusedforstoringanattributeinvariousscopesthroughoutthischapter).

Example16-14.AccessingandremovingarequestattributewiththeJSTL


<html>

<head><title>RequestreadingJSP</title></head>

<body>

<h2>HerearethevaluesfromtheboundRequestObject</h2>

<c:outvalue=

"${requestScope[\"com.jspservletcookbook.ContextObject\"].

values}"escapeXml="false"/>

<%--c:removemaynotbenecessaryasrequestattributespersistonlyaslongasthe

requestisbeinghandled--%>

<br>Removingrequestattributewithc:remove...<c:removevar=

"com.jspservletcookbook.ContextObject"scope="request"/>

</body>

</html>

Thec:removetagremovestheattributenamedinitsvarattributefromthespecifiedscope.Usescope="request"becauseyouareremovingthisattributefromtheJSP'srequestscope.Figure16-2showstheoutputofthedisplayRequest.jsppageinawebbrowser.

Figure16-2.Thebrowserdisplayafteraccessingand

removingarequestattributeinaJSP

TheJSPthatappearsinthebrowser'saddressfield,requestBind.jsp,actuallysettheattributeandforwardedtherequest(seeRecipe16.10).Whencodeusesjsp:forward,theoriginalJSPremainsinthebrowser'saddressfield,eventhoughthebrowserdisplaystheoutputoftheJSPtargetedbytheforwardaction.

SeeAlso

Chapter23onusingtheJSTL;Recipe16.1-Recipe16.4onhandlingServletContextattributesinservletsandJSPs;Recipe16.5-Recipe16.8onhandlingsessionattributesinservletsandJSPs;Recipe16.11onaccessingorremovingrequestattributesinservlets;theJavadocforjavax.servlet.ServletRequestAttributeListener:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequestAttributeListener.html


Chapter17.EmbeddingMultimediainJSPs

Introduction

Recipe17.1.EmbeddinganAppletinaJSPUsingjsp:plugin

Recipe17.2.EmbeddinganAppletinaJSPUsingtheHTMLConverter

Recipe17.3.AutomaticallyCreatingHTMLTemplateforIncludingFlashFiles

Recipe17.4.WritingHTMLTemplatetoEmbedaFlashFile

Recipe17.5.EmbeddingFlashinaServlet

Recipe17.6.EmbeddingaQuickTimeMovieinaJSP

Recipe17.7.EmbeddinganSVGFileinaJSP

Recipe17.8.EmbeddingaBackgroundSoundtrackinaJSP

Introduction

Mostwebsitesincludesometypeofmultimediaandinteractiveprograms,suchasdigitalvideos,digitalaudiofiles,MacromediaFlashmovies,andJavaapplets.Therefore,JavawebsitesoftenintegratethistypeofcontentwithservletsandJavaServerPages(JSPs).ThischapterexplainsthebasicsofembeddingmultimediainJavawebcomponents.Thisprocessinvolvesincludingtheobjectandembedtagsinyourcomponent'sHTMLoutput.

AJSPisthepreferredchoiceforcombiningmultimediawithdynamiccontent,becauseyoucanmakethetagsthatyouusetoembedthemultimediaapartoftheJSP'sHTMLtemplatetext.However,Recipe17.5alsoshowshowtoincludemultimediaaspartofaservlet'soutput.

Ifthepagecontainingthemultimediacontentdoesnothavetoincludeanyothertypeofdynamicoutput,justuseastaticHTMLpageinsteadofexecutingJSPsandservlets.AstaticpagetypicallyrequiresfewerserverresourcestorespondtoHTMLpagerequests.

Recipe17.1EmbeddinganAppletinaJSPUsingjsp:plugin

Problem

Youwanttousethejsp:pluginstandardactiontoexecuteaJavaappletwiththeJavaPlug-insoftware.

Solution

Usethejsp:pluginactionpositionedintheareaofaJSPwhereyouwanttheapplettoappear.

Discussion

TheJSPspecificationprovidesastandardaction,jsp:plugin,whichproducestheobjectandembedtagsthataredesignedtoallowbrowserstoloadaJavaapplet.TheactionwillruntheappletusingSunMicrosystems'sJavaPlug-inorinitiatethedownloadofthePlug-iniftheuserhasnotyetinstalledthePlug-in.

TheJavaPlug-inisdesignedtoexecuteanappletusingSunMicrosystems'sJava2RuntimeEnvironment,ratherthananyJavaruntimeprovidedbythebrowser.TheinstallationoftheJavaJREorSoftwareDevelopmentKitautomaticallyinstallstheJavaPlug-in.

Usenestedjsp:paramelementstoprovidetheappletwithany

necessaryparameterandvaluepairs.Thejsp:paramelementsmustbenestedwithinasinglejsp:paramselement.

Example17-1showsaJSPfilethatusesjsp:plugintoembedanappletnamedClock.class.Inthiscase,theClock.classfileislocatedinthesamedirectoryastheJSPinExample17-1.

ThisappletoriginatesfromSunMicrosystems'ssampleapplets:http://java.sun.com/products/plugin/1.4.1/demos/plugin/applets/Clock/example1.html

Example17-1.EmbeddingaJavaappletwithjsp:plugin



<html>

<head><title>AClockinaJSP</title></head>

<body>

<h2>Thetime...</h2>

<jsp:plugintype="applet"code="Clock.class"codebase=

"http://localhost:8080/home/applets"jreversion="1.4.1">

<jsp:params>

<jsp:paramname="scriptable"value="false"/>

</jsp:params>

<jsp:fallback>

Sorry,weareunabletostarttheJavaplugin<br/>

</jsp:fallback>

http://java.sun.com/products/plugin/1.4.1/demos/plugin/applets/Clock/example1.html

</jsp:plugin>

<br/><c:outvalue="${date}"/>

</body>

</html>

UserswhohaveinstalledInternetExplorerforWindowsdependonanHTMLobjecttagtoprovidethedirectionforloadingtheapplet.InbrowsersthatsupporttheNetscape-styleplug-in,theHTMLusesit'sembedtag.Thejsp:pluginstandardactiongeneratesHTMLthatshouldworkwithbothbrowsertypes(butyoustillshouldtesttheresultingJSP,ofcourse).

Example17-2showstheHTMLtagsgeneratedbythejsp:pluginactionwhentheInternetExplorer5.5andtheNetscapebrowsersrequesttheJSPinExample17-1.

Example17-2.HTMLtagsgeneratedbythejsp:pluginactionforloadingaJavaapplet

<OBJECTclassid=

clsid:8AD9C840-044E-11D1-B3E9-00805F499D93codebase=

"http://java.sun.com/products/plugin/1.2.2/jinstall-1_2_2-win.cab#

Version=1,2,2,0">

<PARAMname="java_code"value="Clock.class">

<PARAMname="java_codebase"value="http://localhost:8080/home/applets">

<PARAMname="type"value="application/x-java-applet;version=1.4.1">

<PARAMname="scriptable"value="false">

<COMMENT>

<EMBEDtype="application/x-java-applet;version=1.4.1"pluginspage=

"http://java.sun.com/products/plugin/"java_code=

"Clock.class"java_codebase=

"http://localhost:8080/home/applets"scriptable="false"/>

<NOEMBED>

Sorry,weareunabletostarttheJavaplugin<br/>

</NOEMBED>

</COMMENT>

</OBJECT>

Figure17-1showstheJSPwiththeembeddedapplet.

Figure17-1.AJSPwithanembeddedapplet

SeeAlso

TheJavaPlug-intechnologypage:http://java.sun.com/products/plugin/;

http://java.sun.com/products/plugin/default.htm

Recipe17.2onembeddinganappletusingtheSunMicrosystemsHTMLConverter.

Recipe17.2EmbeddinganAppletinaJSPUsingtheHTMLConverter

Problem

YouwanttousetheJavaPlug-inHTMLConvertertooltogeneratethetagsforembeddinganapplet.

Solution

UsetheHTMLConvertertoolwithinhtmlconverter.jar,whichislocatedinthelibdirectoryofthedirectorywhereyouhavetheJavaSDKinstalled.

Discussion

AbusydevelopercanlettheJavaPlug-inHTMLConvertertoolproducetheHTMLtagsthatareresponsibleforloadingJavaapplets.TheJavaPlug-inisaJava-basedtoolthatallowsappletstoberunintheSunMicrosystemsJava2runtimeenvironment,ratherthanwithinthewebbrowser'sJavaruntimeenvironment.TheJavaPlug-inisinstalledonyourmachinewhenyouinstalltheJRE,includingtheinstallationoftheSDK.

TheHTMLConvertertoolwillconvertaspecifiedJSPfilethatcontainsanappletHTMLtag,replacingtheapplettagwithamorecomplextagcollectionthatallowsmostbrowserstoloadtheJavaapplet.TheConverterleavestherestofyourJSPcodeuntouched;itonlyreplacestheJSP'sapplettag.

HereishowtousetheHTMLConvertertool:

1. WritetheJSPfile,addinganapplettag.Example17-3showsaJSPthatembedsaClock.classappletreference.ThisJSP,ratherredundantly,dynamicallywritesatimestringbeneaththeapplet.IincludedthiscodetoshowthattheConverterdoesnotchangetheJSPcode;itjustalterstheapplettagtemplatetextincludedwiththeJSP.

Example17-3.AJSPwithanapplettag



<html>


<body>

<h2>Thetime...</h2>

<appletcode="Clock.class"codebase="http://localhost:8080/home/applets">

</applet>


</body>

</html>

Openacommand-linewindowtothelibdirectoryofyourSDKinstallation,suchasH:\j2sdk1.4.1_01\lib.

Typejava-jarhtmlconverter.jar-gui.ThiscommandlaunchestheSwingversionoftheHTMLConvertertool.Figure17-2showswhatthetoollookslike.

Figure17-2.TheHTMLConverter(GUIversion)

TheHTMLConvertercanalsoberunfromthecommandline.SeetheJavaPlug-inDeveloperGuideforsupportedoptions:http://java.sun.com/j2se/1.4.1/docs/guide/plugin/.

4. Ifyouwanttochooseaback-upfolderwherethetoolsavestheoldJSPfile(withtheapplettag),usetheHTMLConverterGUIwindowtochoosethisfolder.

Clickthe"Convert..."buttonwiththeJSPfilespecifiedinthetoptextfield,andtheConverterwilloverwritetheoriginalfilewithadditionalobjectandembedtags.

Example17-4showsthecodethatreplacedtheapplettaginExample17-3(inboldfont),aswellasthecodethattheconvertertooldidnotmodify.

Example17-4.TheobjectandembedtagsproducedbytheHTMLConverter

http://java.sun.com/j2se/1.4.1/docs/guide/plugin

<html>


<body>

<h2>Thetime...</h2>





<OBJECT

classid=

"clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"

codebase=

"http://java.sun.com/products/plugin/autodl/jinstall-1_4-windows-

i586.cab#Version=1,4,0,0"

>

<PARAMNAME=CODEVALUE="Clock.class">

<PARAMNAME=CODEBASEVALUE="http://localhost:8080/home/applets">

<PARAMNAME="type"VALUE="application/x-java-applet;version=1.4">

<PARAMNAME="scriptable"VALUE="false">

<COMMENT>

<EMBED

type="application/x-java-applet;version=1.4"

CODE="Clock.class"

JAVA_CODEBASE="http://localhost:8080/home/applets"

scriptable=false

pluginspage=

"http://java.sun.com/products/plugin/index.html#download">

<NOEMBED>

</NOEMBED>

</EMBED>

</COMMENT>

</OBJECT>






</body>

</html>

UsersmayhavetroubleloadingtheappletintheirbrowsersiftheyhaveseveralinstalledversionsoftheJavaPlug-in.ThisoccurswhenuserssteadilyupgradetheirJREorJavaSDKversions,whichinstallthecorrespondingversionoftheJavaPlug-in.ThesimplestsolutioninthesecasesistouninstalltheoldJavaPlug-ins.

SeeAlso

TheJavaPlug-intechnologypage:http://java.sun.com/products/plugin/;Recipe17.1onembeddingaJavaappletusingthejsp:pluginstandardJSPaction.

http://java.sun.com/products/plugin/default.htm

Recipe17.3AutomaticallyCreatingHTMLTemplateforIncludingFlashFiles

Problem

YouwanttoautomaticallygeneratetherequiredHTMLforembeddingaFlashfileinawebcomponent.

Solution

FromwithinMacromediaFlash6,usethe"File Publish"menucommandtooutputanHTMLfilethatincludestheobjectandembedtags.

Discussion

Withan.swffileopeninMacromediaFlash6,usethe"File Publish"menucommandtocreateanHTMLfile.ThisfileincludesthenecessarytagstoembedtheFlashmovieyouareworkingoninawebcomponent.ThencutandpastethesetagsandattributesintoyourJSP.Example17-5showstheoutputfromusingthismenucommandwithan.swffilenamedexample.swf.

Example17-5.AutomaticallygeneratedtemplatetextfromwithintheFlashapplication

<HTML>

<HEAD>

<metahttp-equiv=Content-Typecontent="text/html;charset=ISO-8859-1">

<TITLE>example</TITLE>

</HEAD>

<BODYbgcolor="#FFFFFF">







<OBJECTclassid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"

codebase=

"http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.

cab#version=6,0,0,0"WIDTH="550"HEIGHT="400"id="example"ALIGN=""

>

<PARAMNAME=movieVALUE="example.swf">

<PARAMNAME=qualityVALUE=high><PARAMNAME=bgcolorVALUE=#FFFFFF>

<EMBEDsrc="example.swf"quality=highbgcolor=#FFFFFFWIDTH="550"HEIGHT=

"400"NAME="example"ALIGN=""

TYPE="application/x-shockwave-flash"PLUGINSPAGE=

"http://www.macromedia.com/go/getflashplayer">

</EMBED>

</OBJECT>

</BODY>

</HTML>

YourJSPprobablyalreadyincludestheboilerplateHTMLsuchasthebodytag;therefore,youonlyhavetocutandpastethenoncommented,emphasizedcodeinExample17-5.

Theexample.swffileresidesinthesamedirectoryastheHTMLfileinthisexample.

Example17-6inthenextrecipeshowsaJSPfilewiththesametypeofFlash-relatedobjectandembedtagsasthoseillustratedinthisrecipe.Figure17-3showstheautomaticallygeneratedHTMLfilefromExample17-5.

Figure17-3.HTMLtemplatetextwithanembeddedFlashfile

ThedisplayedFlashmovieisderivedfromoneoftheFlashsamplesthataccompaniestheFlash6application:Paycheck_calculator.swf.

SeeAlso

Macromediatechnicalnotespage:http://www.macromedia.com/support/flash/technotes.html;anarticleaboutalternativetechniquestousingtheembedtag:http://www.macromedia.com/devnet/mx/dreamweaver/articles/flash_satay.html

http://www.macromedia.com/support/flash/technotes.html

http://www.macromedia.com/devnet/mx/dreamweaver/articles/flash_satay.html

Recipe17.4WritingHTMLTemplatetoEmbedaFlashFile

Problem

YouwanttowritetheHTMLtemplatetexttoembedaFlashfileinyourJSP.

Solution

UsetheobjectandembedtagssothattheHTMLisreadcorrectlybythebrowsersthatsupporteitherofthesetags.

Discussion

YoumaynothavetheMacromediaFlashapplicationthatcanautomaticallygeneratetheHTMLwhichisnecessarytoembedaFlashfile(Recipe17.4).Inthiscase,writetherequiredHTMLtemplatetextforembeddingaFlashmovieinsideaJSP.

Example17-6showsaJSPwithanembeddedFlashfile(theembeddedfilehasa.swfextension).Thesameconceptappliestothisexampleastotheotherrecipes:theobjecttagisfortheInternetExplorerWindowsbrowser,whichembedsthemediafileasanActiveXcontrol,notaNetscape-styleplug-in.Theembedtag,nestedinsidetheobjecttag,isdesignedtoembedtheFlashfileinNetscapeandotherbrowsersthatsupportNetscape-styleplug-ins.

Example17-6isderivedfromatechnicalnoteathttp://www.macromedia.com/support/flash/technotes.html.


Example17-6.AJSPcontainsanembeddedfile



<html>

<head><title>FlashinaJSP</title></head>

<body>

<h2>EnjoytheFlashMovie</h2>

<OBJECTCLASSID=

"clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"CODEBASE=

"http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#

version=6,040,0"width="293"height="423"

>

<PARAMname="movie"VALUE="coolFlashMov.swf">

<PARAMname="quality"VALUE="high">

<PARAMname="bgcolor"VALUE="#FFFFFF">

<EMBEDSRC=

"coolFlashMov.swf"quality="high"width="293"height="423"

bgcolor="#FFFFFF"type="application/x-shockwave-flash"PLUGINSPAGE=

"http://www.macromedia.com/go/getflashplayer"

>

</EMBED>

</OBJECT>


</body>

</html>

BoththeembedandobjecttagsaredesignedtoprompttheendusertodownloadtherequiredversionoftheFlashplug-inorActiveXcontroliftheydonotalreadyhaveitinstalled.

SeeAlso

Macromediatechnicalnotespage:http://www.macromedia.com/support/flash/technotes.html;anarticleaboutalternativetechniquestousingtheembedtag:http://www.macromedia.com/devnet/mx/dreamweaver/articles/flash_satay.html



Recipe17.5EmbeddingFlashinaServlet

Problem

YouwanttoembedaFlashfileinaservlet'soutput.

Solution


methodinthedoGet()methodoftheservletthatincludesthenecessaryHTMLtemplatetext.

Discussion

TheservletcanincludetheHTMLfragmentthatloadstheFlashmovieintothepagebyusingaRequestDispatcher.Thisprocessissimilartoserver-sideincludesintraditionalCommonGatewayInterface(CGI)programs.Whentheservletreceivesarequest,itincludesthetextfragmentcontainingtheFlash-relatedtagsinitsHTMLoutput.ThisdesignseparatestheservletitselffromthetagsandparametersthatloadtheFlashmovie,sothateachoftheseentitiesevolvesindependently.Forexample,youcanchangethefilenameoftheFlashmovieorsomeoftheobjectorembedparameterswithoutrecompilingtheservletcode.

Example17-7isaservletthatusesaRequestDispatchertoincludethetextshowninExample17-8.Thetextappearsinaflash.txtfilethatisstoredatthetoplevelofthewebapplication.

RequestDispatcherstypicallyincludetheoutputofservletsandJSPs,notjust

textfragments.SeeChapter6formoredetailedRequestDispatcher-relatedrecipes.

Example17-7.AservletusesaRequestDispatchertoincludeobjectandembedtags




publicclassFlashServletextendsHttpServlet{






out.println(

"<html><head><title>EmbeddedFlashcontent</title></head><body>");


"/flash.txt");



}//doGet





}//doPost

}

Example17-8showsthetextfragmentincludedbytheservletinExample17-7.

Example17-8.Anincludedtextfragment(flash.txt)thataservletusestoembedFlash

<OBJECTclassid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"codebase=

"http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#

version=6,0,0,0"WIDTH="550"HEIGHT="400"id="example"ALIGN=""

>

<PARAMNAME=movieVALUE="/home/example.swf">

<PARAMNAME=qualityVALUE=high>

<PARAMNAME=bgcolorVALUE=#FFFFFF>

<EMBEDsrc="/home/example.swf"quality=highbgcolor=#FFFFFFWIDTH=

"550"HEIGHT="400"NAME="example"ALIGN=""TYPE=

"application/x-shockwave-flash"PLUGINSPAGE=

"http://www.macromedia.com/go/getflashplayer">

</EMBED>

</OBJECT>

TheresultinawebbrowserlooksexactlylikeFigure17-3.

SeeAlso

Chapter6ondynamicallyincludingcontentintoservlets;Macromedia

technicalnotespage:http://www.macromedia.com/support/flash/technotes.html;anarticleaboutalternativetechniquestousingtheembedtag:http://www.macromedia.com/devnet/mx/dreamweaver/articles/flash_satay.html



Recipe17.6EmbeddingaQuickTimeMovieinaJSP

Problem

YouwanttoembedaQuickTimemovieinyourJSP.

Solution

Usetheembedtagnestedinsidetheobjecttag.TheobjecttaghastocontaintheCLASSIDattributewiththepropervalue.

Discussion

SimilartousingtheJavaPlug-in,aJSPusestheembedtaginsideofanHTMLobjecttagtoproperlyloadoneofAppleComputer'sQuickTimemovies.YoumustincludetheCLASSIDattributevalueexactlyasExample17-9specifies.YoualsomustincludethesameCODEBASEattributevalue.IftheuserhasanInternetExplorerWindowsbrowser,buthasnotyetinstalledtheQuickTimeActiveXcontrol,theCODEBASEattributevaluespecifieswheretheusercandownloadit.

Example17-9.EmbeddingaQuickTimemovieinaJSP



<html>

<head><title>QuickTimeinaJSP</title></head>

<body>

<h2>LadiesandGentlemen,TheWho</h2>

<OBJECTCLASSID=

"clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B"WIDTH="320"

HEIGHT="256"CODEBASE="http://www.apple.com/qtactivex/qtplugin.cab">

<PARAMname="SRC"VALUE="http://www.parkerriver.com/films/who_bene2.mov">

<PARAMname="AUTOPLAY"VALUE="true">

<PARAMname="CONTROLLER"VALUE="true">

<EMBEDSRC=

"http://www.parkerriver.com/films/who_bene2.mov"

WIDTH="240"HEIGHT="196"

AUTOPLAY="true"CONTROLLER=

"true"PLUGINSPAGE="http://www.apple.com/quicktime/download/">

</EMBED>

</OBJECT>


</body>

</html>

IfthebrowserusesNetscape-styleplug-ins,thentheembedtagwillinitiatetheloadingoftheQuickTimemovie.TheJSPinExample17-6properlyloadedthemovieintotheSafariwebbrowseronmyMacintoshlaptop,forinstance.Oneoftheadvantagesoftheembedtagisthatyoucanuseanumberofproprietaryattributesthattheembeddedobject,suchasQuickTime,understands.Example17-9specifiesthatthemovieshouldstartplayingassoonasthebrowserhasloadedenoughdata(AUTOPLAY="true")aswellasthatthebrowsershouldshowthemovie

controls,whichletstheuserstoporstartthemovie(CONTROLLER="true").

Figure17-4showstheQuickTimemovieembeddedintheJSPofExample17-9.

Figure17-4.AQuickTimemovieembeddedinaJSP

SeeAlso

AppleComputer'sguideonembeddingQuickTimeinWebpages:http://www.apple.com/quicktime/authoring/embed.html;Recipe17.3-Recipe17.5onembeddingaFlashfile;Recipe17.7onembeddinganSVGfileinaJSP;Recipe17.8onembeddingabackgroundsoundtrack.

http://www.apple.com/quicktime/authoring/embed.html

Recipe17.7EmbeddinganSVGFileinaJSP

Problem

YouwanttodisplayaScalableVectorGraphics(SVG)imageinsideaJSP.

Solution

UsetheembedHTMLelementtopositiontheSVGintheJSP.

Discussion

DeveloperstypicallyusetheembedtagtoplaceanSVGfileinanHTMLfileorJSP.SVGisanXML-basedgraphicstechnologythatprovidesdevelopersanddesignersleverageinproducinganddisplayinginteractivegraphics.

BrowsersusespecialSVGviewerapplicationstohandletheembeddedSVGfiles.AdobeSystem'sSVGViewerapplicationcanbedownloadedfromhttp://www.adobe.com/svg/viewer/install/.Corel'sSVGViewercanbedownloadedfromhttp://www.corel.com/svgviewer/.

Example17-10embedsanSVGfilenamedtestLogo.svgandpointstheusertotheAdobeSVGViewerdownloadsiteiftheyhavenotinstalledanSVGViewerapplication.

http://www.adobe.com/svg/viewer/install/default.htm

http://www.corel.com/svgviewer/default.htm

SVGfileshaveextensionsofeither.svgor(incompressedform).svgz,eventhoughtheyareXMLfiles.

Example17-10.AnSVGgraphicsfileembeddedinaJSP



<html>

<head><title>SVGinaJSP</title></head>

<body>

<h2>AScalableVectorGraphicsexample</h2>

<embedsrc=

'<c:outvalue="${param.svg_source}"/>.svg'width=

"200"height="200"type="image/svg-xml"pluginspage=

"http://www.adobe.com/svg/viewer/install/"

>


</body>

</html>

Example17-10showshowtoplaceanSVGwithinotherJSPcodeelements,suchasthetaglibdirectiveandthejsp:useBeanstandardaction.Example17-10alsodynamicallyloadsanSVGbasedontherequestparameternamedsvg_source.ThecodeusestheJSTLc:outtagandtheEL'sparamimplicitobjecttooutputtheparametervalue(seeChapter23ontheJSTL).

Figure17-5showstheresultofrequestingtheJSPinExample17-10,includingthenameoftheSVGfileasarequestparameter.Therequest

URLlookslike:

http://localhost:8080/home/svg.jsp?svg_source=testLogo

Figure17-5.AJSPpageshowsanSVGgraphicsfile

TheSVGshowninFigure17-5isderivedfromAdobeSystemsInc.,whichcreatestheAdobeSVGViewerandanSVG-enabledgraphicsapplication,AdobeIllustrator.

SeeAlso

SVGspecificationsattheW3Consortium:http://www.w3.org/Graphics/SVG/Overview.htm8;Adobe'sSVGViewerinstallpage:http://www.adobe.com/svg/viewer/install/;Recipes17-3-5onembeddingaFlashfileinservletsandJSPs;Recipe17.6onembeddingaQuickTimemovieinaJSP.

http://www.w3.org/Graphics/SVG/Overview.htm8

http://www.adobe.com/svg/viewer/install/default.htm

Recipe17.8EmbeddingaBackgroundSoundtrackinaJSP

Problem

YouwanttoembedanaudiofileinyourJSP.

Solution

UsetheembedtagintheJSP.Usethehiddenattributeifyouwanttohidetheaudiocontrols;otherwise,specifyawidthandheightattributeforshowingtheaudiocontrols.

Discussion

TheembedtagisusedtoincludeanaudiofilewithaJSP,sothatwhenauserrequeststheJSP,thebrowserplaysmusic.Specifically,thebrowserisdesignedtodetecttheMIMEtypeoftheembeddedfile,thenactivateahelperapplicationsuchasQuickTimeorRealAudiotohandletheembeddedfileandplaythemusic.

Example17-11showsaJSPthatembedsanMPEG,audiolayer3(MP3)file.TheJSPdisplayssomeinformationabouttheartistbasedonarequestparameter;thisrandominformationisincludedtoshowhowtocombineJSPcodewiththeembedtag.Theembedtagincludeswidthandheightattributestoshowtheaudiocontrolsinthewebpage.Thecontrolsallowtheusertoturnthevolumeoffordowniftheydonotwanttobeserenadedwhilesurfing.

Example17-11.AJSPwithanembeddedaudiofile


<c:setvar="artist"value="${param.artist}"/>

<html>

<head><title>ChooseYourTunes</title></head>

<body>

<h2>Youchosemusicfromtheartist<c:outvalue="${artist}"/></h2>

<embedsrc="ConstantCraving.mp3"width="240"height="160">

</embed>

</body>

</html>

Figure17-6showstheoutputfromtheJSPinExample17-11.

Figure17-6.EmbeddedsongfilecontrolsinaJSP

SeeAlso

Recipe17.1andRecipe17.2onembeddingaJavaappletinaJSP;

Recipe17.3-Recipe17.5onembeddingaFlashfileinaJSP;Recipe17.6onembeddingaQuickTimemovie;Recipe17.7onembeddinganSVGfile.

Chapter18.WorkingWiththeClientRequest

Introduction

Recipe18.1.ExaminingHTTPRequestHeadersinaServlet

Recipe18.2.ExaminingHTTPRequestHeadersinaJSP

Recipe18.3.UsingaFiltertoAlterRequestHeaders

Recipe18.4.AutomaticallyRefreshingaServlet

Recipe18.5.AutomaticallyRefreshingaJSP

Recipe18.6.CountingtheNumberofWebApplicationRequests

Introduction

Anumberofwebapplicationsmustexaminetheclientrequestbeforesendingaresponse.Anexampleisaservletthathastoread(orsniff)thebrowsertype(oftenthroughtheUser-Agentheader).ServletsorotherwebcomponentsreadinformationabouttherequestbyexaminingHTTPrequestheaders.Theseheadersarecomposedofheadernamesfollowedbycoloncharactersandtheirvalues,suchasAccept-Language:en.Theheadersprecedeanymessagebodythattheclientissendingtotheserver,suchastextthathasbeenpostedfromanHTMLform.

HereisanexampleofagroupofrequestheaderssentwitharequestforaJSPnamedcontextBind.jsp:

GET/home/contextBind.jspHTTP/1.1

User-Agent:Opera/5.02(WindowsNT4.0;U)[en]

Host:localhost:9000

Accept:text/html,image/png,image/jpeg,image/gif,image/x-xbitmap,*/*

Accept-Language:en

Accept-Encoding:deflate,gzip,x-gzip,identity,*;q=0

Cookie:mycookie=1051567248639;JSESSIONID=1D51575F3F0B17D26537338B5A29DB1D


TherecipesinthischaptershowhowtoexaminerequestheaderswithservletandJSPs,usefilterstoalterrequests,automaticallyrefreshservletsandJSPs,andcountthenumberofapplicationrequests.

Recipe18.1ExaminingHTTPRequestHeadersinaServlet

Problem

YouwanttoexaminetheHTTPrequestheadersinaservlet.

Solution

Usethejavax.servlet.http.HttpServletRequest.getHeaderNames(

)andgetHeader()methodstoaccessthenamesandvaluesofvariousrequestheaders.

Discussion

TheHttpServletRequest.getHeaderNames()methodreturnsalloftherequestheadernamesforanincomingrequest.YoucanthenobtainthevalueofaspecificheaderbyprovidingtheheadernametothemethodHttpServletRequest.getHeader()method.Example18-1getsanEnumerationofheadernamesintheservlet'sdoGet()method,andthendisplayseachheaderandvalueonitsownlineintheresultingHTMLpage.

Example18-1.Aservletdisplaysrequestheadersandvalues





publicclassRequestHeaderViewextendsHttpServlet{




//getanEnumerationofalltherequestheadernames

Enumerationenum=request.getHeaderNames();



out.println(

"<html><head><title>RequestHeaderView</title></head><body>");

out.println("<h2>RequestHeaders</h2>");

Stringheader=null;

//displayeachrequestheadernameandvalue

while(enum.hasMoreElements()){

header=(String)enum.nextElement();

//getHeaderreturnsnullifarequestheaderofthatnamedoesnot

//existintherequest

out.println("<strong>"+header+"</strong>"+":"+

request.getHeader(header)+"<br>");

}


}//doGet

}

Figure18-1showstheRequestHeaderViewservlet'soutput.

Figure18-1.Aservletshowstherequestheadernamesandvalues

SeeAlso

Recipe18.2onexaminingrequestheadersinaJSP;Recipe18.3onusingafiltertowraptherequestandforwarditalongthefilterchain;Recipe18.6onusingalistenertotrackrequests;Chapter7onhandlingrequestparametersandJavaBeanpropertieswithservlets,JSPs,andfilters.

Recipe18.2ExaminingHTTPRequestHeadersinaJSP

Problem

YouwanttouseaJSPtodisplaytherequestheadersandvalues.

Solution

Usethec:forEachandc:outJSTLtagstoviewtheheadernamesandvalues.

Discussion

TheJSTLv1.0makesallexistingrequestheadersavailableviatheheaderimplicitobject.TheJSTLautomaticallymakesthisvariableavailabletoJSPs;theheaderobjectevaluatestoajava.util.Maptype.

InExample18-2,thec:forEachtagiteratesoverthisMapandstoreseachheadernameandvalueintheloopvariablenamedbyc:forEach'svarattribute(inExample18-2it'scalledreq).Thec:forEachvarattributeisimplementedasajava.util.Map.Entrytype,whichisadatatypethatstoreskeysandtheirvalues.Thec:outtagdisplayseachheadernamebyusingELformat:${req.key}.Consequentlyc:outdisplaysthevaluewith${req.value}.

Example18-2.Viewingtherequestheadernamesand

valuesinaJSP


<html>

<head><title>RequestHeaders</title></head>

<body>

<h2>HerearetheRequestHeadernamesandvalues</h2>

<c:forEachvar="req"items="${header}">

<strong><c:outvalue=

"${req.key}"/></strong>:<c:outvalue="${req.value}"/><br>

</c:forEach>

</body>

</html>

Figure18-2showstheresultinabrowserofrequestingthedisplayHeaders.jsppage.

Figure18-2.AJSPpageshowsrequestheadersusingJSTLtags

SeeAlso

Chapter23onusingtheJSTL;Recipe18.2onexaminingrequestheadersinaservlet;Recipe18.3onusingafiltertowraptherequestandforwarditalongthefilterchain;Recipe18.6onusingalistenertotrackrequests;Chapter7onhandlingrequestparametersandJavaBeanpropertieswithservlets,JSPs,andfilters.

Recipe18.3UsingaFiltertoAlterRequestHeaders

Problem

YouwanttouseafiltertochangetherequestheadersbeforeaservletorJSPreceivestherequest.

Solution

Wraptherequestinyourowncustomrequestclass.PasstherequestwrapperordecoratorclasstotheFilterChain.doFilter()method,insteadoftheoriginalrequestdestination.

Discussion

Thejavax.servlet.http.HttpServletRequestWrapperisaconvenienceclassthatyoucanextendtoprovideadditionalfunctionalityforanHTTPrequest.Hereishowtoalterandforwardarequestusingafilter:

1. CreateaclassthatextendsHttpServletRequestWrapper.

Placethisclassinthewebapplication'sWEB-INF/classes(includingpackage-relateddirectories)directoryorWEB-INF/libiftheclassispartofaJARfile.

Createaclassthatimplementsjavax.servlet.Filter,suchasExample18-3.ThisclassusesyourcustomrequestwrapperclasstoenclosetheServletRequestparameteroftheFilter.doFilter()

method.

StorethefilterclassinWEB-INF/classesorWEB-INF/lib(ifit'sinaJAR).

Registerthefilterinweb.xml.Inthisrecipe,thefilterismappedtoalloftherequestsinthewebapplicationwiththeURLmapping/*.

Example18-3showsthefilterclassthatpassestherequest-wrapperclassalongthefilterchain.ThefileisnamedRequestFilter;thewrapperclassisnamedReqWrapper.

Example18-3.AfilterthatwrapstheHttpServletRequest




publicclassRequestFilterimplementsFilter{


/**CreatesnewRequestFilter*/

publicRequestFilter(){}



}

publicvoiddoFilter(ServletRequestrequest,

ServletResponseresponse,FilterChainchain)throwsjava.io.IOException,

ServletException{

ReqWrapperwrapper=null;

ServletContextcontext=null;

//createtherequestwrapperobject,aninstanceofthe

//ReqWrapperclass.Theclientrequestispassedinto

//ReqWrapper'sconstructor

if(requestinstanceofHttpServletRequest)

wrapper=newReqWrapper((HttpServletRequest)request);

//usetheServletContext.logmethodtologparamnames/values

if(wrapper!=null){

context=config.getServletContext();

context.log("Query:"+wrapper.getQueryString());}

//continuetherequest,responsetonextfilterorservlet

//destination

if(wrapper!=null)

chain.doFilter(wrapper,response);

else


}//doFilter




}//destroy

}

Example18-3usestheservletcontexttologtheReqWrapper'squerystring.TheReqWrapperclassaddsaparametertothequerystring,but

youcouldmakethisclassimplementwhateverbehavioryouneedinyourownapplication.Example18-4showsthefilter-mappingentriesinthedeploymentdescriptor(web.xml),whichensuresthateveryapplicationrequestpassesthroughthisfilter.

Example18-4.Thefiltermappinginweb.xml

<filter>


<filter-class>com.jspservletcookbook.RequestFilter</filter-class>

</filter>

<filter-mapping>



</filter-mapping>

TheReqWrapperisasimpleexampleofanHttpServletRequestWrappersubclassthatencapsulatestheoriginalrequest.ThisclassoverridesthegetQueryString()methodinordertoaddaparametertotherequest'squerystring.

Toaccessthenewfilterparameter,youmustcallgetQueryString()ontherequestonceitreachesitsdestinationservlet,thenparsethegetQueryString()returnvalueforindividualparameters.UsingtheELwillnotworkwithrequestwrappersthatoverridegetQueryString():

//doesnotreturnthenewparametervalue

//addedbytheoverriddengetQueryString

//method

${param.filter}

Therequestthatpassesthroughthefilteristheparameterto

ReqWrapper'sconstructor,sothefilter(inExample18-3)wrapstherequestwiththiscode:

wrapper=newReqWrapper((HttpServletRequest)request);

AURLsenttotheapplicationcontainingthequerystringname=Brucedisplaysthefollowingtextintheserverlog(asaresultoftheServletContext.logmethod):

Query:name=Bruce&filter=com.jspservletcookbook.ReqWrapper.

Example18-5isthecodefortheReqWrapperobject.

Example18-5.TheReqWrapperclassforencapsulatingtheHttpServletRequest



importjavax.servlet.http.HttpServletRequestWrapper;


publicclassReqWrapperextendsHttpServletRequestWrapper{

privatestaticfinalStringAMP="&";

publicReqWrapper(HttpServletRequestrequest){

super(request);

}

publicStringgetQueryString(){

Stringquery=null;

//getthequerystringfromthewrappedrequestobject

query=((HttpServletRequest)getRequest()).getQueryString();

//adda'filter'parametertothisquerystringwiththeclass

//nameasthevalue

if(query!=null)

returnquery+AMP+"filter="+getClass().getName();

else

return"filter="+getClass().getName();

}//getQueryString

}

Themethodcallchain.doFilter(wrapper,response)attheendofExample18-3passestherequest(wrappedinourowncustomclass)andresponsetothenextfilter,ortothedestinationservletorJSPifnootherfiltersareregistered.

SeeAlso

Recipe18.1andRecipe18.2onexaminingrequestheadersinaservletandaJSPrespectively;Recipe18.3onusingafiltertowraptherequestandforwarditalongthefilterchain;Recipe18.6onusingalistenertotrackrequests;Chapter7onhandlingrequestparametersandJavaBeanpropertieswithservlets,JSPs,andfilters.

Recipe18.4AutomaticallyRefreshingaServlet

Problem

Youwanttoautomaticallyrefreshaservlet-generatedpageataspecifiedinterval.

Solution

AddaRefreshresponseheader,usingthejavax.servlet.http.HttpServletResponseobject.

Discussion

SupposethatyourservletismonitoringaRedSoxversusYankeesbaseballgame.Youwanttobeabletoallowausertofollowthegamealmostpitchbypitch,andhaveyourwebapplicationconstantlyupdatethestatusofthegame.IfyouaddaRefreshresponseheadertoyourclientresponse,thebrowserwillcontinuallyrefreshthepageaccordingtothespecifiedinterval.

Example18-6addsaresponseheaderthatthewebcontainerwillsendtotheclientintheformatRefresh:60,whichmeans"requestthispageagainin60seconds."

Example18-6.Refreshingaservletevery60seconds




publicclassAutoServletextendsHttpServlet{




//clientbrowserwillrequestthepageevery60seconds

response.addHeader("Refresh","60");



out.println(

"<html><head><title>ClientRefresh</title></head><body>");

out.println("<h2>WelcometotheRedSox-Yankeesseries...</h2>");

//MoreHTMLordynamiccontent


}//doGet

}

Therearesomecaveatstothisapproachiftheenduserwalksawayfromherdesk,herbrowserwillblithelycontinuetorequestthepage.Ifyourservletdoesn'timposesomecontroloverthis,youcouldaddalotofunnecessaryloadtoyourapplication.Oneexampleofasolutiontothisproblemistokeeptrackofhowmanytimestheservlethasbeenrefreshedwithasessionattribute(detailedinChapter16).Ifthenumberoftimesexceedsacertainlimit,youcouldstopaddingtheheadertotheresponse.Example18-7showspartofadoPost()methodbodyforkeepingtrackofauser'srefreshcount.

Example18-7.Trackingauser'srefreshcount

//insidedoPost(ordoGet)method


Longtimes=(Long)session.getAttribute("times");

//createsessionattributeifitdoesn'texist

if(times==null)

session.setAttribute("times",newLong(0));

//localvariable'temp'willholdthesessionattributevalue

longtemp=1;

//incrementtheattributevaluetoaccountforthisrequest

if(times!=null)

temp=times.longValue()+1;

if(temp<60)//onlyallow60refreshes;aboutanhour'sworth

response.addHeader("Refresh","60");

//updatethesessionattributevalue

session.setAttribute("times",newLong(temp));

ThiscodeworksequallywellinsideofadoGet()method.

SeeAlso

Recipe18.5onautomaticallyrefreshingaJSP;Recipe18.1andRecipe18.2onexaminingrequestheadersinaservletandaJSP;Recipe18.3onusingafiltertowraptherequestandforwarditalongthefilterchain;Recipe18.6onusingalistenertotrackrequests.

Recipe18.5AutomaticallyRefreshingaJSP

Problem

YouwanttorefreshaJSPrequestataspecifiedinterval.

Solution

UseaJSPscriptletthataddsaRefreshresponseheadertotheresponse.

Discussion

ThefollowingscriptletcodeaddsaRefreshheaderthatspecifiesa60-secondintervalforrefreshingtheJSP.PlacethiscodeatthetopoftheJSPbeforeanycontentappears:

<%response.addHeader("Refresh","60");%>

IfyouwanttorefreshtheJSPtoanotherwebcomponentorpage,usethissyntax:

<%response.addHeader("Refresh","10;

http://localhost:8080/home/thanks.jsp");%>

SeeAlso

Example18-6inRecipe18.4onrefreshingaservlet;Example18-7inRecipe18.4onlimitingthenumberofautomaticrefreshesofaservlet;Recipe18.1andRecipe18.2onexaminingrequestheadersinaservlet

andaJSP,respectively;Recipe18.3onusingafiltertowraptherequestandforwarditalongthefilterchain;Recipe18.6onusingalistenertotrackrequests.

Recipe18.6CountingtheNumberofWebApplicationRequests

Problem

Youwanttocountthenumberofrequestshandledbyawebapplication.

Solution

Useajavax.servlet.ServletRequestListenertobenotifiedwheneveranHTTPrequestisinitialized.

Discussion

Arequestlistenerisagoodcandidatefortrackingrequests,becausethewebcontainernotifiesthelistenerofnewrequestsbycallingitsrequestInitialized()method.Example18-8keepstrackoftherequestcountwithastaticclassvariablenamedreqCount.TheprogramincrementsthisvariableinasynchronizedblockwithintherequestInitialized()method.

TheServletContextisusedtologamessageabouttherequestsothatyoucanobservethelistenerbehavior.However,abusyproductionapplicationthatlogsinformationabouteveryrequesttypicallyrepresentsaninefficientuseofwebcontainerresources.Thistypeofloggingactivityshouldbereservedfordevelopmentapplications.

Example18-8.Arequestlistenerclassforcountingapplicationrequests




publicclassReqListenerimplementsServletRequestListener{

privatestaticlongreqCount;

publicvoidrequestInitialized(ServletRequestEventsre){

//usedforloggingpurposes

ServletContextcontext=sre.getServletContext();

//Usedtogetinformationaboutanewrequest

ServletRequestrequest=sre.getServletRequest();

//ThestaticclassvariablereqCountisincrementedinthisblock;

//theincrementingofthevariableissynchronizedsothatone

//threadisnotreadingthevariablewhileanotherincrementsit

synchronized(context){

context.log(

"Requestfor"+

(requestinstanceofHttpServletRequest?

((HttpServletRequest)request).getRequestURI():

"Unknown")+";Count="+++reqCount);

}//synchronized

}

publicvoidrequestDestroyed(ServletRequestEventsre){

//Calledwhentheservletrequestisgoingooutofscope.

}//requestDestroyed

}

YoucanaccessthenewServletRequestinthetwoServletRequestListenermethodsbycallingServletRequestEvent.getServletRequest().YoumustcasttheServletRequestreturnvaluetoanHttpServletRequesttocallthelatterclass'smethods.Example18-8accessesthenewHttpServletRequestsinordertocallthoseobject'sgetRequestURI()method,whichprovidespartoftheinformationthecodeincludesinaloggingmessage.

YoumustregistertheServletRequestListenerinweb.xml:

<listener>

<listener-class>com.jspservletcookbook.ReqListener</listener-class>

</listener>

Thewebcontainerthencreatesaninstanceofthelistenerwhenitstartsup.Hereisanexampleofaserver-logentrywhenarequestismadetotheapplicationwithinwhichtherequestlistenerisregistered:

2003-05-3007:22:21Requestfor/home/servlet/com.jspservletcookbook.SessionDisplay;

Count=2

ForTomcat,thislinewouldbedisplayedinthelogfilefoundin<Tomcat-installation-directory>/logs.

SeeAlso

Recipe18.1andRecipe18.2onexaminingrequestheadersinaservletandaJSP;Recipe18.3onusingafiltertowraptherequestandforwarditalongthefilterchain;Chapter7onhandlingrequestparametersandJavaBeanpropertieswithservlets,JSPs,andfilters.

Chapter19.FilteringRequestsandResponses

Introduction

Recipe19.1.MappingaFiltertoaServlet

Recipe19.2.MappingaFiltertoaJSP

Recipe19.3.MappingMoreThanOneFiltertoaServlet

Recipe19.4.ChangingtheOrderinWhichFiltersareAppliedtoServlets

Recipe19.5.ConfiguringInitializationParametersforaFilter

Recipe19.6.OptionallyBlockingaRequestwithaFilter

Recipe19.7.FilteringtheHTTPResponse

Recipe19.8.UsingFilterswithRequestDispatcherObjects

Recipe19.9.CheckingFormParameterswithaFilter

Recipe19.10.BlockingIPAddresseswithaFilter

Introduction

ServletfilteringwasintroducedwiththeservletAPIv2.3in2001.Filteringisapowerfultechnologyforservletdevelopers,whocanuseittogeneratechainsofJavaclassesthatexecuteinsequenceinresponsetoclientrequests.

DevelopersbeginbycreatingoneormoreJavaclassesthatimplementthejavax.servlet.Filterinterface.Theseclassescanundertakeanumberofactionspriortoaservlet'srequesthandling,creatingachainofactionsbeforetherequestisdeliveredtoitsdestination(includingblockingtherequestaltogether).Theseactionsinclude,accordingtotheFilterAPIdocumentation:

Authenticationofrequests

Dataencryption

Datacompression

Logging

ExtensibleStylesheetLanguageTransformation(XSLT)filtering

Imageconversion

AccesstheJavadocfortheFilterinterfaceat:http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/Filter.html.

Registerafilterinthedeploymentdescriptor,andthenmapthe

http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/Filter.html

registeredfiltertoeitherservletnamesorURLpatternsinyourapplication'sdeploymentdescriptor.Whenthewebcontainerstartsupyourwebapplication,itcreatesaninstanceofeachfilterthatyouhavedeclaredinthedeploymentdescriptor.Thefiltersexecuteintheorderthattheyaredeclaredinthedeploymentdescriptor.

Recipe19.1MappingaFiltertoaServlet

Problem

Youwanttomaporapplyafiltertoanindividualservlet.

Solution

Usethefilterandfilter-mappingelementsinweb.xmltoassociatethefilterwiththeservlet.

Discussion

Thewebcontainerfindsoutaboutthefiltersthatyouwanttoapplytoaservletbyusinginformationinthedeploymentdescriptor.ThefilterelementassociatesafilternamewithaJavaclassthatimplementsthejavax.servlet.Filterinterface.Thefilter-mappingelementthenassociatesindividualfilterswithURLmappingsorpaths,similartotheservlet-mappingelementthatyouhaveprobablyusedbeforeinweb.xml.Example19-1showsadeploymentdescriptorfromtheservletAPIv2.3thatincludesthemappingofafilternamedLogFiltertotheservletpath/requestheaders.

Example19-1.Mappingafiltertoaservlet


<!DOCTYPEweb-app



>

<web-app>



<filter>

<filter-name>LogFilter</filter-name>

<filter-class>com.jspservletcookbook.LogFilter</filter-class>

</filter>

<filter-mapping>


<url-pattern>/requestheaders</url-pattern>

</filter-mapping>



<servlet>

<servlet-name>requestheaders</servlet-name>

<servlet-class>com.jspservletcookbook.RequestHeaderView</servlet-class>

</servlet>



<servlet-mapping>



</servlet-mapping>

</web-app>

Whenaclientsendsarequesttotheservletpath/requestheaders,thewebcontainerappliestheLogFilterfiltertotherequest.Thisservletpath,asin:

http://localhost:8080/home/requestheaders

istheonlyservletpathtowhichthisfilterisapplied.Asyoumighthaveguessed,theLogFilterlogssomeinformationabouttherequestbeforetherequestcontinuesalongtoitsservletdestination.Example19-2showsthefilterclassfortheLogFilterinExample19-1.

Thisfilterclassprovidestheadditionalbenefitofshowingyouhowtologamessageinsideofafilter!

Makesureto:

Createthefilterwithaconstructorthatdoesnottakeanyparameters

Givethefilterclassapackagename

StorethefilterintheWEB-INF/classesdirectoryofthewebapplication,includingitspackage-relateddirectories

Mapthefiltertotheservletinweb.xml,asinExample19-1

Example19-2.Afilterthatlogssomeinformation






publicclassLogFilterimplementsFilter{


privateLoggerlog;

//CreatesnewLogFilter

publicLogFilter(){}



//loadtheconfigurationforthisapplication'sloggersusingthe

//servletLog.propertiesfile

PropertyConfigurator.configure(config.getServletContext().

getRealPath("/")+

"WEB-INF/classes/servletLog.properties");

log=Logger.getLogger(LogFilter.class);

log.info("Loggerinstantiatedin"+getClass().getName());

}//init



HttpServletRequestreq=null;

if(log!=null&&(requestinstanceofHttpServletRequest)){


log.info(

"Requestreceivedfrom:"+req.getRemoteHost()+"for:"+

req.getRequestURL());}

//passrequestbackdownthefilterchain


}//doFilter




log=null;

}

}

ThisfilterlogstheremotehostoftheclientrequestandtheURLthattheclientrequested.Hereisanexampleoftheloggedinformation:

INFO-Requestreceivedfrom:localhostfor:http://localhost:8080/home/requestheaders

Thefilterusesthelog4jlibrary(seeChapter14)fromtheApacheSoftwareFoundation.

Sincethefirstparametertothefilter'sdofilter()methodisajavax.servlet.ServletRequesttype,thisparametermustbecasttoanHttpServletRequesttocallmethodssuchasHttpServletRequest.getRemoteHost().

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoaltertherequest;Recipe19.2-Recipe19.4onmappingfilterstowebcomponents;Recipe19.5onconfiguringfilterinitializationparameters;Recipe19.6onblockingrequests;Recipe19.7onfilteringtheHttpServletResponse;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9onusingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.2MappingaFiltertoaJSP

Problem

YouwanttohavethewebcontainerapplyafiltertorequestsforacertainJSPpage.

Solution

Usetheurl-patternchildelementofthefilter-mappingelementinthedeploymentdescriptortomapthefiltertotheJSP.

Discussion

MapafiltertoaJSPbyspecifyingthepathtotheJSPpageusingthefilter-mappingelement'surl-patternsubelement.Example19-3showsaweb.xmlconfigurationthatmapsthefilterinExample19-2totherequestHeaders.jsp.

Example19-3.MappingafiltertoaJSP



<filter>



</filter>

<filter-mapping>

<url-pattern>/displayHeaders.jsp</url-pattern>

</filter-mapping>



Youcancreateanumberoffiltermappingsforasinglefilter,eachwiththeirowntypeofURLpattern.

WiththeconfigurationofExample19-3,anyrequestsfor/displayHeaders.jspwillpassthroughthefilternamedLogFilter.Example19-2showsthesourcecodefortheLogFilterclass.Thecodelogsamessageabouttherequest,beforetherequestispassedalongthefilterchaintotheJSP.Theloggedmessagelookslike:

INFO-Requestreceivedfrom:localhostfor:http://localhost:8080/home/

displayHeaders.jsp

TheJSPitselfdoesnothavetobeconfiguredinaspecialwayforthefiltertobeappliedtoit.YoucanapplythefiltertoallJSPswiththisconfiguration:

<filter-mapping>


<url-pattern>*.jsp</url-pattern>

</filter-mapping>

TheURLpattern*.jspisanextensionmappingthatassociatestheLogFilterwithanyofthewebapplication'scomponentsthatendwith.jsp.

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.3onmappingmorethanonefiltertoaservlet;Recipe19.4onchangingtheorderfiltersareappliedtoaservlet;Recipe19.5onconfiguringfilterinitializationparameters;Recipe19.6onblockingrequests;Recipe19.7onfilteringtheHttpServletResponse;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9onusingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.3MappingMoreThanOneFiltertoaServlet

Problem

YouwantrequestsforaservletorJSPtopassthroughmorethanonefilter.

Solution

MapeachfiltertotheservletorJSPusingfilter-mappingelementsinthedeploymentdescriptor.Thefiltersareappliedtotheservletintheordertheyappearinthedeploymentdescriptor.

Discussion

Yourwebapplicationmaydefineseveraldifferentfilterswithaspecificpurpose.Forinstance,onefiltermightlogmessages,whileanotherfilterauthenticatesusers.Itisstraightforwardtocreateafilterchainthatapplieseachfilterinaspecifiedordertoaservlet.Youusethefilter-mappingelementtomapeachfiltertothetargetservlet(orJSP).Thewebcontainerthenappliesthefilterstothetargetintheorderthatthefilter-mappingelementsaredefinedinthedeploymentdescriptor.

Example19-4configurestwofilters:AuthenFilterandLogFilter.Thefilter-mappingelementsforthesefiltersthenmaptheservletnamerequestheaderstoeachofthesefilters.Theorderofthefilter-mappingelementsinExample19-4specifiesthattheauthenticationfilter(AuthenFilter)mustbeappliedtotheservletnamedrequestheadersfirst,followedbytheLogFilter.

Tomapafiltertoaservletname,theservlethastoberegisteredinweb.xml.Example19-4registerstherequestheadersservletbeneaththefilterandfilter-mappingelements.

Example19-4.Mappingmorethanonefiltertoaservlet



<filter>

<filter-name>AuthenFilter</filter-name>

<filter-class>com.jspservletcookbook.AuthenticateFilter</filter-class>

</filter>

<filter>



</filter>

<filter-mapping>



</filter-mapping>

<filter-mapping>



</filter-mapping>



<servlet>


<servlet-class>com.jspservletcookbook.RequestHeaderView</servlet-class>

</servlet>

<servlet-mapping>



</servlet-mapping>


Whenauserrequeststherequestheadersservletusingtheservletpath/requestheaders,asspecifiedintheservlet-mappingelement,therequestpassesthroughtheAuthenFilterandLogFilterbeforeitreachesitsservletdestination.

Thesameprocessappliestoafilter-mappingthatusesaurl-patternelementinsteadofaservlet-nameelement.Theorderofthefilter-mappingelementsinthedeploymentdescriptordeterminestheorderofthefiltersappliedtothewebcomponentsthatmatchtheurl-pattern.

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.4onchangingtheorderfiltersareappliedtoaservlet;Recipe19.5onconfiguringfilterinitparameters;Recipe19.6onblockingrequests;Recipe19.7onfilteringtheHttpServletResponse;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9onusingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.4ChangingtheOrderinWhichFiltersareAppliedtoServlets

Problem

Youwanttochangetheorderinwhichfiltersareappliedtowebcomponents.

Solution

Changetheorderoffilter-mappingelementsinthedeploymentdescriptor.

Discussion

Theorderoffilter-mappingelementsinweb.xmldeterminestheorderinwhichthewebcontainerappliesthefiltertotheservlet.Example19-5reversestheorderofthefilter-mappingelementsthatmaptwofilterstotheservletnamedrequestheaders,comparedwithRecipe19.3.TheLogFilteristhusappliedtotheservletbeforetheAuthenFilter.Anyrequestsfortheservletpassthroughachain:LogFilter AuthenFilter requestheadersservlet.

Example19-5.Reversingtheorderoffilter-mappingelements

<filter-mapping>



</filter-mapping>

<filter-mapping>



</filter-mapping>

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.1-Recipe19.3onmappingfilterstowebcomponents;Recipe19.5onconfiguringfilterinitparameters;Recipe19.6onblockingrequests;Recipe19.7onfilteringtheHttpServletResponse;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9onusingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.5ConfiguringInitializationParametersforaFilter

Problem

Youwanttomakeaninitialization(init)parameteravailabletoafilter.

Solution

Usetheinit-paramchildelementofthefilterelementtodeclaretheinitializationparameteranditsvalue.Insidethefilter,accesstheinitparameterbycallingtheFilerConfigobject'sgetInitParametermethod.

Discussion

Example19-6showsafilterdeclaredinthedeploymentdescriptor.Thefilterincludesaninitparameternamedlog-id.

Example19-6.Afilterdeclaredinthedeploymentdescriptorwithaninitparameter

<filter>



<init-param>

<param-name>log-id</param-name>

<param-value>A102003</param-value>

</init-param>

</filter>

Example19-7showsthecodeyouwoulduseinsidethefiltertoaccesstheinitparameteranditsvalue.ThecodeinitializestheFilterConfigobjectinitsinitmethod,whichiscalledoncewhenthewebcontainercreatesaninstanceofthefilter.Thecodethengetsthevalueofthefilter'sinitparameterbycalling:

Stringid=config.getInitParameter("log-id");

MakesurethatthecodecheckswhetherthereturnvaluefromgetInitParameterisnullbeforethecodedoessomethingwiththatobject.

Example19-7.Accessinganinitparamvalueinafilter






publicclassLogFilterimplementsFilter{


privateLoggerlog;

//CreatesnewLogFilter

publicLogFilter(){}



//loadtheconfigurationforthisapplication'sloggers

//usingtheservletLog.propertiesfile

PropertyConfigurator.configure(config.getServletContext().

getRealPath("/")+

"WEB-INF/classes/servletLog.properties");

log=Logger.getLogger(LogFilter.class);

log.info("Loggerinstantiatedin"+getClass().getName());

}




Stringid=config.getInitParameter("log-id");

if(id==null)

id="unknown";

if(log!=null&&(requestinstanceofHttpServletRequest)){


log.info("Logid:"+id+":Requestreceivedfrom:"+

req.getRemoteHost()+"for"+req.getRequestURL());}


}//doFilter




log=null;

}

}

Hereishowthelogoutputappears:

INFO-Logid:A102003:Requestreceivedfrom:localhostforhttp://localhost:8080/

home/requestheaders

YoucanalsousetheFilterConfigobject'sgetInitParameterNamesmethodtogetalloftheinitparameternamesinajava.util.Enumerationobject.

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.1-Recipe19.4onmappingfilterstowebcomponents;Recipe19.6onblockingarequest;Recipe19.7onfilteringtheHttpServletResponse;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9onusingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.6OptionallyBlockingaRequestwithaFilter

Problem

Youwanttheoptiontoblockarequestwithafilter.

Solution

DonotcalltheFilterChainobject'sdoFilter()methodinsideofthefilter.Outputtheresponsetotheclientinsideofthefilter'sdoFilter()methodinstead.

Discussion

Afilterblocksarequestfromgettingtoawebcomponent,suchasaservlet,JSP,orHTMLpage,bynevercallingFilterChain.doFilter()insidethefilter'sowndoFilter()method.

TheBlockFilterclassinExample19-8attemptstoauthenticatetheuserbasedonarequestparameter.Iftheauthenticationfails,thefilterusestheresponseobjecttooutputaresponsetotheclient,andtherequestiseffectivelyblockedfromreachingtherequestedservlet.Afiltercanoutputthefinalresponsetotheclient,notjustinitiateitsfilteringtasks.

Example19-8.Afilteroptionallyblockstherequestandissuesaresponseitself






publicclassBlockFilterimplementsFilter{


/**CreatesnewBlockFilter*/

publicBlockFilter(){}



}


FilterChainchain)throwsIOException,ServletException{


booleanauthenticated=false;

PrintWriterout=null;

if(requestinstanceofHttpServletRequest){


Stringuser=req.getParameter("user");//gettheusername

authenticated=authenticateUser(user);//authenticatetheuser

}

if(authenticated){

//theyareauthenticated,sopassalongtherequest


else{

//havethefiltersendbacktheresponse


out=response.getWriter();

out.println(

"<html><head><title>AuthenticationResponse</title>");

out.println("</head><body>");

out.println("<h2>Sorryyourauthenticationattemptfailed</h2>");


}

}//doFilter




}

privatebooleanauthenticateUser(StringuserName){

//authenticatetheuserusingJNDIandadatabase,forinstance

//returnfalsefordemonstrationpurposes

returnfalse;

}//authenticateUser

}

Thecodeauthenticatestheuserbygettingthehypotheticalusernameas

arequestparameter.Thenameistheparameterforthefilter'sauthenticateUser()method,whichreturnsfalsetodemonstratethefilter'sresponsetotheclient.ThefilterusesthePrintWriterfromthejavax.servlet.ServletResponseobject,whichisaparametertothedoFilter()method.ThePrintWritersendsHTMLbacktotheclient.Figure19-1showstheresponseoutputinawebbrowser.

