1 processing phase translation phase jsp page translation and processing phases client server...
TRANSCRIPT
11
Processing phase
Translation phase
JSP page translation JSP page translation and processing phasesand processing phases
Client Server
Request
Response
Hello.jsp
helloServlet.class
helloServlet.java
Read
Generate
Execute
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Template PagesTemplate Pages
Server Page TemplateServer Page Template
<html><html>
<title><title>
A simple exampleA simple example
</title></title>
<body <body color=“#FFFFFF”>color=“#FFFFFF”>
The time now isThe time now is
<%= new java.util.Date() <%= new java.util.Date() %>%>
</body></body>
</html></html>
Resulting HTMLResulting HTML
<html><html>
<title><title>
A simple exampleA simple example
</title></title>
<body color=“#FFFFFF”><body color=“#FFFFFF”>
The time now isThe time now is
Tue Nov 5 16:15:11 PST Tue Nov 5 16:15:11 PST 20022002
</body></body>
</html></html>
translation
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Dividing Pure ServletsDividing Pure ServletsPublic class MySelect {Public class MySelect {
public void doGet(…){public void doGet(…){
if (isValid(..){if (isValid(..){
saveRecord();saveRecord();
out.println(“<html>”);out.println(“<html>”);
… …..
}}
}}
private void isValid(…){…}private void isValid(…){…}
private void saveRecord(…) private void saveRecord(…) {…}{…}
}}
Servlet
JSP
JavaBeans
Process request
Presentation
Business logic
controller
view
model
Model-View-Controller (MVC) design
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JSP ComponentsJSP Components
There are three main types of JSP There are three main types of JSP constructs that you embed in a page.constructs that you embed in a page.– Scripting elementsScripting elements
You can specify Java codeYou can specify Java code Expressions, Scriptlets, DeclarationsExpressions, Scriptlets, Declarations
– DirectivesDirectives Let you control the overall structure of the servletLet you control the overall structure of the servlet Page, include, Tag libraryPage, include, Tag library
– ActionsActions Enable the use of server side JavabeansEnable the use of server side Javabeans Transfer control between pagesTransfer control between pages
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Types of Scripting Types of Scripting ElementsElements You can insert code into the servlet that You can insert code into the servlet that
will be generated from the JSP page.will be generated from the JSP page. Expressions:Expressions: <%= expression %><%= expression %>
– Evaluated and inserted into the servletEvaluated and inserted into the servlet ’’s output. s output. i.e., results in something like i.e., results in something like out.println(expression)out.println(expression)
Scriptlets:Scriptlets: <% code %><% code %>– Inserted verbatim into the servletInserted verbatim into the servlet ’’s _jspService s _jspService
method (called by service)method (called by service) Declarations:Declarations: <%! code %><%! code %>
– Inserted verbatim into the body of the servlet Inserted verbatim into the body of the servlet class, outside of any existing methodsclass, outside of any existing methods
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JSP ExpressionsJSP Expressions
FormatFormat– <%=<%= Java Expression Java Expression %>%>
ResultResult– Expression evaluated, converted to String, and placed Expression evaluated, converted to String, and placed
into HTML page at the place it occurred in JSP pageinto HTML page at the place it occurred in JSP page– That is, expression placed in _jspService inside out.printThat is, expression placed in _jspService inside out.print
ExamplesExamples– Current time: <%= new java.util.Date() %>Current time: <%= new java.util.Date() %>– Your hostname: <%= request.getRemoteHost() %>Your hostname: <%= request.getRemoteHost() %>
XML-compatible syntaxXML-compatible syntax– <jsp:expression><jsp:expression>Java ExpressionJava Expression</jsp:expression></jsp:expression>– XML version not supported by Tomcat 3. Until JSP 1.2, XML version not supported by Tomcat 3. Until JSP 1.2,
servers are not required to support it.servers are not required to support it.
