servlet technology - web application...

Servlet TechnologyWeb Application Development

Zsolt Tóth

University of Miskolc

2017

Zsolt Tóth (University of Miskolc) Servlet Technology 2017 1 / 26

Back-end Programming Languages

1 Back-endProgramming LanguagesApplication Servers

2 Web ApplicationsStructureDeployment Descriptor

3 J2EEHttpServletFilter



Common Gateway Interface

CGI Program / ScriptPHP, CGenerate HTML

Started by the Web ServerCreate process for eachHTTP RequestCostly



Script Languages

PHPMost popular

Local companies use it.Frameworks

YiiContent ManagementSystems

JoomlaWordPress

Easy–to–startSupported by web serverhosting companiesWikipedia

PythonHigh–level, general purposelanguagePopular but not in MiskolcEasy–to–LearnGoogle, Youtube

RubyRuby on Rails FrameworkNot popular in MiskolcTwitter



Object Oriented Languages

Web ApplicationsComplex,Reliable,Stable

Expensive InfrastructureComponents can beseparated easilyGood, well-tested code(hopefully ,)

DevelopmentSlowStandardized

Fixed rolesMethodologies

DifficultIf you do it well ,Lots of technology

Both Java and C# are used bylocal companies


Back-end Application Servers

Overview

ApplicationMiddlewareSoftware FrameworkEnvironment for DynamicWeb ApplicationsContains

Servlet ContainerJSPEnterprise JavaBeans

ServersGlassFish, WildFly,Geronimo

$ WebSphere, WebLogic,JBoss



Common Tasks

Admin ConsoleDeploymentScaling

Manage NodesClustering

MonitoringServerApplicationsResources

Resource ManagementJDBCJNDIJMS



Installation

Java ApplicationPlatforms

UnixLinuxWindows

No install.exe

Extract and runScript files

bin/startup.shbin/shutdown.sh

Hints for DevelopersYour are not a SystemAdministrator.You should not operate anApplication Server.Logging is essential.Log files grow quickly.Never run as root!



Usage as a Developer

Local DeploymentManual TestingDemonstration

≈ Test Server

IDE IntegrationEclipseIntelliJ IDEANetBeans



Tomcat

Apache Software FoundationLightweightServlet ContainerVersions

8.0Servlet 3.1JSP 2.3

8.5HTTP/2OpenSSL

Popular among developers!



Tomcat

Directoriesbin

Script filesstartup.shshutdown.sh

confXMLserver.xmltomcat-users.xml

webapps

.+-- bin+-- conf+-- lib+-- LICENSE+-- logs+-- NOTICE+-- RELEASE-NOTES+-- RUNNING.txt+-- temp+-- webapps\-- work



Tomcat for Developers

IDEIntelliJ IDEAEclipse

Multiple ServersLocal Configuration

Workspace

Start/Stop ServerDeploymentRefresh / Restart

TasksRun LocallyTest Manually

See alsoDatabase ManagementSoftware TestingOperation Systems


Web Applications Structure






Structure

Web AppExpected Directory StructureStandard LocationsDeployed from Web ARchive

Root DirectoryStatic ContentDirect Access

+-- images+-- index.jsp+-- META-INF| \-- context.xml+-- WEB-INF| +-- jsp| | +-- 401.jsp| | +-- 403.jsp| | +-- 404.jsp| | \-- sessions.jsp| \-- web.xml



Web ARchive

ZIP File

*.war ExtensionContains Web ApplicationCreation

jar cvf ...Maven Packaging

Can be Deployed



WEB-INF

Cannot be Accessed Directly!

classes

*.class filesCompiled Servlet ClassesPackage Structure

lib

*.jar Files3rd Party Dependencies


Web Applications Deployment Descriptor

Deployment Descriptor

WEB-INF/web.xml

Details of Web ApplicationNameDescriptionServlet DefinitionURL MappingListenersFilters. . .

1 <web-app xmlns="..."><servlet>

3 <servlet-name>greetings

5 </servlet-name><servlet-class>

7 org.dummy.Greetings</servlet-class>

9 </servlet><servlet-mapping>

11 <servlet-name>greetings

13 </servlet-name><url-pattern>/</url-pattern>

15 </servlet-mapping></web-app>



Servlet Mapping

servlet tagIdentified by nameservlet-class

Instanceinit-param

Initialization

load

servlet-mapping

Key Value pairExtends application’s URL* wild card

http://host:port/WebAppName/path



Filters

filter

filter-name Identifierfilter-class

Similar to ServletPreprocessingForwarding / Rejection

filter-mapping

filter-name

Selectionurl-patternservlet-name



Context-Param

Context InitializationKey-Value ParisAvailable in JavaPredefined Keys

contextConfigLocation

<context-param><param-name>contextConfigLocation

</param-name><param-value>/dispatcher-servlet.xml/applicationContext.xml

</param-value></context-param>


J2EE HttpServlet





J2EE HttpServlet

Servlet

javax.servlet

InterfaceGeneric Methods

initservicedestroy


J2EE HttpServlet

HttpServlet

javax.servlet.http

Implements ServletRun in Servlet ContainerMethods

doGetdoPostdoPutdoDelete

doGet(2 HttpServletRequest req,

HttpServletResponse resp){4 //do something

}


J2EE HttpServlet

HttpServletRequest

Request InformationgetCookies

getSession

getHeaders

getParameter

getQueryString


J2EE HttpServlet

HttpServletResponse

Servlet ResponseHTTP HeaderCookiesadd*

sendError

getWriter

getOutputStream


J2EE Filter

Filter

PreprocessingMethods

initdoFilterdestroy

TypesAuthentication FiltersLogging and Auditing FiltersImage conversion FiltersData compression FiltersEncryption FiltersTokenizing FiltersFilters that trigger resourceaccess eventsXSL/T filtersMime-type chain Filter


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