Figure19-1.TheHTMLpagereturnedbyablockingfilter

Ifyouregularlyusefilterstosendresponsestoaclient,considercreatingaJavaBeantocustomizetheresponse.StorethebeanclassinitspackagebeneathWEB-INF/classes,andusethebeaninsidethefilter.

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.1-Recipe19.4onmappingfilterstowebcomponents;Recipe19.5onconfiguringinitparametersforafilter;Recipe19.7onfilteringtheHTTPresponse;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9on

usingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.7FilteringtheHTTPResponse

Problem

Youwanttochangetheresponsewithafilterwhiletheclientrequestisenroutetotheservlet.

Solution

Changethejavax.servlet.ServletResponseinsidethefilter'sdoFilter()methodbywrappingtheresponsewithyourownobject.ThenpassthewrappedresponseasaparameterintotheFilterChain.doFilter()method.

Discussion

Herearethestepsforchangingaresponsewithafilterandawrapperclass:

1. CreateaJavaclassthatextendsjavax.servlet.http.HttpServletResponseWrapper.

Placethisclass,includingitspackage-relateddirectories,inWEB-INF/classes.

Usethewrapperclassinthefiltertowraptheresponseobject,whichisaparametertothefilter'sdoFilter()method.

Callthechain.doFilter()methodwiththewrappedresponseasaparameter.

Example19-9showstheJavaclassthatwewillusetowraptheresponseobject.

Ifyouarejustmakingasimpleresponsechange,youdonothavetogotothetroubleofusinganHttpServletResponseWrapperclass.Thiscodeinsideofafilter'smethodaddsaheadertotheresponse,thencallsthechain.doFilter()methodwiththealteredresponse:

if(responseinstanceofHttpServletResponse){

//casttoHttpServletResponsetocall

//addHeader

myHttpResponse=

((HttpServletResponse)response);

myHttpResponse.addHeader("WWW-Authenticate",

"BASICrealm=\"Admin\"");

chain.doFilter(request,response);}

TheResponseWrapperclasscontainstheskeletonofanewmethodnamedgetWebResource.Iwanttoshowthemechanicsofwrappingtheresponseinafilter,sohavekeptthiswrapperclassverysimple.

AlltheotherHttpServletResponse-derivedmethodcallsaredelegatedtothewrappedresponseobject,whichistheconvenienceofextendingHttpServletResponseWrapper.

Example19-9.AnHttpServletResponseWrapperclassforuseinafilter



importjavax.servlet.http.HttpServletResponseWrapper;


publicclassResponseWrapperextendsHttpServletResponseWrapper{

publicResponseWrapper(HttpServletResponseresponse){

super(response);

}

publicStringgetWebResource(StringresourceName){

//ImplementamethodtoreturnaStringrepresenting

//theoutputofawebresource

//SeeRecipe13.5

return"resource";//forthecompiler...

}//getWebResource

}

Example19-10showsthedoFilter()methodinsidethefilterthatusesthisResponseWrapperclass.

TheclassextendingHttpServletResponseWrappermustbeplacedbeneathWEB-INF/classes,withadirectorystructurethatmatchesitspackagename.

Example19-10.ThedoFilter()methodofafilterthatusesaHttpServletResponseWrapperclass



if(responseinstanceofHttpServletResponse){

chain.doFilter(request,

newResponseWrapper((HttpServletResponse)response));

}else{


}

}//doFilter

Thecodecallsthechain.doFilter()methodandpassesinthewrappedresponseasaparameter.Thewebresourceattheendofthechainhasaccesstothecustomizedresponseobjectandcancalltheadditionalmethodtheresponsewrapperclasshasdefined.AlltheothermethodcallsontheHttpServletResponseobject,suchasgetWriter()orgetOutputStream(),arepassedthroughtothewrappedresponseobject.

SeeAlso

Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoaltertherequest;Recipe19.1-Recipe19.4onmappingfilterstowebcomponents;Recipe19.5onconfiguringinitparametersforafilter;Recipe19.6onblockingarequest;Recipe19.8onusingfilterswithRequestDispatchers;Recipe19.9onusingfilterstocheckrequestparameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.8UsingFilterswithRequestDispatcherObjects

Problem

Youwanttoapplyafiltertoaservletwhoseoutputisincludedinanotherservlet.

Solution

Usethejavax.servlet.RequestDispatcherobjecttoincludetheservlet'soutput.Configurethefilterinweb.xmlwithadispatcherelementcontainingthecontent"INCLUDE"(servletAPIv2.4andaboveonly!).

Discussion

TheservletAPIv2.4introducedanewtwistforworkingwithRequestDispatchers.Usingthefilter-mappingelementinthedeploymentdescriptor,youcanspecifythatthefilterappliestoaservletthatispartofaRequestDispatcherincludeorforwardaction.

Example19-11showsaweb.xmlconfigurationforafilter.

Example19-11.ApplyingafiltertoaservletusingaRequestDispatcher



xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation=


http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"version="2.4">

<filter>



</filter>

<filter-mapping>



<dispatcher>REQUEST</dispatcher>

<dispatcher>INCLUDE</dispatcher>

</filter-mapping>

ThedispatcherelementsintheexampleconfigurationspecifythattheLogFilterappliestorequestsfortheservletpath/requestheaders,aswellastoanyRequestDispatchersthatincludetheoutputoftheservletpath/requestheaders.

Similarly,ifyouwanttoinitiateafilterwhenyouareusingaRequestDispatchertoforwardarequesttoanothercomponent,usetheFORWARDvaluewiththedispatcherelement,asin:

<filter-mapping>



<dispatcher>REQUEST</dispatcher>

<dispatcher>FORWARD</dispatcher>

</filter-mapping>

Example19-12showsaservlet'sdoGetmethodthatcreatesaRequestDispatcherspecifyingthepath/requestheaders.Thiscodeincludestheservletoutputrepresentedbythatpath.BecauseofExample19-11sconfigurationinweb.xml,however,thewebcontainerappliesthe

LogFilterbeforetheservletmappedtothe/requestheaderspathisexecuted.

Example19-12.Aservletincludesanotherservlet'soutput,triggeringafilter



/*Theoutputoftheservletatpath"/requestheaders"will

beincludedinthisservlet'soutput,butfirsttherequest

willpassthroughtheLogFilterbeforeitissenttothe

"/requestheaders"servlet*/

RequestDispatcherdispatch=request.getRequestDispatcher(

"/requestheaders");

dispatch.include(request,response);

}

Figure19-2illustratestheprocessoffiltersandRequestDispatchers.

Figure19-2.Alogfilterintervenesbetweenaservlet,includinganotherservlet'soutput

InFigure19-2,awebclientrequeststheservletatpath/home/servlet1,with/homerepresentingthecontextpath.Theservlet1componentusesaRequestDispatchertoincludetheoutputofservlet2.Basedonafilter-mappingelementinweb.xml,anyrequestsforservlet2involvingaRequestDispatcherincludeactionmustfirstpassthroughthelogfilter.Thisfilterisconfiguredwithafilterelementinweb.xmlwiththename"LogFilter"(Figure19-2doesnotshowthisconfiguration;seeExample19-11).

ThistypeofRequestDispatcherset-upisonlysupportedbyServletAPIv2.4andabove.

SeeAlso

Chapter6onincludingcontentusingRequestDispatchers;Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe11.11onusingafiltertomonitorsessionattributes;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.1-Recipe19.4onmappingfilterstowebcomponents;Recipe19.5onconfiguringinitparametersforafilter;Recipe19.6onblockingarequest;Recipe19.7onfilteringtheHTTPresponse;Recipe19.9onusingfilterstocheckrequest

parameters;Recipe19.10onusingfilterstodisallowrequestsfromcertainIPaddresses.

Recipe19.9CheckingFormParameterswithaFilter

Problem

Youwanttouseafiltertocheckthevaluesthatauserhasenteredintoaform.

Solution

UsethedeploymentdescriptortomapthefiltertotheservletorJSPthatisthetargetoftheform.

Discussion

FiltersofferanalternativetoJavaScriptandotherserver-sidelanguagesforcheckingwhethertheuserhasenteredvalidvaluesintoHTMLformfields.ThefilterinthisrecipeinitiatesabasiccheckoftherequestparameterstodetermineiftheyarenullortheemptyString.

Example19-13isaJSPthatcontainsanHTMLform.TheJSPincludessomeembeddedJSTLtagsthatfillinthetextfieldswithanycorrectvaluesiftheformisreturnedtotheuserforcorrections.Inmostcases,auserfillsinthevastmajorityofthefieldscorrectly,butmightmakeamistakeinoneortwoofthem.Youdonotwanttomakehimfilloutallofthefieldsagain.

Example19-13.AJSPcontainingaformforuserstofillout



<html>

<head>

<title>PersonalInformation</title>

</head>


<c:iftest="${!(emptyerrorMsg)}">

<fontcolor="red"><c:outvalue="${errorMsg}"/></font>

</c:if>

<h2>Pleaseenteryournameandemailaddress</h2>

<table>

<formaction="/home/thanks.jsp">

<tr><tdvalign="top">Firstname:</td>

<tdvalign="top">

<inputtype="text"name="first"size="15"value=

'<c:outvalue="${first}"/>'>

</td>

<tdvalign="top">Middleinitial:</td>

<tdvalign="top">

<inputtype="text"name="middle"size="2"value=

'<c:outvalue="${middle}"/>'>

</td>

</tr>

<tr>

<tdvalign="top">Lastname:</td>

<tdvalign="top">

<inputtype="text"name="last"size="20"value=

'<c:outvalue="${last}"/>'>

</td></tr>

<tr>

<tdvalign="top">Youremail:</td>

<tdvalign="top">

<inputtype="text"name="email"size="20"value=

'<c:outvalue="${email}"/>'>

</td></tr>

<tr><tdvalign="top"><inputtype="submit"value="Submit"></td>

<td></td></tr>

</form>

</table>

</body>

</html>

WhentheusersubmitsExample19-13,thebrowsersendstheforminformationtotheURLspecifiedintheformtag'sactionattribute:aJSPpagenamedthanks.jsp.ThedeploymentdescriptormapsthefilterinExample19-14totheURLthanks.jsp.Thefilterisdesignedtocheckthefields'valuestodetermineiftheuserleftanyofthemblankand,ifso,returntheusertotheform(namedform.jsp).

Makesuretodevelopallfilterswithaconstructorthatdoesnottakeanyarguments.

Example19-14.Thefilterthatchecksparametersvalues






publicclassCheckFilterimplementsFilter{


publicCheckFilter(){}



}



//Getalltheparameternamesassociatedwiththeformfields

Enumerationparams=request.getParameterNames();

booleanrejected=false;

//Cyclethrougheachoneoftheparameters;ifanyofthem

//areempty,callthe'reject'method

while(params.hasMoreElements()){

if(isEmpty(request.getParameter((String)params.

nextElement()))){

rejected=true;

reject(request,response);

}//if

}//while

//Passtherequesttoitsintendeddestination,ifeverything

//isokay

if(!rejected)


}//doFilter

privatebooleanisEmpty(Stringparam){

if(param==null||param.length()<1){

returntrue;

}

returnfalse;

}

privatevoidreject(ServletRequestrequest,ServletResponseresponse)

throwsIOException,ServletException{

//Createanerrormessage;storeitinarequestattribute

request.setAttribute("errorMsg",

"Pleasemakesuretoprovideavalidvalueforallofthetext"+

"fields.");

Enumerationparams=request.getParameterNames();

StringparamN=null;

//Createrequestattributesthattheform-relatedJSPwill

//usetofillintheformfieldsthathavealreadybeen

//filledoutcorrectly.Thentheuserdoesnothavetofill

//intheentireformalloveragain.

while(params.hasMoreElements()){

paramN=(String)params.nextElement();

request.setAttribute(

paramN,request.getParameter(paramN));

}

//UseaRequestDispatchertoreturntheusertotheformin

//ordertofillinthemissingvalues


getRequestDispatcher("/form.jsp");


}//reject




}

}

TheJavacommentsinExample19-14explainwhatisgoingoninthisfilter.Basically,theuserisreturnedtotheform,whichdisplaysanerrormessageifanyoftherequestparametersareempty.Example19-15showshowtheCheckFilterismappedinweb.xml.Iftheuserfillsintheformcorrectly,hisrequestissenttothethanks.jsppagewithoutinteruptionbythefilter.

Example19-15.TheCheckFilterisregisteredandmappedinweb.xml



<filter>

<filter-name>CheckFilter</filter-name>

<filter-class>com.jspservletcookbook.CheckFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>CheckFilter</filter-name>

<url-pattern>/thanks.jsp</url-pattern>

</filter-mapping>



Figure19-3showsanHTMLformthatwaspartiallyfilledoutandsubmitted.Thefiltersenttheformbacktotheuserwithamessage(inaredfont).

Figure19-3.AfilterforwardsanerrormessagetoaJSP

SeeAlso

Chapter6onincludingcontentusingRequestDispatchers;Recipe19.8onusingfilterswithRequestDispatchers;Recipe7.9onusingafiltertoreadrequestparametervalues;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.1-Recipe19.4onmappingfilterstowebcomponents;Recipe19.5onconfiguringinitparametersforafilter;Recipe19.6onblockingarequest;Recipe19.7onfilteringtheHTTPresponse.

Recipe19.10BlockingIPAddresseswithaFilter

Problem

YouwanttouseafilterthatcheckstheIPaddressassociatedwiththerequest.

Solution

UseafilterthatcallstheHttpServletRequest'sgetRemoteAddr()methodinsidethedoFilter()methodandblockstherequestbynotcallingchain.doFilter().

Discussion

Atypicaluseofafilterinawebapplicationistochecktherequesttomakesureit'sacceptable.Let'ssayyoursecuritydivisionhasdiscoveredthatacertainrangeofIPaddressesrepresentnastyclientsyouwanttorebuffthosefolkswitha"403Forbidden"HTTPresponse.

Example19-16blocksanyclientIPaddressbeginningwith"192.168."

Example19-16.AfilterforblockingacertainrangeofIPaddresses



importjava.util.StringTokenizer;



publicclassIPFilterimplementsFilter{


publicfinalstaticStringIP_RANGE="192.168";

publicIPFilter(){}



}


ServletResponseresponse,


Stringip=request.getRemoteAddr();

HttpServletResponsehttpResp=null;

if(responseinstanceofHttpServletResponse)

httpResp=(HttpServletResponse)response;

//BreakuptheIPaddressintochunksrepresentingeachbyte

StringTokenizertoke=newStringTokenizer(ip,".");

intdots=0;

Stringbyte1="";

Stringbyte2="";

Stringclient="";

//

while(toke.hasMoreTokens()){

++dots;

//Thistokenisthefirstnumberseriesorbyte

if(dots==1){

byte1=toke.nextToken();

}else{

//Thistokenisthesecondnumberseriesorbyte

byte2=toke.nextToken();

break;//onlyinterestedinfirsttwobytes

}

}//while

//PiecetogetherhalfoftheclientIPaddresssoitcanbe

//comparedwiththeforbiddenrangerepresentedby

//IPFilter.IP_RANGE

client=byte1+"."+byte2;

//iftheclientIPfitstheforbiddenrange...

if(IP_RANGE.equals(client)){

httpResp.sendError(HttpServletResponse.SC_FORBIDDEN,

"Thatmeansgoodbyeforever!");

}else{

//Clientisokay;sendthemontheirmerryway


}

}//doFilter




}

}

Thefilterobtainstheclient'sIPaddresswiththeServletRequest'sgetRemoteAddr()method.ThefilterthanparsesthereturnvaluetodetermineiftheIPaddressfallsintothe"192.168"range.IftheIPaddressdoesfallintothisrange,thenthecodecallstheHttpServletResponsesendError()methodwiththe"403Forbidden"typeHTTPstatuscode,asin:

httpResp.sendError(HttpServletResponse.SC_FORBIDDEN,

"Thatmeansgoodbyeforever!");

Thismethodcalleffectivelyshortcircuitstherequestbypreventingtheuserfromreachingtheiroriginaldestination.IftheIPaddressisacceptable,thecodecallschain.doFilter(),whichpassestherequestandresponseobjectsalongthefilterchain.Inthiscase,theapplicationdoesnotmapanyotherfilterstothanks.jsp,sothewebcontainerinvokesthatJSPpage.

Example19-17showsthemappingforthisfilterinweb.xml.ThefilterismappedtoallrequestswiththeURLmapping"/*."

Example19-17.ThemappingoftheIP-blockingfilter

<filter>

<filter-name>IPFilter</filter-name>

<filter-class>com.jspservletcookbook.IPFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>IPFilter</filter-name>


</filter-mapping>

Figure19-4showsthepagethewebbrowserwilldisplayiftheclientIPaddressisblocked.

Figure19-4.AfilteredoutIPaddressreceivesanHTTPStatus403message

SeeAlso

Chapter9onhandlingerrorsinwebapplications;Recipe19.8onusingfilterswithRequestDispatchers;Recipe18.3onusingafiltertoalterthenforwardtherequest;Recipe19.1-Recipe19.4onmappingfilterstowebcomponents;Recipe19.5onconfiguringinitparametersforafilter;Recipe19.7onfilteringtheHTTPresponse;Recipe19.9on

checkingformparameterswithafilter.

Chapter20.ManagingEmailinServletsandJSPs

Introduction

Recipe20.1.PlacingtheEmail-RelatedClassesonyourClasspath

Recipe20.2.SendingEmailfromaServlet

Recipe20.3.SendingEmailfromaServletUsingaJavaBean

Recipe20.4.AccessingEmailfromaServlet

Recipe20.5.AccessingEmailfromaServletUsingaJavaBean

Recipe20.6.HandlingAttachmentsfromanEmailReceivedinaServlet

Recipe20.7.AddingAttachmentstoanEmailinaServlet

Recipe20.8.ReadingaReceivedEmail'sHeadersfromaServlet

Introduction

ThischapterdescribeshowtomanageemailinyourservletsusingtheJavaMailandJavaBeansActivationFramework(JAF)APIs.JavaMailprovidesJavaclassesfordealingwithmostaspectsofcreating,sending,andaccessingemail.TheJAFisaseparateAPIforhandlingthedatatypesandMultipurposeInternetMailExtension(MIME)typesyoumayencounterwhengeneratingemail,suchasthemanydifferentkindsoffileattachments.BothoftheseAPIsareapartoftheJava2EnterpriseEdition(J2EE)platform.

JavaMailmodelsanemailsystemwithclassesthatrepresentmailsessions(thejavax.mail.Sessionclass),messagestores(thejavax.mail.Storeclass),folders(thejavax.mail.Folderclass,suchastheINBOXfolder),emailmessages(javax.mail.Message),andemailaddresses(thejavax.mail.internet.InternetAddressclass).Forexample,anemailmessageissimilartoaJavaBean,withsettermethodstobuildthevariousmessagecomponents(e.g.,setFrom(),setRecipients(),setSubject(),etc.).

Thefollowingrecipesshowhowtomanagebasicemailmessagingusingasingleservlet,aswellasmethodsforseparatingtheresponsibilityforemailingandhandlingHTTPrequestsintoJavaBeansandservlets.

Recipe20.1PlacingtheEmail-RelatedClassesonyourClasspath

Problem

Youwanttousethejavax.mailandrelatedJavapackagestohandleemailinaservlet.

Solution

DownloadtheZIPfilescontainingthemail.jarandactivation.jararchives.AddtheseJARfilestoashareddirectoryforJARfileswhosecontentsareloadedbythewebcontainer.Ifthisdirectorytypeisnotavailable,addthemail.jarandactivation.jarfilestotheWEB-INF/libdirectoryofyourwebapplication.

Discussion

IfyourclasspathforcompilingservletsalreadyincludestheJARfilesmadeavailablebyyourwebcontainer(suchastheJARfilesinTomcat'scommon/libdirectory),testifanemail-relatedservletsuchasExample20-1compilessuccessfully.Ifthecompilerreportsthatthepackagesjavax.mailandjavax.mail.internetdonotexist,youmustaddtheproperJARfilestoyourclasspath.

SeeRecipe4.3onusingAnttoincludeTomcat'sJARfilesinyourclasspath.

Downloadthemail.jarcomponentfromhttp://java.sun.com/products/javamail/.ThedownloadedfileisaZIParchivecontainingthemail.jararchive.Thisfileincludestherequiredpackagesforhandlingemailinaservlet,suchasjavax.mailandjavax.mail.internet.

ThendownloadtheJAFfromhttp://java.sun.com/products/javabeans/glasgow/jaf.html.Servletscanusetheseclasses,aspartofthejavax.activationpackage,tohandlethedifferentdatatypesthatcanbetransferredwithemailmessages,suchasfileattachments.

YoucanhandlebasicfileattachmentsusingtheJavaMailAPIalone(withoutJAF),asinRecipe20.5andRecipe20.6.SeeRecipe20.7forexamplesofhowtousesomeofthejavax.activationclassestoaddfileattachmentstoemails.

Addthemail.jarandactivation.jararchivestotheWEB-INF/libdirectoryofyourwebapplicationtomaketheJavaMailandJAFpackagesavailabletoaservlet.

SeeAlso

TheSunMicrosystemsJavaMailAPIpage:http://java.sun.com/products/javamail/;theJAFwebpage:http://java.sun.com/products/javabeans/glasgow/jaf.html;Recipe20.2onsendingemailfromaservlet;Recipe20.3onsendingemailusingaJavaBean;Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.7onaddingattachmentstoanemailmessage;Recipe20.8onreadinganemail'sheaders.

http://java.sun.com/products/javamail/default.htm

http://java.sun.com/products/javabeans/glasgow/jaf.html



Recipe20.2SendingEmailfromaServlet

Problem

Youwanttosendemailsfromaservlet.

Solution

Importthejavax.mailandjavax.mail.internetpackagesatthetopoftheservletsourcecode.CreateasendMessage()method(oramethodwithadifferentname)thatcanbecalledfromtheservletmethodsdoGet()ordoPost().

Discussion

ThesendMessage()methodinExample20-1usestheJavaMailAPItoconnectwithamailserver,constructanemailmessage,andthensendthatmessagetooneormorerecipients.Theservletobtainsthevariouscomponentsofanemailthetargetemailaddress,thesender'saddress,thesubjectfield,andtheemail'sbodycontentfromrequestparameters.Theservletcanhandleaformsubmittedbyaclientusingawebbrowser.

Theformtagmightlooklikethis:

<formmethod="POST"action=

"/home/servlet/com.jspservletcookbook.EmailServlet">

Example20-1callsthesendMessage()methodfromtheservicemethoddoPost().ThesendMessage()methodparameterscomprisethepartsofanemail:theSMTPserver,therecipientofthe

email(thevariableto),the"from"addressofthesender,theemailsubject,andtheemail'scontent.

Example20-1.Aservletsendsemailbasedonrequestparametervalues




importjava.util.Properties;

importjavax.mail.*;

importjavax.mail.internet.*;



publicclassEmailServletextendsHttpServlet{

//defaultvalueformailserveraddress,incasetheuser

//doesn'tprovideone

privatefinalstaticStringDEFAULT_SERVER="mail.attbi.com";




//obtainthevaluesforemailcomponentsfrom

//requestparameters

StringsmtpServ=request.getParameter("smtp");

if(smtpServ==null||smtpServ.equals(""))

smtpServ=DEFAULT_SERVER;

Stringfrom=request.getParameter("from");

Stringto=request.getParameter("to");

Stringsubject=request.getParameter("subject");

StringemailContent=request.getParameter("emailContent");



out.println(

"<html><head><title>Emailmessagesender</title></head><body>");

try{

sendMessage(smtpServ,to,from,subject,emailContent);

}catch(Exceptione){

thrownewServletException(e.getMessage());

}

out.println(

"<h2>Themessagewassentsuccessfully</h2>");


}//doPost

privatevoidsendMessage(StringsmtpServer,Stringto,Stringfrom,

Stringsubject,StringemailContent)throwsException{

Propertiesproperties=System.getProperties();

//populatethe'Properties'objectwiththemail

//serveraddress,sothatthedefault'Session'

//instancecanuseit.

properties.put("mail.smtp.host",smtpServer);

Sessionsession=Session.getDefaultInstance(properties);

MessagemailMsg=newMimeMessage(session);//anewemailmessage

InternetAddress[]addresses=null;

try{

if(to!=null){

//throws'AddressException'ifthe'to'emailaddress

//violatesRFC822syntax

addresses=InternetAddress.parse(to,false);

mailMsg.setRecipients(Message.RecipientType.TO,addresses);

}else{

thrownewMessagingException(

"Themailmessagerequiresa'To'address.");

}

if(from!=null){

mailMsg.setFrom(newInternetAddress(from));

}else{


"Themailmessagerequiresavalid'From'address.");

}

if(subject!=null)

mailMsg.setSubject(subject);

if(emailContent!=null)

mailMsg.setText(emailContent);

//Finally,sendthemailmessage;throwsa'SendFailedException'

//ifanyofthemessage'srecipientshaveaninvalidaddress

Transport.send(mailMsg);

}catch(Exceptionexc){

throwexc;

}

}//sendMessage




//doGet()callsdoPost()...


}//doGet

}//EmailServlet

Theservletinteractswithamailserverinthefollowingmanner:

1. Thecodecreatesajavax.mail.Sessionobject,whichcontainsvariousdefaultsandpropertyvalues(suchasmail.smtp.host)thattheotherJavaMailobjectswilluse.YoucanshareasingleSessionobjectinanapplication.

ThecodecreatesaMimeMessageobject(passingintheSessionasaconstructorparameter).

TheservletthenpopulatestheMimeMessagewithanemail'svariouscomponents,suchasthe"to"and"from"emailaddresses,theemailsubject,aswellasthemessagecontent.

Thecodesendstheemailusingthejavax.mail.Transportstaticsend()method.

SeeAlso

TheSunMicrosystemsJavaMailAPIpage:http://java.sun.com/products/javamail/;Recipe20.1onaddingJavaMail-relatedJARstoyourwebapplication;Recipe20.3onsendingemailusingaJavaBean;Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.7onaddingattachmentstoanemailmessage;Recipe20.8onreadinganemail'sheaders.


Recipe20.3SendingEmailfromaServletUsingaJavaBean

Problem

YouwanttouseaJavaBeanorhelperclasstosendemailfromaservlet.

Solution

DevelopaJavaclassthatimplementsasendMessage()method(justanameIgaveit)toconstructanemailandsendit.StorethenewclassintheWEB-INF/classesfolderofthewebapplication,includingtheclass'spackage-relatedfolders.

Discussion

YoumaychoosetoseparatetheresponsibilitiesofhandlingHTTPrequestsandmanagingemailbyencapsulatingthesetasksinseparateclasses.AJavaBeanthatprovidestheessentialfunctionofsendingemailfitsthebillhere.

Recipe20.5andRecipe20.6showJavaBeansthatareusedtoaccessemailandhandleattachments.Abeanthatdoeseverythingemail-relatedgrowsfairlylargeinsize,sodevelopersmustmakeadesigndecisionaboutwhethertoseparatethesetasksintodifferentJavaBeans(orutilityclasses)thatcanbeusedfromservlets.

CreatethebeanandstoreitintheWEB-INF/classesfolder.Example20-

3showsthedoGet()methodofanHttpServletusingaJavaBeantosendanemail.Example20-2showsthebeanclassitself.ThedifferencebetweenthesendMessage()methodofExample20-1andtheoneinExample20-2isinthewaythebeanreceivesthevariousemailparts,suchastherecipient'semailaddress.Thebeanstoresthesepartsaspropertiesandusessettermethodstoprovidethepropertyvalues.

Ontheotherhand,Example20-1usesrequestparametersandmethodargumentstoprovidethesevalues.

Example20-2.AJavaBeanusedtosendemail





importjavax.mail.*;


publicclassEmailBean{

publicEmailBean(){}

//setdefaults

privatefinalstaticStringDEFAULT_CONTENT="Unknowncontent";

privatefinalstaticStringDEFAULT_SUBJECT="Unknownsubject";

privatestaticStringDEFAULT_SERVER=null;

privatestaticStringDEFAULT_TO=null;

privatestaticStringDEFAULT_FROM=null;

static{

//setMaildefaultsbasedonapropertiesfile

java.util.ResourceBundlebundle=

java.util.ResourceBundle.

getBundle("com.jspservletcookbook.mailDefaults");

DEFAULT_SERVER=bundle.getString("DEFAULT_SERVER");

DEFAULT_TO=bundle.getString("DEFAULT_TO");

DEFAULT_FROM=bundle.getString("DEFAULT_FROM");

}//static

//JavaBeanproperties

privateStringsmtpHost;

privateStringto;

privateStringfrom;

privateStringcontent;

privateStringsubject;

publicvoidsendMessage()throwsException{




//instancecanuseit.

properties.put("mail.smtp.host",smtpHost);




try{

if(to!=null){





}else{



}

if(from!=null){


}else{



}

if(subject!=null)


if(content!=null)

mailMsg.setText(content);


//ifanyofthemessage'srecipientshaveaninvalidaddress



throwexc;

}

}//sendMessage

//Thesettermethodsareallthesamestructure,

//sowe'rejustshowingtwo

publicvoidsetSmtpHost(Stringhost){

if(check(host)){

this.smtpHost=host;

}else{

this.smtpHost=DEFAULT_SERVER;

}

}//setSmtpHost

publicvoidsetTo(Stringto){

if(check(to)){

this.to=to;

}else{

this.to=DEFAULT_TO;

}

}//setTo

/*--Notshown:'setter'methodscontinuewithexactlythesamestructurefor

'from','subject',and'content'--*/

privatebooleancheck(Stringvalue){

if(value==null||value.equals(""))

returnfalse;

returntrue;

}//check

}

Example20-3usesthejava.util.ResourceBundleclasstosetdefaultpropertyvaluesforvariablessuchasthenameoftheserver.ThemailDefaults.propertiesfileisstoredinWEB-INF/classes/com/jspservletcookbook.Hereisanexampleofthepropertiesfile'scontents:

DEFAULT_SERVER=smtp.comcast.net

[email protected]

[email protected]

Thebeanallowsthesettingofthevariousemailpartswiththefollowingmethods(Example20-3doesnotshowallofthem):setSmtpHost(),setTo(),setFrom(),setSubject(),andsetContent().

TheservletinExample20-3createsaninstanceofanEmailBean,setsthevariouspartsoftheemailmessage,thencallsthesendMessage()method.Example20-3showsonlythedoGet()method.Theservlet'sdoPost()methodcouldcalldoGet()asin:doGet(request,response).

Example20-3.AservletusestheJavaBeantosendemail






out.println(


EmailBeanemailer=newEmailBean();

emailer.setSmtpHost("mail.attbi.com");

emailer.setTo("[email protected]");

emailer.setFrom("[email protected]");

emailer.setSubject("Thisisnotspam!");

emailer.setContent("PleasecallASAP.");

try{

emailer.sendMessage();

}catch(Exceptione){thrownewServletException(e);}


}//doGet

ThebeanitselfthrowsMessagingExceptionsif,forinstance,the"to"emailaddressthattheuserprovidesisinaninvalidformat.Thebeanrethrowsanyexceptionsthatitcatcheswhilebuildingandsendingtheemail.

SeeAlso

Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.7onaddingattachmentstoanemailmessage;Recipe20.8onreadinganemail'sheaders.

Recipe20.4AccessingEmailfromaServlet

Problem

Youwanttoaccessanddisplaythecontentofemailinaservlet.

Solution

UsetheJavaMailAPIandamethodinsidetheservlettohandleanddisplaythevaluesofemailmessages.

Discussion

FetchingemailmessagesusingJavaMailandaservletisastraightforwardprocess:

1. Importthejavax.mailandjavax.mail.internetpackagesatthetopoftheservletsourcecode.

Insidetheservlet'smail-fetchingmethod,createajavax.mail.Sessionobjecttohandlethismailsession.

Getamessagestoreobject(ajavax.mail.Store)fromthesessiontorepresentthePOP3mailaccount.

ConnecttotheStoreusingtheconnect(Stringhost,Stringuser,Stringpassword)methodoftheStoreobject(thereareoverloadedversionsofthismethod).TheStoreisdesignedtoauthenticateauserandconnectwithamailserver.

AccesstheINBOXfolderfromthemessagestore.

ObtainanymessagesthatfoldercontainsasaMessage[]type,thendowhateveryouwantwitheachmessage,iteratingthroughthearray.

Example20-4fetchesemailmessagesbycallingitshandleMessages()methodinthedoGet()servicemethod.

Example20-4.Aservletthatfetchesemailmessages





importjavax.mail.*;




publicclassMailAccessorextendsHttpServlet{







out.println("<html><head><title>EmailReader</title></head><body>");

//Thismethodaccessesanyemailanddisplaysthecontents

handleMessages(request,out);


}//doGet

privatevoidhandleMessages(HttpServletRequestrequest,

PrintWriterout)throwsIOException,ServletException{

//ObtainuserauthenticationinformationforaPOPserver,

//usedtoaccessemail.Thisinformationisstoredina

//HttpSessionobject

HttpSessionhttpSession=request.getSession();

Stringuser=(String)httpSession.getAttribute("user");

Stringpassword=(String)httpSession.getAttribute("pass");

StringpopAddr=(String)httpSession.getAttribute("pop");

StorepopStore=null;

Folderfolder=null;

if(!check(popAddr))

popAddr=MailAccessor.DEFAULT_SERVER;

try{

//basiccheckfornulloremptyuserandpassword

if((!check(user))||(!check(password)))


"Avalidusernameandpasswordisrequired.");


//Obtaindefault'Session'forthisinteractionwith

//amailserver


//Obtainamessagestore(i.e.,aPOP3emailaccount,from

//theSessionobject

popStore=session.getStore("pop3");

//connecttothestorewithauthenticationinformation

popStore.connect(popAddr,user,password);

//GettheINBOXfolder,openit,andretireveanyemails

folder=popStore.getFolder("INBOX");

if(!folder.exists())


"An'INBOX'folderdoesnotexistfortheuser.");

folder.open(Folder.READ_ONLY);

Message[]messages=folder.getMessages();

intmsgLen=messages.length;

if(msgLen==0){

out.println(

"<h2>TheINBOXfolderdoesn'tcontainanyemail"+

"messages.</h2>");}

//foreachretrievedmessage,usedisplayMessagemethodto

//displaythemailmessage

for(inti=0;i<msgLen;i++){

displayMessage(messages[i],out);

out.println("<br/><br/>");

}


out.println(

"<h2>Sorry,anerroroccurredwhileaccessingtheemail"+

"messages.</h2>");

out.println(exc.toString());

}finally{

try{

//closethefolderandthestoreinthefinallyblock

//if'true'parameter,anydeletedmessageswillbeexpunged

//fromtheFolder

if(folder!=null)

folder.close(false);

if(popStore!=null)

popStore.close();


}

}//printMessages

privatevoiddisplayMessage(Messagemsg,PrintWriterout)

throwsMessagingException,IOException{

if(msg!=null&&msg.getContent()instanceofString){

if(msg.getFrom()[0]instanceofInternetAddress){

out.println(

"Messagereceivedfrom:"+

((InternetAddress)msg.getFrom()[0]).getAddress()+

"<br/>");

}

out.println("Messagecontenttype:"+msg.getContentType()+

"<br/>");

out.println("Messagebodycontent:"+

(String)msg.getContent());

}else{

out.println(

"<h2>Thereceivedemailmessagewasnotofatext"+

"contenttype.</h2>");

}//outerif

}//displayMessage



returnfalse;

returntrue;

}//check

}

ThedisplayMessage()methoddisplayseachmessage's"from"address,themessage'scontenttype(i.e.,theMIMEtypeasintext/plain),andtheemail'scontent.YoucangettheStringfromatypicalemailmessagethatcontainsjustheadersandthetextmessagebycallingMessage.getContent().Gettingthe"from"addressisalittletrickier:

out.println("Messagereceivedfrom:"+

((InternetAddress)msg.getFrom()[0]).getAddress()+"<br/>");

TheMessage.getFrom()methodreturnsanarrayofjavax.mail.Addressobjects.Thiscodeisdesignedtoaccessthefirstemailaddress,sinceanemailistypicallysentbyonepartytoitsrecipient(notincludingthosemaliciousspammers,ofcourse).

Thecodeaccessesthefirstarraymember,caststhereturnvaluetoajavax.mail.InternetAddress,thencallsgetAddress()onthatobject,whichreturnstheStringemailaddress.

Figure20-1showstheservlet'sreturnvalueinabrowserwindow.Sincetheservletreceivesitsemailauthenticationinformationfromsession

attributes,thefirstrequesttargetsaJSP,whichsetsthesessionattributes.ThentheJSPforwardstherequesttotheMailAccessorservlet.Theservletdisplayseachreceivedemailseparatedbytwolinebreaks.Inotherwords,theinformationtheservletdisplaysabouteachemailincludeswhosenttheemail,themail'scontenttype,andthecontentofthemessageitself.

Figure20-1.Aservletfetchesanddisplaystwoemailmessages

SeeAlso

Chapter16onsettingsessionattributes;Chapter25onaccessingajavax.mail.SessionJNDIobjectonBEAWebLogic;SunMicrosystem'sJavaMailAPIpage:http://java.sun.com/products/javamail/;Recipe20.1onaddingJavaMail-relatedJARstoyourwebapplication;Recipe20.2onsendingemailusingaservlet;Recipe20.3onsendingemailusingaJavaBean;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.7onaddingattachmentstoanemailmessage;Recipe20.8onreadinganemail'sheaders.


Recipe20.5AccessingEmailfromaServletUsingaJavaBean

Problem

YouwanttouseaJavaBeanorhelperclasstoaccessanddisplayemailmessages.

Solution

AddthehandleMessages()anddisplayMessage()methodsfromExample20-4totheJavaBeanclassdefinedinExample20-2.ThenusetheJavaBeanfromaservlet'sdoGet()ordoPost()method.

Discussion

WhenwelastencounteredtheEmailBeaninExample20-2itcontainedasendMessage()method,alongwithseveralproperty"setter"methods(suchassetSmtpHost(Stringhost)).IfyouaddthehandleMessages()anddisplayMessage()methodsfromExample20-4tothissameclass,youcanusetheJavaBeantobothsendandaccessemail.

ThiscodeinhandleMessages()fromExample20-4needstobechangedtoincludetheEmailBeanclassname:

//staticreferencetoaconstantvalue

if(!check(popAddr))

popAddr=EmailBean.DEFAULT_SERVER;

However,theEmailBeanclasswillhavegrownquitelargeasaresultofaddingthetwomethods,soyoumightcreatetwoJavaBeansoneforsendingmailandanotherforaccessingit.Example20-5createsandusesaninstanceofaspecialemailJavaBean.YoumuststorethebeanclassintheWEB-INF/classesdirectoryorinaJARfileinWEB-INF/lib.

Example20-6alsoshowsaJavaBeanthatdefineshandleMessages()anddisplayMessage()fordealingwithemailattachments.

Example20-5.AservletusesaJavaBeantoaccessemailmessages





out.println(


EmailBeanemailer=newEmailBean();


emailer.handleMessages(request,out);


}//doGet

SeeAlso

SunMicrosystem'sJavaMailAPIpage:http://java.sun.com/products/javamail/;Recipe20.1onaddingJavaMail-relatedJARstoyourwebapplication;Recipe20.2onsendingemailfromaservlet;Recipe20.3onsendingemailusingaJavaBean;Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.7onaddingattachmentstoanemailmessage;Recipe20.8onreadinganemail'sheaders.


Recipe20.6HandlingAttachmentsfromanEmailReceivedinaServlet

Problem

Youwanttoreadanemailmessageandsaveanyattachmentsfromaservlet.

Solution

UsetheJavaMailAPIandaspecialJavaBeantosavetheInputStreamsfromattachedfilestoaspecifiedfolder.

Discussion

AccessingemailusuallyinvolvesauthenticatingauserwithaPOPaccount,thenconnectingwiththemailserveranddownloadinganyemailmessages.Example20-6usestheSession,Store,Folder,andMessageclassesfromtheJavaMailAPItodownloadanarrayofMessagesfromaparticularuser'semailaccount.However,theservletinRecipe20.4wasdesignedtodealonlywithMessageswhosecontentwasoftypeString(thereturnvalueoftheMessage.getContent()method).

IftheMessage'scontentisoftypeMultipart,thentheprocessofhandlingattachmentsmirrorsthepeelingofanonionmorecodeisinvolved.Example20-6separatestheemail-relatedcodeintoaJavaBeanthatcanbeusedfromaservlet.Thebean'sdisplayMessage()methodteststhecontentofeachMessage.IfthecontentisoftypeMultipart,thenthecodeexamineseachcontained

BodyPart.

PictureaMultipartmessagetypeasacontainer.Thecontainer'sheadersarelikeanyotheremailmessage'sheaders(butwithdifferentvalues).ThecontainerenclosesBodyParts,whicharelikemessagesinsideofmessages.SomeBodyPartsrepresentthetextmessageaccompanyingaMultipartemailmessage.OtherBodyPartsrepresenttheattachedfiles,suchasaMicrosoftWordfileorJPEGimage.

IftheBodyPart'scontentisaString,thenthebeandisplaysthetextmessage.Otherwise,thebeanassumestheBodyPartisanattachedfile;itsavesthefiletoaspecialattachmentsfolder.You'reprobablyalreadyfamiliarwiththehandleMessages()code,soyoucanskiptothedisplayMessage()method,whichdealswithsavinganyfileattachments.

Example20-6.AJavaBeanthathandlesattachmentsanddeliversabrowsermessage


importjava.io.*;


importjavax.mail.*;




publicclassAttachBean{

/*NOTSHOWN:privatebeanfields(or,properties);defaultvariables;

andthesendMessagemethod

SeeExample20-2*/

publicAttachBean(){}



/*gettheuserandpasswordinformationforaPOP

accountfromanHttpSessionobject*/





StorepopStore=null;

Folderfolder=null;

if(!check(popAddr))

popAddr=AttachBean.DEFAULT_SERVER;

try{



"Avalidusernameandpasswordisrequiredtocheckemail.");












if(msgLen==0)

out.println(

"<h2>TheINBOXfolderdoesnotyetcontainany"+

"emailmessages.</h2>");




}//for


out.println(

"<h2>Sorry,anerroroccurredwhileaccessing"+

"theemailmessages.</h2>");


}finally{

try{

if(folder!=null)


if(popStore!=null)

popStore.close();


}

}//handleMessages



if(msg!=null){

/*getthecontentofthemessage;themessagecould

beanemailwithoutattachments,oranemail

withattachments.ThemethodgetContent()willreturnan

instanceof'Multipart'ifthemsghasattachments*/

Objecto=msg.getContent();

if(oinstanceofString){

//justdisplaysomeinfoaboutthemessagecontent

handleStringMessage(msg,(String)o,out);

}elseif(oinstanceofMultipart){

//savetheattachment(s)toafolder

Multipartmpart=(Multipart)o;

Partpart=null;

Filefile=null;

FileOutputStreamstream=null;

InputStreaminput=null;

StringfileName="";

//eachMultipartismadeupof'BodyParts'that

//areoftype'Part'

for(inti=0;i<mpart.getCount();i++){

part=mpart.getBodyPart(i);

ObjectpartContent=part.getContent();

if(partContentinstanceofString){

handleStringMessage(msg,(String)partContent,

out);

}else{//handleasafileattachment

fileName=part.getFileName();

if(!check(fileName)){//defaultfilename

fileName="file"+

newjava.util.Date().getTime();}

//writetheattachment'sInputStreamtoafile

file=newFile(attachFolder+

System.getProperty("file.separator")+fileName);

stream=newFileOutputstream(file);

input=part.getInputStream();

intch;

while((ch=input.read())!=-1){

stream.write(ch);}

input.close();

out.println(

"Handledattachmentnamed:"+

fileName+"<br/><br/>");

}//if

}//for

}//elseifinstanceofmultipart

}else{

out.println(

"<h2>Thereceivedemailmessagereturnednull.</h2>");

}//ifmsg!=null

}//displayMessage

privatevoidhandleStringMessage(Partpart,StringemailContent,

PrintWriterout)throwsMessagingException{

if(partinstanceofMessage){

Messagemsg=(Message)part;


out.println("Messagereceivedfrom:"+

((InternetAddress)msg.getFrom()[0]).getAddress()+

"<br/>");

}

out.println(

"Messagecontenttype:"+msg.getContentType()+

"<br/>");

out.println("Messagecontent:"+emailContent+"<br/>");

}

}



returnfalse;

returntrue;

}//check

/*NOTSHOWN:various'setter'methodsforthebean'sproperties

SeeExample20-2*/

}//AttachBean

OncethedisplayMessage()codeidentifiesaBodyPartasanattachedfile,itreceivesthebytesthatrepresentthefileasanInputStream.ABodyPartimplementsthePartinterface,which

definesthemethodgetInputStream().ThecodesavesthefileusingtheInputStreamandthejava.io.FileOutputStreamclass.

Example20-7showsthedoGet()methodofaservletusingcom.jspservletcookbook.AttachBean.

Example20-7.Aservlet'sdoGet()methodusesaJavaBeantodealwithemailattachments






out.println(


AttachBeanemailer=newAttachBean();


emailer.setAttachFolder(getServletContext().getRealPath("/")+"attachments");

emailer.handleMessages(request,out);


}//doGet

Figure20-2showsthemessagesthattheservlet(usingtheJavaBean)displaysinabrowser.Thefirstemailisasimpletextmessagewithoutattachments.Thesecondemailcontainstwoattachments;itsMIMEtypeismultipart/mixed.

Figure20-2.Aservletdisplaysinformationaboutreceivedattachmentsandmessages

SeeAlso

SunMicrosystem'sJavaMailAPIpage:http://java.sun.com/products/javamail/;Recipe20.1onaddingJavaMail-relatedJARstoyourwebapplication;Recipe20.2onsendingemailfromaservlet;Recipe20.3onsendingemailusingaJavaBean;Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.7onaddingattachmentstoanemailmessage;Recipe20.8onreadinganemail'sheaders.


Recipe20.7AddingAttachmentstoanEmailinaServlet

Problem

Youwanttobuildanemailmessagewithattachmentsinaservlet.

Solution

UsetheJavaMailAPIforbasicemailmessaging,andthetheJavaBeansActivationFramework(JAF)togeneratethefileattachments.

Discussion

TheJAFclassesprovidefine-grainedcontroloversettingupafileattachmentforanemailmessage.

IfyouareusingboththeJavaMailAPIandtheJAF,makesuretoimportthepackagesinyourservletclass:

importjavax.activation.*;

importjavax.mail.*;


//classdefinitioncontinues

ThesendMessage()methodinExample20-8createsanewemailmessage(specifically,anewjavax.mail.internet.MimeMessage),addsitstextmessage,andinsertsafileattachmentinsidethemessage.ThemethodthensendsthemessageusingthecodeyoumayhaveseeninRecipe20.2andRecipe20.3:


Toaccomplishthis,thecodecreatesacontainer(ajavax.mail.Multipartobject)andtwojavax.mail.BodyPartsthatmakeupthethecontainer.ThefirstBodyPartisatextmessage(usedusuallytodescribethefileattachmenttotheuser),whilethesecondBodyPartisthefileattachment(inthiscase,aMicrosoftWordfile).ThenthecodesetsthecontentoftheMimeMessagetotheMultipart.Inanutshell,theMimeMessage(anemailmessage)containsaMultipart,whichitselfiscomposedoftwoBodyParts:theemail'stextmessageandanattachedfile.

IfyouwanttolookattheheadersofaMimeMessagethatcontainsattachments,callthegetAllHeaders()methodontheMimeMessage.SeeRecipe20.8fordetails.

Example20-8.Makingemailattachmentinaservlets


importjava.io.*;


importjavax.activation.*;

importjavax.mail.*;




publicclassEmailAttachServletextendsHttpServlet{

//defaultvalueformailserveraddress,incasetheuser

//doesn'tprovideone







out.println(


StringsmtpServ=request.getParameter("smtp");

if(smtpServ==null||smtpServ.equals(""))

smtpServ=DEFAULT_SERVER;




try{

sendMessage(smtpServ,to,from,subject);

}catch(Exceptione){


}

out.println(

"<H2>Yourattachmenthasbeensent.</H2>");


}//doPost





}//doGet

privatevoidsendMessage(StringsmtpServ,Stringto,Stringfrom,

Stringsubject)throwsException{

Multipartmultipart=null;

BodyPartbpart1=null;

BodyPartbpart2=null;




//instancecanuseit.

properties.put("mail.smtp.host",smtpServ);




try{

if(to!=null){





}else{



}

if(from!=null){


}else{



}

if(subject!=null)


//Thisemailmessage'scontentisa'Multipart'type

//TheMIMEtypeforthemessage'scontentis'multipart/mixed'

multipart=newMimeMultipart();

//Thetextpartofthismultipartemailmessage

bpart1=newMimeBodyPart();

StringtextPart=

"Hello,justthoughtyou'dbeinterestedinthisWordfile.";

//createtheDataHandlerobjectforthetextpart

DataHandlerdata=newDataHandler(textPart,"text/plain");

//setthetextBodyPart'sDataHandler

bpart1.setDataHandler(data);

//addthetextBodyParttotheMultipartcontainer

multipart.addBodyPart(bpart1);

//createtheBodyPartthatrepresentstheattachedWordfile

bpart2=newMimeBodyPart();

//createtheDataHandlerthatpointstoaFile

FileDataSourcefds=newFileDataSource(newFile(

"h:/book/chapters/chap1/chap1.doc"));

//Makesurethattheattachedfileishandledas

//theappropriateMIMEtype:application/mswordhere

MimetypesFileTypeMapftm=newMimetypesFileTypeMap();

//thesyntaxhereistheMIMEtypefollowedby

//spaceseparatedextensions

ftm.addMimeTypes("application/msworddocDOC");

fds.setFileTypeMap(ftm);

//TheDataHandlerisinstantiatedwiththe

//FileDataSourcewejustcreated

DataHandlerfileData=newDataHandler(fds);

//theBodyPartwillcontainthewordprocessingfile

bpart2.setDataHandler(fileData);

//addthesecondBodyPart,theonecontainingtheattachment,to

//theMultipartobject

multipart.addBodyPart(bpart2);

//finally,setthecontentoftheMimeMessagetothe

//Multipartobject

mailMsg.setContent(multipart);

//sendthemailmessage;throwsa'SendFailedException'

//ifanyofthemessage'srecipientshaveaninvalidadress



throwexc;

}//try

}//sendMessage

}//EmailAttachServlet

ThecommentsinExample20-8explainwhathappenswhenyouusethejavax.activationclassestocreateafileattachmentoftheintendedMIMEtype.Themostconfusingpartiscreatingajavax.activation.FileDataSourcethatpointstothefilethatyouwanttoattachtotheemailmessage.ThecodeusestheFileDataSourcetoinstantiatethejavax.activation.DataHandler,whichisresponsibleforthecontentofthefileattachment.

//createtheDataHandlerthatpointstoaFile

FileDataSourcefds=newFileDataSource(newFile(

"h:/book/chapters/chap1/chap1.doc"));

MakesurethattheMimeMessageidentifiestheattachedfileasaMIMEtypeofapplication/msword,sothattheuser'semailapplicationcantrytohandletheattachmentasaMicrosoftWordfile.SettheFileTypeMapoftheFileDataSourcewiththefollowingcode:

//Makesurethattheattachedfileishandledas

//theappropriateMIMEtype:application/mswordhere

MimetypesFileTypeMapftm=newMimetypesFileTypeMap();

//thesyntaxhereistheMIMEtypefollowedby

//spaceseparatedextensions

ftm.addMimeTypes("application/msworddocDOC");

fds.setFileTypeMap(ftm);

AMimetypesFileTypeMapisaclassthatassociatesMIMEtypes(likeapplication/msword)withfileextensionssuchas.doc.

MakesureyouassociatethecorrectMIMEtypewiththefilethatyouaresendingasanattachment,sinceyouexplicitlymakethisassociationinthecode.Seehttp://java.sun.com/j2ee/1.4/docs/api/javax/activation/MimetypesFileTypeMap.htmlforfurtherdetails.

http://java.sun.com/j2ee/1.4/docs/api/javax/activation/MimetypesFileTypeMap.html

Thenthecodeperformsthefollowingsteps:

1. CreatesaDataHandlerbypassingthisFileDataSourceinasaconstructorparameter.

SetsthecontentoftheBodyPartwiththatDataHandler.

AddstheBodyParttotheMultipartobject(whichinturnrepresentsthecontentoftheemailmessage).

SeeAlso

SunMicrosystem'sJavaMailAPIpage:http://java.sun.com/products/javamail/;theJAFwebpage:http://java.sun.com/products/javabeans/glasgow/jaf.html;Recipe20.1onaddingJavaMail-relatedJARstoyourwebapplication;Recipe20.2onsendingemailfromaservlet;Recipe20.3onsendingemailusingaJavaBean;Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.8onreadinganemail'sheaders.



Recipe20.8ReadingaReceivedEmail'sHeadersfromaServlet

Problem

Youwanttoreadtheheadersfromanemailinaservlet.

Solution

UsetheJavaMailAPItoaccesseachemailmessage.CallthegetAllHeaders()methodofthePartinterface,theniteratethroughtheEnumerationreturnvaluetogetthenameandvalueofeachheader.

Discussion

Anadvancedemailprogram,suchasaspamfilter,isdesignedtoexamineanemail'sheaders,notjustitsmessageandfileattachments.

Aheaderiscomposedofaname,acoloncharacter(:),andavalue.Theheadersprovidedetailsabouttheemailmessage,suchaswhosentthemessageandthemailserver(s)thathandledthemessageduringitsnetworktravels.Anexampleheaderis:

To:<[email protected]>

TheJavaMailAPImakesiteasytolistanemail'sheaders.TheMessageobjecthasagetAllHeaders()method(viathePartinterfacethattheMessageclassimplements).Thismethodreturnsajava.util.Enumeration,holdingacollectionof

javax.mail.Headerobjects.TogettheheadernameandvaluefromtheseHeaderobjects,justcalltheirgetName()andgetValue()methods.

ThePartinterfacealsohasagetHeader(StringheaderName)methodthatyoucanusetoobtainthevalueforaparticularheader.ThismethodreturnsaStringarraycontainingthevalue(s)fortheheaderofthatname.

Example20-9showsthesameservletfromRecipe20.4,revisedtolistboththemessagecontentsandtheheadervalues.Theheader-relatedcodeappearsinthedisplayMessage()method.

Example20-9.Aservletdisplaysemailheadernamesandvalues






importjavax.mail.*;




publicclassHeaderAccessorextendsHttpServlet{







out.println("<html><head><title>EmailReader</title></head><body>");

handleMessages(request,out);


}//doGet







StorepopStore=null;

Folderfolder=null;

if(!check(popAddr))

popAddr=HeaderAccessor.DEFAULT_SERVER;

try{



"Avalidusernameandpasswordisrequiredtocheckemail.");












if(msgLen==0)

out.println(

"<h2>TheINBOXfolderdoesnotyetcontainany"+





}//for


out.println(

"<h2>Sorry,anerroroccurredwhileaccessingthe"+



}finally{

try{

if(folder!=null)


if(popStore!=null)

popStore.close();


}

}//handleMessages



if(msg!=null&&msg.getContent()instanceofString){


out.println(

"Messagereceivedfrom:"+

((InternetAddress)msg.getFrom()[0]).getAddress()+"<br/>");

}

out.println("Messagecontenttype:"+msg.getContentType()+

"<br/>");

out.println(

"Messagebodycontent:"+(String)msg.getContent());

//Listeachoftheemailheadersusingaultag

out.println("<ul>");

Headerhead=null;

Enumerationheaders=msg.getAllHeaders();

while(headers.hasMoreElements()){

head=(Header)headers.nextElement();

out.println(

"<li>"+head.getName()+":"+head.getValue()+"</li>");

}//while

out.println("</ul>");

}else{

out.println(

"<h2>Thereceivedemailmessagewasnot"+

"atextcontenttype.</h2>");

}

}//displayMessage



returnfalse;

returntrue;

}

}

Figure20-3showsthebrowserdisplayoftheservletinExample20-9.Eachoftheheadersisprecededbyabulletcharacter,followedbytheheadername,acolon,andtheheadervalue.

Figure20-3.Aservletaccessesanemailanddisplaysitsheaders

SeeAlso

SunMicrosystem'sJavaMailAPIpage:http://java.sun.com/products/javamail/;Recipe20.1onaddingJavaMail-relatedJARstoyourwebapplication;Recipe20.2onsendingemailfromaservlet;Recipe20.3onsendingemailusingaJavaBean;Recipe20.4coveringhowtoaccessemailinaservlet;Recipe20.5onaccessingemailwithaJavaBean;Recipe20.6onhandlingattachmentsinaservlet;Recipe20.7onaddingattachmentstoanemailmessage.


Chapter21.AccessingDatabasesIntroduction

Recipe21.1.AccessingaDatabasefromaServletWithoutDataSource

Recipe21.2.ConfiguringaDataSourceinTomcat

Recipe21.3.UsingaDataSourceinaServletwithTomcat

Recipe21.4.CreatingaDataSourceonWebLogic

Recipe21.5.UsingaJNDILookuptogetaDataSourcefromWebLogic

Recipe21.6.UsingaDataSourcefromWebLogicinaJSP

Recipe21.7.CallingaStoredProcedurefromaServlet

Recipe21.8.CallingaStoredProcedurefromaJSP

Recipe21.9.ConvertingaResultSettoaResultObject

Recipe21.10.ExecutingSeveralSQLStatementsWithinaSingleTransaction

Recipe21.11.UsingTransactionswithJSPs

Recipe21.12.FindingInformationaboutaResultSet

Introduction

IfyouareaJavawebdeveloperwhohasneverwrittendatabase-relatedcode,Ihavesomeadviceforyou:don'tholdyourbreathuntilyoureceivethistypeofassignment!

TheserecipesshowyouhowtoaccessadatabaseresourcebyusingaJavaNamingandDirectoryInterface(JNDI)lookup,whichisthemostefficient(andprobablythemostcommon)methodofaccessingdatabaseresourcesinaportablemanner.JNDIisaJavaAPIthatisdesignedtostoreobjectsinahierarchicaltreestructure,similartoafilesystemcomposedofdirectories,subdirectories,andfiles.ServletsandJSPscanthenusethemethodsoftheJNDIAPI(shownbyseveralexamplesinthischapter)toobtainreferencesfromJavaobjects,suchasJavaBeans,andusethemintheirprograms.

Fordatabasecode,thisusuallymeansjavax.sql.DataSourceobjects,whicharefactoriesfordatabaseconnections.TheDataSourcesprovide"connectionpools,"anotherveryimportantwebdatabasetool.Connectionpoolsaregroupsofdatabaseconnectionssharedbyservlets,JSPs,andotherclasses.ApplicationserverssuchasWebLogicusuallyallowyoutodeterminehowmanyconnectionsarestoredinthepool,whichdatabasetablecanbeusedbytheservertoautomaticallytestaconnectiontodetermineifitisfittobereturnedtothesharedpool,andotherpoolproperties.

TheserecipesexplainthebasicsofsettingupaconnectionpoolonbothTomcatandWebLogic.

Therecipesalsocoversomeotherpracticaldatabasetopics,suchashowtocallstoredproceduresinservletsandJSPs,aswellashowtoincludemorethanoneStructuredQueryLanguage(SQL)statementinatransaction.

Recipe21.1AccessingaDatabasefromaServletWithoutDataSource

Problem

YouwanttoaccessadatabasefromaservletwithoutaDataSourceconfigurationforthedatabase.

Solution

UsetheJavaDatabaseConnectivity(JDBC)APItoaccessajava.sql.Connectionobjectthatconnectstheservletwiththedatabase.

Discussion

Onoccasion,developersrequireaquick,lesselegantsolutiontoaccessingadatabase.Thisrecipeexplainshowtousethejava.sql.DriverManagerclasstoobtainaconnectiontoadatasourceinaservlet.TheDriverManagerclasscommunicateswithadatabasedriver,whichissoftwarethatallowsJavacodetointeractwithaparticulardatabase,suchasMySQLorOracle.

Thepreferreddesignistouseajavax.sql.Datasourcetogetadatabaseconnectionfromaconnectionpool,asdescribedinRecipe21.2-Recipe21.6.

Example21-1accomplishesthistaskinitsdoGet()servicemethod.