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JSP/Servlet JSP/Servlet CorrespondenceCorrespondence Original JSPOriginal JSP
<H1>A Random Number</H1><H1>A Random Number</H1><%= Math.random() %><%= Math.random() %>
Possible resulting servlet codePossible resulting servlet code public void _jspService(HttpServletRequest request,public void _jspService(HttpServletRequest request, HttpServletResponse response)HttpServletResponse response) throws ServletException, IOException {throws ServletException, IOException { request.setContentType("text/html");request.setContentType("text/html"); HttpSession session = request.getSession(true);HttpSession session = request.getSession(true); JspWriter out = response.getWriter();JspWriter out = response.getWriter(); out.println("<H1>A Random Number</H1>");out.println("<H1>A Random Number</H1>"); out.println(Math.random());out.println(Math.random()); ...... }}
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Example Using JSP Example Using JSP ExpressionsExpressions
<BODY><BODY><H2>JSP Expressions</H2><H2>JSP Expressions</H2><UL><UL> <LI>Current time: <LI>Current time: <%= new java.util.Date() %><%= new java.util.Date() %> <LI>Your hostname: <LI>Your hostname: <%= request.getRemoteHost() %><%= request.getRemoteHost() %> <LI>Your session ID: <LI>Your session ID: <%= session.getId() %><%= session.getId() %> <LI>The <CODE>testParam</CODE> form parameter:<LI>The <CODE>testParam</CODE> form parameter: <%= request.getParameter("testParam") %><%= request.getParameter("testParam") %></UL></UL></BODY></BODY>
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Predefined VariablesPredefined Variables(Implicit Objects)(Implicit Objects) They are created automatically when a They are created automatically when a
web server processes a JSP page.web server processes a JSP page. requestrequest: The HttpServletRequest (1st arg to doGet): The HttpServletRequest (1st arg to doGet) responseresponse: The HttpServletResponse (2nd arg to doGet): The HttpServletResponse (2nd arg to doGet) sessionsession
– The HttpSession associated with the request (unless The HttpSession associated with the request (unless disabled with the session attribute of the page directive)disabled with the session attribute of the page directive)
outout– The stream (of type JspWriter) used to send output to the The stream (of type JspWriter) used to send output to the
clientclient applicationapplication
– The ServletContext (for sharing data) as obtained via The ServletContext (for sharing data) as obtained via getServletConfig().getContext().getServletConfig().getContext().
page, pageContext, config, exceptionpage, pageContext, config, exception
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Implicit objects Implicit objects –– Class Class filesfiles applicationapplication: javax.servlet.ServletContext: javax.servlet.ServletContext configconfig: javax.servlet.ServletConfig: javax.servlet.ServletConfig exceptionexception: java.lang.Throwable: java.lang.Throwable outout: javax.servlet.jsp.JspWriter: javax.servlet.jsp.JspWriter pagepage: java.lang.Object: java.lang.Object pageContextpageContext: :
javax.servlet.jsp.PageContextjavax.servlet.jsp.PageContext requestrequest: javax.servlet.ServletRequest: javax.servlet.ServletRequest responseresponse: javax.servlet.ServletResponse: javax.servlet.ServletResponse sessionsession: javax.servlet.http.HttpSession: javax.servlet.http.HttpSession
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Access Client Access Client InformationInformation The getRemoteHost method of the The getRemoteHost method of the
request object allows a JSP to retrieve request object allows a JSP to retrieve the name of a client computer.the name of a client computer.
<<htmlhtml><><headhead>><<titletitle>>Your InformationYour Information</</titletitle>></</headhead><><bodybody>>Your computer's IP address is Your computer's IP address is <<bb>><%= request.getRemoteAddr() %><%= request.getRemoteAddr() %></</bb>><<brbr>>Your computer's name is Your computer's name is <<bb>><%= request.getRemoteHost() %><%= request.getRemoteHost() %></</bb>><<brbr>>Your computer is accessing port number Your computer is accessing port number <<bb>><%= request.getServerPort() %><%= request.getServerPort() %></</bb>></</bodybody></></htmlhtml>>
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Work with the BufferWork with the Buffer
When the page is being processed, the When the page is being processed, the data is stored in the buffer instead of data is stored in the buffer instead of being directly sent to the client browser.being directly sent to the client browser.