Example21-1.AservletaccessesadatabaseusingtheJDBCAPI


importjava.sql.*;



publicclassDatabaseServletextendsHttpServlet{




Stringsql="select*fromathlete";


Statementstmt=null;

ResultSetrs=null;

ResultSetMetaDatarsm=null;



out.println(

"<html><head><title>ServletDatabaseAccess</title></head><body>");

out.println("<h2>Databaseinfo</h2>");

out.println("<tableborder='1'><tr>");

try{

//loadthedatabasedriver

Class.forName("oracle.jdbc.driver.OracleDriver");

//TheJDBCURLforthisOracledatabase

Stringurl="jdbc:oracle:thin:@192.168.0.2:1521:ORCL";

//Createthejava.sql.Connectiontothedatabase,usingthe

//correctusernameandpassword

conn=DriverManager.getConnection(url,"scott","tiger");

//CreateastatementforexecutingsomeSQL


//ExecutetheSQLstatement


//Getinfoaboutthereturnvalueintheformof

//aResultSetMetaDataobject

rsm=rs.getMetaData();

intcolCount=rsm.getColumnCount();

//printcolumnnamesintableheadercells

for(inti=1;i<=colCount;++i){

out.println("<th>"+rsm.getColumnName(i)+"</th>");

}

out.println("</tr>");

while(rs.next()){

out.println("<tr>");

//printthevaluesforeachcolumn

for(inti=1;i<=colCount;++i)

out.println("<td>"+rs.getString(i)+"</td>");


}

}catch(Exceptione){


}finally{

try{

//thiswillcloseanyassociatedResultSets

if(stmt!=null)

stmt.close();

if(conn!=null)

conn.close();


}//finally

out.println("</table><br><br>");



}//doGet

}

Herearethestepsneededtorunaservlet,asshowninExample21-1:

1. TaketheJARfilethatcontainsyourdatabasedriver,andstoreiteitherinacommonserverdirectory,suchasTomcat's<Tomcat-root>/common/libdirectoryorintheWEB-INF/libdirectoryofyourwebapplication.

ChangetheextensionoftheOracleJDBCdriver(suchasclasses12.zip)to.jar,sothattheJavaclassesthatitcontainscanbeloadedproperlyintotheJVM.

2. DerivethedatabaseURLfromvendorliterature,andtheusernameandpasswordforthedatabasefromadatabaseadministrator(thatmightbeyou!)orotherappropriatemeans.Thecodewillnotbeabletoaccessthedatabasewithoutavalidusernameandpassword.

Thedownsideofthisapproachisthatyouaremixingupsensitivedatabasesecurityinformationwithservletcode.Itmakesmoresensetoadoptthestrategiesthattheupcomingfiverecipesdescribe,beginningwithRecipe21.2,"ConfiguringaDataSourceinTomcat."

Figure21-1showstheresultofrunningthisservlet.

Figure21-1.Aservletthatdisplayssomedatabaseinformation

Chapter23ontheJSTLshowshowtouseaJSPtoaccessadatabasewithoutaDataSourceconfiguration.

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Recipe21.2-Recipe21.6onconfiguringandusingDataSourcesonTomcatandWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sqlResult;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.

http://java.sun.com/products/jdbc/download.html

Recipe21.2ConfiguringaDataSourceinTomcat

Problem

Youwanttoconfigureajavax.sql.DataSourceforuseinaservletwiththeTomcatwebcontainer.

Solution

CreatearesourceelementinTomcat'sserver.xmlfileandanassociatedresource-refelementintheweb.xmldeploymentdescriptor.

Discussion

TomcatmakesiteasytosetupaconnectionpoolsothatservletsandJSPscanefficientlysharedatabaseconnections.Inwebsitesthathavemanysimultaneoususers,aconnectionpoolimprovesefficiencybysharingexistingdatabaseconnections,ratherthancreatinganewconnectionandtearingitdowneverytimeanapplicationhastousethedatabase.

AnotherbenefitofconfiguringaconnectionpoolisthatyoucanchangethedatabasesystemthataservletorJSPisusingwithouttouchingtheJavacode,becausethedatabaseresourceisconfiguredoutsideoftheservletorJSP.

HerearethestepsforconfiguringaDataSourcewithTomcat:

1. CreateaResourceandaResourceParamselementinserver.xml,orintheXMLfilethatyouhaveplacedinTomcat's

webappsdirectory.TheseelementsdescribetheJNDIobjectyouarecreatinginordertoprovideyourservletsorJSPswithaDataSource.

Addaresource-refelementtoweb.xml,whichallowsthecomponentsintheassociatedwebapplicationtoaccesstheconfiguredDataSource.

Example21-2showstheResourceandaResourceParamselementsinserver.xml.ThisexampledescribesaDataSourcethatconnectswithanOracle8idatabase.

Example21-2.Theresourceelementinserver.xml

<Resourcename="jdbc/oracle-8i-athletes"scope=

"Shareable"type="javax.sql.DataSource"auth=

"Container"description="HomeOracle8iPersonalEdition"/>

<ResourceParamsname="jdbc/oracle-8i-athletes">

<parameter>

<name>driverClassName</name>

<value>oracle.jdbc.driver.OracleDriver</value>

</parameter>

<parameter>

<name>url</name>

<value>jdbc:oracle:thin:@192.168.0.2:1521:ORCL</value>

</parameter>

<parameter>

<name>username</name>

<value>scott</value>

</parameter>

<parameter>

<name>password</name>

<value>tiger</value>

</parameter>

</ResourceParams>

CreateaResourceandResourceParamselementforeachdatabasethatyourapplicationuses.Example21-3showstheresource-refelementassociatedwiththeResourcespecifiedbyExample21-2.

Example21-3.Aresource-refelementspecifiesaDataSourceinweb.xml



<resource-ref>

<res-ref-name>jdbc/oracle-8i-athletes</res-ref-name>

<res-type>javax.sql.DataSource</res-type>

<res-auth>Container</res-auth>

</resource-ref>



TheJNDIpathtothisDataSource,whichyouuseinaJNDIlookup(seethenextrecipe),isjdbc/oracle-8i-athletes.

Theservlet2.4APIdoesnotrequiretheweb.xmlelementssuchasresource-reftoappearinaspecificorder.Theservlet2.3APIspecifiestheordertheseelementsmustappearinwithaDocumentTypeDefinition(DTD).SeeChapter1.

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Recipe21.3onusingaDataSourceinaservletwithTomcat;Recipe21.4-Recipe21.6onconfiguringandusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sqlResult;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.3UsingaDataSourceinaServletwithTomcat

Problem

YouwanttouseaDataSourcethatyouhaveconfiguredwithTomcat.

Solution

UsetheJNDIAPIclassestoobtaintheDataSource,thenaccessadatabaseconnectionfromthatDataSource.

Discussion

Useclassesfromthejavax.namingpackagetoaccesstheconfiguredDataSource.Forexample,useajavax.naming.InitialContextobjecttolookupaDataSourcethathasbeenboundasaJNDIobject.

Thejavax.namingpackageisapartoftheJavaPlatformStandardEdition1.3and1.4.

Example21-4instantiatesajavax.sql.DataSourceinstancevariableinitsinit()method,whichtheservletcontainercallswhenitcreatesaservletinstance.InTomcat,JNDIobjectsarestoredundertherootlevelspecifiedbythe"java:comp/env"string.

Example21-4.UsingaDataSourceinaservlet


importjava.sql.*;




importjavax.sql.*;



publicclassDbServletextendsHttpServlet{

DataSourcepool;

publicvoidinit()throwsServletException{

Contextenv=null;

try{


//LookupaDataSource,whichrepresentsaconnectionpool


if(pool==null)


"'oracle-8i-athletes'isanunknownDataSource");

}catch(NamingExceptionne){

thrownewServletException(ne.getMessage());

}//try

}






Statementstmt=null;

ResultSetrs=null;


//StartbuildingtheHTMLpage



out.println(

"<html><head><title>TypicalDatabaseAccess</title></head><body>");



try{

//GetaConnectionfromtheconnectionpool


//CreateaStatementobjectthatcanbeusedtoexecute

//aSQLquery


//executeasimpleSELECTquery


//GettheResultSetMetaDataobjectsowecandynamically

//displaythecolumnnamesintheResultSet



//printcolumnnamesintableheadercells



}


//whiletheResultSethasmorerows...

while(rs.next()){


//Printeachcolumnvalueforeachrowwiththe

//ResultSet.getString()method




}//while

}catch(Exceptione){


}finally{

try{

//WhenaStatementobjectisclosed,anyassociated

//ResultSetisclosed

if(stmt!=null)

stmt.close();

//VERYIMPORTANT!ThiscodereturnstheConnectiontothe

//pool

if(conn!=null)

conn.close();


}

out.println("</table></body></html>");

}//doGet

}

Example21-4getsaDataSourcebyusingtheaddressconfiguredinTomcat(Recipe21.2;jdbc/oracle-8i-athletes)inaJNDIlookup.Thiscodelookslikethis:


//LookupaDataSource,whichrepresentsaconnectionpool


ThecodethenobtainsadatabaseconnectionfromtheconnectionpoolbycallingtheDataSourceobject'sgetConnection()method.ItisveryimportanttocalltheConnectionobject'sclose()methodwhentheservletisfinishedwithit,becausethismethodcallreturnsthesharedConnectiontothepool.

RequestingtheservletofExample21-4inabrowsercreatesoutputthatlooksjustlikeFigure21-1.

Chapter23ontheJSTLshowshowtouseaJSPtoaccessadatabasewithaDataSourceconfiguration.

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2onconfiguringaDataSourceonTomcat;Recipe21.4-Recipe21.6onconfiguringandusingDataSourcewithservletsandJSPsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sqlResult;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.4CreatingaDataSourceonWebLogic

Problem

Youwanttocreateajavax.sql.DataSourceonBEAWebLogicforuseinyourservlets.

Solution

UsetheWebLogicconsoletoconfigureanewconnectionpool,thenconfigureanewDataSourceassociatedwiththatpool.

Discussion

ConfiguringaWebLogicDataSourceinvolvesthefollowingsteps:

1. LogintotheWebLogicconsole,whichallowsyoutomanagetheWebLogicserverfromabrowser.TheURLfortheconsoleistypicallyhttp://<localhost:7001>/console(substituteyourhostnamefor"localhost"andtheportnumberthatmatchesyourownWebLogicconfiguration).

ClickonYour-domain-name Services JDBC ConnnectionPoolsonthemenutreeintheconsole'slefthandcolumn.Thenclickon"ConfigureanewJDBCConnectionPool...".

Intheresultingwindow,enteranamefortheconnectionpool,theJDBCURL(e.g.,jdbc:oracle:thin:@192.168.0.2:1521:ORCL),theDriverclassname(e.g.,oracle.jdbc.driver.OracleDriver),aswellastheusernameandpasswordinthe"Properties"textfield.Figure

21-2showsaconfiguredconnectionpoolnamed"OraclePool."Rememberthisnameyou'llneedittoconfigureaDataSourcefurtheralongintheprocess.

Figure21-2.CreatingaconnectionpoolwiththeWebLogicconsoleapplication

4. Clickonthe"Create"buttoninthiswindowtocreatetheconnectionpool,thenchoosethe"Targets"tab.Theresultingscreenallowsyoutochooseaservertowhichtheconnectionpoolwillapply.Afteryouhavechosentheserver,clickonthe"Apply"buttonintheTargetsscreen.Thenameofthenewpoolshouldappearinthelefthandmenuframe.

ClickonYour-domain-name Services JDBC DataSourcesandclickontheURL"ConfigureaNewJDBCDataSource...".Figure21-3showsaDataSourceconfigurationwindowthatincludestheDataSourcename("oracle-8i-athletes")underwhichWebLogicwillbindtheDataSourceasaJNDIobject.Thewindowalsohasatextfieldwhereyoumustenterthenameoftheconnectionpoolthatyoujustconfigured:"OraclePool."Clickthe"Create"buttontocreatethenew

DataSource.Figure21-3showstheJDBCDataSourceswindow.

Takethesamestepsasinstep4withthe"Targets"screentoapplythisDataSourcetotheappropriateserver.Painless,right?

Figure21-3.CreatingaDataSourcewiththeWebLogicconsoleapplication

Figure21-4showstheWebLogicJNDItreewheretheDataSourcethatyouhavejustcreatedisbound.

Figure21-4.AviewoftheWebLogicJNDItreecontainingtheDataSource

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Chapter2ondeployingservletsandJSPsonWebLogic;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.5andRecipe21.6onusingDataSourceswithservletsandJSPsonWebLogic.


Recipe21.5UsingaJNDILookuptogetaDataSourcefromWebLogic

Problem

YouwanttouseaJNDIlookuptoaccessaWebLogicDataSource.

Solution

UsetheJNDIAPIandtheclassesinthejavax.namingpackagetogettheJNDIobjectthatyouhaveboundonWebLogic.

Discussion

AccessingaConnectionfromaWebLogicDataSourceandconnectionpoolusessimilarJavacodecomparedwithTomcat.

1. SetuptheconnectionpoolandDataSourcebyfollowingRecipe21.4sinstructions.

Intheservletcode,gettheDataSourcebyusingaJNDIlookup.Thisinvolvescreatinganinstanceofajavax.naming.InitialContextandthencallingitslookup()methodwiththenamethatyougaveyourDataSource(Recipe21.4).

GetaConnectionfromtheDataSourcebycallingtheDataSource'sgetConnection()method.

Example21-5createsaninstanceofanInitialContextbypassinginaHashtablethatcontainssomepropertyvalues.

Example21-5.AservletthatusesaWebLogicconnectionpool


importjava.util.Hashtable;

importjava.sql.*;




importjavax.sql.*;



publicclassWeblogicDbServletextendsHttpServlet{

DataSourcepool;


Contextenv=null;

Hashtableht=newHashtable();

//Createpropertynames/valuesthatwillbepassedto

//theInitialContextconstructor

ht.put(Context.INITIAL_CONTEXT_FACTORY,

"weblogic.jndi.WLInitialContextFactory");

//t3://localhost:7001isthedefaultvalue

//Addyourownvalueifnecessary:

//ht.put(Context.PROVIDER_URL,"t3://localhost:7001");

try{

env=newInitialContext(ht);

pool=(javax.sql.DataSource)env.lookup(

"oracle-8i-athletes");

if(pool==null)




thrownewServletException(ne);

}

}






Statementstmt=null;

ResultSetrs=null;




out.println(

"<html><head><title>WeblogicDatabaseAccess</title></head><body>");



try{






//printcolumnnames



}


while(rs.next()){





}

}catch(Exceptione){


}finally{

try{

if(stmt!=null)

stmt.close();

//RETURNTHECONNECTIONTOTHEPOOL!

if(conn!=null)

conn.close();


}


}//doGet

}

OnceyouhaveaccessedaConnectionfromtheWebLogicconnectionpool,thecodecanexecutevariousSQLstatementsinordertointeractwiththeassociateddatabase.AlwayscalltheConnection'sclose()methodwhenyouarefinishedwiththeConnection,becausethismethodcallreturnsthesharedConnectiontothepool.

Example21-5cannotworkwithoutaproperlyconfiguredconnectionpoolandDataSource,whichisveryeasytodowiththeWebLogicconsole(asexplainedinRecipe21.4).

TheservletoutputlooksjustlikeFigure21-1,exceptforthedifferentURLinthewebbrowser'saddressfield(http://localhost:7001/dbServlet).

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.6onusingaDataSourcewithaJSPonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sqlResult;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.6UsingaDataSourcefromWebLogicinaJSP

Problem

Youwanttousethejavax.sql.DataSourcethatyousetuponWebLogicinaJSP.

Solution

UseJSPscriptletstoaccesstheDataSourcewithaJNDIlookup,thenusetheJDBCAPIinthescriptletstoaccessthedatabase.

Discussion

TheJSPinExample21-6transplantscodefromaservletinsideofHTMLtemplatetext.TheJSPusesscriptlets,whichcontainJavacodewithin"<%%>"characters.

JSTLSQLtagsarepreferabletoscriptletsinaJSP;however,theJSTLimplementationIuseforthisbook'sexamplescannotaccessaDataSourcefromWebLogic'sJNDIimplementation.SeeRecipe23.6foranexamplethatusestheJSTLSQLtagswithaTomcatDataSource.

Example21-6importsthenecessaryclassesatthetopofthecodeusingthepagedirectiveanditsimportattribute.Otherwise,thisJSPaccomplisheseverythingthattheservletofthepriorrecipedoes,

includingthedisplayofnearlyidenticaloutputinthewebbrowser(seeFigure21-1inRecipe21.1).

Example21-6.UsingaJSPscriptlettoaccessaWebLogicDataSource

<%@pageimport="java.util.Hashtable,java.sql.*,javax.naming.*,javax.sql.*"%>

<html>

<head><title>DatabaseQueryinWebLogic</title></head>

<body>

<h2>QueryingadatabasewithaJSPinWebLogic</h2>

<%

Contextenv=null;

DataSourcepool=null;

Hashtableht=newHashtable();

ht.put(Context.INITIAL_CONTEXT_FACTORY,

"weblogic.jndi.WLInitialContextFactory");

ht.put(Context.PROVIDER_URL,"t3://localhost:7001");

env=newInitialContext(ht);

//LookupthisDataSouceatthetopleveloftheWebLogicJNDItree

pool=(DataSource)env.lookup("oracle-8i-athletes");



Statementstmt=null;

ResultSetrs=null;

ResultSetMetaDatarsm=null;%>

<tableborder='1'><tr>

<%

try{

//getajava.sql.Connectionfromthepool


stmt=conn.createStatement();//createajava.sql.Statement

//executeaSQLstatement,generatingaResultSet




//printcolumnnames

for(inti=1;i<=colCount;++i){%>

<th><%=rsm.getColumnName(i)%></th>

<%}%>

</tr>

<%while(rs.next()){%>

<tr>

<%for(inti=1;i<=colCount;++i){%>

<td><%=rs.getString(i)%></td>

<%}//for%>

</tr>

<%}//while

}catch(Exceptione){

thrownewJspException(e.getMessage());

}finally{

try{

stmt.close();

conn.close();


}%>

</body>

</html>

AftermakingsurethatyouhaveproperlyconfiguredtheconnectionpoolandDataSourceintheWebLogicconsole,viewthisJSP'soutputbycopyingittoWebLogic'sdefaultwebapplication,thenrequestaURLinyourbrowserthatlookslikethisone:http://localhost:7001/sqlWeblogic.jsp.

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Chapter2ondeployingservletsandJSPsonWebLogic;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.4andRecipe21.5onusingDataSourceswithservletsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sqlResult;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12on


findingoutinformationaboutaResultSet.

Recipe21.7CallingaStoredProcedurefromaServlet

Problem

Youwanttocallastoredprocedurefromaservlet.

Solution

Usethejava.sql.CallableStatementclassinsideaservletservicemethod,suchasdoGet()ordoPost().

Discussion

DatabasedeveloperscreatestoredprocedurestypicallyforSQLcodethattheywanttoexecuteonaregularbasis,similartoaJavadeveloper'sreasonforcreatingamethod.AstoredprocedureisapieceofSQLthatthedatabasesystempre-compilesunderaspecificname.ThestoredprocedurethatIuseinthisrecipeisnamedaddEvent.

Naturally,awebdeveloperwhoisusingadatabasewillwanttocallthesestoredprocedures.Thejava.sql.CallableStatementclassencapsulatesaparticularstoredprocedure,sothatyoucanusethesetoolswithinJDBCcode.

Table21-1showsthetableschemaforthetablethataddEventuses.Thetablehasfourcolumns:EVENT_ID,NAME,LOCATION,andRACEDATE.

Table21-1.TheRACEEVENTdatabasetableschema

Name Null? Type

EVENT_ID NOTNULL NUMBER

NAME NOTNULL VARCHAR2(30)

LOCATION NOTNULL VARCHAR2(30)

RACEDATE DATE

Example21-7showstheaddEventdefinitionusingOracle8i'ssyntax.Thisstoredproceduretakesaneventname,location,anddateasarguments.IttheninsertsthesevaluesintoanewrowintheRACEEVENTtable.

Apieceofcodecalledasequencenamedlog_seqprovidesthevalueforthenewrow'sEVENT_IDcolumn.InOracle'sdatabasesystem,asequencecankeeptrackofalongsequenceofnumbers.Thedatabasedevelopercreatesthesequence,justastheywouldcreateastoredprocedure.

Example21-7.ASQLstoredproceduredesignedtoaddarowtotheEVENTtable

createorreplaceprocedureaddEvent(eventnameinvarchar2,

location_invarchar2,date_indate)

as--needtodoinsertsinraceevent

begin

insertintoraceeventvalues(log_seq.nextval,

eventname,location_,date_);

end;

/

Ifyou'reusingadatabasetoolsuchasSQLPLUSfromthecommandline,calltheaddEventprocedureinthefollowingmanner:

execaddEvent('FalmouthTriathlon','FalmouthMA','26-Jul-2003');

Example21-8showshowyoucancalladdEventinaservlet.ThefollowingservletcallsthestoredprocedurefromdoGet()initsownaddRaceEventmethod.Thismethodhasajava.util.Listasanargument.TheListcontainsthevaluesthatthecodeusesasargumentstocalltheaddEventstoredprocedure.

Example21-8.AservletusesCallableStatementtocallthestoredprocedure


importjava.sql.*;

importjava.util.ArrayList;

importjava.util.List;





importjavax.sql.*;



publicclassStoredProcServletextendsHttpServlet{

DataSourcepool;


Contextenv=null;

try{



if(pool==null)





}

}




StringeventName=request.getParameter("eName");

Stringlocation=request.getParameter("eLocation");

Stringdate=request.getParameter("eDate");

ListparamList=newArrayList();

paramList.add(eventName);

paramList.add(location);

paramList.add(date);

try{

addRaceEvent(paramList);

}catch(SQLExceptionsqle){

thrownewServletException(sqle.getMessage());

}//try



out.println("<html><head><title>AddanEvent</title></head><body>");

out.println(

"<h2>TheEventnamed"+eventName+

"hasbeenaddedtothedatabase</h2>");



}//doGet

publicConnectiongetConnection(){


try{



thrownewServletException(sqle.getMessage());

}finally{

returnconn;

}

}

publicvoidaddRaceEvent(Listvalues)throwsSQLException{

if(values==null)

thrownewSQLException(

"InvalidparameterinaddRaceEventmethod.");


conn=getConnection();

if(conn==null)


"InvalidConnectioninaddRaceEventmethod");

Iteratorit=values.iterator();

CallableStatementcs=null;

//CreateaninstanceoftheCallableStatement

cs=conn.prepareCall("{calladdEvent(?,?,?)}");

for(inti=1;i<=values.size();i++)

cs.setString(i,(String)it.next());

//CalltheinheritedPreparedStatement.executeUpdate()method

cs.executeUpdate();

//returntheconnectiontothepool

conn.close();

}//addRaceEvent

}

Example21-8getsaConnectionfromaconnectionpoolusingthetechniquesexplainedinthepriorrecipes.ThecodeusestheConnectiontocreateaCallableStatementthattheexamplecanusetocalltheunderlyingstoredprocedure:


TheStringargumenttotheConnection'sprepareCallmethodcontainsquestionmarks(?)asplaceholdersforthestoredprocedure'sparameters.ThecodethencallstheCallableStatement'ssetString()methodtogivetheseplaceholdersvalues.Finally,thecodecallstheCallableStatement'sexecuteUpdate()methodtoexecuteaddEvent.

Ifcallingthestoredprocedurecausesadatabaseerror,theaddRaceEventmethodthrowsaSQLException.

Theservletreceivesvaluesforthenewrowfromrequestparameters.ThefollowingURLcallstheservletwiththreeparameters:eName,eLocation,andeDate:

http://localhost:8080/home/servlet/com.jspservletcookbook.

StoredProcServlet?eName=

Falmouth%20Triathlon&eLocation=Falmouth%20MA&eDate=26-July-2003

Figure21-5showstheservlet'soutputinawebbrowser.

Figure21-5.ThebrowseroutputoftheStoredProcServlet

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.4-Recipe21.6onusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.8oncallingastoredprocedurefromaJSP;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sqlResult;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.8CallingaStoredProcedurefromaJSP

Problem

YouwanttocallastoredprocedurefromaJSP.

Solution

UsingaJSP2.0container,developanExpressionLanguage(EL)functionthatwillcallthestoredprocedureforyou.

Discussion

JSP2.0introducedfunctions,whicharestaticmethodsthatyoucancallinsideELstatements.

SeeChapter23ifyouneedtofamiliarizeyourselfwiththeEL.

Thisrecipeexplainsthestepsfordevelopingafunctionthatcallsastoredprocedure:

1. Createthestoredprocedureinyourdatabasesystem.

WritetheJavaclassthatimplementsthefunctionasastaticorclassmethod.

DefinethefunctioninaTagLibraryDescriptor(TLD),whichisanXMLconfigurationfilethatyouincudewiththewebapplication.

IntheJSPitself,usethetaglibdirectivetodeclarethetaglibrarythatcontainsthefunction.

CallthefunctionintheJSP,usingtheproperprefixforyourtaglibrary.ThefunctionIuseinthisrecipelookslikethis:

<cbck:addRaceEvent("MyRace","AnytownUSA","11-Dec-2003")/>

Example21-9showstheJavaclassthatimplementsthisfunction.

Example21-9.TheJavaclassthatimplementsanELfunction


importjava.sql.*;




importjavax.sql.*;

publicclassStoredProcUtil{

privatestaticDataSourcepool;

privatestaticContextenv;

static{//staticinitializationoftheContextandDataSource

try{



if(pool==null)

thrownewException(


}catch(Exceptione){

System.out.println(e);

}

}//static

/*ThisstaticmethodwillbeconfiguredinaTLDfileandprovidethe

implementationforanELfunction.Anexampleuseofthefunctionis:

<cbck:addRaceEvent("MyRace","AnytownUSA","11-Dec-2003")/>*/

publicstaticvoidaddRaceEvent(Stringname,Stringlocation,Stringdate){

if((!check(name))||(!check(location))||(!check(date)))


"InvalidparamvaluespassedtoaddRaceEvent()");


try{


if(conn==null)


"InvalidConnectioninaddRaceEventmethod");




cs.setString(1,name);

cs.setString(2,location);

cs.setString(3,date);


cs.executeUpdate();

//returntheconnectiontothepool

conn.close();


}//addRaceEvent

privatestaticbooleancheck(Stringvalue){


returnfalse;

returntrue;

}

}

TheaddRaceEvent()methodcreatesajava.sql.CallableStatement,whichcallstheunderlyingstoredprocedure(addEvent).Recipe21.7explainsthisprocess.

TheJavamethodthatimplementsthefunctionforaJSPmustbedefinedasstatic.

ThisJavaclassmustbestoredinyourwebapplicationbeneaththeWEB-INF/classesdirectory(withasubdirectorystructurematchingitspackagename)orinaJARfilestoredinWEB-INF/lib.Forexample,theJavaclassofExample21-9shouldbestoredinWEB-INF/classes/com/jspservletcookbook/StoredProcUtil.class.

Example21-10showstheTLDfilethatdefinestheELfunction.

TheTLDfilehasa.tldextensionandlivesinaWEB-INFsubdirectoryofyourwebapplication,suchasWEB-INF/tlds.

Example21-10.TheTLDfileforconfiguringtheELfunction

<taglibxmlns="http://java.sun.com/xml/ns/j2ee"xmlns:xsi=

"http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation=

"http://java.sun.com/xml/ns/j2eehttp://java.sun.com/xml/ns/j2ee/

web-jsptaglibrary_2_0.xsd"

version="2.0"

>




<uri>jspservletcookbook.com.tags</uri>


<function>

<name>addRaceEvent</name>

<function-class>

com.jspservletcookbook.StoredProcUtil

</function-class>

<function-signature>

voidaddRaceEvent(java.lang.String,

java.lang.String,java.lang.String)

</function-signature>

</function>

<tag>



</tag>

</taglib>

Example21-10definesthefunctionwiththefunctiontaganditsname,function-class,andfunction-signatureattributes.Makesuretoincludethefullyqualifiedclassnameunderfunction-class.TheJSPcontainerknowshowtocallthefunctionbyinspectingthefunction-signature.Thissignatureincludesthereturntype("void"inthiscase),thefunctionname,andallofitsparametersspecifiedbytheirfullyqualifiedclassnames.

Example21-11isaJSPthatcallsourdefinedfunction.First,thetaglibdirectivedeclaresthetaglibraryandprefix("cbck")thatthefunctionuses.

Example21-11.AJSPusesanELfunctiontocallastoredprocedure


<html>

<head><title>CallingaStoredprocedure</title></head>

<body>

<h2>ThisJSPcallsastoredprocedurewithaJSP2.0function</h2>

${cbck:addRaceEvent("FalmouthTriathlon","FalmouthMA","26-Jul-2003")}

</body>

</html>

SincethisisafeatureoftheEL,thesyntaxencapsulatesthefunctioncallwithinthe"${}"characterstring.Nextcomestheprefix(cbck),acolon,andthefunctioncallitself:

${cbck:addRaceEvent("FalmouthTriathlon","FalmouthMA","26-Jul-2003")}

Thisprocessappearscomplicatedthefirsttimearound,butonceyoucreateyourfirstJSP2.0function,therestofthemwillbemucheasier!ThisfeaturedoesnotinvolvemuchmorethancreatingastaticJavamethod,configuringthefunctionwiththepropervaluesinanXMLfile,thencallingthefunctioninaJSP.Thisisaniftywaytocallstoredprocedures!

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Chapter23ontheJSTL;Chapter22oncreatingcustomtaglibraries;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.5andRecipe21.6onusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.7oncallingastoredprocedurefromaservlet;Recipe21.9onconvertingajava.sql.ResultSetobjecttoajavax.servlet.jsp.jstl.sql.Result;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.9ConvertingaResultSettoaResultObject

Problem

Youwanttoconvertajava.sql.ResultSettoajavax.servlet.jsp.jstl.sql.ResultobjectsothattheobjectcanbeusedwiththeJSTL.

Solution

Usethejavax.servlet.jsp.jstl.sql.ResultSupport.toResult()

method.

Discussion

TheResultinterfaceallowscodetoworkwithResultSetsintheformofJavaarraysorjava.util.Maps.TheJSTLtagsoftenusearraysorMapstoiteratethroughvalues(whichiswhytheyincludedtheResultinterfaceintheJSTLspecification).Therefore,youmightwanttoconvertaResultSettoaResult,thenhandtheResulttoaJSPthatusestheJSTLtags.

Example21-12isaservletthat:

1. CreatesaResultSetbyqueryingadatabase.

ConvertstheResultSettoaResult.

ForwardstheResulttoaJSPbystoringtheResultasasessionattribute.

Example21-12.AservletconvertsaResultSettoaResult


importjava.sql.*;




importjavax.sql.*;

importjavax.servlet.jsp.jstl.sql.Result;

importjavax.servlet.jsp.jstl.sql.ResultSupport;



publicclassDbServletResultextendsHttpServlet{

DataSourcepool;


Contextenv=null;

try{



if(pool==null)





}

}//init





try{

//GetaResultobjectthatrepresentsthereturnvalueoftheSQL

//statement'select*fromathlete'

ResultjspResult=select(sql);


//storetheResultinasessionattribute,

//whereitcanbepassedto

//aJSPandusedwiththeJSTLtags

session.setAttribute(

"javax.servlet.jsp.jstl.sql.Result",jspResult);


"/useResult.jsp");



thrownewServletException(sqle.getMessage());}

}//doGet

privateResultselect(Stringsql)throwsSQLException{

if(sql==null||sql.equals(""))

thrownewSQLException("Invalidparameterinselectmethod");

ResultSetrs=null;


Resultres=null;

//GetaConnectionfromthepool


if(conn==null)

thrownewSQLException("InvalidConnectioninselectmethod");

PreparedStatementstmt=conn.prepareStatement(sql);

//CreatetheResultSet

rs=stmt.executeQuery();

//ConverttheResultSettoa

//ResultobjectthatcanbeusedwithJSTLtags

res=ResultSupport.toResult(rs);

stmt.close();//thiswillcloseanyassociatedResultSets

conn.close();//returnConnectiontopool

returnres;//returnResultobject

}//select

}

Example21-12importsthenecessaryJavaclassesincludingtheResultandResultSupportclasses:

importjavax.servlet.jsp.jstl.sql.Result;

importjavax.servlet.jsp.jstl.sql.ResultSupport;

Theselect()methoddoestheimportantwork:creatingtheResultSet,convertingthisobjecttoaResult,andreturningtheResult.Hereisthecodethatperformstheconversion:

res=ResultSupport.toResult(rs);

TheResultSupportclass'sstatictoResult()methodtakesaResultSetasanargumentandreturnsaResult.

Theservlet'sdoGet()methodthencreatesasessionattributefromtheResultandusesaRequestDispatchertoforwardtherequesttoaJSP.TheJSPisnameduseResult.jsp.

Theuserinitiallyrequeststheservletinhisbrowser,andtheservletpassestherequesttotheJSP.TheuserthenseestheJSP'soutputintheirbrowser.

TheRequestDispatchercodelookslikethis:


"/useResult.jsp");


Example21-13usestheJSTLcoretags(withthe"c"prefix).Thec:settaggainsaccesstothesessionattributeandstorestheattribute'svalueinaresultObjvariable.Thec:forEachandc:outtagsthendisplay

thedatabasevaluesintheJSP.

Example21-13.TheJSPthatusesaResultobjectstoredasasessionattribute


<%@tagliburi="http://java.sun.com/jstl/sql"prefix="sql"%>

<html>

<HEAD>

<TITLE>UsingaResultobject</TITLE>

</HEAD>


<h2>ViewDatabaseData</h2>

<%--storeasessionattribute(theResultobject)inavariablenamed'resultObj'--%>

<c:setvar="resultObj"value=

"${sessionScope[\"javax.servlet.jsp.jstl.sql.Result\"]}"/>

<tableborder="1"cellspacing="2">

<%--foreveryrowintheResult...--%>

<c:forEachitems="${resultObj.rows}"var="row">

<%--foreverycolumnintherow...--%>

<c:forEachitems="${row}"var="column">

<tr>

<tdalign="right">

<b><c:outvalue="${column.key}"/></b>

</td>

<td>

<c:outvalue="${column.value}"/>

</td></tr>

</c:forEach>

</c:forEach>

</table>

</body>

</html>

Thesyntax"${sessionScope[\"javax.servlet.jsp.jstl.sql.Result\"]}"isnecessary,becausethesessionattributenamecontainsperiods(.).Otherwise,theELcanacccessascopedattribute,iftheattributeisnamedmyAttribute,usingthissimplersyntax:

${myAttribute}

Figure21-6showshowawebbrowserdisplaystheJSP'soutput.

Figure21-6.TheJSPpageoutputinawebbrowser

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Chapter23ontheJSTL;Chapter16onusingsessionattributes;Recipe21.1onaccessing


adatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.5andRecipe21.6onusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.10andRecipe21.11onusingtransactionsinservletsandJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.

Recipe21.10ExecutingSeveralSQLStatementsWithinaSingleTransaction

Problem

YouwanttoexecutemorethanoneSQLstatementwithinasingletransaction.

Solution

Usethejava.sql.ConnectionAPIandthesetAutoCommit(),commit(),androllback()methodstocreateatransaction.

Discussion

SomeSQLstatements,suchasthosethatupdatecustomerinformationintwodifferentdatabasetables,aremeanttobeexecutedonlyasagroup.Ifoneofthemdoesnotsucceed,thedatabaseisreturnedtoitspreviousstate.ThisisthepurposeofusingatransactioninyourJavacode.Atransactionisalogicalunitofdatabaseoperationsthatcanbe"rolledback"orcanceledasagroupifsomethinggoeswrongwithoneoftheoperations.

Onceyouhaveadatabaseconnection(aninstanceofjava.sql.Connection),youcancallvariousConnectionmethodstocreateatransaction.Herearethestepsforexecutingatransaction:

1. CalltheConnectionobject'ssetAutoCommit()methodwithfalseastheparameter.ThisturnsoffthedefaultbehaviorforJDBCcode,whichistocommiteachseparateSQLstatement

insteadofautomaticallygroupingsequentialstatementsasasingletransaction.

FollowthesetAutoCommit()methodcallwiththedatabasecodethatyouwanttotreatasasingletransaction.

CalltheConnection'scommit()methodtocommittheSQLstatements,whichwritesanydatabasechangesassociatedwiththeSQL(suchasaDELETEorUPDATEstatement)totheunderlyingdatabasefile.

IntheareaofJavacodereservedfordealingwitherrorsorunexpectedconditions,suchasacatchblock,calltheConnection'srollback()method,whichrollsbacktheSQLthatwasincludedinthetransaction.

Example21-14isaservletthatillustratesthisprocess.

Example21-14.AservletthatusesaSQLtransaction


importjava.sql.*;




importjavax.sql.*;



publicclassDbServletTransextendsHttpServlet{

DataSourcepool;

/*InitializetheDataSourceintheservlet'sinit()method

whichtheservletcontainercallsoncewhenitcreatesaninstanceof

theservlet*/


Contextenv=null;

try{



if(pool==null)





}

}//init





Statementstmt=null;



out.println(

"<html><head><title>Usingtransactions</title></head><body>");

out.println(

"<h2>TheseSQLstatementsarepartofatransaction</h2>");

out.println("CallableStatement.executeUpdate()");


out.println("Statement.executeUpdate()");


try{

//Getaconnectionfromthepool


//DisplaythedefaultvaluesforsetAutoCommit()

//andtheisolationlevel

out.println("AutoCommitbeforesetAutoCommit():"+

conn.getAutoCommit()+"<br><br>");

out.println("Transactionisolationlevel:");

//justoutofcuriosity,displaytheexistingtransaction

//isolationlevel

witch(conn.getTransactionIsolation()){

case0:out.println("TRANSACTION_NONE<br><br>");break;

case1:out.println(

"TRANSACTION_READ_UNCOMMITTED<br><br>");break;

case2:out.println(

"TRANSACTION_READ_COMMITTED<br><br>");break;

case4:out.println(

"TRANSACTION_REPEATABLE_READ<br><br>");break;

case8:out.println(

"TRANSACTION_SERIALIZABLE<br><br>");break;

default:out.println("UNKNOWN<br><br>");

}//switch

//setAutocommittofalsesothatindividualSQLstatementswill

//notbecommitteduntilConnection.commit()iscalled

conn.setAutoCommit(false);

//Transaction-relatedSQLbegins...




cs.setString(1,"SalisburyBeach5-Miler");

cs.setString(2,"SalisburyMA");

cs.setString(3,"14-Aug-2003");


cs.executeUpdate();

Stringsql="updateraceeventsetracedate='13-Aug-2003'"+

"wherename='SalisburyBeach5-Miler'";

intres=0;


res=stmt.executeUpdate(sql);

//committhetwoSQLstatements

conn.commit();

}catch(Exceptione){

try{

//rollbackthetransactionincaseofaproblem

conn.rollback();



}finally{

try{

if(stmt!=null)

stmt.close();

if(conn!=null)

conn.close();


}


}//doGet

}

ThedoGet()methodinExample21-14displaysthedefaultvaluesfor"autocommitting"SQLstatementsandthetransactionisolationlevel(thelevelofdatabase-lockingthatoccursasthetransactionswithinyourJavacodeareinitiated).Forexample,ifyourSQLstatementsincludetheupdatingofdatabasefields,canotherusersofthedatabaseviewthenewcolumnvaluesbeforeyourtransactioniscommitted?Ifallowed,this

typeofbehavioriscalledadirtyread.

Table21-2showsthedifferenttypesoftransactionisolationlevels,fromtheleasttomostrestrictivelevel.Twoothertermsneedaddressingbeforeyouinspectthistable:

Anon-repeatablereadoccurswhenonetransactionreadsarow,anothertransactionchangesthesamerow,andthefirsttransactionreadsthesamerowandreceivesthedifferentvalue.

AphantomreadhappenswhenonetransactionobtainsaresultsetbasedonaWHEREconditionandasecondtransactioninsertsanewrowthatsatisfiesthisWHEREcondition.ThefirsttransactionthenevaluatesthesamedatabasetableagainwiththesameWHEREconditionandretrievesthenew"phantom"row.

Table21-2.Transactionisolationlevels

Transactionisolationlevel

Returnvalueofjava.sql.Connection.

getTransactionIsolation()Definition

TRANSACTION_NONE 0 Thedatabasedriverdoesnotsupporttransactions.

TRANSACTION_READ_

UNCOMMITTED1 Anothertransactioncanseeuncommittedchanges;

"dirtyreads"areallowed.

TRANSACTION_READ_

COMMITTED2 Uncommittedchangesarenotvisibletoother

transactions.

TRANSACTION_

REPEATABLE_READ4

Uncommittedchangesarenotvisibletoothertransactions;nonrepeatablereadsarealsodisallowed.

TRANSACTION_

SERIALIZABLE8

Uncommittedchangesarenotvisibletoothertransactions;nonrepeatablereadsandphantomreadsarealsodisallowed.

Checkyourdatabasevendor'sspecificationsorliteratureforhowthedatabasesystemyouusehandlestransactionisolation.UsetheConnectionobject'sgetTransactionIsolation()methodtofindoutthevalueassociatedwithaparticulardatabasedriverthatJDBC-relatedcodeisusing.Thismethodreturnsanint.Forexample,a"2"returnvaluemeansthattheConnectionisassociatedwithaTRANSACTION_READ_COMMITTEDtransactionisolationlevel.

Example21-14runstwoSQLstatementswithinatransaction:itexecutesastoredprocedureandinitiatesanUPDATEstatement.Thenthecodecallscommit()ontheConnectionobjecttocommitanydatabasechangestotheunderlyingdatastore.IfthisSQLcodethrowsanexception,thetransactionisrolledbackwithacalltoConnection'srollback()method.ThismethodcallpreventsthepriorSQLstatementsfromhavinganyeffectontheunderlyingdatabase.

Figure21-7showstheoutputoftheservletinExample21-14,asitwouldappearinawebbrowser.

Figure21-7.Aservletwithadatabasetransactionprovidesbrowseroutput

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.4-Recipe21.6onusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.11onusingtransactionsinJSPs;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.11UsingTransactionswithJSPs

Problem

YouwanttorunSQLstatementswithin.atransactioninaJSP.

Solution

Usethesql:transactionJSTLtag.

Discussion

TheJSTLhasasql:transactiontagthatexecutesanynestedSQLactions(suchassql:update)inatransaction.

Thesql:transactiontagusesthesamejava.sql.Connectionmethodsthatyouwoulduseinatransaction-relatedservlet(Recipe21.10):setAutoCommit(false),commit(),androllback().

Example21-15usesaDataSourcethatisconfiguredinweb.xml,sothatnoneofthedatabase-relatedinformationappearsintheJSP.SeeRecipe23.6forhowtoconfigureaDataSourceinthedeploymentdescriptor.TheINSERTandSELECTSQLstatementsthatarenestedinsidethesql:transactiontagwillbothberolledbackifanyproblemsarisewithinthetransaction.

Example21-15.AJSPexecutesINSERTandSELECTSQLstatementsinatransaction



<html>

<HEAD>

<TITLE>UsingaTransactionwithaJSP</TITLE>

</HEAD>


<h2>ViewAthleteData</h2>

<sql:transaction>

<sql:update>

insertintoathletevalues(2,'RachelPerry','rlpbwp1996',

'24-Feb-1996','F')

</sql:update>

<sql:queryvar="resultObj">

select*fromathlete

</sql:query>

</sql:transaction>

<table>

<c:forEachitems="${resultObj.rows}"var="row">

<c:forEachitems="${row}"var="column">

<tr>

<tdalign="right">

<b><c:outvalue="${column.key}"/></b>

</td>

<td>

<c:outvalue="${column.value}"/>

</td></tr>

</c:forEach>

</c:forEach>

</table>

</body>

</html>

AfterexecutingSQLwithinatransaction,theJSPdisplaysthedatabasetable'supdatedvalues.Thecontentofthesql:updateandsql:querytagsaretraditionalSQLstatements.

MakesuretoincludethepropertaglibdirectivetouetheJSTL1.0sqltaglibrary:

<%@tagliburi=

"http://java.sun.com/jstl/sql"prefix="sql"%>

Thesql:transactiontagalsohasanisolationattributeinwhichyoucanspecifyanisolationlevelforthetransaction(seeRecipe21.10).Hereisanexample:

<sql:transactionisolation="TRANSACTION_READ_COMMITTED">

<%--SQLstatementsandtagshere...--%>

</sql:transaction>

Figure21-8showstheoutputofthesqlTrans.jspfile.

Figure21-8.AJSPdisplaysanupdateddatabasetable

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;Chapter23ontheJSTLanditssqltaglibrary;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.4-Recipe21.6onusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.10onusingtransactionsinservlets;Recipe21.12onfindingoutinformationaboutaResultSet.


Recipe21.12FindingInformationaboutaResultSet

Problem

Youwanttodynamicallydiscoverdetailsabouttherowsandcolumnsinajava.sql.ResultSet.

Solution

UsetheResultSetMetaDataclassobtainedbycallingthejava.sql.ResultSet'sgetMetaData()method.

Discussion

Webdeveloperssometimesneedtoworkwithdatabasetablesthathaveunknowncolumnnamesandtypes.Thejava.sqlpackagecontainsaveryusefulResultSetMetaDatainterfacethatdefinesmethodsdesignedtoprovideinformationaboutajava.sql.ResultSet.AResultSetencapsulatestherowsreturnedbyaSELECTSQLstatement.

Example21-16showsaservletthatqueriesanOracle8idatabaseforaResultSet,thendisplaysthecolumnnames,thecolumnindex,theSQLtypeofthecolumn,andthenumberofcharactersthecolumnrequirestodisplayitsvalues.

Example21-16.AservletusestheResultSetMetaDataclass


importjava.sql.*;




importjavax.sql.*;



publicclassDbMetaServletextendsHttpServlet{

DataSourcepool;

/*InitializetheDataSourceintheservlet'sinit()method

whichtheservletcontainercallsoncewhenitcreatesaninstanceof

theservlet*/


Contextenv=null;

try{



if(pool==null)





}

}//init






Statementstmt=null;

ResultSetrs=null;




out.println(

"<html><head><title>DiscoveraResultSet</title></head><body>");

out.println("<h2>HereisInfoaboutthereturnedResultSet</h2>");


try{

//Getaconnectionfromthepool


//CreateaStatementwithwhichtorunsomeSQL


//ExecutetheSQL


//GetaResultSetMetaDataobjectfromtheResultSet



//printcolumnnames

printMeta(rsm,"name",out,colCount);

//printcolumnindex

printMeta(rsm,"index",out,colCount);

//printcolumntype

printMeta(rsm,"columntype",out,colCount);

//printcolumndisplaysize

printMeta(rsm,"columndisplay",out,colCount);

}catch(Exceptione){


}finally{

try{

stmt.close();

conn.close();


}


}//doGet

privatevoidprintMeta(ResultSetMetaDatametaData,Stringtype,

java.io.PrintWriterout,intcolCount)throwsSQLException{

if(metaData==null||type==null||out==null)


"IllegalargspassedtoprintMeta()");


if(type.equals("table")){

out.println("<td><strong>Tablename</strong></td>");


out.println("<td>"+metaData.getTableName(i)+"</td>");

}

}elseif(type.equals("name")){

out.println("<td><strong>Columnname</strong></td>");


out.println("<td>"+metaData.getColumnName(i)+"</td>");

}

}elseif(type.equals("index")){

out.println("<td><strong>Columnindex</strong></td>");


out.println("<td>"+i+"</td>");

}

}elseif(type.equals("columntype")){

out.println("<td><strong>Columntype</strong></td>");


out.println("<td>"+metaData.getColumnTypeName(i)+

"</td>");

}

}elseif(type.equals("columndisplay")){

out.println("<td><strong>Columndisplaysize</strong></td>");


out.println("<td>"+metaData.getColumnDisplaySize(i)+

"</td>");

}

}


}//printMeta

}

Example21-16usesResultSetMetaDatamethodstoobtaininformationabouteachofthecolumnsintheResultSet.ThecodecallsthesemethodsinsideitsprintMeta()method.Forexample,thecode:

metaData.getColumnName(1)

returnsthenameofthefirstcolumnthetableschemaspecifies,suchas"USER_ID."Figure21-9showstheservlet'sHTMLoutputinawebbrowser.

Figure21-9.AservletdisplaysmetainformationaboutaResultSet

Usethejava.sql.DatabaseMetaDatainterfacetogetalargeamountofinformationaboutthedatabasesystemassociatedwiththejava.sql.Connectionthecodeisusing.TheConnectionmethodgetMetaData()returnsanobjectthatimplementstheDatabaseMetaDatainterface.

SeeAlso

TheJDBCspecification:http://java.sun.com/products/jdbc/download.html;TheResultSetMetaDataclass:http://java.sun.com/j2se/1.4.1/docs/api/java/sql/ResultSetMetaData.html;Recipe21.1onaccessingadatabasefromaservletwithoutaconnectionpool;Recipe21.2andRecipe21.3onusingaDataSourceonTomcat;Recipe21.4-Recipe21.6onusingDataSourceswithservletsandJSPsonWebLogic;Recipe21.7andRecipe21.8oncallingstoredproceduresfromservletsandJSPs;Recipe21.10andRecipe21.11onusing


http://java.sun.com/j2se/1.4.1/docs/api/java/sql/ResultSetMetaData.html

transactionsinservletsandJSPs.

Chapter22.UsingCustomTagLibrariesIntroduction

Recipe22.1.CreatingaClassicTagHandler



Recipe22.4.PackagingaTagLibraryinaWebApplication

Recipe22.5.PackagingtheTagLibraryinaJARFile

Recipe22.6.UsingtheCustomTaginaJSP

Recipe22.7.HandlingExceptionsinaCustomTagClass

Recipe22.8.CreatingaSimpleTagHandler

Recipe22.9.CreatingaTLDforaSimpleTagHandler

Recipe22.10.UsingaSimpleTagHandlerinaJSP

Recipe22.11.CreatingaJSPTagFile

Recipe22.12.PackagingtheJSPTagFileinaWebApplication

Recipe22.13.PackagingtheJSPTagFileinaJAR

Recipe22.14.UsingaCustomTagAssociatedwithaTagFile

Recipe22.15.AddingaListenerClasstoaTagLibrary

Introduction

AverypowerfulfeatureofJavaServerPagestechnologyistheabilitytocreateyourownXMLtagsforuseinJSPs.CustomtagshavebeenapartoftheJSPspecificationsinceVersion1.1.JSP2.0isdedicatedtomakingcustomtagdevelopmentlesscomplexthanpriorversions.JSP2.0'sintroductionofsimpletaghandlersandtagfiles,whichwecoverinRecipe22.8-Recipe22.14,areabigpartofthisstrategy.

Let'sfamiliarizeourselveswithafewtermsbeforewemoveontocustomtagrecipes.AtagisaninstanceofanXMLelementandamemberofaspecifiednamespace.Forexample,theprefixforalltagsassociatedwiththiscookbookiscbck.TheJSPreferstoanindividualtagassociatedwiththecbcknamespace(say,themyTagtag)asfollows:

<cbck:myTag>whateverthistagdoes...</cbck:myTag>

TagsareXMLelements;therefore,theirnamesandattributesarecasesensitive.Acollectionoftagsthatprovidesimilarfunctionalityorthatlogicallycollaboratewitheachotheriscalledataglibrary.Developerscaninstalloneormoretaglibrariesinawebapplication.

AJavaclasscalledthetaghandlerprovidesthetag'sfunctionalityinaJSP.AcustomactionisatagthatyouinventforuseinJSPsandthatispoweredbehindthescenesbyatag-handlerobjectthatthewebcontainerkeepsinmemory.

AclassictaghandlerusesthetagextensionAPIthatevolvedfromJSPv1.1to1.2.AsimpletaghandlerisaJavaclassthatimplementstheSimpleTaginterface,whichJSP2.0introduced.

AtagfiledefinesacustomtaginJSPsyntax.Itisdesignedtomakelifeeasierfortagdevelopers.ThewebcontainergeneratesfromthetagfileaJavaclassthatimplementstheSimpleTaginterface,andthencreatesanobjectfromthatclasstointerpretthetag'suseinJSPs.

Finally,ataglibrarydescriptor(TLD)isanXMLfilethatprovidesamappingbetweenreferencestotaglibrariesinJSPs(withthetaglibdirective)andthetag-libraryclassesthatyouinstallinthewebapplication.ATLDisaconfigurationfile,similartoawebapplication'sdeploymentdescriptor.Therecipesinthischapterprovideexamplesofhowtocreateclassictaghandlers,simpletaghandlers,andtagfiles.Therecipesalsoshowhowtopackagethesecomponentsinwebapplications.

Recipe22.1CreatingaClassicTagHandler

Problem

YouwanttocreateaclassicJSP1.2-styletaghandlerforacustomaction.

Solution

CreateaJavaclassthatextendsoneoftheTagsupportclassesinthejavax.servlet.jsp.tagextpackage,suchasBodyTagSupport.

Discussion

TherearenumeroustypesofcustomtagsyoucancreateforJSPs,suchasactionsthatignoretheirbodies(emptytags),actionsthatarenestedwithinothercustomactions,andcustomtagsthatusetheirbodycontent.Infact,entirebookshavebeendedicatedsolelytoJSPcustomtagdevelopment!Insteadofbeingexhaustiveinthisbook,IshowhowtocreateafairlysimpleclassictagthataddsanimagelogotoaJSPpagewithatextmessage.Youcantheninferdetailsforyourownprogrammingtasksfromthisexample.

Thesampletagisdesignedtoallowapagedesignertospecifyanlogo'simage,itswidthandheight,andatextmessagetositalongsidetheimage.

Example22-1showstheclassictaghandlerforthiscustomaction.ThisJavaclassextendsBodyTagSupport,sinceitusesthetag'snestedcontentforthelogo'stextmessage.

Example22-1.Aclassictaghandlerforinsertinganimageandmarkup






/**ThistaggeneratesathumbnailimageusingtheHTMLimgtag,nexttoatextmessage.

TheuserspecifiesthecontentofthemessageandtheHeadinglevel(i.e.,<H1>-<H6>)*/

publicclassLogoTagextendsBodyTagSupport{

//Thesevariablerepresentthecustomtag'sattributes

privateStringheading=null;

privateStringimage=null;

privateStringwidth=null;

privateStringheight=null;

//thismethodassumesthatattributepropertieshavebeenset.

publicintdoStartTag()throwsJspException{

try{

inth=newInteger(heading).intValue();

if(!(h>0&&h<7))


"The'heading'attributevaluemustbetween1and6inclusive.");

}catch(Exceptione){thrownewJspException(e.getMessage());}

returnEVAL_BODY_BUFFERED;

}


JspWriterout=pageContext.getOut();

//the'images'directoryislocatedinthewebapp's

//rootdirectory

StringimgDir=((HttpServletRequest)pageContext.

getRequest()).getContextPath()+"/images/";

//getthetextprovidedbetweenthecustomaction's

//startandendtags


try{

//buildtheHTMLimgtag

out.println("<imgsrc=\""+imgDir+image+"\"width=\""+width+

"\"height=\""+height+"\"align=\"left\">"+"<H"+heading+">"+

message+"</H"+heading+">");

}catch(java.io.IOExceptionio){}

returnEVAL_PAGE;

}//doEndTag

//methodsdesignedtosetattributevalues

publicvoidsetHeading(Stringlevel){

this.heading=level;

}

publicvoidsetImage(Stringname){

this.image=name;

}

publicvoidsetWidth(Stringwidth){

this.width=width;

}

publicvoidsetHeight(Stringheight){

this.height=height;

}

//theJSPcontainermaycacheandreusetaghandlerobjects.

//thismethodreleasesinstancevariablessothatthetaghandler

//canbereusedafresh

publicvoidrelease(){

heading=null;

image=null;

width=null;

height=null;

}//release

}

ClassictaghandlersarelikeJavaBeans.Youdeclarethecustomtag'sattributesasinstancevariables,orproperties,anddefinesettermethodsforeachattribute.Ifyoujustwanttomanipulatethecustomtag'sbody,definethedoEndTag()method.WhentheJSPcontainerinvokesdoEndTag(),developerscanusethismethodtoevaluatethebodycontentthatthetaguserhasplacedbetweentheaction'sstartandendtags.Example22-1alsodefinesthedoStartTag()methodtocheck

thatthetaguserhasincludedavalidvaluefortheheaderattribute(anumberbetweenoneandsix,inclusive,forthisexamplecode).

WhenthedoStartTag()methodisinvoked,anyattributevaluesthattheuserhassetareavailable,butthetag'sbodycontentisnot.

ThedoEndTag()methodusesthevarioustagattributevaluestobuildanimgandHtagthatresultsinthedisplayofasimplelogointheJSPpagewherethetagisused.Here'sanexampleofhowaJSPwouldusetheactiondefinedbythistaghandler:

<%--importthetaglibrarywith'taglib'directive--%>


<%--JSPpagecontinues...--%>

<%--Usethe'logo'tag--%>

<cbck:logoheading="1"image="stamp.gif"width="42"height="54">Thanksforvisiting</

cbck:logo>

Figure22-1showsaJSPthatusesthetagdefinedbyExample22-1.

Figure22-1.AJSPpageusesacustomtagthatdisplaysanimageandaheading

TheJSPusingthistagoutputsHTMLthatlookslikethis:

<imgsrc="/home/images/stamp.gif"width="42"height="54"align="left">

<H1>Thanksforvisiting</H1>

Youmightrespondbyexclaiming,"ThedesignercanjustentertheseHTMLtagsmanually,andtheydon'thavetodealwiththecustomtag'ssyntax!"Thisisabsolutelytrue;however,thetagtakescareofthedefaultlocationfortheimagesdirectory,positionsandalignstheimage,andcheckswhethertheattributeleveliscorrect.Inotherwords,itperformsalotofroutineworkandremovesthepossibilityofsillytypographicalmistakes.

Alsoconsiderthatthisisasimpleexample;whatiftheimagewasaFlashfileinstead?AcustomtagcouldtakecareofallofthecomplexdetailsforembeddingtheFlashintheHTMLpageandgeneratingproprietaryattributevalues,leavingthegraphicalpositioningofthemediafileuptothetaguser.

Aniceruleofthumbwithcustomtagsisthis:leaveautomated,complex,ortediousworktothetaghandler,andreserveconfigurabledetailsforthetag'sattributes.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;

http://jcp.org/en/jsr/detail@id=152

Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingtaglibrariesinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustom-tagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).

Recipe22.2CreatingaJSP1.2TLDforaClassicTagHandler

Problem

YouwanttocreateaJSP1.2TLDfileforoneormorecustomtags.

Solution

CreatetheXMLfileusingtheproperDOCTYPEdeclarationforaJSP1.2TLD.

Discussion

ATLDisanXMLfilethatdescribesyourcustomtags,thetag'sattributes(ifany),aswellastheJavaclassesthatprovidethetag'sfunctionality.TheJSPcontainerusesthisconfigurationfilewhenitinterpretscustomtagsthatappearinJSPpages.IfyouareusingaJSPv1.2container,yourtaglibrary'sTLDhastheDOCTYPEdeclarationshowninExample22-2.ThisTLDdescribesthetaghandlerofthepreviousrecipe.

Example22-2.TheTLDfileforaclassicJSP1.2taghandler


<!DOCTYPEtaglib



<taglib>






<uri>com.jspservletcookbook.tags</uri>


<tag>

<name>logo</name>



<tag-class>com.jspservletcookbook.LogoTag</tag-class>


<description>ThistagwritesalogoinsidetheJSP.</description>

<attribute>

<name>heading</name>






<rtexprvalue>true</rtexprvalue>

<description>Theheadinglevelforthelogo;1through6.

</description>

</attribute>

<attribute>

<name>image</name>



<description>Theimagenameforthelogo.</description>

</attribute>

<attribute>

<name>width</name>



<description>Theimagewidthforthelogo.</description>

</attribute>

<attribute>

<name>height</name>



<description>Theimageheightforthelogo.</description>

</attribute>

</tag>

</taglib>

InJSP1.2and2.0,aJSPcontainerautomaticallysearchesWEB-INF,aswellastheMETA-INFdirectoryofyourapplication'sJARfiles,foranyfilethatendswiththeextension.tld.

Because.tldisafixedextension,itismandatorytogiveyourtaglibrarydescriptorfilenamesthatendin.tld.

ThecontainerthenusestheinformationitfindsintheTLDtointerpretcustomtagsthatthewebapplicationmayuse.Forexample,thecontainermapstheurielementsitfindsintheTLDtotheURIsspecifiedbyanytaglibdirectivesinJSPfiles.Example22-2specifiesauriofcom.jspservletcookbook.tagsforthetaglibrarythatcontainsthelogotag.AtaglibdirectivethatusesthistaglibraryinaJSPlookslikethis:

<%@tagliburi="com.jspservletcookbook.tags"prefix="cbck"%>

WhenthelogotagappearslateronintheJSP,theJSPcontainerknowsthatthetagbelongsinthetaglibrarywiththecom.jspservletcookbook.tagsurivalue,andthecontainercanevaluatetheJSP'stagusebasedontheTLD'sspecificationofthetagclassandthetag'svariousattributes.BasedontheTLD,theJSPcontainerknowsthatthelogotag'sattributesareallrequired,soaJSPthatusesthelogotagandomitsanattributefailstocompile.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.3oncreatingaJSP2.0TLDfilefortaglibraries;Recipe22.4andRecipe22.5onpackagingtaglibrariesinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.3CreatingaJSP2.0TLDforaClassicTagHandler

Problem

YouwanttocreateaJSP2.0TLDfileforataglibrary.

Solution

Createataglibrarydescriptorwiththepropertaglibrootelement,includingthetaglib'svariousxmlnsattributesandvalues.

Discussion

IfyouareusinganyJSP2.0featureswithyourtaglibraryandTLD,suchasafunctionortag-fileelement,thenyoumustusetheJSP2.0-styleTLD,asshowninExample22-3.

TheJSP2.0TLDisbackwardcompatiblewithelementsdefinedintheJSP1.2DTD.ThereforeyoucanusethetaglibandtagelementsastheyarespecifiedinanyexistingJSP1.2TLDswhenyouupgradeyourTLDfiletoJSP2.0.Forexample,theonlydifferencebetweentheTLDinExample22-3andtheJSP1.2TLDinExample22-2isthetaglibstarttag,whichmusthaveexactlythesamecontentasshownhere.

Example22-3.TheJSP2.0TLDfileforourclassictaghandler

<taglibxmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation=


http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"

version="2.0"

>








<tag>

<name>logo</name>

<tag-class>com.jspservletcookbook.LogoTag</tag-class>

<body-content>scriptless</body-content>


<attribute>




<description>

Theheadinglevelforthelogo;1through6.

</description>

</attribute>

<attribute>

<name>image</name>




</attribute>

<attribute>

<name>width</name>




</attribute>

<attribute>

<name>height</name>




</attribute>

</tag>

</taglib>

TheJSP2.0TLDisbasedonanXMLSchemafile,ratherthanaDTD(theXMLSchemafile:http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd).

XMLSchemasallowthedefinersofXMLdocumentstocreatemorecomplexelementsandattributesthanthoseallowedinDTDs.XMLSchemasarealsodesignedtobevalidXMLdocumentsthemselves,whichmakesiteasiertointegratethemwithXML-basedapplications.

http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd

ThetaglibelementinExample22-3hasfourattributes.ThexmlnsattributespecifiesthattheTLDhasthesamedefaultnamespaceasallJ2EEdeploymentdescriptors:http://java.sun.com/xml/ns/j2ee.

AnamespaceisauniqueidentifierthathelpsavoidthecollisionoftwoXMLelementsofthesamename.Forexample,thetaglibelementthatispartofthehttp://java.sun.com/xml/ns/j2eenamespaceisdifferentfromataglibelementthatmightbedefinedaspartofthehttp://acme.comnamespace.Anamespacehastobeuniqueonlywithinitsdomain(suchasanInternetURL);itdoesnotnecessarilyrepresentanactualwebdocument.

Thexmlns:xsiattributespecifiesthenamespaceforasetofXMLelementsrelatedtoXMLSchemainstances.Thexsi:schemaLocationattributespecifiesthelocationoftheXMLSchemaonwhichthecurrentXMLdocumentisbased.

AnXMLSchemadescribesarelatedsetofelementsandattributes.AnXMLSchemainstanceisanXMLdocumentthatusesthepreviouslydefinedXMLelementsandattributes.ThisconceptissimilartoaJavaclassanditsobjectinstances.

Finally,thetaglibelement'sversionattributespecifiestheJSP-specificationversiononwhichthetaglibraryisbased,asinJSP2.0.

SeeAlso

TheXMLschemafilefortheJSP2.0TLD:http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd;Recipe22.2oncreatingaJSP1.2TLDfilefortaglibraries;Recipe22.4andRecipe22.5onpackagingtaglibrariesinawebapplication;Recipe22.6on

http://java.sun.com/xml/ns/j2ee

http://java.sun.com/xml/ns/j2ee


usingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).

Recipe22.4PackagingaTagLibraryinaWebApplication

Problem

Youwanttomakeyourtaglibraryavailableinawebapplication.

Solution

PlaceyourTLDfileinWEB-INForaWEB-INFsubdirectory(withtheexceptionofWEB-INF/libandWEB-INF/classes).PlacethetaghandlerclassorclassesinWEB-INF/classes.

Discussion

PackagingyourtaglibraryoutsideofaJARfileistypicallyatwo-stepprocess:

1. StoretheTLDfileintheWEB-INFdirectoryoraWEB-INFsubdirectory,andaJSPcontainer(compliantwithVersions1.2and2.0)automaticallyconfiguresyourtaglibrary.TheTLDfilemusthavea.tldextension.Forexample,ifyoustoreamytags.tldinWEB-INF/tlds,thentheJSPcontainerautomaticallyfindsyourTLDfileandconfigureyourtaglibrary.

TheJSP2.0specificationstatesthatTLDsshouldnotbeplacedinWEB-INF/liborWEB-INF/classes.TheJSPcontainerwillnotlookfortheTLDsintheselocations.

2. Makesurethetaghandlerclassesforyourtaglibraryhaveapackagename(suchascom.jspservletcookbook)andarestoredinWEB-INF/classesorinaJARfileinWEB-INF/lib.

Thenextrecipeshowshowtopackageyourtaglibrary,includingtheTLD,inaJARfile.

SeeAlso

TheXMLschemafilefortheJSP2.0TLD:http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.5onpackagingtaglibrariesinaJARfile;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustom-tagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.5PackagingtheTagLibraryinaJARFile

Problem

YouwanttomakeyourtaglibraryavailableinaJARfile.

Solution

CreateaJARfilethatcontainsyourtaghandlerclassorclassesinthecorrectdirectorystructure(withsubdirectorynamesmatchingthepackagenames).PlacethetaglibrarydescriptorfileintheJAR'sMETA-INFdirectory.ThenputtheJARintheWEB-INF/libdirectoryofyourwebapplication.

Discussion

Tomakeyourtaglibraryportable,storeallofyourtaghandlerclassesandtagfilesinaJARfile.

InaJAR,storeanytagfilesinMETA-INF/tagsorasubdirectoryofMETA-INF/tags.Ifyoudon't,theJSPcontainerwillnotrecognizethemaslegitimatetagfiles.SeeRecipe22.11fordetails.

YoucangeneratethisJARfilefromadirectorythatcontainsyourtaglibraryclasses,includingtheirpackage-relatedsubdirectories.Forexample,thelogotagIdevelopedinthischapterhasapackagename

ofcom.jspservletcookbook,sotherelativepathtothisfileiscom/jspservletcookbook/LogoTag.class.IncludeaMETA-INFdirectoryatthetoplevelofthedirectorywheretheclassesarestored(e.g.,inthesamedirectoryastheonecontainingcom).PlaceyourtaglibrarydescriptorfileintheMETA-INFdirectoryoraMETA-INFsubdirectory.

Ifyourlibraryincludesanytagfiles,placetheminMETA-INF/tagsorasubdirectoryofMETA-INF/tags.Changetothedirectorycontainingallthesesubdirectoriesandtypethefollowingcommandline,substitutingyourownJARfilenameforcookbooktags.jar:

jarcvfcookbooktags.jar.

Don'tforgetthatperiod(.)characterattheend.Thistellsthejartooltoincludeallofthefilesanddirectoriesthatthecurrentdirectorycontainsinthearchive.

Makesureyourcomputer'sPATHenvironmentvariableincludesthepathtothebindirectoryofyourJavaSDKinstallation,asinh:\j2sdk1.4.1_01\bin.ThisallowsyoutotypejaratthecommandlinetolaunchtheJavajartool.

Toinstallthetaglibrary,justtaketheresultingJARfileandmoveitintoyourwebapplication'sWEB-INF/libdirectory.

TheJSPcontainer(inJSP1.2and2.0)automaticallylooksintheJAR'sMETA-INFdirectoryfortheTLDfileyoudonothavetoincludeataglibelementintheweb.xmldeploymentdescriptor.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4onpackagingataglibraryinawebapplicationwithoutusing


aJARfile;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11andRecipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).

Recipe22.6UsingtheCustomTaginaJSP

Problem

Youwanttouseacustomtagthatyouhavedevelopedandinstalled.

Solution

IncludeataglibdirectiveatthetopoftheJSP.Thetaglibdirectivemustidentifytheuriforyourtaglibrary,asthaturiisspecifiedinyourTLDfile.

Discussion

Tousethecustomtagsfromyourtaglibrary,theJSPhastohaveataglibdirective,asinExample22-4.TheuriattributematchestheuriyourTLDfilespecifies(seeRecipe22.5).Theprefixattributespecifiesthenamespaceforyourtags.Example22-4specifiestheprefixcbck;therefore,theJSPusesthelogotagfromthattaglibraryinthemannerof<cbck:logo>...</cbck:logo>.

Ifthetagenclosesbodycontent(it'snotanemptytag),makesuretoclosethetagproperly,asin</cbck:logo>asopposedto</logo>.

IftheJSPdoesnotusethetagasspecifiedintheTLD(forexample,ifitleavesoutamandatoryattribute),theJSPwillfailtocompilethefirsttimeitisrequested.

Example22-4.TheLogotagusedinaJSP


<html>

<head><title>Micasaessucasa</title></head>

<body>

<cbck:logoheading="<%=request.getParameter("level")%>"image="stamp.gif"width="42"

height="54">Thanksforvisiting</cbck:logo>

Here'salltheotherstuffthispagecontains...

</body>

</html>

InExample22-4,thelogotag'sheadingattributetakesaruntimeexpressionvaluesothattheusercandynamicallysettheattributevalue,asinthefollowingURL:http://localhost:8080/home/logoTest.jsp?level=1.

Figure22-2showsthewebbrowserdisplayforthisJSP.

Figure22-2.Thewebbrowserdisplayofacustomtagoutput

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.7HandlingExceptionsinaCustomTagClass

Problem

Youwantyourcustomtaghandlertodealwithanyexceptionsthrowninsidethetag.

Solution

ImplementtheTryCatchFinallyinterfaceinyourtaghandler.

Discussion

ThetagextensionAPIprovidestheTryCatchFinallyinterface,whichyoucanimplementinyourtaghandlerclasstowritecodedealingwithanyexceptionsthetaghandlermightthrow.IftheclassimplementsTryCatchFinally,itmustincludethemethodsdoCatch()anddoFinally().IndoCatch(),thecodehasaccesstoanyThrowableobjectthrownbydoStartTag()ordoEndTag(),forinstance.IndoFinally(),thecodeclosesanyresourcesthetaguses,suchasadatabaseconnection.

Ingeneral,thisinterfaceallowsthetaghandleritselftocatchandhandleanyexceptionsthatdonotaffecttheoutputoftheJSPenclosingthetag.Example22-5usesthesamecodeasExample22-1,butadditionalmethodsareaddedbyimplementingtheTryCatchFinallyinterface.

Example22-5.Alogotaghandlerthatcatchesany

exceptions






/**ThistaggeneratesathumbnailimageusingtheHTMLimgtag,nexttoatextmessage.

TheuserspecifiesthecontentofthemessageandtheHeadinglevel(i.e.,<H1>-<H6>)*/

publicclassLogoTagextendsBodyTagSupportimplementsTryCatchFinally{






publicintdoStartTag()throwsJspException{

try{


if(!(h>0&&h<7))


"The'heading'attributevaluemustbetween1and6"+

"inclusive.");

}catch(Exceptione){

thrownewJspException(e.getMessage());

}

returnEVAL_BODY_BUFFERED;

}


JspWriterout=pageContext.getOut();

StringimgDir=((HttpServletRequest)pageContext.getRequest()).

getContextPath()+"/images/";


try{

out.println("<imgsrc=\""+imgDir+image+"\"width=\""+

width+"\"height=\""+height+"\"align=\"left\">"+"<H"+

heading+">"+message+"</H"+heading+">");


returnEVAL_PAGE;

}//doEndTag

/*Thenexttwomethodshavetobeimplementedinthisclasssincetheclassimplements

TryCatchFinally*/

publicvoiddoCatch(Throwablet){

try{

//printtheexceptionmessageinsidetheJSPwherethetag

//appears

pageContext.getOut().println(t.getMessage()+"<br/>");


}

publicvoiddoFinally(){

//donothinghere,sincewedon'thaveanyresourcesopen

//likedatabaseconnections

}


this.heading=level;

}

/*THERESTOFTHESOURCECODEFROMEXAMPLE22-1CONTINUES...*/

}

Ifthetagthrowsanexception,thenthewebcontainerinvokesthedoCatch()methodandthetaghandlerprintstheexceptionmessagewheretheJSPwouldotherwiseoutputtheimageproducedbythetag.OurdoFinally()methoddoesnotdoanything,becausethiscodedoesnothaveanyopenresourcessuchasaFileInputStream.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition


(O'Reilly).

Recipe22.8CreatingaSimpleTagHandler

Problem

YouwanttocreateaJSP2.0simpletaghandler.

Solution

CreateaJavaclassthateitherimplementstheSimpleTaginterfaceorextendstheSimpleTagSupportclass.

Discussion

Inanefforttosimplifycustomtagdevelopment,theJSP2.0specificationaddedthejavax.servlet.jsp.tagext.SimpleTaginterfaceandtheSimpleTagSupportclass.TheSimpleTagSupportclassisdesignedtobethebaseclassfortaghandlersthatimplementSimpleTag.Thesetaghandlershavetoimplementjustonemethod,doTag().

TheJSP2.0specificationstatesthatvendorsshouldnotcachesimpletaghandlers,sodevelopersdonothavetoworryaboutthereuseoftaghandlerobjectsandreleasingobjectstateintheircode.

Example22-6mimicsthelogotaghandlercreatedinearlierrecipes,butusestheSimpleTagSupportclassfromtheJSP2.0APIinstead.

Example22-6.Asimpletaghandlerdisplayingalogo







/**ThistaggeneratesathumbnailimageusinganHTMLimgtag,alignednexttoatext

message.TheuserspecifiesthecontentofthemessageandtheHeadinglevel(i.e.,<H1>-

<H6>)*/

publicclassSimpleLogoTagextendsSimpleTagSupport{





publicvoiddoTag()throwsJspException,IOException{

//JspContextprovidesaccesstotheJspWriterforgenerating

//textfromthetag.Youcanalsogetanystoredattributevalues

//usingJspContext

JspContextjspContext=getJspContext();


try{


if(!(h>0&&h<7))


"The'heading'attributevaluemustbetween1and6"+

"inclusive.");

}catch(Exceptione){thrownewJspException(e.getMessage());}

//GetaJspWritertoproducethetag'soutput

JspWriterout=jspContext.getOut();

//thevalueofthe'imgDir'attributeisthewebapp's/images

//directory;thedirectorypathisstoredinasessionattribute

StringimgDir=(String)jspContext.findAttribute("imgDir");

if(imgDir==null||"".equals(imgDir))


"Noattributeprovidedspecifyingtheapplication's"+

"imagedirectory.");

//displaytheimgandHHTMLtags

out.println(newStringBuffer("<imgsrc=\"").append(imgDir).

append(image).append("\"width=\"").append(width).

append("\"height=\"").append(height).append("\"align=\"left\">").

append("<H").append(heading).append(">").toString());

//getJspBody()returnsa'JspFragment'object;calling'invoke()'

//onthisobjectwitha'null'parameterwillusetheJSPpage's

//JspWritertooutputthetag'snestedcontentintheJSP

getJspBody().invoke(null);

out.println(newStringBuffer("</H").append(heading).

append(">").toString());

}//doTag

//Attribute-relatedsettermethods


this.heading=level;

}

publicvoidsetImage(Stringname){

this.image=name;

}

publicvoidsetWidth(Stringwidth){

this.width=width;

}

publicvoidsetHeight(Stringheight){

this.height=height;

}

}//SimpleLogoTag

ThissimpletaghandleraccessesaJspContextobjectbycallingtheSimpleTagSupport'sgetJspContext()method.ThecodeusestheJspContexttoobtainthevalueofanattributestoredinthesession,aswellastoaccessaJspWritertogeneratethetag'soutput:

JspContextjspContext=getJspContext();

//furtheralonginthecode...

JspWriterout=jspContext.getOut();

//thevalueofthe'imgDir'attributeisthewebapp'simages

//directory;itisstoredinasessionattribute

StringimgDir=(String)jspContext.findAttribute("imgDir");

//codecontinues...

CallingtheSimpleTagSupport'sgetJspBody()methodreturnsaJspFragmentobject,whichrepresentsachunkofJSPcodeasanobject.Callingthisobject'sinvoke()methodwithnullastheparameterdirectstheoutputofthefragmenttotheJspWriteravailabletothetaghandler:

//Getthetag'sbodycontentandoutputitusingtheJspWriter

//thatisavailablebycallingJspContext.getOut()

getJspBody().invoke(null);

ThiscodedisplaysthecontentortextthattheJSPdeveloperincludedwithinthecustomaction'sstartandendtags.Thetaghandlerusesthetag'sbodycontentasthetextuallogomessage.Figure22-1inRecipe22.1showswhattheJSPpagelookslikeinawebbrowser.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.9oncreatingaTLDforasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.9CreatingaTLDforaSimpleTagHandler

Problem

YouwanttocreateaTLDforasimpletaghandler.

Solution

UsetheJSP2.0-styleTLDforthesimpletaghandler.

Discussion

ThesimpletaghandlerderivesfromtheJSP2.0API,soyoucanusetheTLDversionfromJSP2.0aswell.Example22-7showsthetaglibstarttagandthevariousxmlnsattributesthatyourTLDmustreproduceexactly.Then,unlessyouareusingJSP2.0TLDfeaturessuchasthetag-fileelement,youcanspecifythetagelementanditsnestedelementswiththesameXMLsyntaxthatyouusedforthepriorTLDversion.

Example22-7.AJSP2.0TLDfileforasimpletaghandler



xsi:schemaLocation=



version="2.0"

>








<tag>

<name>simplelogo</name>

<tag-class>com.jspservletcookbook.SimpleLogoTag</tag-class>



<attribute>




<description>

Theheadinglevelforthelogo;1through6.

</description>

</attribute>

<attribute>

<name>image</name>




</attribute>

<attribute>

<name>width</name>




</attribute>

<attribute>

<name>height</name>




</attribute>

</tag>

</taglib>

Tousethesimpletaghandlerinawebapplication,placetheTLDinasubdirectoryofWEB-INFlikeWEB-INF/tlds.Or,storetheTLDinaJARfile'sMETA-INFdirectoryorasubdirectorythereof.ThenputtheJARintheWEB-INF/libdirectory.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2-Recipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4-Recipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclassto


ataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).

Recipe22.10UsingaSimpleTagHandlerinaJSP

Problem

Youwanttouseacustomtagbasedonasimpletaghandler.

Solution

UsethetaglibdirectiveintheJSP,specifyingtheproperuriattributeforthetaglibrary.

Discussion

Makesuretopackagethetaglibrary,thesimpletaghandler,anditsassociatedTLD,asdescribedbyRecipe22.4andRecipe22.5andthenoteinRecipe22.9.Example22-8showstherestofthesetupneededtousethetaginaJSP.

Simpletaghandlersaredesignedtobeeasiertodevelop(byhavingonlyonemethodthatyouneedtoimplement:voiddoTag()).UsetheassociatedtagsinaJSPthesamewayyouusethetagsassociatedwithclassictaghandlers.

Example22-8.AJSPusesatagdefinedbyasimpletaghandler


<html>

<head><title>MeCasaSuCasa</title></head>

<body>

<%session.setAttribute("imgDir",(request.getContextPath()+

"/images/"));%>

<cbck:simplelogoheading=

"<%=request.getParameter(\"level\")%>"image=

"stamp.gif"width="42"height="54">

Thanksforvisitinghere</cbck:simplelogo>


</body>

</html>

TheJSPinExample22-8obtainsthevalueforthelogotag'sheadingattributewithaJSPexpression.TheJSPpageuserprovidesthevalueintheURLasin:

http://localhost:8080/home/logoTest.jsp?level=1

TheJSP'soutputlooksthesameastheoutputshowninFigure22-1ofRecipe22.1.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.11-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.11CreatingaJSPTagFile

Problem

Youwanttocreateacustomtagintheformofatagfile.

Solution

CreatethetagfileusingJSPsyntaxandwithanextensionof.tagor.tagx.PlacethetagfileinWEB-INF/tagsorinMETA-INF/tagsinsideaJARfile,orinasubdirectoryofeitherofthesedirectories.

Discussion

JSP2.0introducedtagfiles,whicharecustomtagsthatyouwriteusingJSPsyntax.TagfilesaredesignedtoallowdeveloperswithlittleornoJavaexperiencetocreatesimpletagsusingonlyJSPandXMLelements.Inaddition,tagfilesdonotrequireaTLD,althoughyoucandescribeatagfileinaTLD(seeRecipe22.12).Ifyoucreatethetagfile,thendropitintheWEB-INF/tagsdirectory,theJSPcontainercompilesthefileintoataghandlerclassthefirsttimeitsassociatedtagisusedinaJSP.

TheJSPcontainerconvertsthetagfileintoaclassthatextendsjavax.servlet.jsp.tagext.SimpleTagSupport.SeeRecipe22.8formoredetailsonthatclass.

Tagfileshaveintroducedafewmoredirectivesandstandardactions,suchasthetagandattributedirectives,aswellasthejsp:doBody

action.Example22-9showsthesenewsyntaxelements.Theexamplecreatesthesamelogotagwehaveworkedonthroughoutthischapter,butusestagfileformat.

Recipe22.14showshowtheresultingcustomtagcanbeusedinaJSP.

Example22-9usesatagdirectivetospecifythatthetag'sbodycontent(thetextthatappearsbetweenthestartandendtags)isscriptless.Thismeansthatthebodycontentcontainsonlytemplatetext,ELcode,andJSPactionelements.

Ifyouaredefininganemptytag,thebody-contentvalueis"empty."IfthetagacceptsJSPcodeinitsbody,use"JSP"forthisvalue.Thefourthbody-contentoptionis"tagdependent,"meaningthatthetagitselfinterpretsthecodeinitsbody(suchasSQLstatements).

SinceatagfilecanusenormalJSPsyntax,Example22-9usesataglibdirectivetousetheJSTL(seeChapter23).Thentheexampledefineseachoneofthetag'sattributes.

Rememberthattagandattributearedirectives,sotheircodestartswith"<%@."

Example22-9.AtagfilegeneratesacustomtagthatinsertsalogoinaJSP

<%@tagbody-content="scriptless"description="WritestheHTMLcodeforinsertingalogo."

%>

<%@taglibprefix="c"uri="http://java.sun.com/jstl/core"%>

<%@attributename="heading"required="true"rtexprvalue=

"true"description="Theheadinglevelforthelogo."%>

<%@attributename="image"required="true"rtexprvalue=

"true"description="Theimagenameforthelogo."%>

<%@attributename="width"required="true"rtexprvalue=

"true"description="Theimagewidthforthelogo."%>

<%@attributename="height"required="true"rtexprvalue=

"true"description="Theimageheightforthelogo."%>

<imgsrc="<c:outvalue="${imgDir}${image}"/>"width=

"<c:outvalue="${width}"/>"height="<c:outvalue=

"${height}"/>"align="left">

<H<c:outvalue="${heading}"/>><jsp:doBody/></H<c:outvalue="${heading}"/>>

TheattributesfortheattributedirectivearethesameastheattributesthatyouuseforaJSP1.2-styleTLDfile(seeRecipe22.2).Sinceatagfileacceptsplaintemplatetext,thisishowwehavesetuptheHTMLimgtagthatthetagfileisdesignedtogenerate.

Theimgtaggetsthevaluesforitsownattributesusingthec:outJSTLtagandtheEL(seeChapter23).Forexample,theexpression"${imgDir}"returnsthevalueforastoredobjectattributeofthesamename,whichspecifiesadirectorythatcontainstheimageusedinthelogo.Theexpression"${image}"returnsthevalueofthetag'simageattributewhich,bythislineofthecode,hasalreadybeensetbytheuser.

Thejsp:doBodystandardactionisaniftywaytooutputthetextbetweenthecustomaction'sstarttagandendtag.

Thejsp:doBodyaction,aswellasthetag,attribute,andvariable(notshowninthisrecipe)directives,canbeusedonlyintagfiles.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.12-Recipe22.14onusingaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.12PackagingtheJSPTagFileinaWebApplication

Problem

Youwanttostorethetagfileforuseinawebapplication.

Solution

PlacethetagfileinWEB-INF/tagsorinMETA-INF/tagsinsideaJARfileorinasubdirectoryofeitherofthesedirectories.IfyoudothisyoudonotneedtodescribethetaginaTLDfile.

Discussion

TheJSPcontainerfindsthetagfilebyusingthetagDirattributeofthetaglibdirective.Inotherwords,thetagDirattributeprovidesthepathtothewebapplicationdirectorywhereyoustoredthetagfile.Here'sanexample:

<%@taglibprefix="cbck"tagdir="/WEB-INF/tags"%>

Aslongasyouplacethetagfile,whichhasa.tagextension(or.tagxextensionifthetagfileisinXMLsyntax)in/WEB-INF/tags,JSPscantousethetagassociatedwiththetagfile.

TheJSPhastopositionthetaglibdirectiveinthecodebeforetheJSPusestheassociatedcustomtag.

TheJSP2.0TLDcanalsospecifythetagfileinthefollowingmanner:

<tag-file>

<name>dbSelect</name>

<path>/WEB-INF/tags/dbtags</path>

</tag-file>

ThisTLDentryspecifiesatagfilenameddbSelect.tag,whichresidesinthe/WEB-INF/tags/dbtagsdirectory.Thepathattributemustbeginwith"/META-INF/tags"ifthetagfileresidesinaJAR,and"/WEB-INF/tags"ifthetagfileislocatedinaWebArchive(WAR)fileorinanonarchivedwebapplication.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.13andRecipe22.14onpackagingatagfileandusingitinaJSP;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.13PackagingtheJSPTagFileinaJAR

Problem

YouwanttostorethetagfileinaJARfile.

Solution

PlacethetagfileintheJAR'sMETA-INF/tagsdirectoryorasubdirectorythereof.

Discussion

DeveloperscommonlydistributetaglibrariesasJARfiles,particularlyiftheyhavedesignedthetaglibrarytobeportable.ForJSP2.0-styletaglibrariesthatareusingtagfiles,placethetagfileinMETA-INF/tagsorasubdirectoryofMETA-INF/tags.Thetagfilemusthavea.tagextension,ora.tagxextensionifit'satagfileinXMLsyntax.

ThenplacetheJARfileinWEB-INF/libofanywebapplicationcontainingJSPsthatwillusethetag.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7


onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.14onusingatagtagfilebasedonatagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).

Recipe22.14UsingaCustomTagAssociatedwithaTagFile

Problem

Youwanttouseacustomtagassociatedwithatagfile.

Solution

UsethetaglibdirectiveintheJSP,beforethecodethatusesthetagfilerelatedtag.

Discussion

Thetaglibdirectiveidentifiesthetagwithitstagdirattribute,whichisthewebapplicationpathtothetagsdirectory.Example22-10usesthetagfromatagfilestoredat/WEB-INF/tags/logo.tag.

ThetagnameintheJSPisthesameasthetagfilename,withoutthe.tagextension.Theprefixattributerepresentsthecustomtag'snamespace,sotheentiretagisusedintheJSPas"<cbck:logoheading=...>...tagcontent...</cbck:logo>."

Example22-10.AJSPusesatagdefinedinatagfile

<%@taglibprefix="cbck"tagdir="/WEB-INF/tags"%>

<html>

<head><title>MeCasaSuCasa</title></head>

<body>

<%session.setAttribute("imgDir",(request.getContextPath()+"/images/"));%>

<cbck:logoheading="<%=request.getParameter(\"level\")%>"image=

"stamp.gif"width="42"height="54">

Thanksforvisitinghere...

</cbck:logo>


</body>

</html>

Iusethesamebasiclogotagthroughoutthischaptertoillustratethevariouscustom-tagsyntaxdifferences.SeeRecipe22.2fordetailsonthelogotagitself.

SeeAlso

TheJSP2.0specificationwebpage:http://jcp.org/en/jsr/detail?id=152;Recipe22.2andRecipe22.3oncreatingTLDfilesfortaglibraries;Recipe22.4andRecipe22.5onpackagingataglibraryinawebapplication;Recipe22.6onusingthecustomtaginaJSP;Recipe22.7onhandlingexceptionsintags;Recipe22.8andRecipe22.9oncreatingasimpletaghandler;Recipe22.10onusingthesimpletaghandlerinaJSP;Recipe22.11-Recipe22.13onsettingupaJSPtagfile;Recipe22.15onaddingalistenerclasstoataglibrary;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).


Recipe22.15AddingaListenerClasstoaTagLibrary

Problem

Youwanttoincludealistenerclasswithyourtaglibrary.

Solution

AddalistenerelementtoyourTLDfile.

Discussion

TheservletAPIincludes"applicationeventlisteners,"whicharespecialJavaclassesthatarenotifiedbythewebcontainerwhencertaineventsoccur,suchasthecreationofanewusersession(seeChapter11).Youcanincludelistenerclasseswithyourtaglibraries.Forexample,youmighthaveasession-relatedtagthatneedstoknowwhensessionsarecreatedordestroyed.

Thelistenerelementhasexactlythesamesyntaxasitmayappearintheweb.xmldeploymentdescriptor.Example22-11showsalistenerelementincludedinaJSPVersion2.0TLD.

Example22-11.AddingalistenerelementtoaJSP2.0TLD

xsi:schemaLocation=



version="2.0"

>






<listener>

<listener-class>

com.jspservletcookbook.ReqListener

</listener-class>

</listener>

<tag>



</tag>

</taglib>

TheJSPspecificationrequirestheJSPcontainertoautomaticallyinstantiateandregisterthelistenersthatareassociatedwithtaglibraries.Alistenercanbeusedwithataglibrarytotrackthenumberofrequeststhewebapplicationisreceiving,asshownintheServletRequestListenerinExample18-8(Recipe18.6).

JSP1.2'sTLDfileusesanXMLDTD.Therefore,theTLDelementsmustappearinaspecificsequence.Thelistenerelementisnestedinsidethetaglibelement;listenerappearsafteralloftheothernestedelementsexceptfortag.Youcanprecedeyourtagelementswiththelistenerelement.IntheJSP2.0TLD,ontheotherhand,youcanpositionthelistenerrightafterthetaglibrootelement.

StoreanylistenerclassesinthesameJARfileastheonecontaininganytaghandlerclasses.

Makesuretospecifythelistenerclassinthelistener-classelementasafullyqualifiedclassname,ortheJSPcontainerwillprobablyhavetroublefindingtheclass.

SeeAlso

Example18-8inRecipe18.6foranexampleofaclassthatimplementsthejavax.servlet.ServletRequestListener;Chapter11andChapter14forseverallistener-relatedrecipes;Recipe22.2oncreatingaJSP1.2TLDfile;Recipe22.3oncreatingaJSP2.0TLD;Recipe22.9oncreatingaTLDforasimpletaghandler;thecustomtagsectionsofHansBergsten'sJavaServerPages,ThirdEdition(O'Reilly).

Chapter23.UsingtheJSTLIntroduction

Recipe23.1.DownloadingtheJSTL1.0andUsingtheJSTLTagsinJSPs

Recipe23.2.DownloadingtheJavaWebServicesDeveloperPack

Recipe23.3.UsingtheCoreJSTLTags

Recipe23.4.UsingtheXMLCoreJSTLTags

Recipe23.5.UsingtheXMLTransformTags

Recipe23.6.UsingtheFormattingJSTLTags

Recipe23.7.UsingASQLJSTLTagwithaDataSourceConfiguration

Recipe23.8.UsingASQLJSTLTagWithoutaDataSourceConfiguration

Recipe23.9.AccessingScopedVariableswiththeEL

Recipe23.10.AccessingRequestParameterswiththeEL

Recipe23.11.UsingtheELtoAccessRequestHeaders

Recipe23.12.UsingtheELtoAccessOneRequestHeader

Recipe23.13.AccessingCookieswiththeEL

Recipe23.14.UsingtheELtoAccessJavaBeanProperties

Recipe23.15.UsingJSTLFunctions

Introduction

JavaServerPage'scustomtagsandtaghandlersaredesignedtohelpyouinventyourowntags.WhilethisisapowerfultoolforJavawebdevelopers,developingcustomtagsentailsasteeplearningcurveandcanbetimeconsuming.Luckily,somehard-workingvolunteersoftwaredevelopershavedevelopedabunchofhighlyusefultagsforyou.ThistagcollectioniscalledtheJavaServerPagesStandardTagLibrary(JSTL).TheJSTLspecificationarisesfromtheJavaCommunityProcess(JSR-052)andtheApacheJakartaProjecthasdevelopedaJSTLimplementation,theStandard1.0taglib.

TheJSTLhasverybroadfunctionality.Itincludestagsthat:

1. Setobjectattributesforwebapplications(c:set).

Outputtexttowebpages(c:outandx:out).

Iterateovercollectionsofdata(c:forEachandx:forEach).

Formatnumbers,dates,andcurrenciesusingdifferentinternationalstyles(e.g.,fmt:formatDate,fmt:formatNumber).

TransformXML(x:transform).

InteractwithdatabasesusingSQL(e.g.,sql:query,sql:update).

AllowyoutoembedfunctioncallsinJSPcodeandtemplatetext(e.g.,fn:substring()).ThisfunctionalityisavailableonlywithJSP2.0andJSTL1.1(seeRecipe23.14).

TheJSTLoriginatedaveryimportantnewJSPtechnology,theExpressionLanguage(EL).ThisisascriptinglanguagebasedgenerallyonJavaScriptandotherscriptingtoolsthat,withJSP2.0,canbe

embeddedinHTMLtemplatetext.

TheELwasoncepartofJSTL1.0buthasnowmigratedtotheJSPspecification.TheELmustbeimplementedwithJSP2.0containerssuchasTomcat5.

ThischapterisdesignedtostartyouquicklywiththeJSTL,whichcommonlyhastobedownloadedandinstalledinawebapplication.ManywebcontainerseventuallyintegrateorhavealreadyintegratedaJSTLimplementationwiththeirservletandJSPengines.

Recipe23.1DownloadingtheJSTL1.0andUsingtheJSTLTagsinJSPs

Problem

YouwanttodownloadandusetheJSTL.

Solution

DownloadtheJSTLdistribution,inaZIPorTARfile,fromtheApacheJakartaProject.

Discussion

TheApacheJakartaProjecthoststhereferenceimplementation(RI)fortheJSTL.AnRIissoftwarethatisdesignedtoimplementaparticularJavatechnologyspecificationinordertodemonstratehowthesoftwareisintendedtofunction.RIsarefreelyavailableforusebysoftwarevendorsanddevelopers.YoucandownloadthebinaryorsourcedistributionoftheJSTLfromhttp://jakarta.apache.org/taglibs/doc/standard-doc/intro.html.

UnpacktheZIPorTARfileintothedirectoryofyourchoice.Thiscreatesajakarta-taglibsdirectory.

ThisrecipeusestheStandardTaglibVersion1.0.3,animplementationoftheJSTL1.0.However,bythetimeyoureadthis,theJakartaTaglibssitewillhaveintroducedStandardTaglibVersion1.1,whichisanimplementationoftheJSTL1.1.Thenewversionincludessomenewfeaturessuchasfunctions,whicharedescribedinRecipe23.14.

http://jakarta.apache.org/taglibs/doc/standard-doc/intro.html

Insidethestandard-1.0.3directoryisalibsubdirectory.ThisdirectorycontainsanumberofJARfiles,includingjstl.jarandstandard.jar.Thejstl.jarcontainstheJSTL1.0APIclasses;standard.jarisacollectionofJSTL1.0implementationclasses.AddalloftheJARfilesfoundinyourJSTLdistribution'slibdirectory(jakarta-taglibs/standard-1.0.3/libintheexample)toWEB-INF/lib.

JSTL1.1onlyrequirestheinstallationofjstl.jarandstandard.jarin/WEB-INF/libifyouareusingJ2SE1.4.2orhigher(aswellasServlet2.4andJSP2.0).

Table23-1describeseachoftheJARfilesfoundinthedistribution'slibdirectory(courtesyoftheStandardTaglib1.0documentation).

Table23-1.ContentsoftheJSTL1.0referenceimplementationlibdirectory

Filename Purpose

jstl.jar JSTL1.0APIclasses

standard.jar JSTL1.0implementationclasses

jaxen_full.jar Xpathengineclasses

jdbc2_0-stdext.jar JavaDatabaseConnectivity(JDBC)implementationclasses(alsoincludedwithJ2SE1.4)

saxpath.jar SimpleAPIforXpathparsing

xalan.jar ApacheXalanExtensibleStyleSheetTransformations(XSLT)processor

dom.jar,jaxp-api.jar,sax.jar,xercesImpl.jar JavaAPIforXMLProcessing(JAXP)1.2APIlibraries

IntheJSPwhereyouwanttousetheJSTLtags,usethepropertaglibdirectiveshowninTable23-2.Forexample,ifyouuseallofthedifferentJSTLfunctions(core,XML,formatting,andSQL),yourJSPcontainsallofthefollowingtaglibdirectives,preferablyatthetopoftheJSPpage(theymustappearbeforethetagsareused).

Table23-2.ThetaglibdirectivesfordifferentJSTLfunctions,version1.0

JSTLlibrary taglibdirective

Core <%@tagliburi="java.sun.com/jstl/core"prefix="c"%>

XMLprocessing <%@tagliburi="java.sun.com/jstl/xml"prefix="x"%>

Formattingdata(suchasdatesandcurrencies)forinternationalusers

<%@tagliburi="java.sun.com/jstl/fmt"prefix="fmt"%>

SQLandDatabaseaccess <%@tagliburi="java.sun.com/jstl/sql"prefix="sql"%>

TheJavacommunityisnowworkingontheJSTLVersion1.1,whichwillrequireaJSP-2.0compatibleJSPcontainer.JSTL1.1willusethesedifferenturivaluesinthetaglibdirective:

http://java.sun.com/jsp/jstl/core,sotheentiretaglibdirectivewouldlooklike:<%@tagliburi="java.sun.com/jsp/jstl/core"prefix="c"%>

http://java.sun.com/jsp/jstl/xml,creatingataglibdirectiveof:<%@tagliburi="java.sun.com/jsp/jstl/xml"prefix="x"%>

http://java.sun.com/jsp/jstl/fmt,asusedinthetaglibdirective:<%@tagliburi="java.sun.com/jsp/jstl/fmt"prefix="fmt"%>

http://java.sun.com/jsp/jstl/sql,creatingataglibdirectiveof:<%@tagliburi="java.sun.com/jsp/jstl/sql"prefix="sql"%>

SeeAlso

TheJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;SunMicrosystem'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingXML-relatedtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8ontheJSTL'sSQLfeatures;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.

http://jakarta.apache.org/taglibs/index.html

http://java.sun.com/products/jsp/jstl/default.htm

Recipe23.2DownloadingtheJavaWebServicesDeveloperPack

Problem

YouwanttodownloadtheJavaWebServicesDeveloperPack(WSDP)sothatyoucanuseaJSTL1.1referenceimplementation.

Solution

VisittheSunMicrosystemsJavaWSDPdownloadsiteathttp://java.sun.com/webservices/jwsdp.

Discussion

TheJavaWSDPVersion1.2containsreferenceimplementationsoftheJSTL1.1,aswellasseveralotherwebtiertechnologies,includingtheServletAPI2.4andJSP2.0.TheWSDPisbundledwithTomcat5,soonceyouinstalltheWSDPyoucanexperimentwiththevarioustechnologies,includingJavaServerFaces,JavaArchitectureforXMLBinding(JAXB),JavaAPIforXMLProcessing,andJavaAPIforXML-basedRPC(Jax-RPC).

TheJavaWSDP1.2installsonbothWindowsandvariousUnixsystems,suchasSolarisandLinux.Recipe23.15showshowtouseJSTL1.1functions;IusetheWSDPforthisrecipe.

UsingTomcat5andthenewJSTL1.1featuressuchasfunctionsandtheembeddingofELcodeintemplatetextrequiresyoutousetheservletAPI2.4versionofweb.xml.SeeRecipe23.15formoredetailsonthisissue.

http://java.sun.com/webservices/jwsdp

SeeAlso

TheSunMicrosystemsJavaWSDPdownloadsiteat:http://java.sun.com/webservices/jwsdp;Recipe23.15onusingJSTL1.1functions;Sun'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingXML-relatedtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8ontheJSTL'sSQLfeatures;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.

http://java.sun.com/webservices/jwsdp


Recipe23.3UsingtheCoreJSTLTags

Problem

YouwanttousethecoreJSTLtagsinaJSP.

Solution

UsethetaglibdirectivewiththecoreuriattributevaluetomakethetagsavailableintheJSP.

Discussion

ThisrecipedemonstratesseveralJSTLtagsthatyouuseallthetime:c:set,c:out,c:forEach,andc:if.Herearethetagsummaries:

Thec:settagsetsobjectattributestopage,request,session,orapplicationscopes.

Thec:outtagdisplaystextliteralsorthevaluesofvariablesorbeanpropertiesinyourJSPs.

Thec:forEachtagiteratesoverMaps,Collections,andarrays.

Thec:iftagtestsexpressionsfortrueorfalsevalues,thenconditionallyexecutesthecodenestedinthec:ifbody.

RemembertousetheprefixforthecertainfunctionalareaoftheJSTL,suchasc,

followedbyacolon,andthetagname,asin"c:forEach."

Example23-1isahelperclassthatIfindnecessarytoproperlyreturnaStringarrayofTimeZoneIDstotheJSPinExample23-2.

Example23-1.AhelperclasstohelpdisplayTimeZoneIDs


importjava.util.TimeZone;

publicclassZoneWrapper{

publicZoneWrapper(){}

publicString[]getAvailableIDs(){

returnTimeZone.getAvailableIDs();

}

}

Example23-2showshowtouseanumberofthecoreJSTLtags.Thecodeusesthejsp:useBeanstandardactiontocreateZoneWrapper(Example23-1)andjava.util.Dateobjectsforusebythetags.

Example23-2.UsingcoreJSTL1.0tagsinaJSP


<jsp:useBeanid="zone"class="com.jspservletcookbook.ZoneWrapper"/>


<html>

<head><title>UsingtheCoreJSTLtags</title></head>

<body>

<h2>HerearetheavailableTimeZoneIDsonyoursystem</h2>

<c:iftest="${date.time!=0}">

<c:outvalue=

"Phew,timehasnotstoppedyet...<br/><br/>"escapeXml="false"/>

</c:if>

<%--Thevariable'zones'containsaStringarrayofTimeZoneIDs;itisstoredasa

'session'objectattribute.The'${zone.availableIDs}'expressionistheequivalentof

callingtheZoneWrapper.getAvailableIDs()method--%>

<c:setvar="zones"value="${zone.availableIDs}"scope="session"/>

<c:forEachvar="id"items="${zones}">

<c:outvalue="${id}<br/>"escapeXml="false"/>

</c:forEach>

</body>

</html>

Thec:iftagusesanELphrasetotestwhethertheDateobject'sgetTime()methodreturnsavaluethatisnotzero(ofcourseitdoes!I'mjustdemonstratinghowtousethec:iftag).

${date.time!=0}

ThepriorcoderepresentsabooleanexpressionthatreturnstrueifDate.getTime()isgreaterthanzero.Iftrue,thenthecodeexecutesthenestedc:outtag,whichwritesamessagethattheclient'sbrowserdisplays.

TheescapeXml="false"codedisplaysthecharacters<br/><br/>correctlyintheHTMLoutputbythec:outtag.SeeTable23-3.

Example23-2setsanobjectattributetosessionscope.ThisobjectisaString[]typecontainingtimezoneIDs,suchas"Pacific/Tahiti."Thec:forEachtagtheniteratesoverallofthesearraymembers,displayingeachIDwiththec:outtag:

<c:forEachvar="id"items="${zones}">


</c:forEach>

Thevarattributeofthec:forEachtagstoresthecurrentarraymemberasc:forEachcyclesoverthecollection.Thec:outtagusesanELexpressiontoaccessthevalueofthecurrentarraymember:


IfyoudonotgivetheescapeXmlattributeafalsevaluewhenusingc:out,thecharacterentitycodesshowninTable23-3willdisplayinsteadoftheescapedcharacters.

Table23-3.Thec:outtag'sescapedcharacters

c:outvalueattributecharacter Characterentitycode

< <

> >

& &

` '

" "

Figure23-1showsapartoftheJSPusingthecodeinExample23-2.

Figure23-1.AJSPusingthevariouscoretagstodisplaytimezoneIDs

SeeAlso

Recipe6.8onincludingcontentinaJSPwiththec:urltag;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.4andRecipe23.5onusingXML-relatedtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8ontheJSTL'sSQLfeatures;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.



Recipe23.4UsingtheXMLCoreJSTLTags

Problem

YouwanttousetheJSTL'sXMLtagsinaJSP.

Solution

UsethevariousXMLtagsafterdeclaringthetaglibrarywiththepropertaglibdirective(uriattributeofhttp://java.sun.com/jstl/xmlforJSTL1.0orhttp://java.sun.com/jsp/jstl/xmlforJSTL1.1).

Discussion

ManywebdevelopershavetowriteprogramsthatparseorreadXMLtofindinformation,ortheyhavetowritecodethatdisplaystheencapsulatedXMLinformationinareadableformat.TheJSTLXMLtagsareanicetoolforthesetasks.Example23-3displayssomeinformationfromanAntbuild.xmlfile.(SeeChapter4ontheAnttoolifyouarenewtoAnt.)I'musingthisXMLfilejustforanexampleofhowtousetheXML-relatedJSTLtags.NoticethatthetaglibdirectivesatthetopofthepageallowtheuseoftheXMLandcoreJSTLtagsfurtheralonginthecode.

Example23-3.AJSPparsesanantbuildfile

<%@tagliburi="http://java.sun.com/jstl/xml"prefix="x"%>


<html>

<head><title>UsingtheCoreXMLtags</title></head>

<body>

<h2>HerearethetargetandpropertyvaluesfromtheXMLfile</h2>

<c:importurl="http://localhost:8080/home/build.xml"var="buildXml"/>

<x:parsexml="${buildXml}"var="antDoc"/>

<h3>Firstthetargetnames...</h3>

<x:forEachselect="$antDoc/project/target">

<x:outselect="@name"/>

<x:ifselect="@depends">:depends=<x:outselect="@depends"/></x:if><br/>

</x:forEach>

<h3>Thenpropertynamesandvalues...</h3>

<x:forEachselect="$antDoc/project/target/property">

<x:outselect="@name"/>:value=<x:outselect="@value"/><br/>

</x:forEach>

</body>

</html>

Example23-3usesthec:importtagtoimportabuildfileandstoreitinavariablecalledbuildXml.Thethex:parsetagthenparsestheimporteddocumentintoaformorobjectthattheotherXMLtagscanworkwith.ThecodestorestheparsingresultinanothervariablenamedantDoc.

TheXMLJSTLtagsusesomeofthesametagnamesasthecorelibrary,butadifferentprefix("x").Thex:forEachtaginExample23-3usesanXPathexpressionasthevalueofthex:forEachselectattribute.

XPathisanXMLtechnologythatisdesignedtosearchforandselectportionsor"nodesets"ofthehierarchicaltreerepresentedbyanXMLdocument.WhileanXPathtutorialiswellbeyondthescopeofthisrecipe(itislikealittleprogramminglanguageinitself),thereareplentyofonlinetutorialsandbooksonthesubject.YoucanstartattheSunMicrosystemswebservicestutorial,whichincludesadiscussionofXPath:http://java.sun.com/webservices/docs/1.3/tutorial/doc/.

Thex:forEachtagmakesnestedelementssuchasx:outavailabletoanynodesgrabbedbytheXPathexpression.ThecodeinExample23-3displaysthenameofeachAnttargetinthebuild.xmlfilebyfirstcollectingasetofallofthetargetelementswiththisexpression:

<%--thisXPathexpressionistheequivalentof"beginattheroot'project'element

andgetallofitsnested'target'elements"--%>

<x:forEachselect="$antDoc/project/target">

Example23-3outputsthenameofeachtargetwiththiscode:

<x:outselect="@name"/>

Theenclosingx:forEachtagestablishesthecontextoftheXPathexpressioninthisx:outtag.

Thefollowingcodestates"returntrueifthecurrentnodehasavaliddependsattribute."

<x:ifselect="@depends">

Ifthatexpressionreturnstrue,thenestedx:outtagoutputsthevalueofthedependsattribute.Figure23-2showstheresultofrequestingtheJSPofExample23-3inabrowser.I'veconvertedtheXMLinformation

http://java.sun.com/webservices/docs/1.3/tutorial/doc/default.htm

intoamorereadableformatforabrowser.XMLmavens(meaningthosewhocansiftthroughallofthesecrazyacronyms!)declarethatyoucanalsouseExtensibleStylesheetLanguageTransformations(XSLT)forconvertingXMLinformationtoHTMLorotherreadableforms.Thisisthenextrecipe'stopic.

Figure23-2.AJSPshowstheoutputofaparsedXMLfile

SeeAlso

TheJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;SunMicrosystem'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.5onusingtheXMLTransformtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8ontheJSTL'sSQLfeatures;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.



Recipe23.5UsingtheXMLTransformTags

Problem

YouwanttousetheJSTL'sXMLandXSLT-relatedtags.

Solution

UsethevariousXMLtagsafterdeclaringthetaglibrarywiththepropertaglibdirective(uriattributeofhttp://java.sun.com/jstl/xmlforJSTL1.0orhttp://java.sun.com/jsp/jstl/xmlforJSTL1.1).

Discussion

AnumberofwebsiteteamsmayalreadyhavedevisedstylesheetsfortransformingXMLintoHTML.Inaddition,youmaywanttoseparatemostoftheXMLtransformationresponsibilitiesfromJSPs,sothatJSPsfocusonlyonpresentingthetransformedinformation.TheJSTLprovidesXML-relatedtagstoeasilyintegratestylesheetsintoJSPs.Example23-4isanExtensibleStylesheetLanguage(XSL)documentthatconvertsanXMLfileintoHTML.ThestylesheetprovidesaconversionofanAntbuildfilesimilartotheonedescribedinRecipe23.3.

Example23-4.ThestylesheetfortransforminganXMLfile


<xsl:stylesheetxmlns:xsl="http://www.w3.org/1999/XSL/Transform"version="1.0">

<xsl:outputmethod="html"/>

<xsl:templatematch="/">

<html><head><title>Listofbuild.xmltargets

</title></head><bodybgcolor="white"><h2>Build.xmltargets</h2>

<xsl:apply-templates/>

</body></html>

</xsl:template>

<xsl:templatematch="/project">

<dl>

<xsl:for-eachselect="./target">

<dt><b>

<xsl:value-ofselect="@name"/></b> </dt>

<xsl:iftest="@depends">

<dd>depends=<xsl:value-ofselect="@depends"/> </dd>

</xsl:if>

</xsl:for-each>

</dl>

</xsl:template>

<xsl:templatematch="text()">

<xsl:value-ofselect="normalize-space()"/>

</xsl:template>

</xsl:stylesheet>

HowdoyouapplythisXSLfiletothebuild.xmlfiletoproduceareadable

format?Example23-5usesthex:transformtagtoassociateastylesheetwithanXMLfile.First,theJSPhastoimportboththestylesheetofthepriorexampleandtheXMLfilethisstylesheettransformsbyusingthec:importtag.Thec:importtagimportstheresourcespecifiedbyitsurlattributeandstoresitinavariable(e.g.,buildXml)thatthex:transformtagcanaccess.

Example23-5.AJSPdisplaystheresultofanXSLtransformation

<%@tagliburi="http://java.sun.com/jstl/xml"prefix="x"%>


<c:importurl="http://localhost:8080/home/build.xml"var="buildXml"/>

<c:importurl="/WEB-INF/xslt/chap23.xsl"var="xslt"/>

<x:transformxml="${buildXml}"xslt="${xslt}"/>

Thex:transformtagmakesthetransformationprocessveryeasy,onceyou'veputtogetheravalidstylesheetfile.Thex:transformtag'sxmlattributespecifiestheXMLfilethatthex:transformtaghandlertransformsbyapplyingastylesheet.Thecodespecifiesthestylesheettouseinthetransformationwiththex:transformtag'sxsltattribute.

Thexmlandxsltattributesofx:transformresolvethevariablesthatrepresentthestylesheetandtheXMLfilebyusingtheEL,asin:

${buildXml}

Figure23-3showstheresultofrunningtheJSPofExample23-5.Inshort,x:transformprovidesyourveryownXSLTprocessorforuseintheJSP.

Figure23-3.AJSPshowstransformedXMLcontent

SeeAlso

TheJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.2onusingthecoretags;Recipe23.3onusingthevariousXML-relatedtags;Recipe23.5onusingtheformattingtags;Recipe23.6andRecipe23.7ontheJSTL'sSQLfeatures;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,requestheadersandparameters,cookies,andJavaBeanproperties.



Recipe23.6UsingtheFormattingJSTLTags

Problem

YouwanttoformatadateoranumberusingtheJSTL.

Solution

Usethefmt:formatDateandfmt:formatNumberactions.

Discussion

Internationalizationor"i18n"istheprocessbywhichwebdevelopersdesigntheirwebsitestoaccommodatevisitorswhousedifferentlanguages.

Theterm"i18n"meansinternationalizationbeginswith"i,"isfollowedby18letters,andendswith"n."Itisdesignedtorelievethetediumofspellingoutthewordseveraltimes.

Localizationmeansaddingspecificresourcestoawebsitetoenablemessagessuchaswebpagegreetingstobetranslatedintothevisitor'slanguage.Forexample,youmightlocalizeasiteforJapanesevisitorsbyaddingresourcesthatcontainJapanesetranslationsoftextthatappearsonwebpages(Icovermorei18n-relatedJavacodeinChapter24).Example23-6usestheJSTLformattingtaglibrarytodisplaythecurrentdateandalargenumberinSwissandU.S.styles.

Example23-6.showingadateandanumberforU.S.andSwissaudiences


<%--includethistaglibfori18nrelatedactions--%>


<html>

<head><title>Formattingnumbersanddates</title></head>

<body>

<h2>DatesandnumbersinSwissandUSstyleformats</h2>

<%--createanobjectrepresentingthecurrentdate--%>

<jsp:useBeanid="now"class="java.util.Date"/>

<%--setthelocaletoGermanlanguage,Swisscountrycode--%>

<fmt:setLocalevalue="de_CH"/>

<strong>Swiss-styledate:</strong>

<%--outputthedate--%>

<fmt:formatDatetype=

"both"value="${now}"dateStyle="full"timeStyle="short"/>

<br/>

<strong>Swiss-stylenumber:</strong>

<%--outputtheequivalentofjava.util.Date.getTime()toshowhownumbersareformatted

--%>

<fmt:formatNumbervalue="${now.time}"/>

<br/><br/>

<%--resetthelocaletoEnglishlanguage,UScountrycode--%>

<fmt:setLocalevalue="en_US"/>

<strong>US-styledate:</strong>

<%--outputthedate--%>

<fmt:formatDatetype="both"value="${now}"dateStyle=

"full"timeStyle="short"/>

<br/>

<strong>US-stylenumber:</strong>

<fmt:formatNumbervalue="${now.time}"/>

<br/><br/>

</body>

</html>

Example23-6usesfmt:setLocaletosetthecontextforformattingdatesandnumbersfirsttoSwiss-German("de_CH"),thenbacktoU.S.English("en_US").

A"locale"representsaparticularcultural,geographic,orpoliticalregion.LocalesaretypicallyspecifiedbyaStringshowingalanguagecodefollowedbyanunderscore"_"andthecountrycode.SeeChapter24foranexpandeddiscussionofi18ntopics.

Bothfmt:formateDateandfmt:formatNumberusethecurrentlocaletoformattheirinformation.Thefmt:formateDatetaghasseveralattributesthataredesignedtoconfigurethedateformat.Thebothattributespecifieswhethertooutputonlythedate,thetime,orboththedateandtime,asinExample23-6.ThedateStyleandtimeStyleattributeshavesettingsthatderivefromthejava.text.DateFormat

class.Example23-6specifiesa"full"datedisplaythatincludesthedayofweek,themonth,andtheyear.Thecodealsospecifiesa"short"timedisplay(suchas"8:07").

Figure23-4showstheJSPthatformatsdatesandnumbersforSwiss-GermanandU.S.Englishspeakers.ThereareseveralotherformattingrelatedJSTLtags,whichtherecipesofChapter24coverinmoredetail.

Figure23-4.Thefmt:formatDateandfmt:formateNumbertagsperformtranslationmagicinaJSP

SeeAlso

Chapter24onusingtheJSTL'sseverali18n-relatedtags;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.5onusingtheXMLTransformtags;Recipe23.7andRecipe23.8ontheJSTL'sSQLfeatures;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.



Recipe23.7UsingASQLJSTLTagwithaDataSourceConfiguration

Problem

Youwanttointeractwitharelationaldatabasebyconfiguringthejavax.sql.DataSourceinthedeploymentdescriptor.

Solution

Addacontext-paramelementtoweb.xml,creatingaparameternamedjavax.servlet.jsp.jstl.sql.dataSourcethatconnectswithaparticulardatabase.

Discussion

TheJSTLSQLtaglibraryallowsaJSPtointeractwithadatabaseusingcustomtags.JavaDatabaseConnectivity(JDBC)andtheclassesinthejavax.sqlpackageallowthistechnologytowork.ThefirststepinthisrecipeistoconfiguretheDataSourcethatthetagswillusetoconnectwithadatabase.

ADataSourceisafactoryforjava.sql.Connectionobjects,whichrepresentasocketconnectionwithaparticulardatabaseserversuchasMySQLorOracle.

Example23-7createsacontext-paramelementinweb.xml.Forthe

JSTL'sSQLtagstoautomaticallyreceivetheirConnectionsfromthissetting,theparamnamemustbejavax.servlet.jsp.jstl.sql.dataSource.Theparamvaluecomprisescomma-separatedphrases:

[JDBCURL],[Drivername],[user],[password]

DeveloperscommonlyderivetheJDBCURLanddrivernamefromdatabasevendordocumentation(andoftenfrommailinglists,becausedebuggingbackenddatabaseconnectionswithJDBCcanbetricky!).ThecodeIshowherecontainsanexampleofaJDBCURLforOracle8iPersonalEdition.

Example23-7.Anexampleweb.xmlconfigurationforajavax.sql.Datasource



<context-param>

<param-name>javax.servlet.jsp.jstl.sql.dataSource</param-name>

<param-value>jdbc:oracle:thin:@192.168.0.2:1521:ORCL,

oracle.jdbc.driver.OracleDriver,scott,tiger</param-value>

</context-param>



TheJSTLsoftwareusesthesevaluestogenerateaDataSourceforitsSQLtags.TheadvantageofusinganexternalsettingfortheDataSourceisthattoswitchdatabases,youcanchangethevalueofthecontext-paramtotheconfigurationrepresentingthenewdatabasewithouttouchingtheJSPcode.TheJSPdealstransparentlywiththeSQLtagsandDataSourceobject.

NowontotheJSP.RememberthattheSQLtags(theonesusingthe"sql"prefix)usetheDataSourcethatwejustsetwiththecontext-paramelementinweb.xml.

Webapplicationsalwayshaveaweb.xmlfileintheWEB-INFdirectory.SeeChapter1ifyouneedafurtherexplanation.

ThetaglibdirectivesatthetopofExample23-8arerequiredifyouwanttousetheJSTL1.0coreandSQLlibraries.

Example23-8.AJSPusesJSTLsqltagstodisplaydatabaseinformation



<html>

<head><title>DatabaseQuery</title></head>

<body>

<h2>QueryingadatabasefromaJSTLtag</h2>

<sql:queryvar="athletes">

SELECT*FROMathlete

</sql:query>

<tableborder="1">

<c:forEachvar="row"items="${athletes.rows}">

<tr>

<th>user_id</th>

<th>name</th>

<th>birthdate</th>

<th>passwrd</th>

<th>gender</th></tr>

<tr>

<td><c:outvalue="${row.user_id}"/></td>

<td><c:outvalue="${row.name}"/></td>

<td><c:outvalue="${row.birthdate}"/></td>

<td><c:outvalue="${row.passwrd}"/></td>

<td><c:outvalue="${row.gender}"/></td>

</tr>

</c:forEach>

</table>

</body>

</html>

Thesql:querytagusesitsnestedcontenttosendtheSQLSELECTstatement"select*fromathlete"toadatabase.ThedatabaseconnectionderivesfromtheDataSourceyouhavealreadyconfigured.Thestatementisdesignedto"selectallrowsfromthetablenamed`athlete.'"Thesql:querytagsavestheresultsetinajavax.servlet.jsp.jstl.sql.Resultobject,inavariablenamedathletes.