<<htmlhtml>>This is a test of the bufferThis is a test of the buffer<<brbr/>/><%<%out.flush();out.flush();for (int x=0; x < 100000000; x++);for (int x=0; x < 100000000; x++);out.print("This test is generated about 5 out.print("This test is generated about 5
seconds later.");seconds later.");out.flush();out.flush();%>%></</htmlhtml>>
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Working with Session Working with Session objectobject The session object has many useful The session object has many useful
methods that can alter or obtain methods that can alter or obtain information about the current session.information about the current session.– setMaxInactiveInterval(second)setMaxInactiveInterval(second)
<<htmlhtml><><headhead>><<titletitle>>Session ValuesSession Values</</titletitle>></</headhead><><bodybody>><%<%session.setMaxInactiveInterval(10);session.setMaxInactiveInterval(10);String name = (String) String name = (String)
session.getAttribute("username");session.getAttribute("username");out.print("Welcome to my site " + name + out.print("Welcome to my site " + name +
"<br>");"<br>");%>%></</bodybody></></htmlhtml>>
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JSP ScriptletsJSP Scriptlets
Format: Format: <%<% Java Code Java Code %>%> ResultResult
– Code is inserted verbatim into servlet's Code is inserted verbatim into servlet's _jspService_jspService
ExampleExample– <% <%
String queryData = request.getQueryString();String queryData = request.getQueryString();out.println("Attached GET data: " + queryData); out.println("Attached GET data: " + queryData); %>%>
– <% response.setContentType("text/plain"); %><% response.setContentType("text/plain"); %> XML-compatible syntaxXML-compatible syntax
– <jsp:scriptlet><jsp:scriptlet>Java CodeJava Code</jsp:scriptlet></jsp:scriptlet>
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JSP/Servlet JSP/Servlet CorrespondenceCorrespondence Original JSPOriginal JSP
<%= foo() %><%= foo() %><% bar(); %><% bar(); %>
Possible resulting servlet codePossible resulting servlet code public void _jspService(HttpServletRequest request,public void _jspService(HttpServletRequest request, HttpServletResponse response)HttpServletResponse response) throws ServletException, IOException {throws ServletException, IOException { request.setContentType("text/html");request.setContentType("text/html"); HttpSession session = request.getSession(true);HttpSession session = request.getSession(true); JspWriter out = response.getWriter();JspWriter out = response.getWriter(); out.println(foo());out.println(foo()); bar();bar(); ...... }}
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JSP JSP Scriptlets Scriptlets ExampleExample
<%<%for (int i=100; i>=0; i--) for (int i=100; i>=0; i--) { { %>%> <%= i %> bottles of beer on the <%= i %> bottles of beer on the
wall.wall.<<brbr>><%<%}}%>%>
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Example Using JSP Example Using JSP ScriptletsScriptlets
<HTML><HTML><HEAD><HEAD> <TITLE>Color Testing</TITLE><TITLE>Color Testing</TITLE></HEAD></HEAD><%<%String bgColor = String bgColor =
request.getParameter("bgColorrequest.getParameter("bgColor");");
boolean hasExplicitColor;boolean hasExplicitColor;if (bgColor != null) {if (bgColor != null) { hasExplicitColor = true;hasExplicitColor = true;} else {} else { hasExplicitColor = false;hasExplicitColor = false; bgColor = "WHITE";bgColor = "WHITE";}}%>%><BODY BGCOLOR=<BODY BGCOLOR="<%= bgColor "<%= bgColor
%>"%>">>
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JSP DeclarationsJSP Declarations
FormatFormat– <%!<%! Java Code Java Code %>%>
ResultResult– Code is inserted verbatim into servlet's class Code is inserted verbatim into servlet's class
definition, outside of any existing methodsdefinition, outside of any existing methods ExamplesExamples
– <%! private int someField = 5; %><%! private int someField = 5; %>– <%! private void someMethod(...) {...} %><%! private void someMethod(...) {...} %>
XML-compatible syntaxXML-compatible syntax– <jsp:declaration><jsp:declaration>Java Java
CodeCode</jsp:declaration></jsp:declaration>
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Original JSPOriginal JSP<H1>Some Heading</H1><H1>Some Heading</H1><%! <%! private String randomHeading() {private String randomHeading() { return("<H2>" + Math.random() + "</H2>");return("<H2>" + Math.random() + "</H2>"); }}%>%><%= randomHeading() %><%= randomHeading() %>
Possible resulting servlet codePossible resulting servlet code
public class xxxx implements HttpJspPage {public class xxxx implements HttpJspPage { private String randomHeading() {private String randomHeading() { return("<H2>" + Math.random() + "</H2>");return("<H2>" + Math.random() + "</H2>"); }} public void _jspService(HttpServletRequest request,public void _jspService(HttpServletRequest request, HttpServletResponse response) throws ServletException, HttpServletResponse response) throws ServletException,
IOException {IOException { request.setContentType("text/html");request.setContentType("text/html"); HttpSession session = request.getSession(true);HttpSession session = request.getSession(true); JspWriter out = response.getWriter();JspWriter out = response.getWriter(); out.println("<H1>Some Heading</H1>");out.println("<H1>Some Heading</H1>"); out.println(randomHeading());out.println(randomHeading()); ...... }}
JSP/Servlet JSP/Servlet CorrespondenceCorrespondence
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Example Using JSP Example Using JSP DeclarationsDeclarations
……<body><body><h1>JSP Declarations</h1><h1>JSP Declarations</h1><%! private int accessCount = 0; %><%! private int accessCount = 0; %><h2>Accesses to page since server reboot: <h2>Accesses to page since server reboot: <%= ++accessCount %><%= ++accessCount %></h2></h2></body></html></body></html>
After 15 total After 15 total visits by an visits by an arbitrary arbitrary number of number of different clientsdifferent clients
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JSP Tags + HTML TagsJSP Tags + HTML Tags<<h2h2>>Table of Square RootsTable of Square Roots</</h2h2>><<tabletable border border==22>> <<trtr>> <<tdtd><><bb>>NumberNumber</</bb></></tdtd>> <<tdtd><><bb>>Square RootSquare Root</</bb></></tdtd>> </</trtr>> <%<% for (int n=0; n<=100; n++) for (int n=0; n<=100; n++) { { %>%> <<trtr>> <<tdtd>><%=n%><%=n%></</tdtd>> <<tdtd>><%=Math.sqrt(n)%><%=Math.sqrt(n)%></</tdtd>> </</trtr>> <% <% } } %>%></</tabletable>>
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JSP DirectivesJSP Directives
Affect the overall structure of the Affect the overall structure of the servletservlet
Two possible forms for directivesTwo possible forms for directives– <%@ directive attribute=<%@ directive attribute=““valuevalue”” %> %>– <%@ directive attribute1=<%@ directive attribute1=““value1value1”” attribute2=attribute2=““value2value2”” …….. attributeN=attributeN=““valueNvalueN”” %> %>
There are three types of directivesThere are three types of directives– PagePage, , includeinclude, and , and taglibtaglib
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Purpose of the page Purpose of the page DirectiveDirective Give high-level information about the Give high-level information about the
servlet that will result from the JSP pageservlet that will result from the JSP page Can controlCan control