Resultobjectsareconvertedfromjava.sql.ResultSetobjects.Resultobjectshavemethods(suchasgetRows())thataredesignedtointeractwiththeJSTLSQLtags.

Thecode:

${athletes.rows}

isanELphrasethatcallstheResultobject'sgetRows()method.Thismethodreturnsajava.util.SortedMap[]typeoranarrayofSortedMaps.Example23-8usesthec:forEachtagtoiterateoverthisarrayandcreateanHTMLtablerowoutofeachofthereturneddatabaserows.

Youcanusethisformofcodetodisplaythecolumnnamesofaresultset(`athletes'isthevariablestoringtheresultset):

<c:forEachvar="col"items=

"${athletes.columnNames}">

<c:outvalue="${col}"/>

</c:forEach>

ThenextrecipeshowshowaJSPaccomplishesthissametaskwithoutacontext-paramconfiguringtheDataSource.

TrytostickwiththestrategyofsettingtheDataSourceinweb.xml,becauseitrepresentsabettersoftwaredesignthanclutteringupaJSPwithaDataSourceconfiguration.

Figure23-5showstheJSPdisplayingthedatabaserowinformationinawebbrowser.

Figure23-5.DisplayingdatabaseinformationinaJSP

SeeAlso

Chapter21onworkingwithdatabases;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.5onusingtheXMLTransformtags;Recipe23.6onusingtheformattingtags;Recipe23.8onusingaSQLJSTLtagwithoutaDataSourceconfiguration;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.



Recipe23.8UsingASQLJSTLTagWithoutaDataSourceConfiguration

Problem

YouwanttospecifytheDataSourcefortheJSTLSQLtagsinsideaJSP.

Solution

Usethesql:setDataSourcetagtoestablishaDataSourcefortheotherSQLtags,suchassql:query.

Discussion

YoucanexplicitlysettheDataSourcefortheJSTLSQLtagsinaJSPusingsql:setDataSourceanditsdataSourceattribute.Example23-9createsthesameDataSourceasRecipe23.6andstoresitinavariablenameddSource.Thesql:querytagthenspecifiesthisDataSourcewithitsowndataSourceattribute.ThecodeotherwiseaccomplishesthesametaskasExample23-8:theJSPsendsaSELECTSQLstatementtothedatabasesystem,thendisplaystheresults.

Example23-9.Usingthesql:setDataSourcetag



<html>

<head><title>DatabaseQuery</title></head>

<body>

<h2>QueryingadatabasefromaJSTLtag</h2>

<sql:setDataSourcedataSource=

"jdbc:oracle:thin:@192.168.0.2:1521:ORCL,oracle.jdbc.driver.OracleDriver,scott,tiger"

var="dSource"scope="application"/>

<sql:queryvar="athletes"dataSource="dSource">

SELECT*FROMathlete

</sql:query>

<tableborder="1">

<c:forEachvar="row"items="${athletes.rows}">

<tr>

<th>user_id</th>

<th>name</th>

<th>birthdate</th>

<th>passwrd</th>

<th>gender</th></tr>

<tr>

<td><c:outvalue="${row.user_id}"/></td>

<td><c:outvalue="${row.name}"/></td>

<td><c:outvalue="${row.birthdate}"/></td>

<td><c:outvalue="${row.passwrd}"/></td>

<td><c:outvalue="${row.gender}"/></td>

</tr>

</c:forEach>

</table>

</body>

</html>

ThecodestorestheDataSourceinanapplication-scopedvariable,sothatanotherJSPcanaccesstheDataSourcethisway:

<sql:queryvar="athletes"dataSource="${dSource}">

SELECT*FROMathlete

</sql:query>

Theonlydifferencebetweenthissql:queryusageandExample23-9isthatthevalueofthedataSourceattributehastoberesolvedusingtheEL;thetaghastofindandgetthevalueofanapplication-scopedvariable(aservletcontextattribute)named"dSource."

YoucanalsospecifyaDataSourceintheJSTLSQLtagsasaJavaNamingandDirectoryInterface(JNDI)string,butwewillreservediscussionofthattopicforChapter21,whichcoversusingdatabaseswithservletsandJSPs.

SeeAlso

Chapter21onworkingwithdatabases;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8onusingtheSQLJSTLtags;Recipe23.9-Recipe23.14onusingtheELtoaccessscopedvariables,cookies,andJavaBeanproperties.



Recipe23.9AccessingScopedVariableswiththeEL

Problem

YouwanttograbanddisplaythevalueofanobjectattributeusingaJSTLcustomtag.

Solution

UsetheELandthec:outtagtogetthevalueofanattributethathasbeenstoredinacertainscope.

Discussion

Anobjectsuchasajava.util.Date,ajava.lang.Integer,oranobjectthatyoudesign,canbestoredinfourdifferentscopes:

page,sothatit'sonlyavailableintheservletorJSPwhereitiscreated

requestscope,whichmakestheobjectavailabletoanypagesthatinteractwiththeJSPusingaRequestDispatcher,suchasarequestthatisforwardedfromoneJSPtoanother

sessionscopestoresobjectattributesforanyservletsorJSPsthatparticipateinthesamesession(seeChapter11)

applicationscope,whichrepresentstheentireservletcontextfor

onewebapplication

Example23-10usesthec:setJSTLtagtosetavariablenamedcom.jspservletcookbook.SessionObjecttosessionscope.Thenc:outaccessesanddisplaysthevalueofthevariable.

Example23-10.Accessingthevalueofanobjectstoredinsessionscope


<html>

<head><title>AccessingaScopedValue</title></head>

<body>

<h2>HereisthevalueoftheSession-ScopedAttribute</h2>

<c:setvar=

"com.jspservletcookbook.SessionObject"value=

"Myobjectattribute.<br/>"scope="session"/>

<c:outvalue=

"${sessionScope[\"com.jspservletcookbook.SessionObject\"]}"escapeXml="false"/>

</body>

</html>

Byconvention,objectattributesarenamedafterfullyqualifiedJavaclasses(usually,aftertheJavatypeofthestoredobject).Therefore,theattributenamehasperiodcharacters(.)init.Thisisthepurposeofthesyntax${sessionScope[\"com.jspservletcookbook.SessionObject\"]}

Iftheattributenamedoesnotcontainperiods,thenyoucanuseanELexpressionconsistingofjustthevariablename,withoutthesessionScopeJSTLimplicitobject,inordertoaccesstheobjectattribute:

<c:outvalue=

"${SessionObject}"escapeXml="false"/>

Ifyoujustincludethescopedobject'sname,asinthepriorcodefragment,thentheJSTLwillsearchthepage,request,session,andapplicationscopesforanattributeofthatname,returningnulliftheJSTLdoesnotfindone.

YoumustusetherequiredcharactersofanELexpression(thedollarsignandcurlybracessurroundingtheexpression:"${...}").Otherwisethec:outtagwilljustoutputaStringliteralsuchas"SessionObject."

SeeAlso

TheJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;SunMicrosystem'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8onusingtheSQLJSTLtags;Recipe23.10-Recipe23.14onusingtheELtoaccessrequestparameters,cookies,andJavaBeanproperties.



Recipe23.10AccessingRequestParameterswiththeEL

Problem

YouwanttoaccessarequestparameterusingtheELinaJSP.

Solution

UsetheparamimplicitobjectinyourJSPcode.

Discussion

TheJSTLprovidesanimplicitobjectnamedparamthatyoucanusetogetarequestparameter.Simplyfollowtheterm"param"withaperiodandtheparametername.UsethisterminologywiththeELtooutputthevalueofarequestparameterwiththec:outtag.Example23-11displaysagreetingwiththevisitor'sname.Therequestmightlooklike:

http://localhost:8080/home/welcome.jsp?name=Bruce%20Perry

IftheURLdoesnotincludethe"name"parameter,theJSPdisplaysthemessage"HelloEsteemedVisitor."

Example23-11.UsingtheJSTLinaJSPtodisplaytheresultofarequestparameter


<html>

<head><title>AccessingaScopedValue</title></head>

<body>

<h2>Hello

<c:choose>

<c:whentest="${emptyparam.name}">

EsteemedVisitor

</c:when>

<c:otherwise>

<c:outvalue="${param.name}"/>

</c:otherwise>

</c:choose>

</h2>

</body>

</html>

ThecodetestswhethertherequestcontainsavaluefornamebyusingtheemptyELkeyword:

<c:whentest="${emptyparam.name}">

Thec:choose,c:when,andc:otherwisetagsarelikeif/then/elsestatementsinJavacode.Iftherequestparameternamedoesnothaveavalue,thebrowserwilldisplay"EsteemedVisitor".Otherwise,itdisplaysthevalueofname.

Figure23-6showsaJSPdisplayingthemessage,includingtheparametervalue.

Figure23-6.HumbleoutputofaJSPusingtheparamJSTLimplicitobject

SeeAlso

Chapter18onworkingwiththeclientrequest;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;SunMicrosystem'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8onusingtheSQLJSTLtags;Recipe23.11-Recipe23.14onusingtheELtoaccessrequestheaders,cookies,andJavaBeanproperties.



Recipe23.11UsingtheELtoAccessRequestHeaders

Problem

YouwanttousetheELtoaccessthevalueofvariousHTTPrequestheaders.

Solution

UsetheheaderimplicitobjectthattheELmakesavailableforcustomtags.

Discussion

Theheaderimplicitobjectisajava.util.Maptypethatcontainsarequestheadervaluemappedtoeachheaderkey(whichistheheadername,suchas"accept"or"user-agent").Webclients(usuallybrowsers)sendtheseheadersorname/valuepairsalongwiththewebaddressofthepagetheyareinterestedin.

Example23-12usesthec:forEachiterationtagtocyclethrougheachoftheMap'sstoredrequestheaders.ThevariablereqHeadstoresthecurrentheader/valuepair.ThecodeusestheELtodisplaytheheadername("${reqHead.key}")andheadervalue("${reqHead.value}").

Example23-12.UsingtheJSTLtodisplayrequestheaders


<html>

<head><title>Requestheaderdisplay</title></head>

<body>

<h2>HerearealltheRequestHeaders</h2>

<%--'header'representsajava.util.Maptypeholdingrequest-headernamesandvalues--%>

<c:forEachvar="reqHead"items="${header}">


"${reqHead.key}"/></strong>:<c:outvalue="${reqHead.value}"/><br/>

</c:forEach>

</body>

</html>

Figure23-7showstheresultofrequestingthisJSPinawebbrowser.

Figure23-7.DisplayingrequestheadersinaJSP

SeeAlso

Chapter18onworkingwiththeclientrequest;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;SunMicrosystem'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.4andRecipe23.5onusingtheSQLJSTLtags;Recipe23.12-Recipe23.14onusingtheELtoaccessonerequestheader,cookies,andJavaBeanproperties.



Recipe23.12UsingtheELtoAccessOneRequestHeader

Problem

YouwanttousetheELtoaccessthevalueofoneparticularHTTPrequestheader.

Solution

UsetheheaderValuesimplicitobjectthattheELmakesavailableforcustomtags.

Discussion

TheheaderValuesimplicitobjectisajava.util.MaptypethatcontainsaStringarray(aString[]type)foreveryheadername.Example23-13displaysonlythevalueofthe"user-agent"requestheader,whichidentifiesthetypeofbrowsertheclientisusing.

Example23-13.UsingtheJSTLtodisplayrequestheaders


<html>

<head><title>UserAgent</title></head>

<body>

<h2>Hereisyouruseragent</h2>

<%--'headerValues'representsajava.util.MaptypeholdingaString[]typeforevery

requestheader--%>


"${headerValues[\"user-agent\"][0]}"/></strong>

</body>

</html>

ThecodeaccessesonlythefirstmemberoftheStringarray(itishighlylikelythattheuser-agentrequestheaderonlyinvolvesonevalue).Theexpression:

${headerValues[\"user-agent\"]}

returnsthearray,andtheentireexpression,includingthe"[0]"arrayoperator,whichreturnsthenameoftheuseragent,suchas"Mozilla/4.0(compatible;MSIE5.5;WindowsNT4.0)."

SeeAlso

Chapter18onworkingwiththeclientrequest;Recipe23.11onhowtousetheELtoaccessalltheavailablerequestheaders;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8onusingtheSQLJSTLtags;Recipe23.10onusingtheELtoaccessrequestparameters;Recipe23.13andRecipe23.14onusingtheELtoaccesscookiesandJavaBeanproperties.



Recipe23.13AccessingCookieswiththeEL

Problem

YouwanttotakealookatallofthecookienamesandvaluesusingELcode.

Solution

UsethecookieELimplicitobjectintheJSPtodisplayanycookienamesandvalues.

Discussion

ThecookieELimplicitobjectisajava.util.Maptypethatmapscookienames(like"JSESSIONID")tojavax.servlet.Cookieobjects.SincethecookiesarestoredinaMap,youcanusethec:forEachtagtocyclethroughthemapanddisplayeachcookienameandvalueusingc:out(seeExample23-14).

MakesuretoincludethetaglibdirectiveatthetopoftheJSPsothepagecanusethecoreJSTLtags.

Example23-14.usingtheELtodisplayeachcookienameandvalueinaJSP


<html>

<head><title>Cookiedisplay</title></head>

<body>

<h2>HerearealltheAvailableCookies</h2>

<%--${cookies.key}equalsthecookiename;${cookies.value}equalstheCookieobject;

${cookies.value.value}returnsthecookievalue--%>

<c:forEachvar="cookies"items="${cookie}">

<strong>

<c:outvalue="${cookies.key}"/>

</strong>:Object=

<c:outvalue="${cookies.value}"/>,value=

<c:outvalue="${cookies.value.value}"/><br/>

</c:forEach>

</body>

</html>

Thec:forEachtagstorestheentryintheMapforeachcookieinavariablenamedcookies.ThecodeusestheELphrase"${cookies.key}"toaccessthenameofeachcookie.Youwouldthink"${cookies.value}"returnsthevalueforeachcookie;however,thissyntaxreturnstheCookieobjectitself.Theweirdsyntax"${cookies.value.value}"returnsthevalueofthecookie.Figure23-8showshowtheJSPdisplaysthisinformation.

Figure23-8.DisplayingacookieobjectandvaluewiththeJSTL

SeeAlso

Chapter10onreadingandsettingcookies;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8onusingtheSQLJSTLtags;Recipe23.9-Recipe23.12onusingtheELtoaccessscopedvariables,requestparameters,andrequestheaders;Recipe23.14onusingtheELtoaccessJavaBeanproperties.



Recipe23.14UsingtheELtoAccessJavaBeanProperties

Problem

YouwanttousetheELtoaccessthepropertiesofaJavaBeaninaJSP.

Solution

Usethejsp:useBeanstandardactiontocreateoraccessaninstanceofthebean,thenusetheELtoaccessthebeanproperties.

Discussion

Youcanusethec:outJSTLcoretagandtheELtodisplaythevaluesofJavaBeanpropertiesinaJSP.Example23-15showstheskeletonofaJavaBeanthatisdesignedtohandleemail.IusedthisbeaninChapter20,whichcontainsdetailsaboutallofitsemail-sendingand-accessingmethods.

Example23-15.AJavaBeanthataJSPwillinstantiateandaccess





importjavax.mail.*;




publicclassEmailBean{

//defaults

privatefinalstaticStringDEFAULT_SERVER="smtp.comcast.net";

privatefinalstaticStringDEFAULT_TO=

"[email protected]";

privatefinalstaticStringDEFAULT_FROM=

"[email protected]";

privatefinalstaticStringDEFAULT_CONTENT="Unknowncontent";

privatefinalstaticStringDEFAULT_SUBJECT="Unknownsubject";

//JavaBeanproperties

privateStringsmtpHost;

privateStringto;

privateStringfrom;

privateStringcontent;

privateStringsubject;

//no-argsconstructorforthebean

publicEmailBean(){}

//configureanemailmessagewithrequestparamsandsendtheemail

publicvoidsendMessage(HttpServletRequestrequest,

PrintWriterout)throwsIOException{

//SEERECIPE20.3AND20.6FORMOREDETAILSONTHISEMAILBEAN

//METHOD

}//sendMessage

//getemailmessagesusingaPOPaccount




//METHOD

}//handleMessages

//displayinfoaboutreceivedemailmessages




}//displayMessage

//getteroraccessormethods

publicStringgetSmtpHost(){

return(smtpHost==null||smtpHost.equals(""))?

EmailBean.DEFAULT_SERVER:smtpHost;

}//getSmtpHost

publicStringgetTo(){

returnto;

}//getTo

publicStringgetFrom(){

returnfrom;

}//getFrom

publicStringgetContent(){

returncontent;

}//getContent

publicStringgetSubject(){

returnsubject;

}//getSubject

//setterormutatormethods

publicvoidsetSmtpHost(Stringhost){

if(check(host)){

this.smtpHost=host;

}else{

this.smtpHost=EmailBean.DEFAULT_SERVER;

}

}//setSmtpHost

publicvoidsetTo(Stringto){

if(check(to)){

this.to=to;

}else{

this.to=EmailBean.DEFAULT_TO;

}

}//setTo

publicvoidsetFrom(Stringfrom){

if(check(from)){

this.from=from;

}else{

this.from=EmailBean.DEFAULT_FROM;

}

}//setFrom

publicvoidsetContent(Stringcontent){

if(check(content)){

this.content=content;

}else{

this.content=EmailBean.DEFAULT_CONTENT;

}

}//setContent

publicvoidsetSubject(Stringsubject){

if(check(subject)){

this.subject=subject;

}else{

this.subject=EmailBean.DEFAULT_SUBJECT;

}

}//setSubject



returnfalse;

returntrue;

}

}

Example23-16showstheJSPthatcreatesaninstanceofthisbeanusingthejsp:useBeanstandardaction.Theidattributeofjsp:useBeanspecifies"emailer"asthebeanname.Thisisthenamethecodeusestoaccessthebeaninstance'spropertyvaluesusingtheEL.

Example23-16.CreatingaJavaBeanandusingtheJSTLtodisplayitspropertyvalues


<jsp:useBeanid="emailer"class="com.jspservletcookbook.EmailBean"/>

<jsp:setPropertyname="emailer"property="*"/>

<html>

<head><title>Beanpropertydisplay</title></head>

<body>

<h2>HerearetheEmailBeanproperties</h2>

<strong>SMTPhost:</strong><c:outvalue="${emailer.smtpHost}"/>

<strong>Emailrecipient:</strong><c:outvalue="${emailer.to}"/>

<strong>Emailsender:</strong><c:outvalue="${emailer.from}"/>

<strong>Emailsubject:</strong><c:outvalue="${emailer.subject}"/>

<strong>Emailcontent:</strong><c:outvalue="${emailer.content}"/>

</body>

</html>

Whenthecodeusesanexpressionsuchas"${emailer.smtpHost},"itcallsthegetSmtpHost()methodoftheEmailBean(theSMTPserverfromwhichyoureceiveemail,suchas"smtp.comcast.net").ThevariableemailerreferstotheinstanceoftheEmailBean.

Example23-16setalloftheEmailBean'ssettablepropertiesfromrequestparametersofthesamename.Thisisthepurposeofthecode:

<jsp:setPropertyname=

"emailer"property="*"/>

Providingthec:outvalueattributewiththisexpressionoutputsthevalueofthebean'sproperty.Figure23-9showstheJSPofExample23-

16inawebbrowser.

Figure23-9.DisplayingaJavaBean'spropertiesusingJSTLc:outtags

SeeAlso

Chapter20onusingJavaBeanstohandleemail;theJakartaProject'sTaglibssite:http://jakarta.apache.org/taglibs/index.html;theSunMicrosystemsJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.3onusingthecoretags;Recipe23.4andRecipe23.5onusingtheXMLtags;Recipe23.6onusingtheformattingtags;Recipe23.7andRecipe23.8onusingtheSQLJSTLtags;Recipe23.9-Recipe23.13onusingtheELtoaccessscopedvariables,requestparameters,requestheaders,andcookies.



Recipe23.15UsingJSTLFunctions

Problem

Youwanttousethebuilt-infunctionsincludedwithJSTL1.1.

Solution

Usethepropertaglibdirective(withtheurivalueof"http://java.sun.com/jsp/jstl/functions")andprefix(e.g.,thefn:infn:contains)inyourJSP.

Discussion

TheJSTL1.1anditsELincludesaniftynewfunctionslibrary.ThesetagsallowJSPdeveloperstocallbuilt-infunctionstohandleandreturnvaluesfromStrings,arrays,Maps,andCollections.Thenatureofthesefunctionswillbefamiliartoanyonewhohasworkedwithjava.lang.Stringanditsnumerousmethods(seeTable23-4).FunctionsrepresentanevolutionofJSTLfrominvolvingacollectionofcustomtagstogivingyoutheabilitytomakefunctioncallsembeddedinsidetemplatetext.

HereisthesetupthatyouneedtouseJSTLfunctionsinyourJSPs:

1. AJSP2.0JSPcontainer

AnimplementationofJSTL1.1(IusetheJavaWebServicesDeveloperPack1.2inthisrecipe)

Aconversionofyourweb.xmlfiletotheservletAPIVersion2.4(seelateroninthisrecipe)

Example23-17showsthenewtagliburiandprefixvaluestousewiththefunctionslibrary.ThisJSPusestheString"IamatestString"asinputtofouroftheavailablefunctions:fn:length(),fn:contains(),fn:toUpperCase(),andfn:split().

Example23-17.AJSPthatusesJSTL1.1functions

<%@tagliburi="http://java.sun.com/jsp/jstl/functions"prefix="fn"%>

<%@tagliburi="http://java.sun.com/jsp/jstl/core"prefix="c"%>

<html>

<head><title>UsingtheJSTLfunctions</title></head>

<body>

<h2>UsingvariousJSTL1.1functions</h2>

<c:setvar="tempStr"value="IamatestString"/>

ThelengthofthetestString:${fn:length(tempStr)}<br/>

DoesthetestStringcontain"test"?${fn:contains(tempStr,"test")}<br/>

PuttingtheStringintouppercaseusingfn:toUpperCase():${fn:toUpperCase(tempStr)}<br

/>

SplittingtheStringintoaStringarrayusingfn:split(),andreturningthearray

length:${fn:length(fn:split(tempStr,""))}

</body>

</html>

JSTL1.1functioncallscanbeintermingledwithtemplatetext,asin

Example23-17.SurroundthefunctioncallswiththeELdelimiters("${...}"),andmakesuretousethefn:prefix,asin${fn:toUpperCase(tempStr)}.

Example23-18showshowyoucanchangeweb.xmltotheservletAPI2.4version,sothattheJSP2.0containerinterpretstheELfunctionsinyourcode.

ThemajordifferencebetweenJSTL1.0and1.1isthattheJSP2.0specificationhastakenovertheELresponsibility.Therefore,theJSP2.0container,nottheJSTLlibraries,nowevaluatestheELsyntax.

IfyoustickwiththeservletAPI2.3deploymentdescriptor,thentheJSP2.0containerwillnotevaluatetheELexpressionsandfunctioncalls.Usingtheoldservlet2.3deploymentdescriptor"turnsoff"ELevaluationbytheJSPcontainer;consequently,youcannotusethefunctionslibraryorincludeELsyntaxintemplatetext.ThisautomaticdisablingofELexpressionsbytheJSPcontainerisdesignedasawayofeasingthemigrationofexistingJSPpagestoJSP2.0.Inshort,aJSPthatincludestheJSTL1.0usagesandisassociatedwithaservlet2.3deploymentdescriptorworksthesameunderaJSP2.0container.

However,youmaywanttousethenewfunctions!Therefore,Example23-18showshowtomigratetotheservlet2.4versionofweb.xml.

Example23-18.Changeweb.xmltoservletAPI2.4touseJSTL1.1features




xsi:schemaLocation=

http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"

version="2.4"

>



</web-app>

Example23-18alterstheweb-appelementtoincludetherequiredattributesoftheservlet2.4deploymentdescriptor(SeeChapter1).Therestofweb.xmlcanremainasitappearedusingtheservlet2.3DTD.

Table23-4describesthepurposeofeachfunctionthattheJSTL1.1includesinitsfunctionlibrary.

Table23-4.JSTL1.1functions

Functionname Arguments Returntype Purpose

fn:contains String,String boolean

FindsoutwhetheraString(firstargument)containsacertainsubstring(secondargument)

fn:containsIgnoreCase String,String boolean

FindsoutwhetheraStringcontainsasubstring(secondargument)inacase-insensitivemanner

fn:endsWith String,String boolean

FindsoutwhetheraString(firstargument)endswithanotherString(secondargument)

fn:escapeXML String String

EscapescharactersthatcouldbeinterpretedasXMLmarkup,suchas">"

fn:indexOf String,String int

ReturnstheindexorpositionofoneString(secondargument)insideanother(firstargument)

JoinsallString[]arrayelements

fn:join String[],String String

intoaString,usingthespecifiedseparator(secondargument)asthecharacterbetweeneacharrayelement.

fn:length

Map,array,

Collection,

Iterator,

Enumeration,or

String

intFindsoutthelengthofthearray,collection,orString.

fn:replaceString,String,

StringString

ReplacesallinstancesofaString(secondargument)inaninputString(firstargument)withanotherString(third)

fn:split String,String String[]

SplitsaStringintoanarray,usingthespecifieddelimiter(s)(secondargument)

fn:startsWith String,String booleanFindsoutwhetheraString(firstargument)startswithanotherString.

fn:substring String,int,int String

ReturnsasubstringfromtheinputString(firstargument),fromtheindexsecondargument(inclusive)totheindexthirdargument(exclusive)

fn:substringAfter String,String String

ReturnsthepartoftheStringafterthespecifiedsubstring(secondargument)

fn:substringBefore String,String String

ReturnsthepartoftheStringbeforethespecifiedsubstring(secondargument),beginingwiththefirstcharacterofthefirstStringargument.

fn:toLowerCase String StringReturnsthespecifiedStringinalllowercase.

fn:toUpperCase String StringReturnsthespecifiedStringinalluppercase.

fn:trim String String RemoveswhitespacefromeachendofthespecifiedString.

Figure23-10showsthewebbrowseroutputofaJSPthatusesvariousmembersoftheJSTL1.1functionslibrary.

Figure23-10.AJSPdisplaystheresultsofusingsomeJSTL1.1functions

SeeAlso

SunMicrosystem'sJSTLinformationpage:http://java.sun.com/products/jsp/jstl/;Recipe23.2onusingthecoretags;Recipe23.3andRecipe23.4onusingXML-relatedtags;Recipe23.5onformattingdatesandnumbers;Recipe23.6andRecipe23.7ontheJSTL'sSQLfeatures;Recipe23.8onaccessingscopedvariables;Recipe23.9onusingtheELwithrequestparameters;Recipe23.10andRecipe23.11onusingtheELwithrequestheaders;Recipe23.12onfindingoutinformationaboutcookies;Recipe23.13onusingtheELtoaccessJavaBeanproperties.


Chapter24.InternationalizationIntroduction

Recipe24.1.DetectingtheClientLocaleinaServlet

Recipe24.2.DetectingtheClient'sLocalesinaJSP

Recipe24.3.CreatingaResourceBundleasaPropertiesFile

Recipe24.4.CreatingaResourceBundleasaJavaClass

Recipe24.5.UsingtheResourceBundleinaServlet

Recipe24.6.UsingtheResourceBundleinaJSP

Recipe24.7.FormattingDatesinaServlet

Recipe24.8.FormattingDatesinaJSP

Recipe24.9.FormattingCurrenciesinaServlet

Recipe24.10.FormattingCurrenciesinaJSP

Recipe24.11.FormattingPercentagesinaServlet

Recipe24.12.FormattingPercentagesinaJSP

Recipe24.13.SettingtheLocalizationContextintheDeploymentDescriptor

Introduction

Theaudienceforalmostallwebsitesisglobal.Manysiteshaveatleastasubsetofcontentthatmustbeadaptedtothelanguageandnationalityoftheirvisitors,sothatthevisitor'sbrowserformatsnumbersanddatesproperlyandtranslatestextintotheproperlanguage.Anobviousexampleisaproductdocumentationorhelpwebsite.WhatifmostofyourcustomersorviewersforthisproductspeakalanguageotherthanEnglish?Javaprovidestoolsthatallowwebdeveloperstointernationalizetheirsites.

BeforeIshowthesetools,let'sfirstexplainafewtermsthatalwaysappearindiscussionsofwebsitetranslation.

1. Internationalization,ori18ninitsabbreviatedversion,meansenablingawebsiteorotherJavaprogramtoprovidedifferentversionsofcontenttranslatedintothevisitor'slanguageornationality.Thistermbasicallymeansmakingyoursiteglobal.

Localization,orl10n,meansaddingresourcestoawebsitetoadaptittoaparticulargeographicalorculturalregion.Anexampleofl10nisaddingKoreanlanguagetranslationstoawebsite.Thewebdeveloperswhohavethisresponsibilityareoftenreferredtoaslocalizers.

Alocaleisaparticularculturalorgeographicalregion.Itisusuallyreferredtoasalanguagesymbolfollowedbyacountrysymbol(separatedbyanunderscorecharacter),asin"en_US"fortheEnglishlocale,"de_DE"forGermanspeakersinGermany,or"de_CH"forSwiss-Germanspeakers,or"fr_CH"forpeopleinSwitzerlandwhospeakFrench.Alocalecanalsorepresentjustthelanguage,asin"ja"forJapaneseor"it"forItalian.Finally,localescanhaveathirdsegmentor"variant"thatreflectsacertainbrowser-typeorvendor,suchas"MAC"forMacintosh.AnexampleofalocaleforEnglishwithaWindowsvariantis"en_US_WIN."

ThelanguageelementisrepresentedbyanInternationalStandardsOrganization(ISO)languagecode(http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt);thecountryisencodedunderISO-3166(http://www.chemie.fu-berlin.de/diverse/doc/ISO_3166.html).

SohowdoyouinternationalizeorlocalizeaJavawebsite?Thisisabigsubjectandthetopicofseveralbooks.Thefollowingrecipesprovidethebasicsofhowtocreatepropertiesfiles(calledResourceBundles).Thesefiles(theycanalsobeimplementedasJavaclasses)providelanguagetranslationsforphrasesthatyourwebpagesuse.Aservletcanthenaccesstheseresourcesandprovidedifferenttextversionsaccordingtotherequester'slocale.

TherecipesinthischapteralsocoverhowtoadaptJSPpagestovisitorswhospeakdifferentlanguagesbyusingtheJSTLtags.IbeginbydescribinghowtodetectthelocaleofarequestusingaservletorJSP.

http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt

http://www.chemie.fu-berlin.de/diverse/doc/ISO_3166.html

Recipe24.1DetectingtheClientLocaleinaServlet

Problem

Youwanttodetecttheclientlocaleinaservlet.

Solution

UsetheServletRequest.getLocale()method.

Discussion

ThelocaleisrepresentedbyaclassinJava:java.util.Locale.TheServletRequestobjectcanaccesstheclient's"preferred"localewithitsgetLocale()method,whichreturnsaLocaleobject.

Thepreferredlocaleistheuser'stoppreference.Forexample,ausermayconfiguretheirbrowserwithaSpanishlanguagelocale("es_ES")asthepreferredone.

JavacodecanaccessthelistoflocalesthatauserconfiguresabrowserwithbycallingServletRequest'sgetLocales()method,whichreturnsanEnumerationobject.Thisobjectcontainsthepreferredandless-preferredlocales.

Tosetthelanguagepreference(s)inNetscape7.1,goto"Edit PreferencesNetscape Languages."IntheMacintoshSafaribrowser,openSystem

Preferencesanddragyourlanguagepreference(s)tothetopofthelist(thenrestartSafari).InInternetExplorer5.5,goto"Tools InternetOptionsLanguages."

Example24-1accessestheclient'spreferredlocalebycallingrequest.getLocale().TheservletthendisplaysinformationaboutthelocalebycallingsomeLocalemethods.Example24-1alsodisplaysinfomationabouttheless-preferredlocalesbyusingthemethodrequest.getLocales().

Example24-1.AccessingtheLocaleobjectinaservlet



importjava.util.Locale;



publicclassLocaleDisplayextendsHttpServlet{




//Gettheclient'sLocales

Enumerationenum=request.getLocales();

//GetthepreferredLocale

Localepreferred=request.getLocale();

StringprefDisplay="";

if(preferred!=null)

prefDisplay=preferred.getDisplayName();

//Displaythepreferredandanyotherlocales



out.println(

"<html><head><title>LocaleDisplay</title></head><body>");

out.println("<h2>HereisyourLocaleinfo...</h2>");

out.println("<b>PreferredLocale:</b>");

out.println(prefDisplay);


out.println("Localecountry:");

if(preferred!=null)

out.println(preferred.getDisplayCountry());


out.println("Localelanguage:");

if(preferred!=null)

out.println(preferred.getDisplayLanguage());


out.println("<h3>LowerpriorityLocales...</h3>");

Localeloc=null;


loc=(Locale)enum.nextElement();

if(!(loc.getDisplayName().equals(prefDisplay))){

out.println("Locale:");

out.println(loc.getDisplayName());


out.println("Localecountry:");

out.println(loc.getDisplayCountry());


out.println("Localelanguage:");

out.println(loc.getDisplayLanguage());


}//if

}//while


}//doGet

}

Figure24-1showsthewebbrowseroutputwhenavisitorwithapreferredlocaleof"en_US"requeststheservlet.

Figure24-1.Theservletdisplaysthepreferredandless-preferredlocales

Thisuserhasconfiguredtheirbrowserwithseveralotherlocales.Asyoucansee,themethodlocale.getDisplayName()isdesignedtoreturnamorereadablename(comparedwith"de_CH")forthelocale.

Thecom.oreilly.servletlibraryincludestheLocaleNegotiatorclass,

whichusestheclientrequesttofigureoutthebestcharset,locale,andresourcebundletousewiththeresponse.SeeRecipe8.4fortipsonusingthecom.oreilly.servletlibrary.Idon'tcoverLocaleNegotiatorinparticularhere,buttheJavadocexplainsthisclass.Seehttp://www.servlets.com/cos/javadoc/com/oreilly/servlet/LocaleNegotiator.html.

SeeAlso

TheJavadocdescribingtheLocaleclass:http://java.sun.com/j2se/1.4.1/docs/api/java/util/Locale.html;Recipe24.2ondetectingthelocaleusingaJSP.

http://www.servlets.com/cos/javadoc/com/oreilly/servlet/LocaleNegotiator.html

http://java.sun.com/j2se/1.4.1/docs/api/java/util/Locale.html

Recipe24.2DetectingtheClient'sLocalesinaJSP

Problem

Youwanttofindoutwhattherequest'spreferredlocaleandless-preferredlocalesareanddisplaythisinformationinaJSP.

Solution

Grabthepreferredlocalewiththeexpression"${pageContext.request.locale}."Getaccesstoallofthelocaleswiththeexpression"${pageContext.request.locales}."

Discussion

TheJSTLtagsmakeiteasytoadaptaJSPforvisitorswhospeakdifferentlanguages.Example24-2usestheELtocreateavariablenamedclientLocalethatrepresentstherequest'spreferredlocale.ThentheJSPdisplaysthelocale'sname,language,andcountry.Example24-2alsodisplaysanyinformationabouttheclient'sless-preferredlocales.

Example24-2.Accessingtherequest'slocaleinaJSP

<%@tagliburi="http://java.sun.com/jsp/jstl/core"prefix="c"%>

<html>

<head><title>LocaleDisplay</title></head>

<body>

<h2>Hereisyourpreferredlocaleinfo...</h2>

<c:setvar="clientLocale"value="${pageContext.request.locale}"/>

<c:setvar="clientLocales"value="${pageContext.request.locales}"/>

Preferredlocale:${clientLocale.displayName}

<br/>

Preferredlocalecountry:${clientLocale.displayCountry}

<br/>

Preferredlocalelanguage:${clientLocale.displayLanguage}

<h3>Lowerprioritylocales...</h3>

<c:forEachvar="loc"items="${clientLocales}"begin="1">

Locale:${loc.displayName}

<br/>

Localecountry:${loc.displayCountry}

<br/>

Localelanguage:${loc.displayLanguage}

<br/><br/>

</c:forEach>

</body>

</html>

Theexpression"${pageContext.request.locale}"getstherequestobjectfromthepageContextimplicitobject,thenaccessestheLocaleobject,representingtheclient'spreferredlocale,fromtherequest.Fairlyefficient,huh?Thenanexpressionsuchas"${clientLocale.displayName}"representstheequivalentofcallingtheLocaleobject'sgetDisplayName()method.

TheELphrase"${pageContext.request.locales}"representstheequivalentofcallingtheServletRequestobject'sgetLocales()method,whichreturnsajava.util.Enumerationtype.TheEnumerationcontainsalloftheclient'sconfiguredlocales,beginingwiththeirpreferredlocale.

Example24-2usesanimplmentationofJSTL1.1andJSP2.0.MakesuretoincludethepropertaglibdirectiveatthetopoftheJSPfile,sothattheJSPcanusetheELandcoretags.Ifallthisterminologyisnewandstrangetoyou,readChapter23ontheJSTL.

Example24-2iteratesthrougheachofthelocalesusingthec:forEachtag,asin:

<c:forEachvar="loc"items="${clientLocales}"begin="1">

Thebegin="1"attributebeginsthec:forEachiterationwiththesecondlocaleobject,sincethefirstlocaleistheclient'spreferredone,andtheJSPhasalreadydisplayedinformationonthatone.Thebeginattributeuses"0"astheindexforthefirstitemintheEnumeration.

Figure24-2showstheJSP'swebbrowseroutput.Thisoutputresultsfromavisitorwhosebrowserspecifiesthelocale"es_ES"aspreferred.

Figure24-2.Abrowserrequestsalocale-sensitiveJSP

SeeAlso

Chapter23ontheJSTL;theJavadocdescribingtheLocaleclass:http://java.sun.com/j2se/1.4.1/docs/api/java/util/Locale.html.

http://java.sun.com/j2se/1.4.1/docs/api/java/util/Locale.html

Recipe24.3CreatingaResourceBundleasaPropertiesFile

Problem

Youwanttostoreyouri18nresourcesinyourwebapplication.

Solution

Createatextfilewithname/valuepairsrepresentingyouri18nresources.NamethefilewithyourglobalresourcenameandstoreitbeneathWEB-INF.

Discussion

Addingi18n-relatedresourcestoyourwebapplicationinvolvescreatingpropertiesfilesorResourceBundleclasses(Recipe24.4).AResourceBundlethattakestheformofapropertiesfileissimplyalistofkeysandvalues,producedinanytexteditor.Thekeysrepresentsthewordsthatyouwanttobetranslated,andthevaluesarethetranslations.Thesefilesaretheresourcesthatthewebapplicationusestodynamicallytranslatetextintotheappropriatelanguage.

Imaginethatyouarecreatingsomeresourceswithaglobalname,orbasename,of"WelcomeBundle."Example24-3showsthesubclassofthisresourceforthevisitorsfromthelocale"es_ES,"orpeoplefromSpainwhospeakSpanish.

Forexample,thekey"Welcome"isassociatedwithitsSpanishequivalent"Holayrecepción."Recipe24.5showshowaservletwoulduseaResourceBundlelikethistodynamicallytranslate"Welcome"to

thevisitor'slanguage.

Example24-3.ThecontentsofaResourceBundlefilenamedWelcomeBundle_es_ES.properties

#Spanishlanguageresources

Welcome=Holayrecepción

Thesearejustkeysandvaluesseparatedbynewlinecharacters.Commentsaredelineatedbyahash(#)character.

Thistextfilehastobestoredinaplacewhereotherwebcomponentscanfindit,similartoinstallingaJavaclassinyourwebapplication.Thisisthepathtothepropertiesfile,whichhasafullyqualifiednameofi18n.WelcomeBundle_es_ES.properties.The.propertiesextensionisanessentialdetail!

WEB-INF/i18n/WelcomeBundle_es_ES.properties

Centralizingthei18nresourcesintheirownWEB-INFsubdirectoryinawebapplicationisasensiblewaytoorganizethisinformationandavoidclutter.

SeeAlso

Recipe24.4oncreatingResourceBundleasaJavaclass;thePropertyResourceBundleJavadoc:http://java.sun.com/j2se/1.4.1/docs/api/java/util/PropertyResourceBundle.html

http://java.sun.com/j2se/1.4.1/docs/api/java/util/PropertyResourceBundle.html

Recipe24.4CreatingaResourceBundleasaJavaClass

Problem

YouwanttocreateaResourceBundleasaJavaclass.

Solution

Createaclassthatextendsjava.util.ListResourceBundle.

Discussion

Ifyourapplicationrequiresmorefunctionalitythanastaticpropertiesfilecanprovide(Recipe24.3),youcancreateyourResourceBundlesasJavaclasses:java.util.ListResourceBundletypes.Forinstance,aparticularresourcemightneedtoselectitstranslationinformationfromadatabase.

Example24-4includesthesameinformationasthepropertiesfileinthepriorrecipe.However,itskey/valuepairsarestoredintheformofatwo-dimensionalObjectarray.Thisclassisstoredinthesameplaceasthe.propertiesfilesinWEB-INF/i18n.

Example24-4.StoringlanguageinformationinaListResourceBundle


importjava.util.ListResourceBundle;

publicclassWelcomeBundle_es_ESextendsListResourceBundle{

staticfinalObject[][]contents={

{"Welcome","Holayrecepción"}

};

publicObject[][]getContents(){

returncontents;

}

}

Thiscodesnippetfromaservletshowshowyoucouldusethisclass.

Example24-5.CallingaListResourceBundlemethodfromaResourceBundlecreatedasaJavaclass



ResourceBundlebundle=ResourceBundle.getBundle(

"i18n.WelcomeBundle_es_ES");

//CallinheritedListResourceBundlegetKeys()method

java.util.Enumerationenum=bundle.getKeys();


//Printsoutkey:"Welcome"

out.println((String)enum.nextElement());


}//while

TheResourceBundle.getBundle()staticmethodtriestofindaJavaclasswiththefullyqualifiedname"i18n.WelcomeBundle_es_ES"(inthisexample).Failingthat,itlooksforapropertiesfileofthesamename(minusthe.propertiesextension):i18n.WelcomeBundle_es_ES.properties.

SeeAlso

TheJavadocforListResourceBundle:http://java.sun.com/j2se/1.4.1/docs/api/java/util/ListResourceBundle.html;Recipe24.3oncreatingaResourceBundleasapropertiesfile.

http://java.sun.com/j2se/1.4.1/docs/api/java/util/ListResourceBundle.html

Recipe24.5UsingtheResourceBundleinaServlet

Problem

Youwantaservlettodynamicallydisplaya"Welcome"messagetovisitorsdependingontheirlocale.

Solution

UsetheservlettoaccessthetranslatedtextdynamicallyfromaResourceBundle.

Discussion

OnceyouhaveaddedResourceBundlestothewebapplication,thenservletscanusethemtodynamicallydisplaytextbasedontheuser'slocale.

Remember,thewebapplicationstoresResourceBundlesas.propertiesfiles(text)orJavaclasses.

Example24-6usesaResourceBundlewithabasenameof"WelcomeBundle."ItisstoredinWEB-INF/i18n,soitsfullyqualifiednameisi18n.WelcomeBundle.

Example24-6.Aservletusesatodynamicallydisplaytranslatedtext






publicclassWelcomeServletextendsHttpServlet{




//Gettheclient'sLocale

Localelocale=request.getLocale();


"i18n.WelcomeBundle",locale);

Stringwelcome=bundle.getString("Welcome");

//Displaythelocale



out.println("<html><head><title>"+welcome+"</title></head><body>");

out.println("<h2>"+welcome+"</h2>");


out.println(locale.getLanguage()+"_"+locale.getCountry());


}//enddoGet

//doPostmethod...

}//WelcomeServlet

HereishowtheapplicationusesthisresourceinresponsetoavisitorfromaSpanishlocale("es_ES"):

1. Theservletaccessesthelocaleasajava.util.Localeobject.

ItpassesthelocaleintotheResourceBundle.getBundle()method,whichusesthelocaletosearchforaResourceBundlenamedi18n.WelcomeBundle_es_ES.Themethodformsthissearchtermbyattachingthecurrentrequest'slocalenametotheendoftheResourceBundlebasename.Inthiscase,thebundleisstoredasaJavaclass(Recipe24.4).

Thebundlethendisplaysthemessagebyaccessingthe"Welcome"key,whichisspecifiedbytheResourceBundle(Example24-4orExample24-5).

Sometimesthebrowsersendsthelocaleinformationasalanguagecodeonly,asin"es"forSpanish(insteadof"es_ES"withlanguagecodeandcountrycode).IftheapplicationhasonlyinstalledaresourcenamedWelcomeBundle_es_ES,butnotWelcomeBundle_es,thenthegetBundle()methoddefaultstoaresourcenamedWelcomeBundle(whichmightnotbetheoptimaloutcome),andthereforemaynotdisplaythetranslatedtext.MakesuretoincludeaWelcomeBundle_esresourcetocoverthesecases.

Figure24-3showstheservlet'soutputinresponsetoarequestfromaSpanishlocale.

Figure24-3.ASpanishclientrequeststheLocaleServlet

Figure24-4showstheservlet'sresponsewhenitdealswithalocaleforwhichtheapplicationhasnotprovidedaresource.Inthiscase,thebrowserissetfortheJapaneselanguage,buttheapplicationhasnotyetprovidedaresourceforthislocale.

Figure24-4.AbrowsersetforJapanesevisitsreceivesthedefaultmessage

Thetextthatthebrowserdisplaysderivesfromthedefaultpropertiesfile:WelcomeBundle.properties(noticetheabsenceofanylocale-relatedsuffixinthefilename).

SeeAlso

Recipe24.6onusingtheResourceBundleinaJSP;TheJavadocforResourceBundle:http://java.sun.com/j2se/1.4.1/docs/api/java/util/ResourceBundle.html.

http://java.sun.com/j2se/1.4.1/docs/api/java/util/ResourceBundle.html

Recipe24.6UsingtheResourceBundleinaJSP

Problem

YouwanttodynamicallydisplaytextintheJSPaccordingtothelocaleoftherequest.

Solution

UsetheJSTLtagsfromtheformattinglibrary.

Discussion

TheJSTL'sformattingtagsmakeiteasytodynamicallydisplaytextbasedonthebrowser'slanguagesetting.Example24-7makesavailabletheformattingandcoreJSTLtagswiththetaglibdirective.Thenitusesthefmt:setBundletagtospecifythei18nresourcesthatwillbeusedbythepage(thelocalizationcontext).

Example24-7.Usingtheformattingtagstodisplayalocale-sensitivemessageinaJSP



<fmt:setBundlebasename="i18n.WelcomeBundle"/>

<html>

<head><title><fmt:messagekey="Welcome"/></title></head>

<body>

<h2><fmt:messagekey="Welcome"/></h2>

Locale:<c:outvalue=

"${pageContext.request.locale.language}"/>_<c:outvalue=

"${pageContext.request.locale.country}"/>

</body>

</html>

Justliketheservletcodeinthepriorrecipe,thetagdynamicallyusestheWelcomeBundleresourcebasedontherequest'slocale.Inotherwords,ifthebrowser'slocaleis"es_ES,"aSpanishlocale,thenthefmt:messagetagsusesthekeysandvaluesfromtheWelcomeBundle_es_ESpropertiesfileorJavaclass(howeveritisimplemented).

Ifyousetthelocalizationcontextasacontext-paramelementinthedeploymentdescriptor,theJSPdoesnothavetousethefmt:setBundletag.SeeRecipe24.13.

IntheJSP,thecode:

<fmt:messagekey="Welcome"/>

isreplacedbythevalueofthe"Welcome"keyinthechosenResourceBundlefile("Holayrecepción").TheresultofrequestingthisJSPlooksjustlikeFigure24-3inRecipe24.5.

SeeAlso

Recipe24.5onusingtheResourceBundleinaservlet;Chapter23ontheJSTL;theJavadocforResourceBundle:http://java.sun.com/j2se/1.4.1/docs/api/java/util/ResourceBundle.html.

http://java.sun.com/j2se/1.4.1/docs/api/java/util/ResourceBundle.html

Recipe24.7FormattingDatesinaServlet

Problem

Youwanttoformatadatefordisplayinaservletbasedontherequest'slocale.

Solution

Usethejava.text.DateFormatclass.

Discussion

Differentcountrieshavetheirownwaysofdisplayingthedateandtime.TheDateFormatclass,likemanyoftheclassesinthejava.textpackage,is"localesensitive."Yourcodedisplaysthedatedependingonthebrowser'slanguagesetting.AllyouhavetodoispasstheLocaleobjecttothestaticDateFormat.getDateTimeInstance()method,asintheservletofExample24-8.

Example24-8.DisplayingadateStringinalocale-sensitivemanner








publicclassDateLocaleServletextendsHttpServlet{









Stringdate=DateFormat.getDateTimeInstance(DateFormat.FULL,

DateFormat.SHORT,locale).format(newDate());

//Displaythelocale




out.println("<h2>"+bundle.getString("Hello")+""+

bundle.getString("and")+""+

welcome+"</h2>");

out.println(date+"<br/><br/>");




}//doGet

//implementdoPostandcalldoGet(request,response);

}

TheDateFormat.getDateTimeInstance()methodincludesparametersintheformofconstants(e.g.,DateFormat.FULL)thatallowyourcodetocustomizethedateformat.Example24-8displaysthedateinawaythatincludesthenameofthedayoftheweekandashortformforthetime.Youcanexperimentwiththeseconstantsinordertodeterminehowbrowsersdisplaytheservlet'soutput.Figure24-5showshowthedateisdisplayedinresponsetoaGerman-languagelocaleof"de_DE."

Figure24-5.Displayingthedateinaservletaccordingtotherequest'slocale

SeeAlso

TheJavadocfortheDateFormatclass:

http://java.sun.com/j2se/1.4.1/docs/api/java/text/DateFormat.html;Recipe24.8onformattingdatesinaJSP.

http://java.sun.com/j2se/1.4.1/docs/api/java/text/DateFormat.html

Recipe24.8FormattingDatesinaJSP

Problem

YouwanttodisplayadateinaJSPthatiscustomizedfortheuser'slocale.

Solution

Usethefmt:formatDateJSTLtag.

Discussion

TheJSTLincludesthe"formatting"library,whichallowsJSPcodetodisplaydatesinalocale-sensitivemanner.Example24-9usesthefmt:formatDatetag.Thecodeusesthestandardactionjsp:useBeantocreateajava.util.Dateobjectrepresentingthecurrentdateandtime.Thecodepassesthedateobjecttofmt:formatDate'svalueattribute.WhenauserrequeststheJSP,thefmt:formatDatetagisreplacedbytextdisplayingtheformatteddate.

Example24-9.Formattingadateusingfmt:formatDate




<html>


<body>

<h2><fmt:messagekey="Hello"/><fmt:messagekey="and"/>

<fmt:messagekey="Welcome"/></h2>

<fmt:formatDatevalue="${date}"type="both"dateStyle=

"full"timeStyle="short"/><br/>

Locale:<c:outvalue=

"${pageContext.request.locale.language}"/>_<c:outvalue=

"${pageContext.request.locale.country}"/>

</body>

</html>

Thefmt:messagetagsheredependonaconfigurationparameter,orcontext-paramelement,inthedeploymentdescriptor.Thecontext-paramelementspecifiesthei18n-relatedresources.SeeRecipe24.13.

TheelementhasattributesnameddateStyleandtimeStylethatallowthecodetocustomizetheformatofthedateandtimeStrings.

SeetheJavadocfortheDateFormatclassformoredetails:http://java.sun.com/j2se/1.4.1/docs/api/java/text/DateFormat.html.

TheoutputoftheJSPinExample24-9looksjustlikeFigure24-5inthepriorrecipe.


SeeAlso

TheJavadocfortheDateFormatclass:http://java.sun.com/j2se/1.4.1/docs/api/java/text/DateFormat.html;Chapter23ontheJSTL;Recipe24.7onformattingdatesinaservlet.


Recipe24.9FormattingCurrenciesinaServlet

Problem

Youwanttoformatacurrencyvalueaccordingtotherequest'slocale.

Solution

Usethejava.text.NumberFormatclass.

Discussion

TheNumberFormatclasscanformatanumber,suchasalongordoubletype,asapercentage.ThisclasshasastaticgetCurrencyInstance()method.Thismethodcantakeajava.util.Localeobjectasaparameter,todisplaythecurrencyaccordingtotheuser'slanguagesetting.

Example24-10isaservletthatdemonstratesthelocale-sensitivedisplayofacurrency,byshowingboththecurrencyamountandthelocalelanguageandcountrycode.

Example24-10.Formattinganumberasapercentageinaservlet


importjava.text.NumberFormat;





publicclassCurrLocaleServletextendsHttpServlet{









NumberFormatnft=NumberFormat.getCurrencyInstance(locale);

StringformattedCurr=nft.format(1000000);

//Displaythelocale






welcome+"</h2>");




out.println(formattedCurr);


}//doGet

//implementdoPost()tocalldoGet()...

}

TheNumberFormatclass'format()methodreturnsaStringthatrepresentstheformattedcurrency.Figure24-6showstheservlet'soutputwhenrequestedbyabrowserwheretheuserhassetthelanguagesettingtothelocale"en_GB"(Englishlanguage,GreatBritain).

Figure24-6.ABritishvisitorseestheformattedcurrencydisplayofonemillionpounds

SeeAlso

TheJavadocfortheNumberFormatclass:

http://java.sun.com/j2se/1.4.1/docs/api/java/text/NumberFormat.html;Recipe24.10onformattingcurrenciesinaJSP.

http://java.sun.com/j2se/1.4.1/docs/api/java/text/NumberFormat.html

Recipe24.10FormattingCurrenciesinaJSP

Problem

YouwanttoformatcurrencyvaluesinaJSP.

Solution

UsetheJSTLtagfmt:formatNumber.

Discussion

Thefmt:formatNumbertagisdesignedtodisplayacurrencyvaluebasedonthevisitor'slocale.Example24-11firstusesthetaglibdirectivetomaketheJSTL1.0formattinglibraryavailabletotheJSP.

Example24-11.formattinganumberusingtheJSTL1.0tags


<%--theformattinglibraryincludesfmt:formatNumber--%>


<html>


<body>

<h2><fmt:messagekey="Hello"/><fmt:messagekey="and"/><fmt:messagekey="Welcome"/></

h2>

Locale:<c:outvalue="${pageContext.request.locale.language}"/>_<c:out

value="${pageContext.request.locale.country}"/>

<br/><br/>

<fmt:formatNumbervalue="1000000"type="currency"/>

</body>

</html>

Thefmt:formatNumbertagisquitestraightforward.Thevalueattributetakesthenumberyouwanttoformatasacurrency,andthevalueofthetypeattributemustbe"currency."ThetextrepresentingtheformattednumberthenreplacesthetagwhenabrowserdisplaystheJSP'soutput.TheJSPinExample24-11displaysthesamebrowserinformationasshowninFigure24-6ofthepriorrecipe.

SeeAlso

Chapter23ontheJSTL;theJavadocfortheNumberFormatclass:http://java.sun.com/j2se/1.4.1/docs/api/java/text/NumberFormat.html;Recipe24.9onformattingcurrenciesinaservlet.


Recipe24.11FormattingPercentagesinaServlet

Problem

Youwanttoformatnumbersaspercentagesanddisplaytheminaservlet.

Solution

Usethejava.txt.NumberFormatclassanditsstaticgetPercentInstance()method.

Discussion

Example24-12usestheNumberFormat.getPercentInstance()method,withtheuser'slocaleasanargument,togetaNumberFormattypefordisplayinganumberasapercentage.ThecodeinExample24-12callstheNumberFormat'sformat()method,withanumberasanargument.

Theformat()methoddisplaysthenumber51as"5100%";adoubletypeincludingthedecimalpoint,suchas0.51producestheintendedresult(51%).

Example24-12.UsingNumberFormattodisplayapercentageinaservlet


importjava.text.NumberFormat;





publicclassPerLocaleServletextendsHttpServlet{









NumberFormatnft=NumberFormat.getPercentInstance(locale);

Stringformatted=nft.format(0.51);

//Displaythelocale






welcome+"</h2>");




out.println("NumberFormat.getPercentInstance():"+formatted);


}//doGet

//implementdoPost()tocalldoGet()...

}

Figure24-7showstheservlet'soutputinabrowser.

Figure24-7.Thebrowserdisplaysapercentageforacertainlocale

SeeAlso

TheJavadocfortheNumberFormatclass:http://java.sun.com/j2se/1.4.1/docs/api/java/text/NumberFormat.html;


Recipe24.12onformattingpercentagesinaJSP.

Recipe24.12FormattingPercentagesinaJSP

Problem

YouwanttodisplayanumberasapercentageinaJSP.

Solution

Usethefmt:formatNumbertag.

Discussion

TheJSTL'sfmt:formatNumbertagcandisplayanumberthecodeprovidesinthetag'svalueattributeasapercentage.Thevalueofthetypeattributemustbe"percent"(not"percentage").Example24-13passestheString".51"tothevalueattribute.Thiscodedisplaysthetext"51%"inthebrowser.

Example24-13.Usingthefmt:formatNumbertaginaJSPtodisplayapercentage



<html>


<body>

<h2><fmt:messagekey="Hello"/><fmt:messagekey="and"/><fmt:messagekey="Welcome"/></

h2>

Locale:<c:outvalue="${pageContext.request.locale.language}"/>_<c:out

value="${pageContext.request.locale.country}"/>

<br/><br/>

<fmt:formatNumbervalue=".51"type="percent"/>

</body>

</html>

Figure24-8showstheJSP'soutput.

Figure24-8.AJSPdisplaysanumberformattedasapercentage

SeeAlso

TheJavadocfortheNumberFormatclass:http://java.sun.com/j2se/1.4.1/docs/api/java/text/NumberFormat.html;Chapter23ontheJSTL;Recipe24.12onformattingpercentagesinaservlet.


Recipe24.13SettingtheLocalizationContextintheDeploymentDescriptor

Problem

YouwanttoconfigurethelocalizationcontextfortheJSTLtagsusedbyawebapplication.

Solution

Useacontext-paramelementintheapplication'sdeploymentdescriptor.

Discussion

AlocalizationcontextisasetofresourcessuchasResourceBundlesthatyourwebapplication'susetoprovidelocaleinformationforaJSP.IftheJSPisdisplayingtranslatedtext,itcanuseJSTLtags(suchasfmt:fmtMessage)thatdetecttheuser'slocale,andthensearcheswithinthelocalizationcontextforthepropertexttodisplay.

Setthelocalizationcontextwithacontext-paramelementinweb.xml.Theparameternamemustbejavax.servlet.jsp.jstl.fmt.localizationContext.ItsvalueisthefullyqualifiedbasenameoftheResourceBundlethatyouhaveinstalledinthewebapplication.Example24-14showsacontext-paramelementthatpointstotheResourceBundlewehaveusedthroughoutthischapter.

Addthistypeofelementtoyourdeploymentdescriptorasanalternative

tousingtheJSTLtagfmt:setBundleinsideJSPstospecifyaResourceBundle.

Example24-14.SettingthelocalizationcontextforJSTLtags



<context-param>

<param-name>

javax.servlet.jsp.jstl.fmt.localizationContext

</param-name>

<param-value>i18n.WelcomeBundle</param-value>

</context-param>



SeeAlso

Chapter23ontheJSTL;Recipe24.2ondetectingtheclientlocaleinaJSP;Recipe24.6onusingaResourceBundleinaJSP;Recipe24.8onformattingdates;Recipe24.10onformattingcurrencies;Recipe24.12onformattingpercentages.

Chapter25.UsingJNDIandEnterpriseJavaBeans

Introduction

Recipe25.1.ConfiguringaJNDIObjectinTomcat

Recipe25.2.AccessingtheTomcatJNDIResourcefromaServlet

Recipe25.3.AccessingtheTomcatJNDIResourcefromaJSP

Recipe25.4.ConfiguringaJNDIResourceinWebLogic

Recipe25.5.ViewingtheJNDITreeinWebLogic

Recipe25.6.AccessingtheWebLogicJNDIResourcefromaServlet

Recipe25.7.AccessingtheWebLogicJNDIResourcefromaJSP

Recipe25.8.AccessinganEJBUsingtheWebLogicJNDITree

Introduction

TheJavaNamingandDirectoryInterface(JNDI)isanAPIthatJavadevelopersusetoaccessnaminganddirectoryservices.TheseservicesaretechnologiesthatJavaprogramsusetostoreorbindobjectsforlateruse,aswellassearchforor"lookup"objectreferences.ThepurposeofJNDIistoseparatetheresponsibilityofmaintainingarepositoryofcommonlyusedobjectsfromthewidevarietyofJavaclassesthatusethoseobjects,includingservletsandJSPs.