– Which classes are importedWhich classes are imported– What class the servlet extendsWhat class the servlet extends– What MIME type is generatedWhat MIME type is generated– How multithreading is handledHow multithreading is handled– If the servlet participates in sessionsIf the servlet participates in sessions– The size and behavior of the output bufferThe size and behavior of the output buffer– What page handles unexpected errorsWhat page handles unexpected errors
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The import AttributeThe import Attribute
FormatFormat– <%@ page import="package.class" %><%@ page import="package.class" %>– <%@ page <%@ page
import="package.class1,...,package.classN" import="package.class1,...,package.classN" %>%>
PurposePurpose– Generate import statements at top of servletGenerate import statements at top of servlet
NotesNotes– Although JSP pages can be almost anywhere on server, Although JSP pages can be almost anywhere on server,
classes used by JSP pages must be in normal servlet classes used by JSP pages must be in normal servlet dirsdirs
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......<BODY><H2>The import Attribute</H2><BODY><H2>The import Attribute</H2><%-- JSP page directive --%><%-- JSP page directive --%><%@ page import="java.util.*,cwp.*" %><%@ page import="java.util.*,cwp.*" %>
<%-- JSP Declaration --%><%-- JSP Declaration --%><%!<%!private String randomID() {private String randomID() { int num = (int)(Math.random()*10000000.0);int num = (int)(Math.random()*10000000.0); return("id" + num);return("id" + num);}}private final String NO_VALUE = "<I>No Value</I>";private final String NO_VALUE = "<I>No Value</I>";%>%><%<%Cookie[] cookies = request.getCookies();Cookie[] cookies = request.getCookies();String oldID = String oldID = ServletUtilitiesServletUtilities.getCookieValue(cookies, "userID", .getCookieValue(cookies, "userID",
NO_VALUE);NO_VALUE);String newID;String newID;if (oldID.equals(NO_VALUE)) { newID = randomID();if (oldID.equals(NO_VALUE)) { newID = randomID();} else { newID = oldID; }} else { newID = oldID; }LongLivedCookie cookie = new LongLivedCookie("userID", newID);LongLivedCookie cookie = new LongLivedCookie("userID", newID);response.addCookie(cookie);response.addCookie(cookie);%>%><%-- JSP Expressions --%><%-- JSP Expressions --%>This page was accessed at <%= This page was accessed at <%= new Date()new Date() %> with a userID %> with a userIDcookie of <%= oldID %>.cookie of <%= oldID %>. </BODY></HTML></BODY></HTML>
Example of Example of import import AttributeAttribute
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Example of import Example of import AttributeAttribute
First accessFirst access
SubsequentSubsequentaccessesaccesses
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The contentType The contentType AttributeAttribute FormatFormat
– <%@ page contentType="MIME-Type" <%@ page contentType="MIME-Type" %>%>
– <%@ page contentType="MIME-Type;<%@ page contentType="MIME-Type; charset=Character-Set"%> charset=Character-Set"%>
PurposePurpose– Specify the MIME type of the page Specify the MIME type of the page
generated by the servlet that results generated by the servlet that results from the JSP pagefrom the JSP page
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First Last Email AddressFirst Last Email Address
Marty Hall [email protected] Hall [email protected]
Larry Brown [email protected] Brown [email protected]
Bill Gates [email protected] Gates [email protected]
Larry Ellison [email protected] Ellison [email protected]
<%@ page contentType="application/vnd.ms-excel" %><%@ page contentType="application/vnd.ms-excel" %>
<%-- There are tabs, not spaces, between columns. --%><%-- There are tabs, not spaces, between columns. --%>
Generating Generating Excel Excel SpreadsheetSpreadsheetss