ExamplesofJNDIservicesaretheRemoteMethodInvocationregistryandtheLightweightDirectoryAccessProtocol(LDAP).TheJNDIAPI,representedbythejavax.namingpackage,providesacommonimplementationforaccessingobjectsthatareboundtotheseservices.

Thejavax.namingpackageispartoftheJava21.3and1.4SoftwareDevelopmentKits(SDKs).

Eachofthesetechnologieshasanamingschemewithwhich"JNDIobjects"canbefound.Thestructureoftheseschemesisoftenhierarchical;youstartatthetopoftheJNDItree,thenworkyourwaydowntoeachofthebranchestofindwhatyouarelookingfor.UsingJNDI,Javaprogramsbeginwithan"initialcontext,"similartotheforwardslash(/)fromwhichUnixbeginstodescribethelocationofafile.The/representstherootofastoragemediumorharddisk;youcanfindtheUsersfolderatthetoplevelofthediskbyentering/Users.

InTomcat,theinitialcontextofitsbuilt-inJNDIimplementationistheaddressjava:comp/envalllookupsstartfromthere.Chapter21describeshowtoaccessajavax.sql.DatasourcefromaJNDIimplementationbystartingattheinitialcontextjava:comp/env,andthenlookinguptheDataSourceattheaddressjdbc/MyDataSource.AllDataSourcesare

storedunderjdbc,sothisishowJavacodeaccessesaDataSourcenamed"MyDataSource."Usingafilesystemanalogy,the"root"folderinTomcat'sJNDIstructureis"java:comp/env"andspecificDataSourcesarestoredunderthejdbcsubdirectory.

YoucanuseJNDItogetaccesstoanyJavaobject,notjustDataSources.ThischapterdescribeshowtostoreaJavaBeanusingTomcat'sJNDIimplementation,andthenlookupthebeanusingaservletorJSP.Thechapteralsodescribeshowtoconfigureamailsession(withajavax.mail.Sessionobject)usingBEAWebLogic'sJNDIimplementation,andthentogainaccesstothatmailsessionbyenablingaservletorJSPtosendemail.

AservletcanalsoaccessEnterpriseJavaBeans(EJBs)usingJNDI.

AnEJBisaJavaclassthatresidesinthe"businesstier"oftheJava2EnterpriseEditon(J2EE)multi-tierarchitecture.TheJ2EEincludesawebtiercontainingourfamiliarservletsandJSPs,andanEnterpriseInformationSystem(EIS)tierinvolvingdatabasesystems.Seethe"SeeAlso"sectionofRecipe25.8.

TheservletsorJSPsmayrepresentthepresentationlogicofasystemthatusesEJBstoaccessdatabasesandimplementtasksthatarespecifictoabusinessororganization.ThelastrecipeshowshowtoaccessanEJBfromaservletusingBEAWebLogicastheapplicationserver.

Recipe25.1ConfiguringaJNDIObjectinTomcat

Problem

YouwanttoconfigureaJavaBeanasaJNDIobjectusingTomcat4.

Solution

CreateResourceandResourceParamelementsinserver.xmlorintheXMLfilethatrepresentsyourwebapplication(locatedinTomcat'swebappsfolder).Thenaddaresource-env-refelementtoweb.xml.

Discussion

TheJNDIobjectforTomcatissetupinconf/server.xml.IfyouhaveconfiguredawebapplicationasaseparateXMLfileinTomcat'swebappsfolder,thenconfiguretheJNDIresourceinthisXMLfileinstead.Example25-1showsthesetupforbindingaJavaBeanasaJNDIobject.Thebeanisnamedcom.jspservletcookbook.StockPriceBean.

Example25-1.Theserver.xmlelementforconfiguringaJNDIobject

<Resourcename="bean/pricebean"type=

"com.jspservletcookbook.StockPriceBean"auth="Container"description=

"Awebharvestingbean"/>

<ResourceParamsname="bean/pricebean">

<parameter>

<name>factory</name>

<value>org.apache.naming.factory.BeanFactory</value>

</parameter>

</ResourceParams>

Example25-1includesaResourceelementandaResourceParamselementthatreferencestheResourcebyname("bean/pricebean").ThisnameistheaddressbywhichJavacodeaccessesabeaninstanceusingtheJNDIAPI.

Example25-2showstheresource-env-refelementthatmustappearinthedeploymentdescriptor(web.xml)inorderforwebapplicationcodetoaccesstheJNDIobject.Storethecom.jspservletcookbook.StockPriceBeanclassinWEB-INF/classesorinaJARfileplacedinWEB-INF/lib.

Example25-2.Placethiselementinthedeploymentdescriptorweb.xml



<resource-env-ref>

<description>

AfactoryforStockPriceBean

</description>

<resource-env-ref-name>

bean/pricebean

</resource-env-ref-name>

<resource-env-ref-type>

com.jspservletcookbook.StockPriceBean

</resource-env-ref-type>

</resource-env-ref>


Example25-3showsasnippetofcodethatusestheJNDIAPI,justtostartyouonhowtheconfigurationfitsinwithJNDI-relatedcode.

Example25-3.CodesnippetforaccessingaTomcatJNDIresource




//Thiscodemayappearinaservlet'sinit()methodorperhaps

//indoGet()ordoPost()

Contextenv=null;

StockPriceBeanspbean=null;

try{


spbean=(StockPriceBean)env.lookup("bean/pricebean");

if(spbean==null)


"bean/pricebeanisanunknownJNDIobject");

//closetheInitialContext

env.close();


//closetheContextifyou'renotusingitagain

try{env.close();}catch(NamingExceptionnex){}


}

Example25-3importsthenecessaryclassesfromthejavax.namingpackage.ThentwolookupstakeplacetogetareferencetoaJavaBeanthathasbeenboundtoaJNDIimplementation.Thefirstlookupprovidestheinitialcontext:


ThesecondlookupattemptstoreturnaStockPriceBeanobject:


ThecodeclosestheInitialContexttoreleasetheobject'sresources,ifthecodeisnotgoingtousethecontextagainforanotherlookup.ThenextrecipeusescodelikethisfromservletsandJSPs.

SeeAlso

Recipe25.2onaccessingtheTomcatJNDIobjectfromaservlet;Recipe25.3onaccessingtheTomcatJNDIobjectfromaJSP;Chapter21onaccessingDataSourceswithJNDI.

Recipe25.2AccessingtheTomcatJNDIResourcefromaServlet

Problem

YouwanttoaccessaJNDIobjectwithaservletusingTomcat'sJNDIimplementation.

Solution

Usethejavax.namingclassesintheservlet'sinit()methodtolookupaJNDIobject.ThenusetheobjectinaservicemethodlikedoGet().

Discussion

AservletcanaccessaJavaBeanasaJNDIregisteredresourceafteryouhave:

1. DevelopedtheJavaBeanclassandstoreditinWEB-INF/classesorinaJARinWEB-INF/lib.

Changedtheserverconfigurationfileandweb.xmlasdescribedinRecipe25.1,inordertobindtheobjecttotheTomcatJNDItree.

Example25-4createsajavax.naming.InitialContextinitsinit()method,thenlooksupaJavaBean:com.jspservletcookbook.StockPriceBean.ThisbeanisboundtotheJNDIimplementationunderthename"bean/pricebean."Theinit()methodiscalledonlywhentheservletcontainercreatesaservlet

instance,sotheservlethasaccesstooneinstanceofStockPriceBean.

Example25-4.UsingaTomcatJNDIobjectfromaservlet









publicclassBeanServletextendsHttpServlet{

privateStockPriceBeanspbean;


Contextenv=null;

try{



//closetheInitialContext,unlessthecodewilluseitfor

//anotherlookup

env.close();

if(spbean==null)


"bean/pricebeanisanunknownJNDIobject");




}//try

}//init






//useaPrintWritertosendtextdatatotheclient




out.println("<title>StockPriceFetcher</title></head><body>");

out.println("<h2>Pleasesubmitavalidstocksymbol</h2>");

//makesuremethod="POST"sothattheservletservicemethod


out.println(

"<formmethod=\"POST\"action=\""+request.getContextPath()+

"/namingbean\">");


out.println("Stocksymbol:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"symbol\"size=\"10\">");


out.println(




}//doGet



throwsjava.io.IOException{

Stringsymbol;//thiswillholdthestocksymbol

floatprice=0f;

symbol=request.getParameter("symbol");

booleanisValid=(symbol==null||symbol.length()<1)?

false:true;



//useaPrintWritersendtextdatatotheclient




out.println("<title>Lateststockvalue</title></head><body>");

if((!isValid)||spbean==null){

out.println(

"<h2>Sorry,thestocksymbolparameterwaseither"+

"emptyornull</h2>");

}else{

out.println("<h2>Hereisthelatestvalueof"+symbol+"</h2>");

spbean.setSymbol(symbol);

price=spbean.getLatestPrice();

out.println((price==0?

"Thesymbolisprobablyinvalid.":""+price));

}


}//doPost

}//BeanServlet

Example25-4callsclose()ontheInitialContexttofreeupanyresourcesthisobjectisusing,sincethecodedoesnotuseitagaintoinitiatealookup.ThentheservletusesthebeanobjecttoaccessalivestockquoteinitsdoGet()method.Theservletfirstcallsthebean'ssettermethodsetSymbol()tonotifythebeanaboutwhichstocksymbolitislookingup.

Example25-5showsthebeanthatTomcathasstoredasaJNDIobject(it'sthesamebeanusedinExample25-4).Chapter26explainsthisbean,which"scrapes"astockpriceoffofawebpage.Chapter26coversthebean'sdetails;themethodsthischapter'sservletusesaresetSymbol()andgetLatestPrice().Thebeanhandlesallthedetailsofdownloadingthestockprice.

Example25-5.ThebeanthatisstoredasaJNDIobject


importjava.io.BufferedReader;


importjava.io.InputStreamReader;

importjava.net.URL;


importjavax.swing.text.html.HTMLEditorKit.ParserCallback;

importjavax.swing.text.MutableAttributeSet;

importjavax.swing.text.html.parser.ParserDelegator;

publicclassStockPriceBean{

privatestaticfinalStringurlBase=

"http://finance.yahoo.com/q?d=t&s=";

privateBufferedReaderwebPageStream=null;

privateURLstockSite=null;

privateParserDelegatorhtmlParser=null;

privateMyParserCallbackcallback=null;

privateStringhtmlText="";

privateStringsymbol="";

privatefloatstockVal=0f;

publicStockPriceBean(){}//no-argumentsconstructorforthebean

publicvoidsetSymbol(Stringsymbol){

this.symbol=symbol;

}

publicStringgetSymbol(){

returnsymbol;

}

//Innerclassprovidesthecallback

classMyParserCallbackextendsParserCallback{

privatebooleanlastTradeFlag=false;

privatebooleanboldFlag=false;

publicMyParserCallback(){

if(stockVal!=0)

stockVal=0f;

}

publicvoidhandleStartTag(javax.swing.text.html.HTML.Tagt,

MutableAttributeSeta,intpos){

if(lastTradeFlag&&(t==javax.swing.text.html.HTML.Tag.B)){

boldFlag=true;

}

}//handleStartTag

publicvoidhandleText(char[]data,intpos){

htmlText=newString(data);

if(htmlText.indexOf("Nosuchtickersymbol.")!=-1){


"InvalidtickersymbolinhandleText()method.");

}elseif(htmlText.equals("LastTrade:")){

lastTradeFlag=true;

}elseif(boldFlag){

try{

stockVal=newFloat(htmlText).floatValue();

}catch(NumberFormatExceptionne){

try{

//teaseoutanycommasinthenumberusingNumberFormat

java.text.NumberFormatnf=java.text.NumberFormat.

getInstance();

Doublef=(Double)nf.parse(htmlText);

stockVal=(float)f.doubleValue();

}catch(java.text.ParseExceptionpe){


"Theextractedtext"+htmlText+

"cannotbeparsedasanumber!");

}//innertry

}//outertry

lastTradeFlag=false;

boldFlag=false;

}//if

}//handleText

}//MyParserCallback

publicfloatgetLatestPrice()throwsIOException,MalformedURLException{

stockSite=newURL(urlBase+symbol);

webPageStream=newBufferedReader(newInputStreamReader(stockSite.

openStream()));

htmlParser=newParserDelegator();

callback=newMyParserCallback();//ParserCallback

synchronized(htmlParser){

htmlParser.parse(webPageStream,callback,true);

}//sychronized

//resetsymbol

setSymbol("");

returnstockVal;

}//getLatestPrice

}//StockPriceBean

TheParserDelegator.parse()methodissynchronizedandthereforedesignedtoonlyallowonethreadatatimetoparsethewebpageandpulloutthestockquote.

Figure25-1showsthewebpageformgeneratedbytheservlet'sdoGet()method.Theuserentersastocksymbolintothisform,thensubmitstheformtotheservlet'sdoPost()method.

Figure25-1.Enterastocksymbolforalivestockprice

Figure25-2showsthestockinformationthattheJNDIobjectfoundfortheservlet.

Figure25-2.Theservlet'sdoPost()methodgeneratesalivestockquoteusingaJNDIobject

SeeAlso

Recipe25.1onconfiguringaJNDIobjectwithTomcat;Recipe25.3onaccessingtheTomcatJNDIobjectfromaJSP;Chapter21onaccessingDataSourceswithJNDI;Chapter26onharvestingwebinformation.

Recipe25.3AccessingtheTomcatJNDIResourcefromaJSP

Problem

YouwanttoaccessaJNDIresourcefromaJSP.

Solution

Useafiltertoplacetheobjectinrequestorsessionscope.AccesstheobjectintheJSPwiththec:setandc:outJSTLtags.

Discussion

AnicejobforafilterisaccessingaJNDIobject,thenplacingareferencetothatobjectinasessionforaJSPtouse.SeeChapter19formoreinformationonfilters.

HerearethestepsneededtouseafilterwithJNDIandaJSP:

1. Developandcompilethefilter,includingano-argumentsconstructor.

UsetheJNDIAPIandjavax.namingpackageinthefiltertosetasessionattributeusingtheJNDIobject.

PlacethefilterinWEB-INF/classesorinaJARinWEB-INF/lib.

Addfilterandfilter-mappingelementstoweb.xml;mapthefiltertotheJSPthatwillusetheJNDIobject(Example25-7).

CreateaJSPthatusesthesessionattribute.

Example25-6showsthefilter.Thefilterinitializesajavax.naming.Contexttypeinitsinit()method(whentheservletcontainercreatesthefilterinstance).ThedoFilter()methodgrabsaJNDIobjectandstorestheobjectasasessionattribute.ThefilterchainendsattheJSPtowhichthefilterismapped;therefore,theJSPhasaccesstothesessionattribute(i.e.,theJNDIobject).

Example25-6.AFilteraccessesaJNDIobjectandsetstheobjectasasessionattribute








publicclassJndiTFilterimplementsFilter{


privateContextenv;

//No-argumentsconstructorrequiredforafilter;we'vemadeit

//explicithere,eventhoughthecompilerwouldhavecreatedone

//intheabsenceofthisoranyotherconstructor

publicJndiTFilter(){}



try{


env.close();




}

}


ServletResponseresponse,FilterChainchain)throwsIOException,

ServletException{

StockPriceBeanspbean=null;

try{


}catch(NamingExceptionne){}

HttpServletRequesthRequest=null;

if(requestinstanceofHttpServletRequest)

hRequest=(HttpServletRequest)request;

HttpSessionhSession=hRequest.getSession();

if(hSession!=null)

hSession.setAttribute("MyBean",spbean);


}//doFilter




}

}//Filter

Thefilter'sdoFilter()methodiscalledeachtimeaclientrequeststheJSP,soeachclientisassociatedwithadifferentbeaninstance.Inotherwords,eachsessionstoresitsownbeaninstance.

TheJSPcouldthenremovethesessionattribute(ifitwasnotgoingtobeusedagain)toconserveserverresources.SeeChapter16forrecipesonsettingandremovingsessionattributes.

Example25-7showsthefilterandfilter-mappingelementsthatyoucanaddtothedeploymentdescriptor.Thiscausestheservletcontainertocreateaninstanceofthefilter(callingthefilter'sinit()method).Thenthecontainercallsthefilter'sdoFilter()methodwheneveritreceivesarequestmatchingtheURL(s)associatedwiththefilter-mappingelement.

Example25-7.ThefilterandelementsforaJNDI-relatedfilter



<filter>

<filter-name>JndiTFilter</filter-name>

<filter-class>com.jspservletcookbook.JndiTFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>JndiTFilter</filter-name>

<url-pattern>/jndiJsp.jsp</url-pattern>

</filter-mapping>



Example25-7mapstheJndiTFiltertothewebcomponentattheURL/jndiJsp.jsp.Example25-8showstheJSPthatusesthesessionattribute,called"MyBean"todisplayastockquote.

Example25-8.AJSPusesasessionattributeoriginatingasaJNDIobject


<html>

<head><title>JndiBean</title></head>

<body>

<h2>GettingaStockPriceBeanobjectviaJNDI...</h2>

<c:setvar="priceBean"value="${MyBean}"/>

<%--setthe'symbol'propertytothestocksymbol--%>

<c:settarget="${priceBean}"property="symbol"value="${param.symbol}"/>

<%--getthelatestpricebycallinggetLatestPrice()onthebeanobject--%>

Thelatestprice:<c:outvalue="${priceBean.latestPrice}"/>

</body>

</html>

Figure25-3showsthisJSP'soutput.Example25-5inRecipe25.2showsthecodefortheJavaBeanthatthisJSPuses.

Figure25-3.AJSPusesasessionattributeviaJNDItodisplayastockprice

SeeAlso

Recipe25.1onconfiguringaJNDIobjectwithTomcat;Recipe25.2onaccessingtheTomcatJNDIobjectfromaservlet;Chapter21onaccessingDataSourceswithJNDI.

Recipe25.4ConfiguringaJNDIResourceinWebLogic

Problem

YouwanttobindanobjecttoBEAWebLogic'sJNDIimplementation.

Solution

UsetheWebLogicAdministrationconsole.

Discussion

Herearethestepsneededtobindajavax.mail.Sessionobject(whichIuseasanexampleforthisrecipe)toWebLogic'sJNDIimplementation.TheadvantageofthisapproachisthattheavailableSessionisalreadyconfiguredwithelementssuchasitsSMTPhost(seeTable25-1).TheSessionis"readytogo"forthecodethatwilleventuallylookupandusetheobject.

1. LogintotheWebLogicAdministrationconsole,whichinvolvesusingabrowserURLsuchashttp://localhost:7001/console.

GotoYour-domain-name Services Mailinthelefthandcolumnmenu.

Clickon"ConfigureanewMailSession..."ThisproducesthewindowshowninFigure25-4.

Figure25-4.Configuringajavax.mail.SessiontypeasaJNDIobjectusingtheWebLogicAdministrationconsole

4. Fillinthetextfieldsintheresultingwindow.GivetheSessionobjectaJNDIname(under"JndiName"),whichisthenamethatthecodeusestolookuptheobject.

EnteranypropertiesfortheSessionbytypinginthepropertyname,anequalssign(=),andthepropertyvalue.SeeTable25-1.

Clickthe"Apply"button,thenchoosethe"Targets"tab.TheresultingscreenallowsyoutoassociatetheJNDIobjectwithoneormoreservers.

NowtheJNDIobjectisavailabletoJavaprogramsusingtheJNDIAPIandthenameyouboundtheobjectunder.Recipe25.5showshowtoviewtheJNDItreegraphicallytoverifythattheobjecthasbeenboundproperly.

Table25-1.JavaMailpropertiessetforthisrecipe'sSessionJNDIobject

Propertyname Description Example

mail.host Thedefaultmailserver mail.comcast.net

mail.smtp.host Protocol-specificmailhost;defaultstomail.hostvalue mail.comcast.net

mail.user Theusernameforconnectingtothemailserver bruceperry

mail.from Thereturnaddresstousewhensendingmail. [email protected]

SeeAlso

Recipe25.6onaccessingaJNDIobjectwithaservletonWebLogic;Recipe25.7onaccessingaJNDIobjectwithaJSPonWebLogic;Chapter2ononaccessingaJNDIobjectwithaJSPonWebLogic;Chapter2ondeployingwebcomponentswithWebLogic.

Recipe25.5ViewingtheJNDITreeinWebLogic

Problem

YouwanttoviewtheWebLogicJNDItreeingraphicalform.

Solution

RightclickontheservernameintheWebLogicAdministrationconsoleandchoose"ViewJNDITree."

Discussion

AfteryouhaveboundanobjecttoJNDIusingtheAdministrationconsole,youcanthenviewtheJNDItreetoseeifWebLogichasboundyourobjectasintended.Right-clickon"My-domain-name ServersServer-name"inthelefthandmenuandchoose"ViewJNDITree."ThisgeneratesanewbrowserwindowthatlooksliketheoneinFigure25-5.

Thenewobject("MyEmail")isrepresentedatthetopofthetreeasapurpledot.ThisisanicegraphicalwayofviewingthehierarchicalstructureoftheJNDItree,includingitssubdirectoriesandvariousobjects,thatareavailabletoaWebLogicserver.

Figure25-5showsthe"MyEmail"boundobjectselectedintheJNDItree.Informationabouttheobjectisdisplayedintherighthandframeofthebrowserwindow.

Figure25-5.AgraphicaldisplayoftheWebLogicJNDItree

SeeAlso

Recipe25.4onconfiguringaJNDIobjectonWebLogic;Recipe25.6onaccessingaJNDIobjectwithaservletonWebLogic;Recipe25.7onaccessingaJNDIobjectwithaJSPonWebLogic;Chapter2ondeployingwebcomponentswithWebLogic.

Recipe25.6AccessingtheWebLogicJNDIResourcefromaServlet

Problem

YouwanttoaccesstheJNDIobjectcreatedandboundonWebLogic.

Solution

UsetheJNDIAPIintheservlettoaccessareferencetotheboundobject.

Discussion

Example25-9isanHttpServletthatobtainsajavax.mail.SessionobjectfromWebLogic'sJNDIimplementation.Theservletusesthisobjecttobuildanemailmessage.TheservletinitiatestheJNDIlookupinitsinit()methodforanobjectboundunderthename"MyEmail"(Recipe25.4).Theservletcontainercallstheinit()oncewhenthecontainercreatestheservletinstance.

Example25-9.Servlettoobtainajavax.mail.SessionobjectfromWebLogic'sJNDIimplementationandbuildanemailmessage







importjavax.mail.*;




publicclassEmailJndiServletextendsHttpServlet{

privateSessionmailSession;


Contextenv=null;

try{

env=(Context)newInitialContext();

mailSession=(Session)env.lookup("MyEmail");

if(mailSession==null)


"MyEmailisanunknownJNDIobject");


env.close();




}

}//init






out.println(





StringemailContent=request.getParameter("emailContent");

try{

sendMessage(to,from,subject,emailContent);


thrownewServletException(exc.getMessage());

}

out.println(

"<h2>Themessagewassentsuccessfully</h2></body></html>");


}//doPost




//doGet()callsdoPost()


}

privatevoidsendMessage(Stringto,Stringfrom,Stringsubject,

StringbodyContent)throwsException{

MessagemailMsg=null;

mailMsg=newMimeMessage(mailSession);//anewemailmessage


try{

if(to!=null){





}else{



}

if(from!=null)

mailMsg.setFrom(from);

if(subject!=null)


if(bodyContent!=null)

mailMsg.setText(bodyContent);


//ifanyofthemessage'srecipientshaveaninvalidadress



throwexc;

}//sendMessage

}//EmailJndiServlet

ThedoPost()methodcallstheservlet'ssendMessage()method,passingintheemailmessagepartssuchastherecipientandtheemail'scontent.Theservletderivesthisinformationfromrequestparametersthattheusersubmits.Atypicalrequestfortheservletlookslike:

http://localhost:7001/[email protected]&

[email protected]&subject=hello&

emailContent=Awebmessage

AusercanalsoPOSTinformationtotheservletwithanHTMLform.

Theservlet'ssendMessage()methodusestheJNDIobjectinthejavax.mail.internet.MimeMessageconstructorwhenthemethodcreatesanewemailmessage.

Figure25-6showstheservlet'ssimplereturnmessageinabrowserwindow.

Figure25-6.Theservletsendstheemailsuccessfully

SeeAlso

Recipe25.4onconfiguringaJNDIobjectonWebLogic;Recipe25.5onviewingtheWebLogicJNDItreewiththeAdministrationconsole;Recipe25.7onaccessingaJNDIobjectwithaJSPonWebLogic;Chapter2ondeployingwebcomponentswithWebLogic.

Recipe25.7AccessingtheWebLogicJNDIResourcefromaJSP

Problem

YouwanttouseaWebLogicJNDIobjectinaJSP.

Solution

CreateafilterthataccessestheJNDIobjectandsetstheobjectasasessionattribute.

Discussion

Anysenseofdejávucomesfromafewrecipesago,whenyouusedafiltertopassaJNDIobjecttoaJSPonTomcat.TheonlydifferenceinthisrecipeisthattheapplicationserverusedisWebLogicandtheJNDIobjectisaJavaMailSession,notaJavaBean.

ThefilteraccessestheobjectusingtheJNDIAPIonWebLogic.Thenthefiltersetstheobjectasasessionattribute,sothattheJSPcanaccessthejavax.mail.Session.Example25-10showsthecodeforthefilterthatrecipeusesontheWebLogicserver.

Example25-10.AfilterstoresaWebLogicJNDIobjectinasessionattribute








publicclassJndiFilterimplementsFilter{


privateContextenv;

publicJndiFilter(){}



try{




}

}//init



javax.mail.SessionmailSession=null;

try{

mailSession=(javax.mail.Session)env.lookup("MyEmail");

}catch(NamingExceptionne){}

HttpServletRequesthRequest=null;

if(requestinstanceofHttpServletRequest){

hRequest=(HttpServletRequest)request;

HttpSessionhSession=hRequest.getSession();

if(hSession!=null)

hSession.setAttribute("MyEmail",mailSession);

}//if


}//doFilter




}

}

Example25-11showsthefilterconfigurationinsidethedeploymentdescriptor.ThisdeploymentdescriptormustaccompanyawebapplicationthatyouoranotherdeployerhasinstalledonWebLogicserver.

Example25-11.AfilterthataccessesaJNDIobjectonWeblogic



<filter>

<filter-name>JndiFilter</filter-name>

<filter-class>com.jspservletcookbook.JndiFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>JndiFilter</filter-name>

<url-pattern>/jndiJsp.jsp</url-pattern>

</filter-mapping>



Example25-12showsaJSPthataccessestheJNDIobject.Thiscodedisplaystheclassnameoftheobject,ajavax.mail.SessiontypethatRecipe25.4boundasaJNDIobjectonWebLogic.ThefilterinExample25-11thensettheobjectasasessionattribute(nottobeconfusedwiththeSessiontypeoftheobject).Thisattributeisavailabletoallwebcomponentsthatparticipateinthesamesession.Therefore,thec:settaginthisJSPusesthefollowingELcodetogetaccesstotheattribute.

${MyEmail}

Thenthec:outtagdisplaystheclassnameofthesessionattribute,inordertoverifythattheobjectisajavax.mail.Session.Recipe25.6givesthecompleteJavaMailcodeforsendinganemail.

Example25-12.TheJSPaccessestheJavaMailobjectasasessionattribute


<html>

<head><title>JndiEmail</title></head>

<body>

<h2>Gettingajavax.mail.SessionobjectviaJNDI...</h2>

<c:setvar="mSession"value="${MyEmail}"/>

<c:outvalue="${mSession.class.name}"/>

</body>

</html>

Figure25-7showsawebbrowserwindowafterauserhasrequestedtheJSP.

Figure25-7.AJSPaccessesaJNDIobjectviaaservletfilter

SeeAlso

Chapter19onfilters;Chapter23ontheJSTL;Recipe25.4onconfiguringaJNDIobjectwithWebLogic;Recipe25.6onaccessingaJNDIobjectwithaservletonWebLogic;Chapter2ondeployingwebcomponentswithWebLogic.

Recipe25.8AccessinganEJBUsingtheWebLogicJNDITree

Problem

YouwanttoaccessanEnterpriseJavaBean(EJB)fromaservletonWebLogic.

Solution

FindouttheEJB'sJNDInameandusethejavax.namingpackagetogetareferencetotheEJBObjectorremoteinterfacesothatyoucancalltheEJB'smethods.

Discussion

AservletaccessesanEJBbyusingaspecifiedJNDIname.Theprocessisthereforetransparenttotheservletdeveloper.AnyEJBsanapplicationusescomprisethebusinesstierofanapplication.TheservletsandJSPsrepresentthewebtierwithinthemulti-tiereddistributedarchitectureofatypicalJava2EnterpriseEdition(J2EE)application.AllyouneedtoknowistheJNDInameassociatedwiththeEJBinordertousetheEJBinyourprograms.

EnterpriseJavaBeansisacomprehensivetopic;however,thisrecipeisdevotedtoshowinghowaservletcanconnecttoanEJB.The"SeeAlso"segmentofthisrecipeincludesseverallinkstoEJBandJ2EEinformationandbooks.

YoushouldbeawareoftheEJB'sbusinessmethods,butdonothavetobeanexpertonthejavax.ejbpackagetousetheEJB.Example25-13showsthesourcecodeforastatelesssessionEJBthatismanagedbyBEAWebLogic7.0applicationserver.

AcertaintypeofEJB,astatelesssessionbeanencapsulatesbusinesslogicthatdoesnotrequirepersistenceorthesavingoftheobject'sstatebetweenmethodcalls.Ontheotherhand,astatefulsessionbean(suchasashoppingcartobject),mustremembertheobject'sstate(suchasthevalueofvariousinstancevariables)betweenmethodcalls,aspartofaconversationwiththeEJBclient.

Example25-13providesajava.util.MapthatlinksU.S.statenameswiththeirpostalabbreviations.Thesessionbeanincludesonebusinessmethod,getAbbreviation(),whichreceivesastatenameasaparameterandreturnsitspostalabbreviation.

Example25-13.ThestatelesssessionEJB


importjavax.ejb.*;



publicclassAbbrevBeanimplementsSessionBean{

privateSessionContextcontext;

privateMapabbrevMap;

publicAbbrevBean(){//thebean'sno-argumentsconstructor

//AMapcontainingthenamesofstatesandabbreviations

abbrevMap=newHashMap();

abbrevMap.put("ALABAMA","AL");

abbrevMap.put("ALASKA","AK");

abbrevMap.put("AMERICANSAMOA","AS");

abbrevMap.put("ARIZONA","AZ");

abbrevMap.put("ARKANSAS","AR");

abbrevMap.put("CALIFORNIA","CA");

abbrevMap.put("COLORADO","CO");

abbrevMap.put("CONNECTICUTT","CT");

abbrevMap.put("DELAWARE","DE");

abbrevMap.put("DISTRICTOFCOLUMBIA","DC");

abbrevMap.put("FEDERATEDSTATESOFMICRONESIA","FM");

abbrevMap.put("FLORIDA","FL");

abbrevMap.put("GEORGIA","GA");

abbrevMap.put("GUAM","GU");

abbrevMap.put("HAWAII","HI");

abbrevMap.put("IDAHO","ID");

abbrevMap.put("ILLINOIS","IL");

abbrevMap.put("INDIANA","IN");

abbrevMap.put("IOWA","IA");

abbrevMap.put("KANSAS","KS");

abbrevMap.put("KENTUCKY","KY");

abbrevMap.put("LOUISIANA","LA");

abbrevMap.put("MAINE","ME");

abbrevMap.put("MARSHALLISLANDS","MH");

abbrevMap.put("MARYLAND","MD");

abbrevMap.put("MASSACHUSETTS","MA");

abbrevMap.put("MICHIGAN","MI");

abbrevMap.put("MINNESOTA","MN");

abbrevMap.put("MISSISSIPPI","MS");

abbrevMap.put("MISSOURI","MO");

abbrevMap.put("MONTANA","MT");

abbrevMap.put("NEBRASKA","NE");

abbrevMap.put("NEVADA","NV");

abbrevMap.put("NEWHAMPSHIRE","NH");

abbrevMap.put("NEWJERSEY","NJ");

abbrevMap.put("NEWMEXICO","NM");

abbrevMap.put("NEWYORK","NY");

abbrevMap.put("NORTHCAROLINA","NC");

abbrevMap.put("NORTHDAKOTA","ND");

abbrevMap.put("NORTHERNMARIANAISLANDS","MP");

abbrevMap.put("OKLAHOMA","OK");

abbrevMap.put("OREGON","OR");

abbrevMap.put("PALAU","PW");

abbrevMap.put("PENNSYLVANIA","PA");

abbrevMap.put("PUERTORICO","PR");

abbrevMap.put("RHODEISLAND","RI");

abbrevMap.put("SOUTHCAROLINA","SC");

abbrevMap.put("SOUTHDAKOTA","SD");

abbrevMap.put("TENNESSEE","TN");

abbrevMap.put("TEXAS","TX");

abbrevMap.put("UTAH","UT");

abbrevMap.put("VERMONT","VT");

abbrevMap.put("VIRGINISLANDS","VI");

abbrevMap.put("VIRGINIA","VA");

abbrevMap.put("WASHINGTON","WA");

abbrevMap.put("WESTVIRGINIA","WV");

abbrevMap.put("WISCONSIN","WI");

abbrevMap.put("WYOMING","WY");

}//constructor

publicvoidsetSessionContext(SessionContextctx)throws

EJBException{

context=ctx;

}//setSessionContext

publicMapgetAbbrevMap(){

returnabbrevMap;

}

//Thebean'sbusinessmethod

publicStringgetAbbreviation(Stringstate){

return(String)abbrevMap.get(state);

}

//javax.ejb.SessionBeanmethod;ithastobeimplementedinasession

//bean,butisnotrelevanttoStatelesssessionbeans.

publicvoidejbActivate(){}

//javax.ejb.SessionBeanmethod;ithastobeimplementedinaSession

//bean,butisnotrelevanttostatelesssessionbeans.

publicvoidejbPassivate(){}

//javax.ejb.SessionBeanmethod;

publicvoidejbRemove(){}

}

Example25-13couldeasilybeimplementedasanordinaryJavahelperorutilityclass.However,IshowasimpleexampleofanEJBsothattherecipecanfocusonhowaservletconnectstotheseobjects.

EJBshaveadeploymentdescriptor,similartotheweb.xmlfilethatwebapplicationsuse.TheEJBdeploymentdescriptormustbenamedejb-jar.xml.WhenyoupackagetheEJB(s)beforetheyaredeployedonanapplicationserver,includethisdeploymentdescriptoraspartofthearchive.Theejb-jar.xmlfiledescribestherelatedEJBcomponent(s);theapplicationserverusesthisdescriptiveinformationinordertoproperlydeploytheEJB.

Forexample,theejb-jar.xmlfileinExample25-14specifiesthetypeof

EJB(e.g.,statelesssessionbean)andthefullyqualifiedclassnamesofitsrelatedJavaclasses,suchasitsremoteinterface.

Example25-14.Theejb-jar.xmlfile

<?xmlversion="1.0"?>

<!DOCTYPEejb-jarPUBLIC"-//SunMicrosystems,Inc.

//DTDEnterpriseJavaBeans2.0//EN"

"http://java.sun.com/dtd/ejb-jar_2_0.dtd"

>

<ejb-jar>

<enterprise-beans>

<session>

<ejb-name>AbbreviationEjb</ejb-name>

<home>com.jspservletcookbook.AbbrevHome</home>

<remote>com.jspservletcookbook.Abbrev</remote>

<local-home>com.jspservletcookbook.AbbrevLocalHome</local-home>

<local>com.jspservletcookbook.AbbrevLocal</local>

<ejb-class>com.jspservletcookbook.AbbrevBean</ejb-class>

<session-type>Stateless</session-type>

<transaction-type>Container</transaction-type>

</session>

</enterprise-beans>

</ejb-jar>

ThepackagethatcontainsthisEJB,andwithwhichtheEJBisdeployedontheapplicationserver,isaJARfilenamedmyejb.jar(justanameIconcocted;youdonothavetousethesamename).

SincethisstatelesssessionbeanisdeployedonBEAWebLogicServer,theJARfilemustincludeavendor-specificdeploymentdescriptornamedweblogic-ejb-jar.xml.ThisdeploymentdescriptorgivesthedeployertheopportunitytoconfigureseveralaspectsofhowtheEJBisdeployedonWebLogic,suchastheJNDInamesofitshomeandlocalhome

interfaces.

The"home"objectisanimplementationofthe"home"interface,andthe"localhome"objectisanimplmentationofthelocalhomeinterface.Theseobjectsare"factories"forEJBobjects,whichdelegatethebusiness-methodcallstotheEJBdeployedintheserver.AfactoryisaJavaclassthatgeneratesobjectsofadifferentkindofJavaclass.Inthisrecipe'scase,theclientusesJNDItogetareferencetothehomeobject,whichcreatesanEJBobject.Theservlet(client)thencallstheEJBobject'sgetAbbreviation()method;theEJBobjectisaremoteobjector"stub"thatdelegatesthismethodcalltotheoriginalEJBstoredontheserver.

Youwillencounterthehomeobject'sJNDInameintheservletdepictedlateroninthisrecipe.

WhenyoudeployanEJBonWebLogicusingtheAdministrationConsole,WebLogicautomaticallybindsthehomeandlocalhomeobjectswithintheWebLogicJNDItree,usingthenamesspecifiedbytheweblogic-ejb-jar.xmldeploymentdescriptor.

Example25-15showstheweblogic-ejb-jar.xmldeploymentdescriptorforourstatelesssessionbean.

Example25-15.Theweblogic-ejb-jar.xmlfile

<!DOCTYPEweblogic-ejb-jarPUBLIC

'-//BEASystems,Inc.//DTDWebLogic7.0.0EJB//EN'

'http://www.bea.com/servers/wls700/dtd/weblogic-ejb-jar.dtd'>

<weblogic-ejb-jar>

<weblogic-enterprise-bean>

<ejb-name>AbbreviationEjb</ejb-name>

<stateless-session-descriptor>

<pool>

<initial-beans-in-free-pool>1</initial-beans-in-free-pool>

</pool>

</stateless-session-descriptor>

<jndi-name>AbbrevHome</jndi-name>

<local-jndi-name>AbbrevLocalHome</local-jndi-name>

</weblogic-enterprise-bean>

</weblogic-ejb-jar>

AnEJBmoduleisacomplicatedpackagethatincludesbeanclasses,remoteinterfaces,andtwodifferentdeploymentdescriptors.Example25-16showsthecontentsofthemyejb.jarfile.Iusethejartvfmyejb.jar.commandinacommand-linewindowtodisplaythecontentsofthespecifiedJARfile(itworksinbothUnixandWindows).

Example25-16.Thecontentsoftheejb-jar.xmlfile

H:\book\cookbook\code\chap27\src\ejbs\ejbjar>jartvfmyejb.jar

META-INF/

META-INF/MANIFEST.MF

com/

com/jspservletcookbook/

com/jspservletcookbook/Abbrev.class

com/jspservletcookbook/AbbrevBean.class

com/jspservletcookbook/AbbrevHome.class

com/jspservletcookbook/AbbrevLocal.class

com/jspservletcookbook/AbbrevLocalHome.class

META-INF/ejb-jar.xml

META-INF/weblogic-ejb-jar.xml

InExample25-16,thesessionbeanisAbbrevBean.class,theremoteinterfaceisAbbrev.class,andthehomeobject(thefactoryforEJBobjectsthatimplementtheAbbrevinterface)isAbbrevHome.class.

Finally,Example25-17showstheservletthatusesthesessionbeanfromExample25-13.Thecodeisself-explanatory.TheimportantthingtorememberisthattheservletreceiveseareferencetotheAbbrevHomeobjectfromtheWebLogicJNDItree.Thentheservlet,initsdoGet()method,callstheAbbrevHomeobject'screate()methodtogetaninstanceofthesessionbean'sremoteinterface(inthisexample,it'sanAbbrevtype).

Example25-17.AservletthataccessestheEJBonWebLogicusingJNDI







importjavax.rmi.PortableRemoteObject;



publicclassWebJndiServletextendsHttpServlet{




//Therequestparameterlookslike'state=Massachusetts'

Stringstate=request.getParameter("state");

Contextenv=null;

Abbrevabbrev=null;

AbbrevHomehome=null;

try{


//LookupthehomeorfactoryobjectontheWebLogicJNDItree

ObjectlocalH=env.lookup("AbbrevHome");

//ThismethodcallisnecessaryforEJBcodethatusesa

//technologycalledRMI-IIOP

home=(AbbrevHome)PortableRemoteObject.narrow(localH,

AbbrevHome.class);


env.close();

if(home==null)


"AbbrevHomeisanunknownJNDIobject");

//Gettheremoteinterfacebycallingthehomeobject'screate()

//method

abbrev=(Abbrev)PortableRemoteObject.narrow(home.create(),

Abbrev.class);




}catch(javax.ejb.CreateExceptionce){

thrownewServletException(ce);

}





out.println("<title>Stateabbreviations</title></head><body>");

out.println("<h2>Hereisthestate'sabbreviation</h2>");

//CalltheEJBObject'sgetAbbreviation()method;theEJBObject

//delegatesthismethodcalltothesessionbean.Puttherequest

//parameterinallupper-case,becausethisishowthesessionbean's

//java.util.Mapstoresthestatenames,whicharetheMap'skeys

if(state!=null)

out.println(abbrev.getAbbreviation(state.toUpperCase()));

try{

//TheservletisthroughwiththeEJBObject;callitsremove()

//method

abbrev.remove();

}catch(javax.ejb.RemoveExceptionre){}


}//doGet





}//doPost

}//WebJndiServlet

Thevalueoftheabbreviationforastatesuchas"Oregon"isultimatelyretrievedontheserversidebycallingthesessionbean's

getAbbreviation()method.Figure25-8showsawebbrowserwindowafterauserhasrequestedtheservlet.TheURLlookssomethinglikehttp://localhost:7001/webjndi?state=Oregon.TheURLpattern/webjndiismappedinweb.xmltotheservletofExample25-17.

Figure25-8.AnEJB-accessingservlet'swebbrowserdisplay

SeeAlso

Recipe25.4onconfiguringaJNDIobjectwithWebLogic;Recipe25.6onaccessingaJNDIobjectwithaservletonWebLogic;Chapter2ondeployingwebcomponentswithWebLogic;aweblinkforthejavax.ejbAPI:http://java.sun.com/j2ee/1.4/docs/api/javax/ejb/package-summary.html;thedocumentationpageforWebLogicServer7.0:http://edocs.bea.com/wls/docs70/index.html;alinktoJ2EEtutorials,includinganEnterpriseJavaBeantutorial:http://java.sun.com/j2ee/tutorial/index.html;EnterpriseJavaBeans,ThirdEdition(O'Reilly);J2EEDesignPatterns(O'Reilly).

http://java.sun.com/j2ee/1.4/docs/api/javax/ejb/package-summary.html

http://edocs.bea.com/wls/docs70/index.html

http://java.sun.com/j2ee/tutorial/index.html

Chapter26.HarvestingWebInformationIntroduction

Recipe26.1.ParsinganHTMLPageUsingthejavax.swing.textSubpackages

Recipe26.2.UsingaServlettoHarvestWebData

Recipe26.3.CreatingaJavaBeanasaWebPageParser

Recipe26.4.UsingtheWebPageParsingJavaBeaninaServlet

Recipe26.5.UsingtheWebPageParsingJavaBeaninaJSP

Introduction

TheWebcontainsinformationgalore.Muchofthisinformationisfreelyavailablebysimplysurfingovertoanorganization'swebsiteandreadingtheirpagesorsearchresults.However,itcanbedifficultseparatingthedrossfromthegems.Thevastmajorityofawebpage'svisualcomponentsaretypicallydedicatedtomenus,logos,advertisingbanners,andfancyappletsorFlashmovies.WhatifallyouareinterestedinisatinynuggetofdataawashinanoceanofHTML?

TheanswerliesinusingJavatoparseawebpagetoextractonlycertainpiecesofinformationfromit.Thewebtermsforthistaskareharvestingorscrapinginformationfromawebpage.Perhapswebservices(Chapter27)willeventuallyreplacetheneedtoharvestwebdata.ButuntilmostmajorsiteshavetheirwebservicesAPIsupandrunning,youcanuseJavaandcertainjavax.swing.textsubpackagestopullspecifiedtextfromwebpages.

Howdoesitwork?Basically,yourJavaprogramusesHTTPtoconnectwithawebpageandpullinitsHTMLtext.

ParsingtheHTMLfromwebsitesstillinvolvestransferringtheentirewebpageoverthenetwork,evenifyouareonlyinterestedinafractionofitsinformation.Thisiswhyusingwebservicesisamuchmoreefficientmannerofsharingspecificdatafromawebsite.

ThenuseJavacodetoparsetheHTMLpageinordertopullfromitonlythepieceofdatayouareinterestedin,suchasweatherdataorastockquote.ThefollowingrecipesshowtheJavaclassesthatyoucanusetoharvestwebinformation.ThentherecipesshowaservletandaJSPusingaJavaBeantograbanddisplay,asanexample,alivestockquote.

Recipe26.1ParsinganHTMLPageUsingthejavax.swing.textSubpackages

Problem

YouwanttousetheclassestheJava2StandardEdition(J2SE)makesavailableforparsingHTML.

Solution

Usethevarioussubpackagesofthejavax.swing.textpackagetocreateaparserforHTML.

Discussion

TheJ2SE1.3and1.4versionsincludethenecessaryclassesforsiftingthroughwebpagesinsearchofinformation.TheJavaprogramstheserecipesuseimportthefollowingclasses:

javax.swing.text.html.

HTMLEditorKit.ParserCallback;

javax.swing.text.MutableAttributeSet;

javax.swing.text.html.parser.ParserDelegator;

Thedesignpatternthattheseclassesusetoreadwebpagesinvolvesthreemainelements:

1. Ajava.net.URLobjectthatopensupasocketorInputStreamtothewebpageusingHTTP.Thecodethenusesthisobjecttoreadthewebpage.

AParserDelegatorobjectwithwhichthecodesiftsthroughthewebpagebycallingthisobject'sparse()method.

AParserCallbackobjectthattheParserDelegatorusestotakecertainactionswhileitisparsingthewebpage'sHTMLtext.AcallbackingeneralisanobjectthatJavacodetypicallypassesintoanotherobject'sconstructor.Theenclosingobjectthendrivesthecallbackbyinvokingthecallback'smethods,whichtheJavaprogrammerimplementsaccordingtowhattheywanttoaccomplishbyparsingtheHTML.Theroleofthecallbackwillbecomeclearerasyoureadthroughtheserecipes.

TheservletandJavaBeandefinedinthischapteruseaninnerclasstoimplementthecallback.Example26-1showsthecallbackthatextendsjavax.swing.text.html.HTMLEditorKit.ParserCallback.

Example26-1.Acallbackclassforsiftingthroughwebpages


//breadcrumbsthatleadustothestockprice




//Resettheenclosingclass'stock-priceinstancevariable

if(stockVal!=0)

stockVal=0f;

}

//Amethodthattheparsercallseachtimeitconfrontsastarttag




boldFlag=true;

}

}//handleStartTag

//Amethodthattheparsercallseachtimeitreachesnestedtextcontent







lastTradeFlag=true;

}elseif(boldFlag){

try{



try{

//teaseoutanycommasinthenumberusingNumberFormat


getInstance();







}//try

}//try

//Resettheinnerclass'sinstancevariables


boldFlag=false;

}//if

}//handleText

}//MyParserCallback

Acallbackincludesmethodsthatrepresenttheattainmentofacertainelementofawebpageduringtheparsingprocess.Forexample,theparser(theobjectthatenclosesthecallbackobject)callshandleStartTag()wheneveritrunsintoanopeningtagasittraversesthewebpage.Examplesofopeningtagsare<html>,<title>,or<body>.Therefore,whenyouimplementthehandleStartTag()methodinthecode,youcancontrolwhatyourprogramdoeswhenitfindsanopeningtag,suchas"preparetograbthetextthatappearswithintheopeningandclosingtitletag."

Example26-1usesaparticularalgorithmtosearchawebpageforanupdatedstockquote,andthisiswhatthetwomethods(handleStartTag()andhandleText())accomplishintheMyParserCallbackclass:

1. Itlooksforthetext"LastTrade"inthehandleText()callbackmethod;ifit'sfound,thelastTradeFlagbooleanvariableissettotrue.Thisislike"droppingabreadcrumb"astheprogramtravelsthroughthevastHTMLofthewebpage.

IfhandleStartTag()findsabtagrightafter"LastTrade"isfound(thelastTradeFlagflagistrue),itgrabsthenestedcontentofthatbtag,becausethiscontentrepresentsthestockquote.

Thebignegativeofwebharvesting,whichwebservicesispartlydesignedtosolve,isthatwhenthewebpageyouareparsingischanged,yourprogramthrowsexceptionsandnolongerpullsouttheinformation,becauseitsalgorithmsarebasedontheoldpagestructure.

Example26-2showsasnippetofcodethatusestheParserDelegator

andMyParserCallbackobjects,justtogiveyouanideaofhowtheyfittogetherbeforewemoveontotheservletandJSP.

Example26-2.Acodesnippetshowstheparserandcallbackclassesatwork

//Instancevariables



//InitializeaBufferedReaderandaURLinsideofamethodforconnecting

//toandreadingawebpage

BufferedReaderwebPageStream=null;

URLstockSite=newURL(BASE_URL+symbol);

//Connectinsideofamethod

webPageStream=newBufferedReader(

newInputStreamReader(stockSite.openStream()));

//Createtheparserandcallback



//Callparse(),passingintheBufferedReaderandcallbackobjects


Theparse()methodofParserDelegatoriswhattriggersthecallingofthecallback'smethods,withthecallbackpassedinasanargumenttoparse().

Nowlet'sseehowtheseclassesworkinaservlet,JavaBean,andJSP.

SeeAlso

AJavadoclinkforParserDelegator:http://java.sun.com/j2se/1.4.1/docs/api/javax/swing/text/html/parser/ParserDelegator.htmlChapter27onusingwebservicesAPIstograbinformationfromwebservers.

http://java.sun.com/j2se/1.4.1/docs/api/javax/swing/text/html/parser/ParserDelegator.html

Recipe26.2UsingaServlettoHarvestWebData

Problem

Youwanttouseaservlettoharvestwebinformation.

Solution

UsetheHTMLparsingAPIclassesoftheJava2SoftwareDevelopmentKit(SDK).

Discussion

Thelastrecipeintroducedtherelevantsubpackagesofthejavax.swing.textpackage;thisiswhereIshowhowtousetheminaservlet.Example26-3importsthenecessaryclassestoparseanHTMLpage.Theservlet'sdoGet()methoddisplaysaforminwhichtheuserentersastocksymbol(suchas"INTC,"caseinsensitive).

ThenthedoPost()methodattemptstogetalivestockquoteforthatsymbolbyparsingawebpagefromfinance.yahoo.com.

Example26-3.Harvestingwebdatafromaservlet






importjava.net.URL;







publicclassHtmlParseServletextendsHttpServlet{

privatestaticfinalStringBASE_URL="http://finance.yahoo.com"+

"/q?d=t&s=";












//useaPrintWritertosendtext






//makesuremethod="post"sothattheservletservicemethod


out.println(

"<formmethod=\"post\"action=\""+request.getContextPath()+

"/stockservlet\">");





out.println(




}//doGet



throwsjava.io.IOException{


floatprice;//Thestock'slatestprice



false:true;







if(!isValid){

out.println(

"<h2>Sorry,thestocksymbolparameterwaseitherempty"+

"ornull</h2>");

}else{


price=getLatestPrice(symbol);

out.println((price==0?"Thesymbolisprobablyinvalid.":

""+price));

}


}//doPost

privatefloatgetLatestPrice(Stringsymbol)throwsIOException,

MalformedURLException{

BufferedReaderwebPageStream=null;

URLstockSite=newURL(BASE_URL+symbol);


openStream()));


callback=newMyParserCallback();

//thecodeisdesignedtomakecallingparse()thread-safe



}//synchronized

returnstockVal;

}//getLatestPrice






//Resettheenclosingclass'instancevariable

if(stockVal!=0)

stockVal=0f;

}




boldFlag=true;

}

}//handleStartTag







lastTradeFlag=true;

}elseif(boldFlag){

try{



try{

//teaseoutanycommasinthenumberusing

//NumberFormat


getInstance();







}//try

}//try


boldFlag=false;

}//if

}//handleText

}//MyParserCallback

}//HttpServlet

TheMyParserCallbackinnerclassdefinestheparsingalgorithmfortheservlet,whichisexplainedinRecipe26.1.ThegetLatestPrice()methodusesthiscallbackclassandanHTMLparsertoreturnastockquoteasafloattype.

TheParserDelegatorobjectissynchronizedasitcallsparse(),sothatonlyonethreadisparsingthewebpageandsettingthevalueofstockVal(aninstancevariablerepresentingthestockvalue)atonetime.

Thisservletisalittletoocomplicatedforoneclass,asitusesservletAPIandHTMLparsingAPIclasses.AbetterdesignwouldseparatetheseresponsibilitiesintodifferentJavaclasses.TheupcomingrecipescreateaJavaBeanwhoseresponsibilityistoparseHTMLforalivestockquote.

Figure26-1showstheoutputoftheservlet'sdoGet()method.

Figure26-1.Theuserentersastocksymbolandsubmitstheform

Figure26-2showstheservlet'sdoPost()methodoutputinaNetscapebrowser.

Figure26-2.Theservletreturnsthelateststockpriceforthesymbol

SeeAlso

Recipe26.3oncreatingaJavaBeanasaweb-pageparser;Recipe26.4andRecipe26.5onusingthebeanwithaservletandaJSP,respectively.

Recipe26.3CreatingaJavaBeanasaWebPageParser

Problem

YouwanttocreateaJavaBeanthatwebcomponentscanusetoparseanHTMLpage.

Solution

UsetheJavaAPIclassesforparsingHTMLfromthejavax.swing.textsubpackages.StoretheJavaBeaninWEB-INF/classesorinaJARplacedinsideWEB-INF/lib.

Discussion

Example26-4isaJavaBeanwhosesolepurposeistoparseawebpageforlivestockquotes.AservletorJSPcanusethisJavaBeanforitsspecialpurpose,andthusavoidtheclutteroftakingontheparsingresponsibilityitself.Allofthecode,includingtheinnerclassrepresentingaParserCallback,isreproducedfromthischapter'searlierrecipes.What'snewisthesetterormutatormethodforthebean'sstocksymbol:setSymbol(Stringsymbol).

Example26-4.AJavaBeanforusewithservletsandJSPs





importjava.net.URL;





publicclassStockPriceBean{

privatestaticfinalStringurlBase="http://finance.yahoo.com/"+

"q?d=t&s=";

privateBufferedReaderwebPageStream=null;

privateURLstockSite=null;




privateStringsymbol="";


publicStockPriceBean(){}

//Setterormutatormethodforthestocksymbol

publicvoidsetSymbol(Stringsymbol){

this.symbol=symbol;

}






//Resettheenclosingclass'instancevariable

if(stockVal!=0)

stockVal=0f;

}




boldFlag=true;

}

}//handleStartTag







lastTradeFlag=true;

}elseif(boldFlag){

try{



try{

//teaseoutanycommasinthenumberusing

//NumberFormat


getInstance();







}//try

}//try


boldFlag=false;

}//if

}//handleText

}//MyParserCallback

publicfloatgetLatestPrice()throwsIOException,MalformedURLException{

stockSite=newURL(urlBase+symbol);


openStream()));





}//synchronized

//resetsymbol

symbol="";

returnstockVal;

}//getLatestPrice

}//StockPriceBean

ThisbeanresetsthesymbolinstancevariabletotheemptyStringwhenit'sfinishedfetchingthestockquote.TheMyParserCallbackclassresetsthestockValinstancevariableto0,sothatthepreviouslyattainedstockpricedoesnotlingerbetweendifferentthread'scallstogetLatestPrice().

Nowlet'sseehowaservletandJSPusethebean.

SeeAlso

Recipe26.4onusingthisJavaBeaninaservlet;Recipe26.5onusingthebeaninaJSP.

Recipe26.4UsingtheWebPageParsingJavaBeaninaServlet

Problem

YouwanttousetheJavaBeanforparsingHTMLinaservlet.

Solution

Createaninstanceofthebeanintheappropriateservicemethod(e.g.,doGet()ordoPost())andcallitsmethods.

Discussion

TheJavaBeanhastobeavailabletotheservlet,andthereforestoredinWEB-INF/classes,includingsubdirectoriesthatmatchthebean'spackagename.TheJavaBeancanalsobestoredinaJARinsideofWEB-INF/lib.

SincetheJavaBeaninExample26-5sharestheservlet'spackage(com.jspservletcookbook),theservletclassdoesnothavetoimportthebeanclass.

IftheJavaBeanresidesinadifferentpackageinthewebapplication,thentheservlethastoincludeanimportstatementsuchasthefollowingexample:

importcom.parkerriver.beans.BeanParserServlet;

ThedoGet()methodprovidesanHTMLformforenteringastocksymbol(suchas"intc").ThedoPost()methodthencreatesan

instanceoftheStockPriceBean,callsthebean'ssetSymbol()method,andfinallydisplaysthestockpricebycallingthebean'sgetLatestPrice()method.

Example26-5.AservletusesaspeciallydesignedJavaBeantogetalivestockquote






publicclassBeanParserServletextendsHttpServlet{














out.println(


"/stockbean\">");





out.println("<inputtype=\"submit\"value=\"SubmitInfo\"></td></tr>");



}//doGet





floatprice=0f;



false:true;








if(!isValid){

out.println(

"<h2>Sorry,thestocksymbolparameterwaseitherempty"+

"ornull</h2>");

}else{


StockPriceBeanspbean=newStockPriceBean();

spbean.setSymbol(symbol);

price=spbean.getLatestPrice();

out.println((price==0?"Thesymbolisprobablyinvalid.":

""+price));

}//if


}//doPost

}//HttpServlet

Theservlet'sHTMLform(generatedbythedoGet()method)andthestockpricedisplay(generatedbydoPost())hasthesamewebbrowserdisplayastheoneshowninFiguresFigure26-1andFigure26-2.

SeeAlso

Recipe26.3oncreatingaJavaBeanasawebpageparser;Recipe26.5onusingawebpageparsingJavaBeaninaJSP.

Recipe26.5UsingtheWebPageParsingJavaBeaninaJSP

Problem

YouwanttouseaJavaBeanandJSPtoharvestinformationfromawebpage.

Solution

Usethejsp:useBeanstandardactiontocreateaninstanceofthebean.

Discussion

ThesameJavaBeanthatpriorrecipescreatedandstoredinthewebapplicationinWEB-INF/classescanbeusedbyaJSP.TheJSPinExample26-6usesjsp:useBeantocreateaninstanceofthebeannamedpriceFetcher.Iftherequestdoesnotcontainasymbolparameter,theJSPdisplaystheHTMLformshowninFigure26-1.

TheJSPusestheJSTLcoretagstogeneratethisconditionalbehavior.Thesetagsincludec:choose,c:when,andc:otherwise.

IftherequesttotheJSPcontainsasymbolparameter,theJSPsetsthepriceFetcher'ssymbolpropertytothevalueofthisrequestparameter.Thiscodeistheequivalentofcallingthebean'ssetSymbol()method;itpassesthenameofthestocksymboltothebeansothatitcangrabalivestockquotefromthewebpage.

Example26-6.AJSPusesjsp:useBeantoemployaweb-harvestingJavaBean


<jsp:useBeanid="priceFetcher"class=

"com.jspservletcookbook.StockPriceBean"/>

<html>

<head><title>PriceFetch</title></head>

<body>

<c:choose>

<c:whentest="${emptyparam.symbol}">

<h2>Pleasesubmitavalidstocksymbol</h2>


'<c:outvalue="${pageContext.request.contextPath}"/>/priceFetch.jsp'>

<tableborder="0"><tr><tdvalign="top">Stocksymbol:</td>

<tdvalign="top">

<inputtype="text"name="symbol"size="10"></td></tr>



</table></form>

</c:when>

<c:otherwise>

<h2>Hereisthelatestvalueof<c:outvalue="${param.symbol}"/></h2>

<jsp:setPropertyname="priceFetcher"property="symbol"value=

"<%=request.getParameter(\"symbol\")%>"/>

<jsp:getPropertyname="priceFetcher"property="latestPrice"/>

</c:otherwise>

</c:choose>

</body>

</html>

NowthattheJSPhasseededthebeanwiththestocksymbol,thiscodewillcallthebean'sgetLatestPrice()method:

<jsp:getPropertyname="priceFetcher"property="latestPrice"/>

TheJSP'soutputreplacesthejsp:getPropertystandardactionwiththestockprice,aslongasthestocksymbolsenttothebeanwithjsp:setPropertywasvalid.

TheoutputoftheJSPinExample26-6looksjustliketheoutputshowninFiguresFigure26-1andFigure26-2.

SeeAlso

Chapter23ontheJSTL;Recipe26.4onusingawebpageparsingJavaBeaninaservlet.