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<%-- processOrder.jsp --%><%-- processOrder.jsp --%><%@ page errorPage="orderError.jsp" <%@ page errorPage="orderError.jsp" import="java.text.NumberFormat" %>import="java.text.NumberFormat" %><<h3h3>>Your order:Your order:</</h3h3>><% <% String numTees = request.getParameter("t-shirts");String numTees = request.getParameter("t-shirts"); String numHats = request.getParameter("hats");String numHats = request.getParameter("hats"); NumberFormat currency = NumberFormat currency =
NumberFormat.getCurrencyInstance();NumberFormat.getCurrencyInstance();%>%>Number of tees: Number of tees: <%= numTees %><%= numTees %><<brbr>>Your price: Your price: <%= <%=
currency.format(Integer.parseInt(numTees)*15.00) currency.format(Integer.parseInt(numTees)*15.00) %>%><<pp>>
Number of hats: Number of hats: <%= numHats %><%= numHats %><<brbr>>Your price: Your price: <%= <%=
currency.format(Integer.parseInt(numHats)*10.00) currency.format(Integer.parseInt(numHats)*10.00) %>%><<pp>>
<!--<!-- orderForm.htm orderForm.htm -->--><<h1h1>>Order FormOrder Form</</h1h1>>What would you like to purchase?What would you like to purchase?<<pp>><<formform name name==orders actionorders action==processOrder.jspprocessOrder.jsp>><<tabletable border border==00>> <<trtr><><thth>>ItemItem</</thth>> <<thth>>QuantityQuantity</</thth>> <<thth>>Unit PriceUnit Price</</thth>> <<trtr><><trtr>>……
Form Form ProcessinProcessingg
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JSP ActionsJSP Actions
There are There are sevenseven standard JSP actions. standard JSP actions.– Include, param, forward, plugin, Include, param, forward, plugin, ……– Include action is similar to include Include action is similar to include
directive.directive.– You can add additional parameters to the You can add additional parameters to the
existing request by using the param action.existing request by using the param action.– The plugin action inserts object and embed The plugin action inserts object and embed
tags (such as an applet) into the response tags (such as an applet) into the response to the client.to the client.
– In the coming slides, we will talk about In the coming slides, we will talk about ““includeinclude”” and and ““pluginplugin”” actions. actions.
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Including Pages at Including Pages at Request TimeRequest Time FormatFormat
– <jsp:include page="Relative URL" <jsp:include page="Relative URL" flush="true" flush="true" //>>
PurposePurpose– To reuse JSP, HTML, or plain text contentTo reuse JSP, HTML, or plain text content– JSP content cannot affect main page: JSP content cannot affect main page:
only output of included JSP page is usedonly output of included JSP page is used– To permit updates to the included To permit updates to the included
content without changing the main JSP content without changing the main JSP page(s)page(s)
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Including Pages: Example Including Pages: Example CodeCode
......<BODY><BODY><TABLE BORDER=5 ALIGN="CENTER"><TABLE BORDER=5 ALIGN="CENTER"> <TR><TH CLASS="TITLE"><TR><TH CLASS="TITLE"> What's New at JspNews.com</TABLE>What's New at JspNews.com</TABLE><P><P>Here is a summary of our three most recent news stories:Here is a summary of our three most recent news stories:<OL><OL> <LI><LI><jsp:include page="news/Item1.html" flush="true" /><jsp:include page="news/Item1.html" flush="true" /> <LI><LI><jsp:include page="news/Item2.html" flush="true" /><jsp:include page="news/Item2.html" flush="true" /> <LI><LI><jsp:include page="news/Item3.html" flush="true" /><jsp:include page="news/Item3.html" flush="true" /></OL></OL></BODY></HTML></BODY></HTML>
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Background: What Are Background: What Are Beans?Beans?
Classes that follow certain conventionsClasses that follow certain conventions– Must have a zero-argument (empty) constructorMust have a zero-argument (empty) constructor– Should have no public instance variables (fields)Should have no public instance variables (fields)– Persistent values should be accessed through Persistent values should be accessed through
methods called getXxx and setXxxmethods called getXxx and setXxx If class has method getTitle that returns a String, class If class has method getTitle that returns a String, class
is said to have a String property named titleis said to have a String property named title Boolean properties use isXxx instead of getXxxBoolean properties use isXxx instead of getXxx
For more on beans, see For more on beans, see http://java.sun.com/beans/docs/http://java.sun.com/beans/docs/
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Basic Bean Use in JSPBasic Bean Use in JSP
Format: Format: <jsp:useBean id="name" <jsp:useBean id="name"
class="package.Class" />class="package.Class" /> Purpose: Purpose: Allow instantiation of classes Allow instantiation of classes
without explicit Java syntaxwithout explicit Java syntax NotesNotes
– Simple interpretation: JSP actionSimple interpretation: JSP action<jsp:useBean id="book1" class="cwp.Book" /><jsp:useBean id="book1" class="cwp.Book" />
can be thought of as equivalent to the scriptletcan be thought of as equivalent to the scriptlet<% cwp.Book book1 = new cwp.Book(); %><% cwp.Book book1 = new cwp.Book(); %>
– But useBean has two additional featuresBut useBean has two additional features Simplifies setting fields based on incoming request Simplifies setting fields based on incoming request
paramsparams Makes it easier to share beansMakes it easier to share beans
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Accessing Bean Accessing Bean PropertiesProperties Format: Format: <jsp:getProperty <jsp:getProperty
name="name" name="name" property="property" />property="property" />
Purpose: Purpose: Allow access to bean Allow access to bean properties (i.e., calls to getXxx properties (i.e., calls to getXxx methods) without explicit Java codemethods) without explicit Java code
NotesNotes– <jsp:getProperty name="book1" property="title" /><jsp:getProperty name="book1" property="title" />
is equivalent to the following JSP is equivalent to the following JSP expressionexpression<%= book1.getTitle() %><%= book1.getTitle() %>
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Setting Bean Setting Bean Properties: Properties: Simple CaseSimple Case Format: Format: <jsp:setProperty <jsp:setProperty
name="name" name="name" property="property" value="value" /> property="property" value="value" />
PurposePurpose– Allow setting of bean properties (i.e., calls Allow setting of bean properties (i.e., calls
to setXxx) without explicit Java codeto setXxx) without explicit Java code NotesNotes
– <jsp:setProperty name="book1" <jsp:setProperty name="book1" property="title" property="title" value="Core Servlets and JSP" /> value="Core Servlets and JSP" />
is equivalent to the following scriptletis equivalent to the following scriptlet<% book1.setTitle("Core Servlets and JSP"); %><% book1.setTitle("Core Servlets and JSP"); %>
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Example: StringBeanExample: StringBean
publicpublic class StringBean { class StringBean { private String message = "No message private String message = "No message
specified";specified"; publicpublic String getMessage() { String getMessage() { return(message);return(message); }} publicpublic void setMessage(String message) { void setMessage(String message) { this.message = message;this.message = message; }}}}
Installed in normal servlet directoryInstalled in normal servlet directory
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<jsp:useBean id="stringBean" class="cwp.StringBean" /><jsp:useBean id="stringBean" class="cwp.StringBean" /><OL><OL><LI>Initial value (getProperty):<LI>Initial value (getProperty): <I><I><jsp:getProperty name="stringBean" <jsp:getProperty name="stringBean" property="message" />property="message" /></I></I><LI>Initial value (JSP expression):<LI>Initial value (JSP expression): <I><I><%= stringBean.getMessage() %><%= stringBean.getMessage() %></I></I><LI><LI><jsp:setProperty name="stringBean" <jsp:setProperty name="stringBean" property="message" property="message" value="Best string bean: Fortex" />value="Best string bean: Fortex" /> Value after setting property with setProperty:Value after setting property with setProperty: <I><I><jsp:getProperty name="stringBean" <jsp:getProperty name="stringBean" property="message" />property="message" /></I></I><LI><LI><% stringBean.setMessage("My favorite: Kentucky Wonder"); <% stringBean.setMessage("My favorite: Kentucky Wonder");