Chapter27.UsingtheGoogleandAmazonWebAPIs

Introduction

Recipe27.1.GettingSetUpwithGoogle'sWebAPI

Recipe27.2.CreatingaJavaBeantoConnectwithGoogle

Recipe27.3.UsingaServlettoConnectwithGoogle

Recipe27.4.UsingaJSPtoConnectwithGoogle

Recipe27.5.GettingSetUpwithAmazon'sWebServicesAPI

Recipe27.6.CreatingaJavaBeantoConnectwithAmazon

Recipe27.7.UsingaServlettoConnectwithAmazon

Recipe27.8.UsingaJSPtoConnectwithAmazon

Introduction

GoogleandAmazon.comarebothearlyadoptersintheemergingfieldofwebservices.

Googleisagiantwebsearchengineanddirectory.Amazon.comisae-commercewebsitethatbeganasanonlinebookstoreandhassincebranchedoutintonumerousproductssuchassoftwareandelectronics.BothsitesseparatelyoffersoftwaredeveloperswebservicesApplicationProgrammingInterfaces(APIs)thatgiveyoutheabilitytomanageGooglesearchesusingJavaobjectsandaccessAmazon'scomprehensiveproductcatalogswithyourJavacode.

ForusJavadevelopers,webservicesmeansmakingrequestsandreceivingresponsesusingaspecialXMLformat.Inotherwords,youmakearequestusingXMLelementsandattributesintextform,andreceivearesponseinthesameformat.WebservicestypicallyuseanXML-basedprotocolnamedSimpleObjectAccessProtocol(SOAP)totransferinformation.

Inanutshell,SOAPrepresentstheabstractionofanenvelope,thatinturncontainsoptionalheadersandthemessagebody.Themessage,composedofitsouterenvelope,aswellastheheadersandbody,ismadeupofXMLelementsthatareassociatedwithspecifiednamespaces.ThetechnologiesthischapterdescribesuseHTTPtocarrytheseXML-basedSOAPmessages.

IneverreallyunderstoodSOAPmessagesuntilIlookedatsomesamples.Example27-1ispartofaSOAPresponsetoanAmazonWebServiceskeyword-searchrequestusingthequery"LanceArmstrong."

TheresponseisanXMLfilecomposedofaProductInforootelement,whichcontainsoneormoreDetailselements.EachoneoftheseDetailsrepresentsabookfromAmazon'scatalog(IomittedallbutoneoftheDetailselements,justtomakethesampleeasiertoview).Onlyoneofthereturnedbooksisshown.

Example27-1.ASOAPresponsefromAmazonWebServicesbasedonasearchfortheterms"LanceArmstrong"

<?xmlversion="1.0"encoding="UTF-8"?>

<!DOCTYPEProductInfoPUBLIC"-//Amazon.com//DTDAmazonProductInfo//EN"

"http://xml.amazon.com/schemas/dev-lite.dtd">

<ProductInfoxmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation=

"http://xml.amazon.com/schemas/dev-lite.xsd">

<Detailsurl=

"http://www.amazon.com/exec/obidos/ASIN/0399146113/webservices-20?

dev-t=DCJEAVXSDVPUD%26camp=2025%26link_code=xm2">

<Asin>0399146113</Asin>

<ProductName>It'sNotAbouttheBike:MyJourneyBacktoLife

</ProductName>

<Catalog>Book</Catalog>

<Authors>

<Author>LanceArmstrong</Author>

<Author>SallyJenkins</Author>

</Authors>

<ReleaseDate>June,2000</ReleaseDate>

<Manufacturer>PutnamPubGroup</Manufacturer>

<ImageUrlSmall>

http://images.amazon.com/images/P/0399146113.01.THUMBZZZ.jpg

</ImageUrlSmall>

<ImageUrlMedium>

http://images.amazon.com/images/P/0399146113.01.MZZZZZZZ.jpg

</ImageUrlMedium>

<ImageUrlLarge>

http://images.amazon.com/images/P/0399146113.01.LZZZZZZZ.jpg

</ImageUrlLarge>

<ListPrice>$24.95</ListPrice>

<OurPrice>$17.47</OurPrice>

<UsedPrice>$9.99</UsedPrice>

</Details>

</ProductInfo>

ThreeprincipalreasonsforadoptingSOAP-basedwebservicesare:

1. SOAPisstandards-based,soyoucanuseanytechnologythathasdevelopedaSOAPAPIortoolkit,includingJava,.NET,Perl,andPython.Object-orientedtechnologies(likeJava)allowyoutobuildandreadSOAPmessagesusingobjects,insteadofhavingtodealwithrawXML,whichcanmakewebservicesgratifyingtoworkwith.

Webservicesrepresentinteroperabilitybetweentechnologies.AserverthatisusingJ2EEtechnologiessuchasservletsandJSPscaneasilyexchangemessageswithaserverrunning.NET,becausetheyspeakthesamelanguage:SOAPandXML.

SOAPmessagescaneasilybeexchangedbetweenwebserverswithoutrunningafoulofthelimitationsoffirewalls,becausethemessagesaremadeofupXMLtextandcarriedbyHTTP(inaverygeneralway,justlikeanHTMLpage).DevelopersareembracingSOAPasaneasierformofdistributedcomputing:itallowsanobjectresidinginthememoryofoneservertocallmethodsononeormoreobjectsresidingondistantcomputersbyexchangingSOAPmessages.

ArecipeintroductioncannotdojusticetoacomplicatedtopicsuchasSOAP,butthereareplentyofbooksandfreetutorialsonthistopic(seethischapter's"SeeAlso"sectionsforsomesuggestions).

Mostlyinabetastageofdevelopment,theAmazonandGooglewebservicesAPIsallowaJavaprogramtocreateveryusefulandcomplexsystemsthatinteractwithAmazonandGoogle.TheAmazonandGooglewebservicesprogramsaredesignedtofamiliarizedeveloperswiththesenewwaysofhandlingrequestsandresponsestothetwopopularwebdestinations.

Theprogramsgenerallyinvolvecreatingadeveloper'saccountandrecievingakey,ortoken,thatwillaccompanyeachoneofyourrequeststothesesites.ThischapterdescribeshowtogetsetupwithusingAmazonandGooglewebservices,thenshowsyouhowtointegratetheseAPIswithaservletandJSP.

Recipe27.1GettingSetUpwithGoogle'sWebAPI

Problem

YouwanttouseGoogle'sWebAPItomakeJava-enabledsearchesofGoogle'svastwebindex.

Solution

DownloadtheGoogleWebAPIsSDK.CreateaGoogleaccountandgetalicensekeythatallowstheuseofGoogle'sWebAPI.

Discussion

TheGoogleWebAPIsSDKincludesanarchivenamedgoogle.jar.ThisfilecontainstheclassesthatyourprogramwillusetoconnectwithGoogleduringsearches.HerearethespecificstepsyoutaketopreparethewebapplicationforconnectingwithGoogle:

1. DownloadthezippedSDKfromhttp://www.google.com/apis/download.html.Unpackthisfileintoadirectory(namedgoogleapiinBetaVersion3.0oftheGoogleWebAPIs).Thisdirectorycontainsgoogle.jar,alongwithalotofcodesamplesanddocumentation.

CreateaGoogleaccountandgetalicensekey,whichisencodedtextthatlookslike"5W1ABCyzPSyI3rIa5Pt3DtXMatsdzaSGB."YourJavacodeusesthiskeywhenitqueriesGoogle'sindex.Thequerywillfailifitisnotaccompaniedbyavalidkey.

http://www.google.com/apis/download.html

Placethegoogle.jarfileintheWEB-INF/libdirectoryofthewebapplication.

DevelopyourJavaclassesforconnectingwithGoogle,usingthecom.google.soap.searchpackagefromthegoogle.jarfile.

SeeAlso

ThehomefortheGoogleWebAPIs:http://www.google.com/apis/;theGooglewebAPIsSDK:http://www.google.com/apis/download.html.

http://www.google.com/apis/default.htm


Recipe27.2CreatingaJavaBeantoConnectwithGoogle

Problem

YouwanttouseGoogle'sWebAPIstomakeJava-enabledsearchestoGoogle'ssite.

Solution

CreateaJavaBeansothatyoucanusethebeaninbothaservletandJSP.

Discussion

ThefirstthingtodoisgetsetupwithaGoogleWebServicesaccount,asdescribedinRecipe27.1.NowcreateaJavaBeanthatwillmakekeywordsearchesofGoogleandreturntheresults.

Example27-2firstimportsthepackagecontainedingoogleapi.jar:com.google.soap.search.Remember,youstoredthatJARfileinWEB-INF/lib.ThismeansthatthewebapplicationcanfindtheJavaclassesinthatpackageandtheGoogleBeaninExample27-2canuseit.

Example27-2.AJavaBeanthatsearchesGoogle'swebdatabase


importcom.google.soap.search.*;

publicclassGoogleBean{

privateGoogleSearchsearch;

privateGoogleSearchResultgoogleRes;

privatefinalstaticStringGOOGLE_KEY=

"5W1BWPyzPSyI3rIa5Pt3DtXMatsniSGB";

privateStringlineSep="\n";

//Settablebeanproperties

privateStringquery;

privatebooleanfilter;

privateintmaxResults;

privateintstartRes;

privatebooleansafeSearch;

privateStringrestrict;

privateStringlangRestrict;

publicGoogleBean(){//No-argumentsconstructorforthebean

query="";

restrict="";

langRestrict="";

}

publicStringstructureResult(GoogleSearchResultres){

//EachGoogleSearchResultElement

GoogleSearchResultElement[]elements=res.getResultElements();

Stringurl="";

Stringresults="Estimatedtotalresultscount:"+

res.getEstimatedTotalResultsCount()+lineSep+lineSep;

for(inti=0;i<elements.length;i++){

url=elements[i].getURL();

results+=("Title:"+elements[i].getTitle()+lineSep+

"URL:<ahref=\""+url+"\">"+url+"</a>"+lineSep+

"Summary:"+elements[i].getSummary()+lineSep+

"Snippet:"+elements[i].getSnippet()+lineSep+lineSep);

}

returnresults;

}

publicStringgetSearchResults()throwsGoogleSearchFault{

search=newGoogleSearch();

search.setKey(GOOGLE_KEY);

search.setFilter(filter);

if(restrict.length()>0)

search.setRestrict(restrict);

search.setQueryString(query);

googleRes=search.doSearch();

returnstructureResult(googleRes);

}

publicvoidsetLineSep(StringlineSep){

this.lineSep=lineSep;

}

publicStringgetLineSep(){

returnlineSep;

}

publicvoidsetQuery(Stringquery){

this.query=query;

}

publicStringgetQuery(){

returnquery;

}

publicvoidsetRestrict(Stringquery){

this.restrict=restrict;

}

publicStringgetRestrict(){

returnrestrict;

}

publicvoidsetLangRestrict(StringlangRestrict){

this.langRestrict=langRestrict;

}

publicStringgetLangRestrict(){

returnlangRestrict;

}

publicvoidsetFilter(booleanfilter){

this.filter=filter;

}

publicbooleangetFilter(){

returnfilter;

}

publicvoidsetSafeSearch(booleansafeSearch){

this.safeSearch=safeSearch;

}

publicbooleangetSafeSearch(){

returnsafeSearch;

}

publicvoidsetMaxResults(intmaxResults){

this.maxResults=maxResults;

}

publicintgetMaxResults(){

returnmaxResults;

}

publicvoidsetStartRes(intstartRes){

this.startRes=startRes;

}

publicintgetStartRes(){

returnstartRes;

}

}//GoogleBean

TheinterestingactioninExample27-2occursinthemethodsgetSearchResults()andstructureResults().

IngetSearchResults(),thecodecreatesaGoogleSearchobject,whichisthencustomizedwithGooglesearchoptionsbeforetheGoogleSearchdoSearch()methodiscalled.TheGoogleSearchobjectusessettermethodstodesignaspecificgoogle.comsearch.Forexample,thesetQueryString()methodprovidestheuser'ssearchterms.TheJavaobjectsthatareusingthebeanprovidesthesearchtermsbycallingthebean'ssetQuery()method.

YoucansetthevariousoptionsforGooglesearchesbycallingtheGoogleSearchsettermethods.Forexample,callingsetFilter(true)filtersoutalltheresultsthatderivefromthesamewebhost.AndyoucanrestrictthesearchtospecificGooglesubsitesbycallingsetRestrict("mac").Seehttp://www.google.com/apis/reference.html.

EverySOAP-relatedsearchofGooglemustcalltheGoogleSearchsetKey()methodwiththeproperlicensekey,orthesearchisrejected.

ThestructureResults()methodformatsthesearchresults.GooglesearchresultsareencapsulatedbyaGoogleSearchResultobject.ThisobjectcontainsanarrayofGoogleSearchResultElementobjects,whichrepresenteachURLthattheGooglesearchhasreturned.

http://www.google.com/apis/reference.html

TheGoogleSearchResultgetResultElements()methodreturnstheGoogleSearchResultElementarray.

Thecodetheniteratesthroughthearray.Eachreturnedelement(theGoogleSearchResultElementobject)hasgetteroraccessormethodsthatprovidesinformationabouttheweb-pagesearchresult:

getURL()returnstheURLofthefounditem

getTitle()returnsthetitleofthefoundHTMLpage

getSnippet()returnsasnippet(asmall,possiblyambiguous,pieceoftextfromthewebpage)

getSummary()returnsatextsummaryofthefoundwebpage

ThebeanusesthesemethodstodisplaytheURL,title,snippet,andsummaryofeachwebpagethesearchreturns.Figure27-2showshowtheseresultsaredisplayed.

SeeAlso

ThehomeforGoogleWebService:http://www.google.com/apis/;theGoogleWebAPIsSDK:http://www.google.com/apis/download.html;Recipe27.1onsettingupyourprogrammingenvironmentforusewiththeGoogleWebAPIs.



Recipe27.3UsingaServlettoConnectwithGoogle

Problem

YouwanttoconnecttoGooglewithaservletandinitiateasearch.

Solution

UsetheJavaBeandescribedinRecipe27.2asaGooglesearchutilityclass.

Discussion

TheservletinExample27-3usestheGoogleBeanfromRecipe27.2toinitiategoogle.comsearchesanddisplaytheresults.

TheservletdisplaysanHTMLforminitsdoGet()method.TheclientusesthisformtoinputGooglesearchparameters,andthenPOSTtheformparametersbacktothesameservlet.Finally,theservlet'sdoPost()methodcreatesaninstanceoftheGoogleBeantoinitiatethesearch.Inthiscase,usethedeploymentdescriptortomapanyrequestsoftheform"/googleservlet"toExample27-3.

Example27-3.AservletusesaspecialJavaBeantosearchGoogleanddisplayanyresults






publicclassGoogleServletextendsHttpServlet{







out.println("<title>InitiateaGoogleSearch</title></head><body>");

out.println("<h2>Pleaseenteryoursearchterms</h2>");

//Makesuremethod="POST"sothattheservletservicemethod


out.println(


"/googleservlet\">");


out.println("Searchterms:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"query\"size=\"15\">");


out.println(

"RestricttoGooglesub-site...</td><tdvalign=\"top\">");

out.println(

"<selectname=\"restrict\"><option>unclesam</option>"+

"<option>linux</option>option>mac</option><option>bsd</option>"+

"</select>");


out.println(




}//doGet




Stringquery=request.getParameter("query");

Stringrestrict=request.getParameter("restrict");

booleanisValid=(query==null||query.length()<1)?

false:true;





out.println("<title>Googleresults</title></head><body>");

if(!isValid){

out.println(

"<h2>Sorry,thequeryparameterwaseitheremptyornull</h2>");

}else{

out.println("<h2>Hereareyoursearchresults</h2>");

GoogleBeangb=newGoogleBean();

gb.setFilter(true);

//Configureforwebdisplay

gb.setLineSep("<br/>");

if(restrict!=null&&restrict.length()>0)

gb.setRestrict(restrict);

gb.setQuery(query);

try{

out.println(gb.getSearchResults());

}catch(Exceptione){


}

}//if


}//doPost

}//GoogleServlet

UsingtheGoogleBeanclassindoPost()isstraightforward.Thecodesetsafewsearchoptions(suchassetFilter(true)),thencallsthebean'sgetSearchResults()method.ThismethodreturnsaStringofformattedsearchresults,whichtheservlet'sPrintWritersendstothebrowserfordisplay.

Figure27-1showsthesimpleHTMLformdisplayedintheservlet'sdoGet()method.

Figure27-1.EnterkeywordstosearchGooglewithaservlet

The"RestricttoGooglesub-site..."partallowstheusertochooseoneofnone,unclesam,linux,mac,orbsd.Theuserentersthesearchterm

"LanceArmstrong"intheHTMLform'stextfield,thenpressesthe"SubmitInfo"button.Figure27-2showsthesearchresultsdispalyedbytheservlet'sdoPost()method.

TheGoogleWebAPIsdisplayamaximumof10resultspersearch.

Figure27-2.AservletusingtheGoogleWebAPIsdisplayssomesearchresults

SeeAlso

ThehomeforGoogleWebService:http://www.google.com/apis/;theGoogleWebAPIsSDK:http://www.google.com/apis/download.html;Recipe3.1onmappingaservlettoanameinweb.xml;Recipe27.1onsettingupyourprogrammingenvironmentforusewiththeGoogleWebAPIs;Recipe27.4onusingaJSPtoconnectwithGooglewebservices.



Recipe27.4UsingaJSPtoConnectwithGoogle

Problem

YouwanttosearchGoogleusingtheGoogleWebAPIsandaJSP.

Solution

Usethejsp:useBeanstandardactiontogetaccesstotheGoogleBeanfromExample27-2,thenusethisbeaninstancetoconnectwithGoogle'swebtools.

Discussion

TheJSPinExample27-4usestheJSTLcoretagstodetermineiftheuserhassentasearchqueryalongwiththeirrequest.Ifthequeryrequestparameterisempty,thentheJSPdisplaysaform(seeFigure27-1).SeeChapter23fordetailsontheJSTLcoretags.

Iftherequestparameterisfilledbyasearchquery,theJSPusestheGoogleBeantosearchgoogle.comanddisplaytheresults.TheJSPusesthejsp:useBeanstandardactiontocreateaninstanceofthebean,whichisstoredintheWEB-INF/libdirectory.

Example27-4.AJSPusesaJavaBeantosearchgoogle.com


<html>

<head><title>SearchGooglefromaJSP</title></head>

<body>

<c:choose>

<c:whentest="${emptyparam.query}">

<h2>Pleaseenteryoursearchterms...</h2>

<%--DisplaytheHTMLform...--%>

<formmethod="POST"action='<c:outvalue=

"${pageContext.request.contextPath}"/>/google.jsp'>

<tableborder="0">


Searchterms:</td><tdvalign="top">

<inputtype="text"name="query"size="15">

</td></tr>


RestricttoGooglesub-site...</td><tdvalign="top">

<selectname="restrict">

<optionselected>none</option><option>unclesam</option>

<option>linux</option>

<option>mac</option><option>bsd</option></select>

</td></tr>



</table></form>

<%--EndoftheHTMLform...--%>

</c:when>

<c:otherwise>

<%--CreateaninstanceoftheGoogleBean--%>

<jsp:useBeanid="gBean"class="com.jspservletcookbook.GoogleBean"/>

<h2>Hereareyoursearchresults</h2>

<%--Setthequery,restrict,andlineSeppropertiesoftheGoogleBean--%>

<jsp:setPropertyname="gBean"property="query"param="query"/>

<jsp:setPropertyname="gBean"property="restrict"param="restrict"/>

<jsp:setPropertyname="gBean"property="lineSep"value="<br/><br/>"/>

<%--Nowdisplayanyresultsofthesearch--%>

<jsp:getPropertyname="gBean"property="searchResults"/>

</c:otherwise>

</c:choose>

</body>

</html>

TheJSPusesthejsp:setPropertystandardactiontothebeaninstance'squery,restrict,andlineSepproperties.Thequeryrepresentsthesearchterms;restrictcanhavevaluesofmac,linux,bsd,orunclesam,representingvariousGooglesub-sites,andthelineSeppropertydeterminestheline-separationcharacterstousewhenformattingtheresults(<br/>inthisexample).

Finally,thecodeusesjsp:getPropertytoeffectivelycalltheGoogleBean'sgetSearchResults()method,whichsendsaSOAPmessagetoGoogleandformatstheresponse.

SeeAlso

ThehomeforGoogleWebService:http://www.google.com/apis/;theGooglewebAPIsSDK:http://www.google.com/apis/download.html;Recipe27.1onsettingupyourprogrammingenvironmentforusewiththeGoogleWebAPIs;Recipe27.3onusingaservlettoconnectwithGooglewebservices.



Recipe27.5GettingSetUpwithAmazon'sWebServicesAPI

Problem

YouwanttoconnecttoAmazonWebServices(AWS)withaservletorJSP.

Solution

DownloadtheAmazonWebServicesSDK,acquireanAmazondeveloper'stoken,andcreateaJava-SOAPpackageforinteractingwithAWS.

Discussion

TheprocessforsettingupAWSgoeslikethis:

1. DownloadtheAWSSDKathttp://www.amazon.com/gp/aws/download_sdk.html/002-2688331-0628046.Thiskit.zipfileincludesseveralcodesamplesandwebservicesAPIdocumentationinHTMLformat.

Acquireadeveloper'stokenfrom:http://associates.amazon.com/exec/panama/associates/join/developer/application.html/002-2688331-0628046.SimilartothelicensekeyyouusewithGoogle'sWebAPIs,thefree-of-chargetokencomprisesaseriesofencodedcharactersthatmustaccompanyeachinteractionbetweenyourJavacodeandAWS.

http://www.amazon.com/gp/aws/download_sdk.html/002-2688331-0628046

http://associates.amazon.com/exec/panama/associates/join/developer/application.html/002-2688331-0628046

DeveloptheJavaAPIformakingSOAPrequeststoAWS.TheendresultisaJARfilecontainingtheclassesthatyourservletsorJSPsusetomakeSOAPrequests.TherestofthisrecipedescribeshowtogeneratethisJARfile,becauseitisamultistepprocess.

InteractingwithAWSusingSOAPmessagesisoneoptionthatAmazonmakesavailabletodevelopers.AnotheroneinvolvesencodingthewebservicesrequestsinURLs,andtherebymakingAWSrequestsviaHTTP(called"XMLoverHTTP").Recipe27-7showsanexampleofthisURLsearch(theyareusefulfordebuggingyourSOAPapplications).IfyoustoreanXSLTfileontheWeb,AWSusesthisfiletoformattheresponsetoXML-over-HTTPrequests.SeetheSDKdocumentationformoredetails.

SOAPwithApacheAxis

ThecreationofaJava-SOAPAPIforusingAWSbeginswithdownloadinganopensourceSOAPtoolkitnamedApacheAxis(http://ws.apache.org/axis/).HerearethestepsinvolvedincreatingtheAPI:

1. DownloadAxisandextracttheAxisZIPfiletothedirectoryofyourchoice(thiscreatesadirectorynamedaxis-1_1).

Insidetheaxis-1_1/libdirectoryareseveralJARfiles.PlacetheseJARfilesonyourclasspathandthenrunaprogramnamedorg.apache.axis.wsdl.WSDL2JavatogenerateJavasourcefiles.TheseJavasourcefilescomprisetheJavaAPIyouwillusewithAWSwhenyoucompilethefiles.

DownloadtheWebServicesDescriptionLanguage(WSDL)fileassociatedwiththeAmazonWebServices.Atthiswriting,thefilecanbefoundat:http://soap.amazon.com/schemas3/AmazonWebServices.wsdl.

http://ws.apache.org/axis/default.htm

http://soap.amazon.com/schemas3/AmazonWebServices.wsdl

Thefollowingcommandlinegeneratesthecom.amazon.soap.axispackageforyourJavaAPI.ThecommandlinesinthisrecipeworkonbothWindows-andUnix-basedmachines.ThecommandlineisdesignedtorefertotheAmazonWebServices.wsdlfileinthecurrentdirectory.TheWSDL2JavaprogramgeneratesJavaclassesbasedontheXMLelementsdescribedbytheWSDLXMLfile(XML-to-Javaconversion).ThisallowsyoutoworkwithAWSusingonlyJavaobjects,whichisveryniceit'swhyyouareenduringtheinitialpainofcreatingtheseJavaclasses!Breakupthiscommandlineintoseparatelinestomakeitmorereadable,butwhenyouactuallyrunit,thecommandsmustallbecombinedononeline:

java-cp.;lib/axis.jar;lib/commons-discovery.jar;lib/commons-

logging.jar;lib/jaxrpc.jar;lib/saaj.jar;lib/wsdl4j.jar

org.apache.axis.wsdl.WSDL2JavaAmazonWebServices.wsdl--verbose

--packagecom.amazon.soap.axis

ThiscommandlinegeneratesJavasourcefilesinadirectorytreethatmatchesthespecifiedpackagename(com.amazon.soap.axis).Nowyouhavetocompiletheseclasseswiththejavactool,asinthefollowingcommandline(thecurrentdirectorycontainsthecomdirectory).Onceagain,webreakupthissingle-linecommandintoseparatelinesjustforthesakeofreadability(youhavetorunthecommandlineunbrokenbyanynewlinecharacters):

javac-classpath.;lib/axis.jar;lib/commons-discovery.jar;lib/commons-

logging.jar;lib/jaxrpc.jar;lib/saaj.jar;lib/wsdl4j.jar

com/amazon/soap/axis/*.java

NowJARupallthesefiles.Inthesamedirectorycontainingthetop-levelcomdirectory,thiscommandcreatesaJARfilenamedamazonapi.jar,whichisjustanameIcreatedforit:

jarcvfamazonapi.jar./com

Taketheamazonapi.jar(orwhateveryou'venamedtheJARfile)and

placeitinWEB-INF/lib.There'sonemorestepleft.

MakesurethattheJARfilesorlibrariesthatthecom.amazon.soap.axispackagedependsonarealsoavailabletothewebapplication.Theamazonapi.jarfiledependsonthesameAxislibrariesthatyouaddedtotheclasspathinthepriorjavaandjavaccommand-linesequences.YouhavetoaddtheseJARstoWEB-INF/libaswell(unlessyourapplicationservermakesalloftheselibrariesgenerallyavailabletowebapplications).

Okay,nowforthefunpart,whereyourJavacodegetstoexplorebooksandotherstuffatAmazonusingservlets.Yourservletsshouldusethecom.amazon.soap.axispackageforthispurpose.

SeeAlso

TheAWSSDKhttp://www.amazon.com/gp/aws/download_sdk.html/002-2688331-0628046;ApacheAxis:http://ws.apache.org/axis/;theAmazonWebServicesWSDLfile:http://soap.amazon.com/schemas3/AmazonWebServices.wsdl.


http://ws.apache.org/axis/default.htm

http://soap.amazon.com/schemas3/AmazonWebServices.wsdl

Recipe27.6CreatingaJavaBeantoConnectwithAmazon

Problem

YouwanttocreateaJavaBeanasatypeofAmazonsearchutilityclass.

Solution

SetupyourAmazonAPIasdescribedinRecipe27.5,thencodeaJavaBeanthatusesthecom.amazon.soap.axispackagefromthisAPI.

Discussion

TheJavaBeaninExample27-5,namedAmazonBean,importsthecom.amazon.soap.axispackage.Thispackageisstoredinamazonapi.jar,which(generatedbyRecipe27.5).StoretheJARinthewebapplication'sWEB-INF/libdirectoryandtheAmazonBeaninWEB-INF/classes(oralsoinaJARinWEB-INF/lib).

Example27-5connectswithAmazoninitsgetSearchResults()method.TheAmazonBeanformatsanddisplaysthesearchresultsinstructureResults().Thecodecommentsdescribewhat'sgoingonindetail.

Example27-5.AJavaBeanclassthatsearchesAmazon


importjava.net.URL;

importcom.amazon.soap.axis.*;

publicclassAmazonBean{

//Thedeveloper'stoken

privatefinalstaticStringAMAZON_KEY="DCJEAVDSXVPUD";

//NOTE:AWSVersion3uses"http://xml.amazon.com/xml3"

privatefinalstaticStringEND_POINT=

"http://soap.amazon.com/onca/soap";

privatefinalstaticStringAMAZON_TAG="webservices-20";

privateURLendpointUrl;

privateStringlineSep="\n";

privateStringtotalResults;

privateStringkeyword;

privateStringpage;

privateStringtype;

privateStringmode;

publicAmazonBean(){}//no-argumentsconstructorrequiredforabean

//aneasywaytotestthebeanoutsideofaservlet

publicstaticvoidmain(String[]args)throwsException{

AmazonBeanbean=newAmazonBean();

bean.setKeyword("Lance%20Armstrong");

bean.setType("heavy");

bean.setMode("books");

bean.setPage("1");

System.out.println(bean.getSearchResults());

}

//StructurethesearchresultasaString

publicStringstructureResult(ProductInfoinfo){

//AmazonsearchesreturnProductInfoobjects,which

//containsarrayofDetailsobject.ADetailsobject

//representsanindividualsearchresult

Details[]details=info.getDetails();

Stringresults="";

//eachfoundbookincludesanarrayofauthorsinitsDetails

String[]authors=null;

StringusedP=null;//UsedPriceobject

Stringrank=null;//SalesRankobject

//foreachreturnedsearchitem...

for(inti=0;i<details.length;i++){

if(mode!=null&&mode.equals("books")){

authors=details[i].getAuthors();}

//Includetheproductname

results+=

"<strong>"+(i+1)+".Productname:</strong>"+

details[i].getProductName()+lineSep;

//Iftheyarebooksincludeeachauthor'sname

if(mode!=null&&mode.equals("books")){

for(intj=0;j<authors.length;j++){

results+="Authorname"+(j+1)+":"+authors[j]+

lineSep;

}//for

}//if

usedP=details[i].getUsedPrice();//gettheusedprice

rank=details[i].getSalesRank();//getthesalesrank

results+="Salesrank:"+(rank==null?"N/A":rank)+

lineSep+"Listprice:"+details[i].getListPrice()+lineSep+

"Ourprice:"+details[i].getOurPrice()+lineSep+

"Usedprice:"+(usedP==null?"N/A":usedP)+lineSep+

lineSep;

}

returnresults;

}//structureResult

//ConnectwithAmazonWebServicesthencallstructureResult()

publicStringgetSearchResults()throwsException{

endpointUrl=newURL(END_POINT);

AmazonSearchServicewebService=newAmazonSearchServiceLocator();

//ConnecttotheAWSendpoint

AmazonSearchPortport=webService.getAmazonSearchPort(endpointUrl);

KeywordRequestrequest=getKeywordRequest();

//Returnresultsofthesearch

ProductInfoprodInfo=port.keywordSearchRequest(request);

//SettotalResultswithanyprovidedresultstotal

setTotalResults(prodInfo.getTotalResults());

//Makesurethebook-searchresultsarestructuredanddisplayed

returnstructureResult(prodInfo);

}//getSearchResults

//Setterandgettermethods...

publicvoidsetLineSep(StringlineSep){

this.lineSep=lineSep;

}

publicStringgetLineSep(){

returnlineSep;

}

//AKeywordRequestobjectinitializedwithsearchterms,themode,the

//numberofpagestobereturned,thetype('lite'or'heavy'),andthe

//developer'stoken.

publicKeywordRequestgetKeywordRequest(){

KeywordRequestrequest=newKeywordRequest();

request.setKeyword(keyword);//thesearchterms

request.setMode(mode);//themode,asin'books'

request.setPage(page);//thenumberofpagestoreturn

request.setType(type);//thetype,'lite'or'heavy'

request.setDevtag(AMAZON_KEY);//developer'stoken

request.setTag(AMAZON_TAG);//thetag,'webservices-20'

returnrequest;

}

publicvoidsetKeyword(Stringkeyword){

this.keyword=keyword;

}

publicStringgetKeyword(){

returnkeyword;

}

publicvoidsetMode(Stringmode){

this.mode=mode;

}

publicStringgetMode(){

returnmode;

}

publicvoidsetPage(Stringpage){

this.page=page;

}

publicStringgetPage(){

returnpage;

}

publicvoidsetType(Stringtype){

this.type=type;

}

publicStringgetType(){

returntype;

}

publicvoidsetTotalResults(Stringresults){

totalResults=results;

}

publicStringgetTotalResults(){

returntotalResults;

}

}//AmazonBean

Thebeanhasamain()methodthatallowsyoutotestthebeanfromthecommandline.Hereiscodefromthatmethodthatcreatesabeaninstance,searchesforabookusingthesearchterms"LanceArmstrong,"anddisplayssomeresults:

AmazonBeanbean=newAmazonBean();

bean.setKeyword("Lance%20Armstrong");

bean.setType("heavy");

bean.setMode("books");

bean.setPage("1");

System.out.println(bean.getSearchResults());

Torunthebeanfromacommandline,makesureincludeallofthenecessaryAxis-relatedlibrariesonyourclasspath(seeRecipe27.5).Thefollowingcommandlinerunsthebeantotestit.Notethatthiscommandlineincludestheamazonapi.jarfilegeneratedbyRecipe27.5:

java-cp.;jaxrpc.jar;axis.jar;amazonapi.jar;commons-logging.jar;commons-discovery.

jar;saaj.jarcom.jspservletcookbook.AmazonBean

Ifyousetthetypeoptiontoheavy(asopposedtolite),thenthesearchreturnsthebook'ssalesrankatAmazon.TheliteSOAPresponsesdonotincludeavalueforsalesrank.

SeeAlso

TheAWSSDKhttp://www.amazon.com/gp/aws/download_sdk.html/002-2688331-0628046;Recipe27.7onusingaservletandaJavaBeantoconnectwithAWS.


Recipe27.7UsingaServlettoConnectwithAmazon

Problem

YouwanttoconnectwithAWSusingaservlet.

Solution

UseaspeciallydesignedJavaBeantopeformtheAWS-relatedtasks.

Discussion

Example27-6usesthesamedesignthattheGooglerecipesused,soyoushouldfindthisservletcodeveryfamiliarifyouhaveworkedthroughthoseexamplesbefore.TheservletgeneratesanHTMLforminresponsetoaGETHTTPrequest,whichsendstheAmazonsearchtermsbacktothesameservlet.TheinterestingactiontakesplaceinthedoPost()method,wheretheservletusesanAmazonBeanclass(fromRecipe27.6)toconnectwithAWSanddisplayanysearchresults.

Example27-6.AservletusesaJavaBeantoconnectwithAWS






publicclassAmazonServletextendsHttpServlet{









out.println(

"<title>InitiateanAmazonBookSearch</title></head><body>");

out.println("<h2>PleaseenteryourAmazonsearchterms</h2>");

//DisplayanHTMLformthatsendstherequestbacktothis

//'/amazonservlet'whichwillcausethecallingofdoPost()



out.println(


"/amazonservlet\">");


out.println("Searchterms:</td><tdvalign=\"top\">");

out.println("<inputtype=\"text\"name=\"query\"size=\"15\">");

out.println("</td></tr>");

out.println("<tr><tdvalign=\"top\">");

out.println(




}//doGet




Stringquery=request.getParameter("query");

booleanisValid=(query==null||query.length()<1)?

false:true;




out.println("<title>Amazonbookresults</title></head><body>");

if(!isValid){

out.println(

"<h2>Sorry,thequeryparameterwaseitheremptyornull</h2>");

}else{

AmazonBeanamBean=newAmazonBean();

amBean.setKeyword(query);

amBean.setType("lite");

amBean.setMode("books");

amBean.setPage("1");

amBean.setLineSep("<br/>");

out.println("<h2>Hereareyoursearchresults</h2>");

try{

out.println(amBean.getSearchResults());

}catch(Exceptione){

out.println(

"Thesearchtermseitherreturnedzeroresults"+

"orwereinvalid.");

}

}


}//doPost

}//AmazonServlet

Tokeepthecodesimple,limitthekeywordsearchtobooks.AWSoffersacomprehensivemethodofsearchingitsseveralcatalogs,however,withtheAPInotlimitedtokeywordsearchesofbooks.Forexample,theproductmodesincludeDVD,electronics,music,hardware,software,andtoys.Youcanalsoinitiateseveraldifferentsearchtypes(inadditiontokeywords),suchasAmazonStandardItemNumber(ASIN)searches.

Figure27-3showsthereturnvalueoftheservlet'sdoGet()method.

Figure27-3.Aservlet'sHTMLformacceptsAmazonsearchterms

Figure27-4showspartsoftheservlet'sdisplayedresultsthatarehandledbytheservlet'sdoPost()method.

Figure27-4.TheresultsofanAmazonbooksearch

OnceyouhavedownloadedandunpackedtheAWSSDK,thesoftwaredocumentationislocatedat:AmazonWebServices/APIGuide/index.html.

TohelpdebugyourAWSsearchesandservlets,youcaninitiateanAWSsearchusingaUniformResourceLocator(URL)inyourbrowser.ThefollowingURLinitiatesakeywordseachforabookusingtheterms"BritishEmpire."

http://xml.amazon.com/onca/xml?v=1.0&t=webservices-20&

dev-t=DCJEAVXSDVPUD&KeywordSearch=British%20Empire&mode=books&

type=lite&page=1&f=xml

AnrequestforthisURLreturnsanXMLfilethatlookssimilartoExample27-1.Thesalesrankreads"N/A"becausethesearchoptiontype=litereturnsanullvalueforthisranking.Usetype=heavytogetavaluefortheAmazonsalesrank.

SeeAlso

TheAWSSDKhttp://www.amazon.com/gp/aws/download_sdk.html/002-2688331-0628046;WebServicesEssentials(O'Reilly);Recipe3.1onmappingaservlettoanameinweb.xml;Recipe27.8onusingaJSPandaJavaBeantoconnectwithAWS.


Recipe27.8UsingaJSPtoConnectwithAmazon

Problem

YouwanttoconnectwithAWSusingaJSP.

Solution

Usethejsp:useBeanstandardactiontocreateaninstanceoftheAmazonBeanfromRecipe27.6.UsethisinstancetomanagetheAWSsearchandresults.

Discussion

ThisrecipeusesthesamestrategyastheJSPinRecipe27.4:createaJavaBeaninstancethathandlestheAWSsearchanddisplaysthesearchresults.Thejsp:useBeanstandardactioncreatesaninstanceofcom.jspservletcookbook.AmazonBean,whichislocatedinWEB-INF/classes.

Thenthecodeusesjsp:setPropertytosetsomesearchoptions,beforetheJSPusesjsp:getPropertytolaunchtheseach.Example27-7usestheJSTLtagc:catchtocatchanyexceptionsthrownbytheAmazonBean'sgetSearchResults()method.ThevariableexceptisofthetypeThrowable,anditserrormessageisdisplayedbythec:outtagifthesearchqueryisinvalid.TheJSPinExample27-7displaystheHTMLformandsearchresultsshowninFiguresFigure27-3andFigure27-4.

Thisjsp:getPropertycodeistheequivalentofcallingtheAmazonBean'sgetSearchResults()method,whichreturnsaStringofformattedsearchresults.

Example27-7.AJSPlaunchesanAWSbooksearch


<html>

<head><title>SearchAmazon.comforaBook</title></head>

<body>

<c:choose>

<c:whentest="${emptyparam.keyword}">

<h2>PleaseenteryourAmazonsearchterms...</h2>

<%--DisplaytheHTMLform...--%>


'<c:outvalue="${pageContext.request.contextPath}"/>/amazon.jsp'>

<%--formandtabletags...--%>


Searchterms:</td><tdvalign="top">

<inputtype="text"name="keyword"size="15">

</td></tr><tr><tdvalign="top">



</table></form>

</body></html>

</c:when>

<c:otherwise>

<jsp:useBeanid="aBean"class="com.jspservletcookbook.AmazonBean"/>

<jsp:setPropertyname="aBean"property="keyword"param="keyword"/>

<jsp:setPropertyname="aBean"property="mode"value="books"/>

<jsp:setPropertyname="aBean"property="page"value="1"/>

<jsp:setPropertyname="aBean"property="type"value="lite"/>

<jsp:setPropertyname="aBean"property="lineSep"value="<br/>"/>

<h2>Hereareyoursearchresults</h2>

<c:catchvar="excep">

<%--Nowdisplayanyresultsofthesearch--%>

<jsp:getPropertyname="aBean"property="searchResults"/>

</c:catch>

<%--Printanyerrormessages,suchas'BadRequest'ifthesearch

termsaremeaningless--%>

<c:outvalue="${excep.message}"/>

</c:choose>

</body>

</html>

SeeAlso

TheAWSSDK:http://www.amazon.com/gp/aws/download_sdk.html/002-2688331-0628046;WebServicesEssentials(O'Reilly);Recipe27.7onusingaservletandaJavaBeantoconnectwithAWS;Chapter23on


usingtheJSTL.

Colophon

Ourlookistheresultofreadercomments,ourownexperimentation,andfeedbackfromdistributionchannels.Distinctivecoverscomplementourdistinctiveapproachtotechnicaltopics,breathingpersonalityandlifeintopotentiallydrysubjects.

TheanimalonthecoverofJavaServletandJSPCookbookisafennecfox(Fennecuszerda),alsoknownasthedesertfox.FennesfoxesliveinaridsandyregionsofnorthernAfrica,theSahara,theSinaiPeninsulaandArabiaandareoneofthetiniestmembersofthecaninefamily(eightinchesatthetallestandusuallylessthanafootlong).Theirrelativelyhugeearsandbeadyblackeyesgivethemadistinctiveappearance.Thefennecfox'sbushytailischaracteristicofmostfoxes,andathickcreamycoatcamouflagesthemintheirsandyhabitat.

Fennecfoxesliveinburrowsandarenocturnalhunters,eatingplants,smallrodents,birdsandtheireggs,lizards,andinsects.Theirhearingissoacutethattheycanheareventhesmallestofpreywalkingacrossdesertsand.Thesefoxesoftenstalktheirpreyandpounceuponit;theirverticalleapistwofeethighandtheycanjumpfourfeethorizontallyfromastandingposition,astoundingfeatsforananimalofsuchsmallstature.Theyarerapidandprolificdiggers,knownfor"disappearing"intosandwhileappearingtostandstill.Somereportsnotethatthisspeciescandiga20-foot-longtunnelinonenight!

Thefennecfoxisnotlistedasendangered,butisnowconsideredrareinsomeareaswhereitwasoncecommon.Theyhavebeenhuntedextensivelyandaresometimestakenfromthewildforthepettrade.

PhilipDanglerwastheproductioneditorandcopyeditorforJavaServletandJSPCookbook.SarahShermanandMattHutchinsonweretheproofreaders.RegAubryandMaryAnneWeeksMayoprovidedqualitycontrol.EllenTroutmanZaigwrotetheindex.

EmmaColbydesignedthecoverofthisbook,basedonaseriesdesignbyEdieFreedman.Thecoverimageisa19th-centuryengravingfromAnimateCreations,VolumeOne.EmmaColbyproducedthecoverlayout

withQuarkXPress4.1usingAdobe'sITCGaramondfont.

MelanieWangdesignedtheinteriorlayout,basedonaseriesdesignbyDavidFutato.ThisbookwasconvertedJulieHawkstoFrameMaker5.5.6withaformatconversiontoolcreatedbyErikRay,JasonMcIntosh,NeilWalls,andMikeSierrathatusesPerlandXMLtechnologies.ThetextfontisLinotypeBirka,theheadingfontisAdobeMyriadCondensed,andthecodefontisLucasFont'sTheSansMonoCondensed.TheillustrationsthatappearinthebookwereproducedbyRobertRomanoandJessamynReadusingMacromediaFreeHand9andAdobePhotoshop6.ThetipandwarningiconsweredrawnbyChristopherBing.ThiscolophonwaswrittenbyPhilipDangler.

TheonlineeditionofthisbookwascreatedbytheSafariproductiongroup(JohnChodacki,BeckiMaisch,andMadeleineNewell)usingasetofFrame-to-XMLconversionandcleanuptoolswrittenandmaintainedbyErikRay,BennSalter,JohnChodacki,andJeffLiggett.

[TeamLiB][SYMBOL][A][B][C][D][E][F][G][H][I][J][K][L][M][N][O][P][Q][R][S][T][U][V][W][X]

[TeamLiB]

${}ELexpressiondelimitersdereferencingvariableandpropertyvaluesencapsulatingfunctioncallwithin%inconversionpatterns,inTomcatserver.xmlfilecomments<%%>,inJSPscriptlets<%----%>inJSPcomments<%@syntax,JSPdirectives2nd*(asterisk)**patterninAntelements,forzeroormoredirectories2ndwildcardcharacterinURLpatterns.(dot)inattributenamesspecifyingcurrentdirectory.(dot)operator.jspfiles.jspxfiles2nd3rd.swffileextension2nd/(forwardslash)/*inURLpatternsforcontrollerservlet2ndforinvokerservletoverridenbycontrollerservletinURLpatterns2ndexcludingfromextensionmapping401UnauthorizedHTTPstatuscode403ForbiddenHTTPstatuscode404NotFoundHTTPstatuscode500InternalServerErrorHTTPstatuscode

[TeamLiB]


abort()(LoginModule)actionsinJSPscreatedasXMLfilesactivation.jararchiveActiveXcontrol,FlashfileembeddedinJSPbyInternetExploreraddCookie()(HttpServletResponse)addresses,email2ndAdministrationconsole(WebLogic)configuringJNDIresourceviewingJNDItreeAdobeSystem'sSVGViewerapplicationaliasestoservlets,creatinginweb.xmlfilealready.deployedproperty(Ant,build.xmlfile)AmazonWebServicesconnectingtowithaJSPconnectingtowithaservletcreatingJavaBeantoconnectwithsettingupSOAPresponsetokeywordsearchrequestAnttoolbuild.xmlfilecompilingandcreatingWARfileswithcompilingservletclassescompilingservletwithbuildfilecreatingJARfilesdeployingservletonWebLogicServer7.0deployingsingleservletonTomcatdeployingwebapplicationonTomcatbuild.propertiesfile(example)build.xmlfile(example)stepsinprocessdeployingwebapplicationonWebLogicServer7.0global.propertiesfileobtainingandsettingupdownloadingbinaryorsourcedistributionJAXP-compliantXMLparseronlinemanualforstartingTomcatapplicationwithstoppingTomcatapplicationwithtargets,usingbuild.xmlfile,executingexecutingseveraltargetsinspecifiedsequenceTomcatJARfiles,includinginAntclasspathWARfiles,creatingANT_HOMEenvironmentvariableantcallelementantcalltaskApacheAnt[SeeAnttool]Xerces2XMLparserApacheJakartaProjectlog4jdistribution,downloadingfromreferenceimplementation(RI)fortheJSTL

Standard1.0taglibApacheSoftwareFoundation,Log4jlibraryApacheSoftwareLicenseappBasedirectory(Tomcat,server.xmlfile)appendersaddingtorootloggerConsoleAppenderinheritanceoflayoutspecificationrollingfileappenderusingapatternwithAppleComputer'sQuickTimemoviesapplettags(HTML)appletsembeddinginJSPswithHTMLConvertertoolembeddinginJSPswithjsp:pluginexample(SunMicrosystems)applicationeventlistenersapplicationimplicitobject2ndapplicationname(webapplications)applicationscope2ndbindinganobjecttoapplicationserversBEAWebLogic,recipesinthisbookforapplicationScopeJSTLimplicitobjectArithmeticExceptionclassarrayofcookies2ndarraysGoogleSearchResultElementarrayiteratingoverwithc:forEachtagofSortedMaps,iteratingoverattachments,emailaddingtoanemailinaservlethandlingforemailreceivedinaservletattributedirective2ndattributeAdded()(HttpSessionAttributeListener)attributeRemoved()(HttpSessionAttributeListener)attributeReplaced()(HttpSessionAttributeListener)attributescookiescustomloggingtagdefinitionofJSPscopedattribute,settingtovalueofformpapameterobject,namingconventionforServletContext,settinginJSPsServletContext,settinginservletsobjectthatservletbindstoServletContextservletthatbindsobjecttoServletContextattributionforuseofcodeexamplesaudiofilesembeddinginJSPssendingasMP3filesauth-constraintelement(web.xml)rolesinauth-methodelement(web.xml)form-basedauthentication

valuesforauthentication2ndauthorizationvs.BASICauthentication,usewithwebapplicationsonTomcatcreatingusernamesandpasswordswithTomcatform-basedloggingoutuserJAASconfigurationfile,creatingJAAS,usinginaJSPJAAS,usinginaservletLoginModule,creatingwithJAASSSL,settinguponTomcatauthorization[SeealsoJAAS]authenticationvs.availabletask(Ant,build.xmlfile)

[TeamLiB]


backgroundsoundtrack,embeddinginaJSPBase64content-encodingmechanismbasedirattributeAntjartaskAntprojectelementBASICauthenticationform-basedauthentication,usingwithusingwithwebapplicationsonTomcatweb.xmlelementsforinitiationofBasicConfiguratorclassbatchfile,forprecompilingJSPswithTomcatBEAWebLogic[SeeWebLogic]binarydataPDFfile,sendingaswordprocessingfile,sendingasXMLfile,sendingasbindingobjectslisteningforbindingorunbindingofsessionobjectsSessionobject,toWebLogicJNDIimplementationtotheServletContextwithaJSPwithaservletblockingfiltersIPaddresses,blockingrequestsfromrequests,optionallyblockingbodytags(HTML)BodyPartclass2nd3rdBodyTagSupportclass2ndboundarypatternseparatingfilesinHTTPuploadrequestsbrowserwindows,creatingwithJavaScriptinaJSPinaservletbrowserscookiessupportedbydetectingMIMEtypeforembeddedMP3fileandactivatinghelperapplicationtoplaymusicdisplayingXMLfilesinreadableformatembeddingFlashfileinaJSPJavaScriptinviewerapplicationsforSVGfilesBufferedInputStreamclassbuilddirectoryinclusionofnesteddirectoriesinWARfilewithAntwartaskbuildfiles(Ant)command-linesequenceforexecutingcompilingservletwithdeployingwebapplication(example)editedtodeployonWebLogic7.0executingseveraltargetsinspecifiedsequencefunctionsofimportingbuild.propertiesfileintoJSPparsing,usingJSTLXMLtagsnamesotherthanbuild.xml

TomcatManagerapplication,usingfromtransformingintoHTML,usingXSLstylesheetwl.propertiesforWebLogicAntfilebuild.propertiesfile(Ant)deployingwebapplicationonWebLogicServer7.0build.xmlfile[Seebuildfiles]Builder(WebLogic)

[TeamLiB]


Clanguage,printffunctionc:choosetagc:forEachtag2ndinterationsperformedbyiteratingovermapvaluesiteratingthroughaMap'sstoredrequestheadersc:iftagtestingexpressionsforconditionalcodeexecutionuseinaJSP(example)c:importtagimportingAntbuildfileintoJSPincludingJavaScriptmoduleinaJSPJavaScriptmodule,importingintoaJSPusebyJSPtoaccessforbiddenresourcec:otherwisetagc:outtag2nd3rddisplayingaJavaBean'spropertiesdisplayingforminputviaaJavaBeandisplayingindividualparametervaluesescapedcharactersexceptioninformation,displayingforJSPpassingvalueofrequest_uriattributetosummaryoffunctionsuseinaJSP(example)c:paramtags,includingparametervaluesinJSPc:settagbindinganobjecttoapplicationscopesettingvariabletosessionscopesummaryoffunctionsc:whentagCallableStatementclassexecuteUpdate()servletusingtocallstoredprocedureCallbackHandlerclass2nd3rdcallbacksclassforsiftingthroughwebpagesdefinitionofParserDelegator,usingwithcasesensitivityurlpatterninservlet-mappingelementsusernamesandpasswordsintomcat-users.xmlfilecastingrequestparametersServletRequesttypetoHttpServletRequestCauchoResin(servletengine)cbck:log(customJSPtag)2ndCDATAsectionsinXMLfiles,usingtopasswell-formedtestCGI(CommonGatewayInterface)characterentitycodes2ndescapedcharactersinc:outtaglistingofCheckEmailfunction,JavaScript

classesJavaServerPageimplementationclassservlet2ndservlet-classelementinweb.xmlclassesdirectory2ndlog4j.propertiesfilespecifyingclasseswithAntwartaskTLDsandWebLogic7.0server,pastingservletclassintoclasseselement(Ant)classictaghandlerscreatingforacustomactioncreatingJSP1.2TLDforcreatingJSP2.0TLDforclasspathelement(Ant)nestedinsidethejavactaskCLASSPATHenvironmentvariable,precompilingJSPsandclasspathsAntclasspaththatincludesTomcatJARfilesemail-relatedclasses,placingoninbuild.xmlfile,forJARfilesinTomcatdirectoriesuser,representedbyCLASSPATHenvironmentvariableWLCLASSPATHenvironmentvariableclientauthentication[Seeauthentication]clientrequestscountingforwebapplicationexaminingHTTPrequestheadersinaJSPexaminingHTTPrequestheadersinaservletfilter,usingtoalterrequestheadersrefreshingaJSPautomaticallyrefreshingaservletautomaticallyclientstateClockclass(exampleapplet)referenceto,embeddedbyJSPclose()InitialContextclassPrintWriterclassclosingdatabaseconnections2ndcodeexamplesinthisbook,useofCollectionsclass,synchronizedMap()com.oreilly.servletlibraryclassesforfileuploadsLocaleNegotiatorclassMultipartFilterclasscom.oreilly.servlet.multipartpackagecommentattribute(cookies)commentsJSPuncommentingConnectorelementinTomcatserver.xmlcommercialservletenginescommit()Connectionclass2ndLoginModuleclassCommonGatewayInterface(CGI)compilingservlets2nd[SeealsoprecompilingJSPs]Anttool,using

PATHenvironmentvariableforjavacwithAntbuildfileconfigure()(BasicConfigurator)configure()(PropertyConfigurator)specifyingnameoflog4j.propertiesfileConnectionclasscommit()2ndgetMetaData()getTransactionIsolation()listingofisolationlevelsrollback()2ndsetAutoCommit()connections,databasecreatingconnectionpoolwithWebLogicConsoleDataSourceasfactoryforopeningandclosingservletusingWebLogicconnectionpoolConnectorelement(server.xml)ConsoleAppenderclasscontainer-managedsecuritycontent[Seealsodynamicallyincludingcontent;staticcontent]non-HTML,sendingaudiofilesPDFfilesviewinginternalresourcesinaservletwordprocessingfilesXMLfilescontenttypesemail2ndMultipartmultipart/form-dataContent-Dispositionheader2ndContent-LengthheaderContent-Typeheaderapplication/mswordMIMEtypescontentTypeattribute(jspdirective.pageelement)contextdefault,forservletsincludingJSPfile,importingcontentfromoutsideContextelement(Tomcatserver.xmlfile)2ndcontextpathforwebapplicationpathattributeofContextelement(Tomcat)context-paramelement(web.xml)cookieage,valuesfordataSourceparameterthatconnectswithadatabaseinternationalizationresourcesJSPthatopenspop-upwindowlocalizationcontext,setting2ndprovidingpathforanincludedfileinaJSPcontext-relativepathcontextDestroyed()(ServletContextListener)contextInitialized(ServletContextListener)ContextObjectclass(example)controllerservlet

exclusiveaccesstocertainservlets,settingupmappingallrequeststowhilepreservingallservletmappingsconversionofaJSPintoaservletconversionpatterns,layoutofloggedmessagesconversionspecifiersinpatternlanguageCookieclassgetName()andgetValue()2ndgetPath()getterandsettermethodsforattributessetMaxAge()2ndargumentvalueofzerosetValue()cookieimplicitobject(JSTL)2ndCookierequestheadercookies2ndaccessingwithELdefinitionofdeletionbyusersdisabledbyusersname/valuepairoptionalattribute/valuepairsoverwritingorremovingexistingcookiesreadingvalueswithaJSPreadingvalueswithaservletsessiontracking,useindisabledcookiessettingwithaJSPsettingwithaservletstoringrequestcookiesinanarraycopytask(Ant)Copyrightservlet(example)CoreJ2EEBlueprintswebpageCorel'sSVGViewercos.jarfilecountrycodes(ISO)2ndcreate-jartarget(Ant)create-wartarget(Ant,build.xmlfile)CreateWindowfunction,JavaScriptcreatingnewbrowserwindowinaservletcreationtimeforsessionstrackingwithJSPstrackingwithservletscurrencies,formattingforlocalesinaJSPinaservletcustomactions2nd[Seealsocustomtags]JSPusingtoaccesslog4jcustomtags2nd3rdassociatedwithatagfile,usingcbck:logtaglogginglevelconfigurationfile,includingyourowncreatingclassictaghandlerforcreatingJSP1.2TLDforclassictaghandlercreatingJSP2.0TLDforclassictaghandlercreatingTLDforasimpletaghandler

functioncallsembeddedintemplatetexthandlingexceptionsincustomtagclassJSPtagfile,creatinglistenerclass,addingtotaglibrarypackagingataglibraryinawebapplicationpackagingJSPtagfileinaJARpackagingtaglibraryinaJARfilesimpletaghandler,creatingsimpletaghandler,usinginaJSPtagfile,packaginginwebapplicationtagthatuseslog4jTLDforcustomloggertagusinginaJSP

[TeamLiB]


DatabaseMetaDatainterfacedatabasesaccessingfromservletwithoutDataSourceconfigurationcallingstoredprocedurefromaJSPconfiguringDataSourceinTomcatconvertingResultSettoResultobjectcreatingDataSourceonWebLogicDataSource,usinginservletwithTomcatexecutingseveralSQLstatementsinonetransactioninteractingwithbyconfiguringDataSourceinweb.xmlJNDIlookup,usingtoaccessaWebLogicDataSourceJSTLtagsthatinteractwithResultSetinformation,findingoutstoredprocedure,callingfromaservlettransactions,usingwithJSPsWebLogicDataSource,usinginaJSPDataHandlerclassDataSourceconfigurationinweb.xmlconfiguringforservletinTomcatconfiguringinweb.xmlforSQLJSTLtagscreatingDataSourceobjectonWebLogicconfiguration,stepsinexplicitlysettingforJSTLSQLtagsinaJSPgetConnection()2ndJNDI,accessingwithusinginservletwithTomcatWebLogicDataSource,usinginaJSPDataSourceLoginModule2ndDateclass,getTime()DateFormatclass2ndformat()getDateTimeInstance()datesandtimescreationandlast-accessedtimeforsessionstrackingwithJSPstrackingwithservletsexpirationforcookiesformattingdatesaccordingtorequestlocaleinaJSPinaservletformattingwithJSTLtagscurrentdateinSwissandU.S.stylefmt:formatDatetag,attributesofJSPthatdisplayscurrentlog4jdateformatterofloggingactivitydateStyleandtimeStyleattributes(fmt:formatDate)Davidson,JamesDuncanDEBUGlevellogging2ndinrootloggerdeclarativesecurity

defaultattribute(Antprojectelement)DefaultFileRenamePolicyclassfile-uploadingJavaBean,useindeletingacookiedependsattribute(Anttargetelements)deploy-applicationtarget(Ant,build.xmlfile)editedtodeployonWebLogic7.0deploy-servlettarget(Ant,build.xmlfile)2ndDeployerutility(WebLogic)deployingservletsandJSPsdeployingaspartofTomcat'sContextelementinserver.xmlfileindividualJSP,deployingonTomcatindividualJSP,deployingonWebLogicindividualservlet,deployingonTomcatAnttool,usingstepsinprocessindividualservlet,deployingonWebLogicServer7.0Antfile,usingeditingweb.xmlfiletoregisterservletredeployingwebapplicationwebapplication,deployingonTomcatAntbuildfile,usingwebapplication,deployingonWebLogicusingAnttoolusingWebLogicAdministrationConsoleusingWebLogicBuilderusingweblogic.Deployercommand-lineutilitydeploymentdescriptors[Seealsoweb.xmlfile]creatingforservletAPI2.3servletAPI2.4web.xmlfilecontentsEJBvendor-specific(weblogic-ejb-jar.xml)J2EE,namespaceofopeningandeditinginWebLogicBuildersecurity-relatedelementsinversionsotherthanservletv2.4storageinWEB-INFdirectorytaglibelementweb.xmlfileinWEB-INFdirectorydescriptionattribute(Anttargetelements)destfileattributeAntjartaskAntwartaskdigitalcertificate,creatingforTomcatserverdirattributesAntclasseselementAntfilesetelementsdirectives,JSPinwell-formedXMLfileXMLequivalentsfordirectories**patterninAntelements(zeroormoredirectories)2ndlocal,savingfileuploadstoURLsthatspecifyadirectoryonlydirectorystructureofwebapplications

forapplicationdeployedbyAnttoolexampleofexplodeddirectoryformatJSPfilesindirtyreaddispatcherelements(web.xml)2nddisplayMessage()AttachBeanclass(example)EmailBeanclass(example)HeaderAccessorclass(example)MailAccessorclass(example)distributedcomputing,SOAPaseasierformofdoCatch()(TryCatchFinally)docBaseattribute(Contextelement,Tomcat)DocumentTypeDefinition(DTD)inJSP1.2TLDfileJSP1.2orderforelementsinweb.xml(servlet2.3API)XMLSchemavs.doEndTag()2nddoFilter()blockingrequestscastingrequestparameterchangingservletresponsefilterusingHttpServletResponseWrapperclassFilterChainclassdoFinally()(TryCatchFinally)doGet()encodeRedirectURL,usinginFirstServletclass(example)outputdisplayedinbrowserHttpServletclassincludingcontentinJavaBean,usingtosendemailPrivacyServletclass(example),includingresourcespecifiedbyinitparameterservletaccessingdatabaseusingJDBCservletmethodtowhichfilterismappedservletusingaJavaBeantohandleemalattachmentsservletusingJavaBeantosendemaildomainattribute(cookies)doPost()FirstServletclass(example)outputdisplayedinbrowserHttpServletclassincludingcontentinPOSTHTTPrequests,respondingtotrackingauser'srefreshcountdoStartTag()2nddoTag()simpletaghandlersdownloadprogress,showingtouserDriverManagerclassDTD[SeeDocumentTypeDefinition]dynamiccontent,combiningmultimediawithinJSPsdynamicallyincludingcontentconfiguringincludedresourceinexternalfile

externalconfigurationfile,usingtoincluderesourceinaJSPimportingaresourceeachtimeservlethandlesarequestincludingcontentfromoutsideacontextinJSPincludingcontentinaJSPforeachrequestincludingXMLfragmentinJSPdocumentresourcesnestedatmultiplelevelsinservletexceptioninformation,displayingfirstinnerincludedservletouterincludingservletrequestattributes,accessbyincludedresourcessecondincludedservletresourcesthatseldomchange,includinginJSPserverperformanceand

[TeamLiB]


EAR(EnterpriseApplicationArchive)fileechotask(Ant)EIS(EnterpriseInformationSystems)ejb-jar.xmlfilecontentsof,displayingEJBs(EnterpriseJavaBeans)accessinganEJBonWebLogicfromaservlet,usingJNDIdeploymentdescriptor(ejb-jar.xml)deploymentdescriptor,vendor-specificservlet(example)statelesssessionbean(example)EL[SeeExpressionLanguage]elements,XMLAnttasksbuild.xmlfile(Ant)Contextelement(Tomcatserver.xmlfile)inweb.xmlfileforservletAPI2.3inweb.xmlfileforservletAPI2.4orderinvalidXMLfileemailaccessingfromaservletaccessingfromaservletusingaJavaBeanaddingattachmentstoanemailinaservletJavaBeansActivationFramework(JAF)JavaMailAPIplacingclassesrelatedtoonclasspathreadingreceivedemailheadersfromaservletreceivedinaservlet,handlingattachmentsfromsendingfromaservletservletinteractionwithmailserversendingfromaservletusingaJavaBeanEmailBean(example)servletusingJavaBeantosendemailsettingemailpartswithbeanmethodsemailaddresses,validatinginforminputwithJavaScriptembedtags(HTML)2ndautomaticHTMLfilegenerationbyFlashproducedbyHTMLConverterencodeRedirectURL(HttpServletResponse)encodeURL()(HttpServletResponse)EnterpriseApplicationArchive(EAR)fileEnterpriseInformationSystems(EIS)EnterpriseJavaBeans[SeeEJBs]entitycodesforspecialcharacters2ndc:outtag,escapedcharacterslistingofentrySet()(Map)2ndEnumerationtypeERRORlevelloggingerror-pageconfigurationauthenticationfailurepage(/loginError.html)elementinweb.xmlforIOExceptions

inweb.xml,exampleofoverriddenbypagedirectivedeclarationerror-pageelement(web.xml)2ndconfiguringerrorpagesErrorDataclasserrorPageattribute(pagedirective)escapedcharacters,c:outtagescapeXmlattribute(c:outtag)EventObjectclassexamplecodefromthisbook,useofexceptionimplicitobjectexception-typeelement(web.xml)exceptionsincustomtagclasshandlinginwebapplicationscreatingerror-handlingJSPdeclaringexceptionhandlersinweb.xmldeclaringexception-handlingJSPforotherJSPsexception-handlingservletsendingerrorfromaJSPsendingerrorfromaservletthrownduringincludeoperationsexcludeelement(Ant)executeUpdate()(CallableStatement)expirationforcookiessettingsettingwithjsp:setPropertyexpiresattribute(cookies)explodeddirectoryformatExpressionLanguage(EL)callingLoginBean'sgetLoginSuccess()clientlocales,preferredandless-preferredcookieimplicitobjectcookies,accessingwithcreatinghperlinksinURLrewritingcreationtimeforsessions,fetchingdereferencingofvariableandpropertyvaluesfunctionthatcallsastoredprocedureJavaclassthatimplementsfunctionJSP,useinTLDfileforconfiguringfunctionfunctionsinJSPerrorpageinJSPusedaserrorpageintemplatetext(JSP2.0specification)JavaBeanproperties,accessingwithJSPexamplepage,useinJSTLandmapentrykey/valuepairsrequestheaders,accessingwithvalueofaparticularheaderrequestparameters,accessing2ndscopedattributes,accessingscopedvariables,accessingwithtemplatetext,usingELexpressionsdirectlyinURLforJavaScriptwindowinaJSP,gettingfromacontextparameter

ExtensibleStylesheetLanguage(XSL)ExtensibleStylesheetLanguageTransformations(XSLT)extensionmappingURLpatternsassociatingfilterwithany.jspfilemappingallreferencestoJSPpagestoasingleservletmappingstaticcontenttoaservletexternal-includeproperty

[TeamLiB]


FATALlevelloggingfileextensionsassociatingMIMEtypeswithfileuploads[Seeuploadingfiles]FileDataSourceclassFilerConfigclassgetInitParameter()FileRenamePolicyinterfacefilesetelements(Ant)2ndnestedwithinjartasknestingmultipleinpathelementfilterelements(web.xml)2ndinit-paramchildelementFilterinterfaceactionsthatfilterscanundertakefilter-mappingelements(web.xml)2ndapplyingfiltertoaservletusingaRequestDispatcherchangingorderofmappingmultiplefilterstoaservleturl-patternnestedelementFilterChainclassdoFilter()2nd3rdFilterConfigclassgetInitParameterNames()filteringblockingIPaddresseswithchangingorderinwhichfiltersareappliedtoservletsconfiguringinitializationparametersforafilterfilterconfigurationinweb.xmlfile(servletAPI2.3)HTTPresponsesinterceptingandreadingforminputJNDIobject,accessingfromaJSPsettingobjectassessionattributemappingafiltertoaJSPmappingafiltertoaservletfilterthatlogssomeinformationmappingmultiplefilterstoaservletmonitoringsessionattributesMultipartFilterclassoptionallyblockingarequestwithafilterpassingJNDIobjecttoJSPonWebLogicrequestheaders,alteringusingfilterswithRequestDispatcherobjectsvalidatingforminputwithafilterFlashfilesembeddinginaservletHTMLtemplateforembeddinginaJSPautomaticallygeneratingwritingfmt:formatDatetagcurrentlocale,usingtoformatdatesandnumbersfmt:formatNumbertag

currentlocale,usingtoformatnumbersdisplayingcurrencyvalueforalocaledisplayingnumbersaspercentagesfmt:messagetagsfmt:setBundletagfmt:setLocaletagfn:contains()fn:length()fn:split()fn:toUpperCase()Folderclass2ndfootersegmentincludedinJSPwithjsp:includeactionformtags(HTML)actionattributeaction,methodandenctypeattributesforfileuploadsform-basedauthenticationformforusewithloggingoutuseronsystemthatusesform-login-configelementformat()DateFormatclassNumberFormatclass2ndformattingtags(JSTL)displayingdateinJSPforuserlocaledisplayingtextinJSPforrequestlocaleFORWARDvalue(dispatcherelements)forward()(RequestDispatcher)forwardingrequestscontrollerservletforwardingwithRequestDispatcher.forward()withforward()(RequestDispatcher)withgetNamedDispatcher()(ServletContext)initiatingafilterforbyobjectsimplementingRequestDispatcherinterface,withouttriggeringsecurityconstraintsfragments,JSPincludedinaservletbyusingRequestDispatchernowreferredtoasJSPsegmentsFrontControllerdesignpattern(SunMicrosystems)fullyqualifiedclassnamesinvokingregisteredservletthroughlistenerclassinlistenerclasselementobjectattributenamesandfunctioncallsembeddedinJSPcodewithJSTL2ndfunctiontagfunctionsExpressionLanguage,callingstoredprocedureJavaclassthatimplementsfunctionJSP,useinTLDfileforconfiguringfunctionJavaScriptJSTLlistingof,withpurposeofeachusinginJSPs

[TeamLiB]


GETrequestssecurityconstraintsonservletresponsetogetAllHeaders()MessageclassPartinterfacegetAttribute()(ServletContext)getBundle()(ResourceBundle)2ndgetConnection()(DataSource)2ndgetContent()(Message)getContextPath()(HttpServletRequest)getCookies()(HttpServletRequest)2ndgetCurrencyInstance()(NumberFormat)getDateTimeInstance()(DateFormat)getDisplayName()(Locale)getFilesystemName(MultipartRequest)getFrom()(Message)getHeader()HttpServletRequestclassPartinterfacegetHeaderNames()(HttpServletRequest)getID()(HttpSession)getInitParameter()(FilterConfig)getInitParameterNames()(FilterConfig)getInputStream()PageDataclassPartinterfacegetInputStream()(PageData)getJspBody()(SimpleTagSupport)getJspContext()(SimpleTagSupport)getLastAccessedTime()(HttpSession)getLocale()(ServletRequest)getLocales()getLoginSuccess()LoginBeanclass(example)getMaxInactiveInterval()(HttpSession)getMetaData()ConnectionclassResultSetclassgetName()Cookieclass2ndHeaderclassgetNamedDispatcher()(ServletContext)getParameter()(ServletRequest)2ndhandlingposteddatagetParameterMap()HttpServletRequestclassServletRequestclass2ndhandlingposteddatagetParameterNames()(ServletRequest)getParameterValues()(ServletRequest)getPath()(Cookie)

getPercentInstance()(NumberFormat)getQueryStringHttpServletRequestclassgetQueryString()requestwrappersthatoverridegetRealPath()(ServletContext)getRemoteAddr()(HttpServletRequest)getRemoteUser()(HttpServletRequest)getRequestDispatcher()(ServletRequest)getRequestURI()(HttpServletRequest)getRequestURL()(HttpServletRequest)getResultElements()(GoogleSearchResult)getRows()(Result)getSearchResults()2ndgetServletContext()getServletRequest()(ServletRequestEvent)getSession()HttpServletRequestclass2nd3rd4thHttpSessionBindingEventclassHttpSessionEventclassgetSnippet()(GoogleSearchResultElement)getSource()(EventObject)getSummary()(GoogleSearchResultElement)getTitle()(GoogleSearchResultElement)getTransactionIsolation()(Connection)2nd3rdgetURL()(GoogleSearchResultElement)getValue()Cookieclass2ndHeaderclassHttpSessionBindingEventclassglobal.propertiesfile(Ant)exampleof2ndGoogleWebServicesconnectingtowithaJSPconnectingtowithaservletcreatingaJavaBeantoconnectwithoptionsforsearches,settingsettingupwithGoogleSearchclass(example)GoogleSearchResultclassGoogleSearchResultElementclass

[TeamLiB]


handleMessages()EmailBeanclass(example)MailAccessorclass(example)handleStartTag()harvestingWebinformationcreatingJavaBeanasHTMLparserJavaBeanforHTMLparsingusinginaJSPusinginaservletparsingHTMLpagewithjavax.swing.textsubpackagescallbackclass(example)usingaservletHashtableclassHeaderclassheaderimplicitobject2ndheadersegmentincludedinJSPwithjsp:includeactionheadersemail,readingfromaservletHTTP[Seerequestheadersresponseheaders]headerValuesimplicitobjectheadingattribute(customtag)2ndhomeandlocalhomeinterfaces(EJBonWebLogic)Hostelement(Tomcatserver.xmlfile)2ndhrefattributeHTMLcodeforJSPthathandlesHTTPrequestsconvertingXMLfileintowithXSLstylesheeterrorpagesenttoclientfileuploadpage,preparingcomponenttoreceivefileandstoreinlocaldirectoryformtag2ndonSubmiteventhandlerheadtaginputtagJavaBeanforparsingcreatingusinginaJSPusinginaservletparsingAPIclasses,useinservletsrcattributeofscripttag,usingtoimportJavaScriptmoduletemplateforembeddingFlashfilesgeneratingautomaticallytemplateforincludingFlashfileswritingHTMLConverter(JavaPlug-in)HTMLformsaddingparameterstoquerystringusingaJSPusingaservletinterceptingandreadingforminputwithafilterpostingsubmitteddatafromaJSPservlethandlingof

FirstServletclass(example)servlet,acceptingAmazonsearchtermsettingpropertesofJavaBeantovaluesenteredinsettingscopedattributeinaJSPtovalueofaformparametersubmissiontoserver-sideprogramviaPOSTmethodvalidatinginputwithafilterfilterthatchecksvalues(example)JSPthatcontainsaform(example)HTMLtagsapplettagembedtag2ndgeneratedwithJavaPlug-inHTMLConverterforloadingappletsobjecttag2ndHTMLEditorKitclassHTTPdevelopingJSPforhandlingofrequestsGETmethod[SeeGETrequests]POSTmethod[SeePOSTrequests]requestheaders[Seerequestheaders]requestsforfileuploadingresponseheaders[Seeresponseheaders]secureconnections[SeeSecureSocketsLayer]securityconstraintsonmethodsXML-basedSOAPmessagesonHTTPresponsecodes403or404,handlingbywebcontainer500,returnedbywebcontainerintparameterofsendError()http-methodelementssecurityconstraintsforHttpClient(JakartaCommons)automatingdatapostingfromservlettootherprogramsdownloadingservletusingtopostdatatoaJSPuseinJavaBeanthatpostsdatafromJSPpagehttps://,URLsthatstartwithHttpServletclassinit(),includingcontentinservice()HttpServletRequestclasscheckingsessionexistencegetContextPath()getCookies()2ndgetHeader()getHeaderNames()getParameterMap()getQueryString()getRemoteAddr()getRemoteUser()getRequestURI()getRequestURL()getSession()2nd3rdisUserInRole()HttpServletRequestobjectsHttpServletRequestWrapperclassHttpServletResponseclass

addCookie()encodeRedirectURL()encodeURL()Refreshresponseheader,addingsendError()2ndsendRedirect()2ndHttpServletResponseobjectsHttpServletResponseWrapperclass,forusewithafilter(example)HttpSessionclassgetId()getLastAccessedTime()getMaxInactiveInterval()invalidate()removeAttribute()setAttribute()setMaxInactiveInterval()2ndHttpSessionActivationListenerinterfaceHttpSessionAttributeListenerinterfaceHttpSessionBindingEventclassgetSession()getValue()HttpSessionBindingListenerinterfaceHttpSessionEventclass,getSession()HttpSessionListenerinterfacenotificationofsessioncreationanddestructionsessionCreated()andsessionDestroyed()

[TeamLiB]


i18n[Seeinternationalization]if/then/elsestatementsIllegalStateException,handlinginwebapplicationsimgtag(HTML)implicitobjects2nd3rdimplicitobjects,JSPsapplicationexceptionpageContext2ndresponsesessionimplicitobjects,JSTLapplicationScopecookie2nd3rdheader2ndheaderValuesinitParam2ndparam2nd3rd4threquestScope2ndsessionScope2nd3rdimportcustomactionincludedirectivechangesmadetoincludedpage,reflectioninincludingpageinJSPdocument,expansionbyXMLviewincludingseldomchangingresourceinaJSPincludingXMLfragmentinJSPdocumentjsp:includeactionvs.2ndruleofthumbforusingincludeelement(Ant)includemechanismsfordynamiccontentconfiguringincludedresourceinexternalfileexternalconfigurationfile,usingtoincluderesourceinaJSPimportingaresourceeachtimeservlethandlesarequestincludingcontentfromoutsideacontextinJSPincludingcontentinaJSPforeachrequestincludingXMLfragmentinJSPdocumentresourcesnestedatmultiplelevelsinservletexceptioninformation,displayingfirstinnerincludedservletouterincludingservletrequestattributes,accessbyincludedresourcessecondincludedservletresourcesthatseldomchange,includinginJSPINCLUDEvalue(dispatcherelements)include()(RequestDispatcher)2ndembeddingFlashinaservletincludingJavaScriptCreateWindowfunctioninaservletincludingtop-levelservletfileservletimportingJavaScriptfilevalidatingJavaScript,includinginservletincludesattribute(Antjartask)IncludeServletclass(example)

INFOlevellogginginheritancestructureinlog4j2nd3rdinittarget(Ant,build.xmlfile)2ndinit-paramelement(web.xml)specifyingincludingresourcewithtimeoutvalueforservlet,configuringURLforloadingnewwindowcreatedbyJavaScriptfunctioninaservletinitialcontextInitialContextclass2ndclose()lookup()2ndinitializationparametersconfiguringforafilterservlet,registerednameandinitialize()(LoginModule)initParamimplicitJSTLobject2ndinputtags(HTML)multiplefileuploadstype,name,andacceptattributes,forfileuploadsInputStream,XMLviewofJSPpagereturnedas2ndINSERTstatement(SQL),executinginJSPinatransactioninternalresourcesfromwebapplication,viewinginternationalization2ndclientlocale,detectinginaJSPclientlocale,detectinginaservletcreatingResourceBundleasaJavaclassdefinitionofformattingcurrenciesinaJSPformattingcurrenciesinaservletformattingdatesinaJSPformattingdatesinaservletformattingpercentagesinaJSPinaservletlocalizationcontext,settinginweb.xmlResourceBundleaspropertiesfile,creatingResourceBundle,usinginaJSPResourceBundle,usinginaservletInternetExplorerembeddingFlashfilesinwebcomponentsHTMLobjecttag,loadingappletwithlanguagepreference,setting(v.5.5)InternetAddressclass2ndinvalidate()(HttpSession)invoke()(JspFragment)invokerservletsinvokingservletsregisteredinweb.xmloverridingtodirectallrequeststocontrollerservletIOExceptionclass2ndJSPthatthrows(example)webapplications,handlinginIPaddresses,blockingrequestsfromwithafilteris-xmlelementisErrorPageattribute(pagedirective)ISO(InternationalStandardsOrganization)countrycodes2nd

languagecodesisolationlevelsfortransactionsinsql:transactiontagisUserInRole()(HttpServletRequest)iteratingovercollectionsofdatac:forEachtag,iteratingoverarrayiteratingposteddatawithJSTLIteratorclassnext()iterator()(Set)

[TeamLiB]


J2EE(Java2EnterpriseEdition)CoreBlueprintswebpageEJBinbusinesstierJavaMailandJavaBeansActivationFramework(JAF)J2SE(Java2StandardEdition)JAAS(JavaAuthenticationandAuthorizationService)authenticatingservletclientsconfigurationfile,creatingflagvalues,listingoflocationoffileLoginModuleclassCallbackHandlerforexamplecodeonlinedocumentationusinginaJSPJAF(JavaBeansActivationFramework)2ndJakartaCommonsHttpClient[SeeHttpClient]JakartaTomcat[SeeTomcat]JAR(JavaARchive)filescreatingwithAntforJakartaCommonsHttpClientincludingTomcatJARfilesinAntclasspathlog4j.jarmail.jarandactivation.jarpackagingJSPtagfileinpackagingtaglibraryinSunMicrosystemsspecificationforWEB-INF/libdirectory,storageinjartask(Ant)2ndbasedirattributedestfileattributefileset(nested)elementincludesattributemanifestfile,creatingjartoolplacingtaglibraryinaJARfilejartool,creatingWARfileswithJasper(TomcatJSPcontainer)jasper-runtime.jarJASPER_HOMEenvironmentvariableJava2EnterpriseEdition[SeeJ2EE]JavaAPIforXMLProcessing(JAXP)2nd3rdJavaAuthenticationandAuthorizationService[SeeJAAS]javacommand-linetool,settinguserclasspathJavaDatabaseConnectivity[SeeJDBC]JavaDevelopmentKit(JDK)JavaNamingandDirectoryInterface[SeeJNDI]JavaPlug-indifferentinstalledversions,causingproblemsloadingappletsHTMLConverter,embeddingappletinaJSPJavaRuntimeEnvironment(JRE)applets,runningin

executingappletwithJavaPlug-inJavaVirtualMachine(JVM),servletsandJavaWebServicesDeveloperPack(WSDP)JavaWebServicesDeveloperPack,downloadingJAXPJava-basedwebapplicationsJAVA_HOMEenvironmentvariablesettinginAntinstallationJavaBeansaccessingemailfromaservletconfiguringasaJNDIobjectwithTomcatcookies,creatingCookieBean(example)creatingaswebpageparsercreatingtosearchAmazoncreatingtosearchGooglewebdatabasecustomizingresponsessenttoclientsemailattachments,handling(example)file-uploading(example)GooglesearchutilityclassJAASAPI,usingforauthenticationJSPdata,postingdynamicallytoanotherserver-sideprocessJSPusingtosearchgoogle.compropertiesaccessingwithELsettinginaJSPsendingemailfromaservletEmailBean(example)servletusingJavaBeantosendemailsettingofemailpartswithbeanmethodsservletusingtoconnecttoAmazonWebServicesasTomcatJNDIresourceaccessingfromaservletwebpageparserusinginaJSPusinginaservletJavaBeansActivationFramework(JAF)2nd3rdjavaccompilerbuilt-in,withSunMicrosystemsJDKjavactask(Ant)classpathelementnestedinsideofcompilingapplicationservletsintobuilddirectoryJavaMailfetchingemailmessageslistingemailheaderspropertiessetforSessionJNDIobjectSession,Store,Folder,andMessageclassesJavaScriptcreatingnewbrowserwindowinaJSPcreatingnewbrowserwindowinaservletincludingJavaScriptmodulesinaJSPincludingJavaScriptmodulesinaservletvalidatingforminputinaservletvalidatingformvaluesinaJSPJavaServerPages[SeeJSPs]JavaServerPagesStandardTagLibrary(seeJSTL)javaxsub-packagesforBEAWebLogic

javax.mailpackagejavax.mail.internetpackagejavax.namingpackage2ndjavax.servlet.jsp.tagextpackagejavax.sqlpackageJDBC(JavaDatabaseConnectivity)accessingdatabasefromservletusingJDBCcallingstoredprocedurefromaservletwithCallableStatementConnectionobjectsdatabasedriverandstoragelocation2ndDriverManagerclassjavax.sql.DataSourceobjectcreatingonWebLogiconWebLogic,usinginaJSPSQLJSTLtag,usingwithOracleclasses12.zipdriverResultSet,convertingtoResultobjectResultSetMetaDatainterfacespecification,addressfordownloadingtransactionAPIJDK(JavaDevelopmentKit)version1.1,AntsupportofJNDI(JavaNamingandDirectoryInterface)2ndconfiguringJNDIobjectinTomcatconfiguringJNDIresourceinWebLogiclookup,usingtoaccessWebLogicDataSourceTomcatJNDIresourceaccessingfromaJSPaccessingfromaservletusingAPIclassestoobtainDataSourceWebLogicJNDIresourceaccessingfromaaJSPaccessingfromaservletWebLogicJNDItreeaccessinganEJBwithforaDataSourceviewingJRE(JavaRuntimeEnvironment)applets,runninginexecutingappletwithJavaPlug-injsp-property-groupelement2ndjsp:directive.includeelementjsp:directive.pageelementaddedtoJSPdocumentbyXMLviewjsp:doBodyaction2ndjsp:forwardactionjsp:getPropertyactionjsp:idattributeforXMLelementsinJSPdocumentjsp:includeactionexternalconfigurationfile,usingtoincluderesourceinaJSPimmediatereflectionofchangestoincludedfilesincludedirectivevs.2ndruleofthumbforusingincludingresourceinJSPeachtimeitreceivesrequestincludingXMLfragmentinJSPdocumentjsp:paramaction

jsp:paramelements,providingembeddedappletswithparameterandvaluepairsjsp:pluginactionembeddingappletinaJSPHTMLtagsgeneratedforloadingJavaappletjsp:rootelement2ndaddedbyXMLviewtoJSPdocumentjsp:setPropertyactioncookieproperties,settingcookievalue,settingsettingdirectorynameforsavinguploadedfilesettingJavaBeanpropertytosubmittedformvaluejsp:textelementjsp:useBeanaction2nd3rd4th5thcookie-creatingbean,usinginJSPidattributeinstantiatingfile-uploadingbeaninaJSPuseinsettingbeanpropertytosubmittedformvaluejsp_precompileparameterjspc(weblogic.jspcprecompilationtool)JspCcommand-linetool(Tomcat)JspContextclassJspFragmentinterface.jspffilesvs.JSPs(JavaServerPages)applicationserversassoftwarehostsforasXMLdocumentscreatingfromscratchasJSPdocumentcreatingJSP-typeURLforaservletcustomXMLtags[Seecustomtagstags]deploying[SeedeployingservletsandJSPs]2nd[SeedeployingservletsandJSPs]fragmentsgeneratingXMLviewfromimplementationclasspackaginginWARfilesprecompiled,mappingtopageimplementationclassprecompilinginTomcatinWebLogicprecompilationprotocol,usingrequestattributes,accessbyincludedresourceswritingasXMLfilesbasicstepsinviewingoutputinbrowserJspWriterclassJSTL(JavaServerPagesStandardTagLibrary)2ndarraysorMaps,usingtoiteratethroughvaluesc:choose,c:when,andc:otherwisetagsc:forEachtag2nd3rd4th5thiteratingposteddatawithc:iftag2ndc:importtag2nd3rd4th5thc:outtag2nd3rd4th5th6thescapedcharactersexceptioninformation,displayingforaJSPsummaryoffunctions

useinaJSP(example)c:paramtagc:settag2nd3rdsummaryoffunctionscookieimplicitobjectcookies,accessingwithELcoretags,usinginaJSPcurrentsessionID,displayingcustomtagsinJSPscreatedasXMLfilesdownloadingandusing1.0referenceimplementation,libdirectorycontentsJSTL1.1taglibdirectivesfordifferentJSTL1.0librariesdownloadingJavaWebServicesDeveloperPackExpressionLanguage(EL)[SeeExpressionLanguage]fmt:formatDatetagfmt:formatNumbertagdisplayingnumbersaspercentagesformattingcurrencyvalueforalocalefmt:messagetagfmt:setBundletagfmt:setLocaletagformattingnumbersaspercentagesformattingsessioncreationandlast-accessedtimesformattingtagsdisplayingtextinJSPforclientlocalefunctionalityoffunctions,usinginJSPsheaderimplicitobjectinJSPerrorpage2ndJavaBeanproperties,accessingwithELJSPusingResultobjectstoredassessionattributelocalizationcontextfortags,settinginweb.xmlrequestheaders,accessingwithELvalueofaparticularheaderrequestparameters,accessingwithELscopedvariables,accessingwithELsessiondate/timesformattedwithSQLtagswithDataSourceconfigurationwithoutDataSourceconfigurationsql:querytag2ndsql:setDataSourcetagsql:transactiontagsql:updatetagurlcustomactionx:outtagx:parsetagx:transformtag2nd3rdXMLandXSLTtags,usingXMLcoretags,usinginaJSPJVM(JavaVirtualMachine),servletsand

[TeamLiB]


key/valuepairs(cookies)keystorefilekeytoolutility

[TeamLiB]


l10n[Seelocalization]languagecodes(ISO)languageelementlanguagepreference,settinginNetscape7.1last-accessedtimeforsessionstrackingwithJSPstrackingwithservletslayoutsforloggedmessagesininheritedappenderspatternusedforBasicConfiguratorPatternLayoutSimpleLayoutclass,inrootloggermessageslibdirectory2ndinclusionofnesteddirectoriesinWARfilewithAntwartaskJARfiles,storinginlog4j.jarfileTLDsandlibelement(Ant)listenerelement(web.xml)listenersaddinglistenerclasstoataglibraryapplicationeventconfigurationinweb.xmlfile(servletAPI2.3)examiningHTTPrequestswithmonitoringsessionattributesrequests,trackingforawebapplicationservletcontexteventlistener,usinginloggingsessioneventusinginloggingtrackingsessionlifecyclevalidatingforminputwithListResourceBundleclassload-on-startupelement(web.xml)localhomeinterface(EJBonWebLogic)localedefinitionof2nddetectingforclientinaJSPdetectingforclientinaserverdisplayingmessageappropriateforusingJSTLformattingtagsformattingcurrencyvaluesforinaJSPinaservletformattingdatefordisplayinaJSPinaservletpreferredlocalizationdefinitionoflocalizationcontextsettinginweb.xmllocalizerslocationelement(web.xml)

Locationheaderlog()(ServletContext)2nd3rd4th5thlog4jApacheLog4jlibraryconfigurationfileusedbyservletcontextlistenersessioneventlistenerthatusessettinguplog4j.propertiesfileappenderconfigurationspecifyingdifferentnameforLoggerTagclass2ndloggingappendersaddingtoroootloggerfilterthatlogssomeinformation(example)layoutslog4jandservletcontexteventlistener,usinglog4j,usinginaJSPLogFilter(example),mappedtoaservletloggerscreatingyourownandgivingitanappenderusingwithoutconfigurationfilerequestssessioneventlistener,usingsettinguplog4j2ndwithservletthatusesServletContext.log()loggingoutusers,applicationwithform-basedauthenticationlogin()DataSourceLoginModuleclass2ndLoginContextclass2ndLoginModulelogin-configelements(web.xml)auth-methodnestedelementvaluesforusingwithsecurity-constraintelementlogin.htmlpage(example)LoginBeanclass(example)getLoginSuccess()LoginContextclassloginError.htmlpageloginError.jsppageLoginModuleclassexamplecodemethodsvalidatingusernameandpasswordagainstdatabaseinformationlogout()(LoginModule)longdatatypesreturnedbydate-relatedHttpSessionmethods2ndlookup()(InitialContext)2nd

[TeamLiB]


MacromediaFlash[SeeFlashfiles]mail[Seeemail]mailserver,interactionwithemail-sendingservletmailsessions2ndservletgettingfromWebLogicJNDImail.jararchivemailDefaults.propertiesfileManagerapplication(Tomcat)onlinedocumentationforStopTaskclassmanifestfileforJARfilesMapobjectsContextObjectclass(example)2ndmethodsaddingkeysandvaluestomapcookieELimplicitobjectEntrysubclass,getKey()andgetValue()entrySet()headerimplicitobject2ndheaderValuesimplicitobjectJSPparameterspassedforpostingtoJavaBeanMessageclassgetAllHeaders()getContent()getFrom()messagestores2ndMessagingExceptionclassMETA-INFdirectory,TLDsinmethodattribute(HTMLformtag)Methodobjectsmethods(JavaBean),namingconventionsforMicrosoftWordfileasemailattachmentsendingasbinarydataMIMEtypesapplication/mswordapplication/pdfassociatingfileextensionswithcommon,listingofMicrosoftWorddocumentMP3filesmultipart/mixedMimeMessageclass2nd3rdMimetypesFileTypeMapclassmodules,JavaScriptexampleoforganizationandstorageofvalidatingforminput(validate.js)MPEGaudiolayer3(MP3)embeddedfileinaJSPsendingaudiofileasmultimedia,embeddinginJSPsembeddingappletwithHTMLConvertertool

embeddingappletwithjsp:pluginembeddingbackgroundsoundtrackinaJSPembeddingFlashinaservletembeddingQuickTimemovieinaJSPembeddingSVGfileinaJSPHTMLtemplateforembeddingFlashfilesgeneratingautomaticallywritingMultipartclassMultipartcontenttypemultipart/form-datacontenttypeMultipartFilterclassMultipartParserclassMultipartRequestclassfile-uploadingJavaBean,useinservletthatuses,creatingMultipurposeInternetMailExtensions[SeeMIMEtypes]MutableAttributeSetclass

[TeamLiB]


nameattribute(Antprojectelement)namespacedefinitionofidentifiedbyprefixattributeoftaglibdirectiveforXMLelementsrelatedtoXMLSchemainstancesxmlnsattributeoftaglibelementnamingconventions,log4jnamingservletscreatingmultiplemappingstoaservletcreatingwelcomefilesforwebapplicationinvokingservletwithoutaweb.xmlmappingJSP-typeURLforservletsmappingallrequestsfromawebapplicationtoaservletmappingallrequeststocontrollerwhilepreservingallservletmappingsmappingservlettonameinweb.xmlmappingstaticcontenttoaservletrestrictingrequestsforcertainservletsNetscapedisablingcookiesJavaScript,developers'websitesettinglanguagepreference(v.7.1)next()(Iterator)non-repeatablereadnullrolesecurityroleNumberFormatclassformat()2ndgetCurrencyInstance()getPercentInstance()numbers,formattingwithJSTLtagsfmt:setLocaletag

[TeamLiB]


objectattributesforwebapplicationssettingscopewithc:settagobjecttags(HTML)2ndautomaticHTMLfilegenerationbyFlashproducedbyHTMLConverter(example)objectsEJB,factoriesforscopesofonSubmiteventhandler(HTMLformtag)2ndopensourceapplicationsopenConnection()(URL)Oracle8idatabaseservletthatqueriesforaResultSetstoredprocedureaddingrowtotableOraclesequencesorg.apache.jasper.runtimepackageoverwritingacookie

[TeamLiB]


packagesfully-qualifiedclassnamesandforservletandutilityclassespageattribute(jsp:include)2ndpagedirectiveerrorPageattributeimportattributeisErrorPageattributeoverridingerror-pageconfigurationpageimplementationobjectpagerelativepathpagescope2ndpageContextimplicitobject2ndPageDataclass,getInputStream()2ndpageEncodingattribute(jspdirective.pageelement)PAM(PluggableAuthenticationModule)paramimplicitobject2nd3rd4thparam-valueelement,alteringtoimportincludedresourceparse()(ParserDelegator)2ndsynchronizationofParserCallbackParserDelegatorclasscallbacks,usingwithparse()2ndsynchronizationofparsingHTMLwithjavax.swing.textsubpackagesJSPsbeforeconversiontopageimpelementationXMLJAXP-compliantparsersx:parsetagPartinterfacegetAllHeaders()getHeader()getInputStream()passwords[Seealsoauthentication]creatingintomcat-users.xmlfileforkeystorefileanddigitalcertificatepathattribute(Contextelement,Tomcat)pathattribute(cookies)accessingvaluesforsettingtonameofcontextpathpathelement(Ant)2nd3rdnestingthreefilesetsinPATHenvironmentvariableAnt/bindirectory,addingtoincludingpathtothebindirectoryofyourJavaSDKinstallationforSunJDKjavaccompilerpathparameterpathscontext-relative

cookie,settingwithjsp:setPropertypage-relativetosavedirectory,forfileuploadservlet2ndservletcreatingforwebapplicationusersdifferencesamongservletenginespatternlanguageforconvertingloggedmessagelayoutsPatternLayoutclass2ndPDF(PortableDocumentFormat)filespercentagesformattinginaJSPformattinginaservletpermissionsforusingcodeexamplesphantomreadPluggableAuthenticationModule(PAM)pop-upwindow,creatingwithJavaScriptfunctioninaservletportnumbers,usedbysecurevs.insecureHTTPconnectionsPortableDocumentFormat(PDF)filesPortableDocumentFormatfiles[SeePDFfiles]POSTrequestsdeliveryofHTMLformdatatoserver-sideprogramviafileuploadsandhandlinginaJSPhandlinginaservletwithServletRequest.getParameter()andgetParameterMap()postingdatafromaJSPpostingdatafromaservlettootherserver-sideprogramsHttpClient,usingtopostdatatoaJSPsecurityconstraintsonPRECLASSPATHenvironmentalvariableprecompilingJSPs2ndinTomcatinWebLogicwithprecompilationprotocolservletmappingspreferredlocaleprefixattribute(taglibdirective)preparetarget(Ant,build.xmlfile)2ndprintffunctioninCPrintWriterclassHTMLpagereturnedbyblockingfilterPrivacyServletclass(example)doGet(),includingresourcespecifiedbyinitparameterJSPfragmentincludedbyprogrammaticsecurityprojectelement(Ant)arrangingtargetelementsinsidepropertiesAntglobal.propertiesfileloadingintobuild.xmlmakingavialabletobuildfileAntpropertytask,importingglobal.propertiesfilebuild.propertiesfile(Ant),forwebapplicationdeploymentcookie,settingexternalfile(include.properties),specifyingresourcetoincludeinJSPjar-nameproperty

JavaBeanaccessingwithELemailpartsstoredassettinginaJSPlog4j.propertiesfilemailDefaults.propertiesfilepassingtoanAntfilecommandline,usingpropertytask,usingpropertiesfileforautomaticallygeneratedXMLviewtagattributesaswl.propertiesfileforWebLogicAntbuildpropertiesfile,ResourceBundleaspropertytask(Ant)2ndPropertyConfiguratorclass

[TeamLiB]


querystringsaddingparametertowithaservletaddingparameterstowithaJSPrequest,addingparametertoQuickTimemovie,embeddinginaJSP

[TeamLiB]


redirectingrequests(aftercheckingsessionvalidity)referenceimplementationforJSTLrefidattribute(Antclasspathelement)2ndreflection,usinginloggingRefreshheaderJSPthataddstotheresponserefreshingaJSPautomaticallyrefreshingaservletautomaticallyregisterednamesforservletsfilters,mappingtoinvokingregisteredservletswithinvokerservletreloadableattribute(Contextelement,Tomcat)2ndRemoteMethodInvocationregistryremoveAttribute()(HttpSession)renaminguploadedfileswithyourownJavaclassrequestandresponseobjectserrorpageaccesstorequestattributesaccessbyerror-handlingservletaccessbyincludedresourcesinJSPsexceptioninformationfromrequestheadersaccessingwithELimplicitobjectvalueofoneparticularheaderexamininginaJSPexamininginaservletfilter,usingtoalterrequestimplicitobjectrequestparametersaccessingwithELimplicitobject2ndgettingforCallbackHandlerrequestphase(JSPs)requestscope2ndrequest,ServletRequestListenersRequestDispatcherinterface2ndforward()2ndforwardingofHTTPrequestswithouttriggeringsecurityconstraintsforwardingrequeststoservletsundersecurityconstraintsinclude()2ndembeddingFlashinaservletincludingJavaScriptCreateWindowfunctioninaservletincludingtop-levelservletfileincludingvalidatingJavaScriptmoduleinaservletservletimportingJavaScriptfileJSPfragmentincludedinaservletwithRequestDispatcherobjects,usingfilterswithrequestInitialized()requestsblockingfromanIPaddresswithafilteroptionallyblockingwithafilter

requestScopeimplicitJSTLobject2ndResourceelements(server.xml)2nd3rdresource-env-refelement(web.xml)2ndresource-refelement(web.xml)ResourceBundleobjects2ndcreatingasaJavaclasscreatingasapropertyfilegetBundle()2ndlocalizationcontextsetinweb.xmlusinginaJSPusinginaservletResourceParamselements(server.xml)2nd3rdresponsecodes,HTTP[SeeHTTPresponsecodes]responseheadersdefinitionofRefreshJSPs,addingtoresponseimplicitobject(JSP)responsescustomizingwithaJavaBeanfilteringHTTPresponsesrestrictingrequestsforcertainservletsResultinterface2ndResultobjectsconvertingResultSettoResultSetobjectsfindingoutinformationaboutResultSetMetaDatainterfaceservletthatusesResultSupportclasstoResult()rolescheckingforuserswhorequestservletspecifiedinauth-constraintelementrollback()(Connection)2ndrollingfileappenderRollingFileAppenderclassrootelement[Seejsp:rootelement]rootloggeraddinganappenderto

[TeamLiB]


save-direlement(web.xml)SAX(SimpleAPIforXML)ScalableVectorGraphics(SVG)file,embeddinginaJSPscopedattributesusingELandc:outtagtogetvalueofscopesboundobjectsforstoredobjectsscrapinginformationfromawebpage[SeeharvestingWebinformation]scriptblocks(JavaScript)scriptletsSDK(SoftwareDevelopmentKit)GoogleWebAPIsSDKPATHenvironmentvariablesecureattribute(cookies)SecureSocketsLayer(SSL)built-insessiontrackingmechanismsettinguponTomcatsecurityconfiguringweb.xmlwithwebapplicationsecurityelementsrelatedto,indeploymentdescriptorsnotusingservletv2.4includingsecurity-relatedcodeinservletsrestrictingrequestsforcertainservletsservletaccess,restrictingtocontrolleronlysecurityrolesnullrole,preventingusermappingtointomcat-users.xmlsecurity-constraintelements(web.xml)auth-constraintnestedelementblockingallrequestsexceptfromRequestDispatcher.forwardexampleofinitiatingauthenticationwithaJSPlogin-configelement,usingwithrestrictingrequestsforcertainservletsservletaccess,restrictingtocontrollerservletonlyspecifyingwebresourcesrequiringauthenticationweb-resource-collectionnestedelementsecurity-roleelements(web.xml)2nd3rdsegments,JSPselectattribute(x:forEach)SELECTstatement(SQL)executinginJSPinatransactionsendingtodatabasewithsql:querytagself-signeddigitalcertificate,creatingforTomcatsend()(Transport)2ndsendError()(HttpServletResponse)2ndsendingnon-HTMLdataaudiofilesPDFfilesviewinginternalresourcesinaservletwordprocessingfilesXMLfilessendRedirect()(HttpServletResponse)2nd

sequences,Oracleserverresponsecodes[SeeHTTPresponsecodes]serverstatuscode403Forbiddenserver.xmlfile(Tomcat)ConnectorelementContextelementResourceandResourceParamselementsservers,applicationservice()(HttpServlet)servletAPI2.3deploymentdescriptorthatconfigureserrorpagessessions,configurationinweb.xmlweb.xmlfile2nd[Seealsoweb.xmlfile]servletAPI2.4filters,usingwithRequestDispatchersweb.xmlfile2nd[Seealsoweb.xmlfile]3rdweb.xml,usewithTomcat5andJSTL1.1servletAPIdocumentationservletcontainersservletelements(web.xml)associatingwithmultipleservlet-mappingelementsgeneratedbyJspC,mappingservletstoload-on-startupnestedelementservletengines,commercialServletinterfaceservlet-classelement(web.xml)servlet-mappingelements(web.xml)associatingmultiplewithoneservletelementcreatingaliastoaservletgeneratedbyJspC,mappingservletstoJSP-styleURLpatterninmappingallrequestsfromwebapplicationtoaservletremovingoralteringanyelementsallowingrequeststobypasscontrollerservletmappingstaticcontenttoaservletremovingoralteringanythatallowrequeststobypasscontrollerservletservletswithout,invokingurl-patternelementWebLogicServer7.0servlet-nameelement(web.xml)*wildcardsymbol,notusedinservlet.jar,inclusioninPRECLASSPATHenvironmentvariableServletConfiginterfaceServletContextattributessettinginJSPssettinginservletsobjectthatservletbindstoServletContextservletthatbindsobjecttoServletContextServletContextclass2ndgetAttribute()getRealPath()log()2nd3rd4th5threturninganulldispatchersetAttribute()2ndServletContextListenerinterfacecontextInitialized()andcontextDestroyed()

ServletExceptionclass2ndServletOutputStreamclassServletRequestinterfacegetLocale()getParameter()getParameter()andgetParameterMap()getParameterMap()getRequestDispatcher()methods,usinginservlet'sdoPostmethodServletRequestEventclass,getServletRequest()ServletRequestListenerclassServletResponseclasschangingresponsewithafiltersetBufferSize()servlets2ndapplicationserversassoftwarehostsforcompiling[Seecompilingservlets]conversionofJSPsintodeploying[SeedeployingservletsandJSPs]deploymentdescriptorforservletAPI2.3deploymentdescriptor,creatingforservletAPI2.4JavaServerPages[SeeJSPs]naming[Seenamingservlets]packaginginWARfileswritingFirstServletclass(example)lifecycle,managementofpackages,creatingforSessionclass2nd3rd4thbindingobjecttoWebLogicJNDIservletgettingSessionobjectfromWebLogicJNDIsessioneventlistenerssessionIDdisplayingwithJSTLtagURLsthatautomaticallyinclude,creatingsessionimplicitobject2ndsessionscope2ndJNDIobjectplacedin,usingafiltersession-configelement(web.xml)2ndsessiontimeoutforallTomcatapplicationssession-timeoutelement(web.xml)sessionCreated()(HttpSessionListener)2nd3rdsessionDestroyed()(HttpSessionListener)2nd3rdsessionDidActivate()(HttpSessionActivationListener)SessionFilterclass(example)sessionscheckingexistenceofinHttpServletRequestconfigurationinweb.xmlfileforservletAPI2.3definitionofinvalidatingtologoutusermonitoringsessionattributeswithafiltermonitoringsessionattributeswithalistenertimeout,settinginallTomcatwebapplicationsinservletcode

inweb.xmltrackinglifecyclewithalistenertrackingsessionactivityinJSPstrackingsessionactivityinservletstrackingwithURLrewritinginaJSPtrackingwithURLrewritinginaservletsessionScopeimplicitJSTLobject2nd3rdsessionWillActivate()(HttpSessionActicationListener)Setclass,iterator()Set-Cookieresponseheader2ndsetAttribute()HttpSessionclassServletContextclasssetAutoCommit()(Connection)setBufferSize()(ServletResponse)setContent()setFrom()setKey()(GoogleSearchsetKey)setMaxAge()(Cookie)callingwithargumentvalueofzerosetMaxInactiveInterval()(HttpSession)2ndsetQuery()setQueryString()(GoogleSearch)setValue()(Cookie)shellscriptsforprecompilingJSPfiles(onUnix)forprecompilingallJSPpagesinapplication(onUnix)Tomcat,shuttingdownshow-propstarget(Ant)SimpleAPIforXML(SAX)SimpleObjectAccessProtocol[SeeSOAP]simpletaghandlercreating(JSP2.0)creatingaTLDforusinginaJSPSimpleLayoutclassmessagesloggedbyrootloggerSimpleTaginterface2ndSimpleTagSupportclass2ndgetJspBody()getJspContext()SOAP(SimpleObjectAccessProtocol)responsefromAmazonbasedonkeywordsearch(example)webservicesbasedon,reasonstousesocketconnectionwithadatabaseserverSoftwareDevelopmentKit(SDK)GoogleWebAPIsPATHenvironmentvariablesoundtrack,embeddinginaJSPSQL(StructuredQueryLanguage)executingseveralstatementsinonetransactionservletusingtransactionJSTLSQLtags2ndwithDataSourceconfigurationSQLJSTLtagwithoutDataSourceconfigurationstoredprocedures

transactions,usingwithJSPsSQLPLUSdatabase,addEventstoredprocedure(example)sql:querytagsendingSQLSELECTstatementtodatabasesql:setDataSourcetagsql:transactiontagsql:updatetagsrcattribute(HTMLscripttag),importingJavaScriptmoduleintoservletsrcdirectorySSL[SeeSecureSocketsLayer]startandstoptasks(Ant,build.xmlfile)startingTomcatfromAntStartTasktaskstatelessSessionbean(EJB)definitionofstaticcontentmappingtoaservletrequestsfor,interceptedbycontrollerservletserverperformanceandstaticmethods,JavamethodimplementingELfunctionforJSPstaticpageformultimediacontentstatuscodes,HTTP[SeeHTTPresponsecodes]status_codeattributestopandstarttasks(Ant,build.xmlfile)stoppingaTomcatapplicationwithAntStopTaskclassStoreclass2nd3rdstoredprocedurescallingfromaJSPcallingfromaservletstructureResults()2ndstylesheets(XSL),integratingintoJSPsSunMicrosystemsFrontControllerdesignpatternJAASdocumentationJARfilespecificationJavaDevelopmentKit(JDK)JavaWSDPdownloadsiteonlinetutorialssampleappletswebservicestutorialthatincludesXPathSVGfile,embeddinginaJSPsynchronizedMap()(Collections)

[TeamLiB]


t:toxmlelementtagdirectivetagfilescreatingcustomtagassociatedwith,usingpackaginginaJARpackaginginawebapplicationtaghandlersclassiccreatingcreatingJSP1.2TLDforpackagenameforclassessimplecreatingcreatingTLDforusinginaJSPtaglibrarylistenerclass,addingtopackaginginaJARfilepackaginginawebapplicationTagLibraryDescriptor(TLD)files2ndaddinglistenerelementtoconfiguringanELfunctioncreatingforsimpletaghandlercreatingJSP1.2TLDforclassictaghandlercreatingJSP2.0TLDforclassictaghandlercustomloggertagcustomtaginformation,providingdefinitionofforXMLviewcustomtagplacingintaglibraryJAR'sMETA-INFdirectoryspecifyingvalidatorforurifortaglibraryXMLDTD,useinJSP1.2taglibdirectives2ndforcustomtag,identifyingurifortaglibraryfordifferentJSTL1.0librariesinincludedJSPsegment,foruseofc:outJSTL1.0tagsJSPsegmentcontaining(example)requiredforuseofJSTL1.0coreandSQLlibrariesspecifyingcoretaglibraryfromJSTLuriandprefixvaluestousewithfunctionslibraryuriattributevaluesinJSTL1.1taglibelementversionattributexmlnsattributexmlns:xsiattributexsi:schemaLocationattributeTagLibraryValidatorclassusingXMLviewtovalidatecustomtagsinJSPpagetagscustom[Seealsocustomtags]

customtagsinJSPsdefinitionofincludingtaglibrariesasnamespaceattributesinJSPdocumentspre-builtforJSPs(JSTL)TagSupportclass2ndtargetelements(Ant),groupingoftasksintargets(Ant)inbuild.xml,displayingnamesoftaskdefelement(Ant,buildfile)starttask,definingstoptask,definingtasks(Ant)filesetsgroupof,representedbytargetelementpropertytasktextfiles,JSPswrittenasthreadnameinloggingmessagesThrowableclassThrowableobjectsaccessinginJSPerrorpageassociatedwithexceptions,accessingthrownexceptions,informationaboutinJSPerrorpage2ndtimeoutforsessionssettinginallTomcatwebapplicationssettinginservletcodesettinginweb.xmltimeStyleattribute(fmt:formatDate)TimeZoneIDs,helperclasstodisplayTLD[SeeTagLibraryDescriptorfiles]tldfileextensionTomcatcompilingservletonconfiguringDataSourcetouseinservletcontextelement(conf/server.xml),forJSPcontentimportedfromoutsidecontextcreatingusernamesandpasswordsDataSource,usinginaservletdeployingindividualJSPondeployingindividualservletonAnttool,usingstepsinprocessdeployingservletaspartofContextelementinserver.xmldeployingwebapplicationonAntbuildfile,usingpointingtoexternaldirectorycontainingwebapplicationerrorpagedisplayedbyerrorhandlingservletimplicitmappingtoitsJSPcompilerandexecutionservletfor.jsprequestsincludingJARfilesinAntbuildfileclasspathinitialcontextofbuilt-inJNDIimplementationinvokerservletcommentingoutJasper(JSPcontainer)JNDIobject,configuringJNDIresourceaccessingfromaJSPaccessingfromaservletJSPpageimplementationclass,viewing

JSTL1.1features,usingwithversion5logfilesprecompilingJSPsinsecurity-constraintelementinweb.xml,usingsessiontimeout,settingforallwebapplicationsSSL,setlingupstartingwebapplicationwithAntstoppingwebapplicationwithAnttomcat-users.xmlfileexampleofatypicalfilemanagerrole,usermappingtonullrollsecurityrole,preventingusermappingtousermappingtosecurityrolesusernamesandpasswords,case-sensitivityofusernames,passwords,androlesforauthenticationtoResult()(ResultSupport)2ndToXmlValidatorclasstransactionscreatingwithConnectionmethodsexecutingseveralSQLstatementsinsingletransactionservletthatusestransactionisolationlevelsusingwithJSPstransformingXML,usingJSTLXMLandXSLT-relatedtagstranslationphase(forJSPs)2ndincludingJSPsegmentintoJSPpageTransportclass,send()2ndtry/catchblock,forexceptionsthrownduringincludeoperationsTryCatchFinallyinterfacetutorials,online(SunMicrosystems)

[TeamLiB]


unbindingsessionobjects,listeningforundeploytarget(Ant,build.xmlfile)Unixkeytoolutility,creatingdigitalcertificatewithshellscriptforprecompilingallJSPpagesinapplicationshellscriptforprecompilingJSPfilesUnix-basedMacOSX10.2system,PATHvariableforjavacUPDATEstatement(SQL)uploadingfilescom.oreilly.servletclassesforfileuploadsJSP,handlingwithfileuploadingJavaBean,creatingJSPthatuploadsanddisplaysinformationaboutmultiplefileuploads2ndpreparingHTMLpageforcomponenttoreceivefileuploadandstoreinlocaldirectoryrenaminguploadedfileswithyourownJavaclassuriattribute(taglibdirective)JSTL1.1,differentvaluesinURIsmappingurielementsinTLDasspecifiedbytaglibdirectiveinJSPfilesrequest,usebyJSPerrorpageurlcustomactionaddingparameterswithencodeURL()vs.rewritingURLswithURLpatterns*.jspisanextensionmapping/sqlJsp.jsp,initiationofBASICauthenticationforaimingallrequestsatacontrollerservletexactmatchingrequirementforJSP-type,creatingforaservletrestrictinganyrequestsfromreachingspecifiedbysecurity-constraintelementsURLrewriting2ndusinginaJSPusinginaservleturl-patternelement(web.xml)*wildcardcharacterincasesensitivityofmappingallrequestsfromwebapplicationtoaservletmappingfiltertoaJSPURLConnectionclassURLsconnectionto,openingexternalimportingintoJSPwithc:importtaginitiatingAmazonsearchwithinvoker-style,forservletsspecifyingadirectoryonlyforstaticcontent,mappingtoaservletuserclasspath

userroles[Seeroles]User-Agentheaderusersmanagerrole(Tomcat)tomcat-users.xmlfilemappingtosecurityrolesusernames,passwords,androlesin

[TeamLiB]


validpartialrequestsValidateHandlerclassvalidatingcustomtagsinJSPpagesforminputfilter,usingforJavaBean,usingJavaScript,usinginaJSP2ndJavaScript,usinginaservlet2ndXMLdocuments,specifyingvalidatorforTLDfilevarattribute(c:forEachtag)variabledirectivevariables(scoped),accessingwithEL2ndvariant(inlocales)versionattributecookiestaglibelementviewerapplicationsforSVGviewinginternalresourcesinaservlet

[TeamLiB]


WAR(WebARchive)filescreatingwithAntdeployingwebapplicationas,usingWebLogicAdministrationConsolefindingoutifalreadydeployedonTomcatforservletsandJSPsgeneratingwithAntwartaskopeininginWebLogicBuildertoeditweb.xmlfileviewingcontentsofwartask(Ant)2ndclasses,lib,andfileset(nested)elementsdestfileandwebxmlattributesWARNlevelloggingwebapplicationsconfiguringlog4jmechanismcountingnumberofrequestsforcreatingwelcomefilesfordefinitionofdeployingonTomcatAntbuildfile,usingconfiguringTomcattopointtoapplicationinexternaldirectorydeployingonWebLogicusingAnttoolusingWebLogicAdministrationConsoleusingWebLogicBuilderusingweblogic.Deployercommand-lineutilitydeploymentdescriptor,creatingfordirectorystructure[Seedirectorystructureofwebapplications]Java-basedmappingallrequeststocontrollerservletpackagingJSPtagfileinpackagingtaglibraryinservletcontextinstanceservlet,writingforstartingonTomcatusingAntfilestoppingonTomcatusingAntfileWARfiles[SeeWARfiles]webbrowsers[Seebrowsers]webcomponentswebcontainers2nd[SeealsoTomcat]exceptionhandlinginwebdevelopertasks,recipesinthisbookimplementationwithBEAWebLogicwebdirectory,inclusionofnesteddirectoriesinWARfilewithAntwartaskwebpageforthisbookwebservices[SeealsoAmazonWebServices;GoogleWebServices]2ndAmazonandGoogleAmazon,settingupGoogleWebAPI,settingupSOAP,usingforinformationtransferSOAP-based,reasonstoadoptweb-appelement(web.xml)requiredattributesofservlet2.4deploymentdescriptor

WEB-INFdirectory2ndcontentsofWEB-INF/jspf(optionaldirectory)WEB-INF/tlds(optionaldirectory)web-resource-collectionelements(web.xml)protectedresourcesinsecurity-constraintelementspecifyingsecurityrestraintsweb.xmlfile2nd[Seealsoservlet-mappingelements]BASICauthentication,initiatingwithJSPfilecontentsofcontextparametersave-direlementcontext-paramelement,addingforincludedfileinaJSPcreatingmultiplemappingstoaservletcreatingwithJspCutilityDataSource,configuringindeclaringexceptionhandlersineditingforWebLogictoregisteraservleterror-pageattribute,mappingexceptiontypestoaJSPerror-pageconfigurationfiltersconfiguringinmappedtotheservletpath(example)mappingofmappingtoaJSPform-basedauthentication,settingupform-checkingfilterregisteredandmappedinIOExceptions,elementformanagingIPblockingfilter,mappingofjsp-property-groupelement2ndJSP-typeURLforaservletlistenerelementlisteners[Seealsolisteners]configurationinservletAPI2.3forservletrequests,registeringmappingallreferencestoJSPpagestoasingleservletmappingservlettoanamepreventingrequeststonon-controllerservletsresource-refelementrestrictingrequestsforcertainservletsservletAPI2.3convertingto2.4forJSTL1.1featuresservletAPI2.4usewithTomcat5andJSTL1.1servletelementwithload-on-startupnestedelementservletthatcreatespop-upwindowservletswithoutamappinginsessiontimeoutforallTomcatwebapplicationssessiontimeout,settingviewingwithaservletwebappsfolder(Tomcat)WebLogiccreatingDataSourceonconfiguration,stepsinJNDIlookup,usingtoaccessDataSourceJNDIresourceaccessingfromaJSP

accessingfromaservletconfiguringinJNDItreeaccessinganEJBwithviewingprecompilingJSPsinrecipesforcommontasksservletclassesandjavaxsub-packagesWebLogicServer7.0deployingindividualJSPondeployingindividualservletonAntfile,usingeditingweb.xmltoregisterservletredeployingwebapplicationdeployingwebapplicationonusingAnttoolusingWebLogicAdministrationConsoleusingWebLogicBuilderusingweblogic.Deployercommand-lineutilitysecurityconfigurationinweblogic.xmlweblogic-ejb-jar.xmlfileweblogic.Deployercommand-lineutilityweblogic.jspcutilityweblogic.xmlfile,securityconfigurationinwebxmlattribute(Antwartask)welcomefilesforawebapplicationwelcome-file-listelement(web.xml)wildcardsinURLpatternsoverridingwithspecificmappingswindoidWindowssystemslaunchingWebLogicBuilderlocalvariantforPATHenvironmentvariableforjavaccompiler(onNT)precompilingallJSPpagesinapplicationwithweblogic.jspcshellscriptforrunningJspCwindows,browser[Seebrowserwindows,creatingwithJavaScript]wl.applicationsproperty(Ant,build.propertiesfile)wl.propertiesfile(forWebLogicAntbuildfile)WLCLASSPATHenvironmentvariablewordprocessingfiles,sendingWSDP(WebServicesDeveloperPack)

[TeamLiB]


x:forEachtag2ndx:iftagx:outtagx:parsetagx:transformtagassociatingastylesheetwithanXMLfilexmlattributexsltattributeXerces2XMLparserXMLAntbuildfilecreatingJSPdocumentasXMLfileincludingXMLfragmentinaJSPdocumentJSPdocumentvs.XMLviewJSPsasXMLfiles2ndXMLequivalentsofJSPdirectivesJSTLXMLandXSLTtags,usinginaJSPJSTLXMLcoretags,usinginaJSPsendingXMLfileasbinarydataSOAPmessagesonHTTPTLD(TagLibraryDescriptor)filestransforming(x:transform)webservicesXMLelementsAnttaskscase-sensitivityinelementandattributenamescustomtagsusedinJSPnamespaceforelementsrelatedtoXMLSchemainstancesnamespace,definitionofpathelement,definingAntclasspathXMLparsers,JAXP-compliantXMLSchemainstancesXMLSchemasforJSP2.0TLDinservletAPI2.4web.xmlfileXMLviewautomaticallygeneratingforJSPpagegeneratingfromaJSPpageJSPXMLdocumentvs.xmlnsattribute(taglibelement)xmlns:xsiattribute(taglibelement)XPathxsi:schemaLocationattribute(taglibelement)XSL(ExtensibleStylesheetLanguage)XSLT,convertingXMLtoreadableformat

[TeamLiB]

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