%>%> Value after setting property with scriptlet:Value after setting property with scriptlet: <I><I><%= stringBean.getMessage() %><%= stringBean.getMessage() %></I></I></OL></OL>
JSP Page JSP Page That Uses That Uses StringBeaStringBeann
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JSP Page That Uses JSP Page That Uses StringBeanStringBean
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Associating Bean Properties Associating Bean Properties with Request (Form) with Request (Form) ParametersParameters If property is a String, you can doIf property is a String, you can do
– <jsp:setProperty ... value=<jsp:setProperty ... value='<%= request.getParameter("...") '<%= request.getParameter("...") %>'%>' /> />
Scripting expressions let you convert types, but Scripting expressions let you convert types, but you have to use Java syntaxyou have to use Java syntax
The The paramparam attribute indicates that: attribute indicates that:– Value should come from specified request paramValue should come from specified request param– Simple automatic type conversion performedSimple automatic type conversion performed
Using "Using "**" for the property attribute indicates that:" for the property attribute indicates that:– Value should come from request parameter whose Value should come from request parameter whose
name matches property namename matches property name– Simple type conversion should be performedSimple type conversion should be performed
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Setting Bean Properties Setting Bean Properties Case 1:Case 1:Explicit Conversion & Explicit Conversion & AssignmentAssignment
<!DOCTYPE ...><!DOCTYPE ...>......<jsp:useBean id="entry" <jsp:useBean id="entry"
class="cwp.SaleEntry" /> class="cwp.SaleEntry" />
<%-- getItemID expects a String --%><%-- getItemID expects a String --%><jsp:setProperty <jsp:setProperty name="entry" name="entry" property="itemID"property="itemID" value='<%= request.getParameter("itemID") value='<%= request.getParameter("itemID")
%>'%>' /> />
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Setting Bean Properties Setting Bean Properties Case 1:Case 1:Explicit Conversion & Explicit Conversion & AssignmentAssignment<%<%
int numItemsOrdered = 1;int numItemsOrdered = 1;try {try { numItemsOrdered =numItemsOrdered = Integer.parseInt(request.getParameter("numItems"));Integer.parseInt(request.getParameter("numItems"));} catch(NumberFormatException nfe) {}} catch(NumberFormatException nfe) {}%>%><%-- getNumItems expects an int --%><%-- getNumItems expects an int --%><jsp:setProperty <jsp:setProperty name="entry" name="entry" property="numItems"property="numItems" value="<%= numItemsOrdered %>"value="<%= numItemsOrdered %>" /> />
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Setting Bean Properties Setting Bean Properties Case 1:Case 1:Explicit Conversion & Explicit Conversion & AssignmentAssignment
<% <% double discountCode = 1.0;double discountCode = 1.0;try {try { String discountString = String discountString = request.getParameter("discountCode");request.getParameter("discountCode"); discountCode = discountCode = Double.valueOf(discountString).doubleValue();Double.valueOf(discountString).doubleValue();} catch(NumberFormatException nfe) {}} catch(NumberFormatException nfe) {}%>%><%-- getDiscountCode expects a double --%><%-- getDiscountCode expects a double --%><jsp:setProperty <jsp:setProperty name="entry" name="entry" property="discountCode"property="discountCode" value="<%= discountCode %>"value="<%= discountCode %>" /> />
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Case 2: Associating Individual Case 2: Associating Individual Properties with Input Properties with Input ParametersParameters<jsp:useBean id="entry" <jsp:useBean id="entry"
class="cwp.SaleEntry" />class="cwp.SaleEntry" /><jsp:setProperty <jsp:setProperty name="entry"name="entry" property="itemID"property="itemID" param="itemID"param="itemID" /> /><jsp:setProperty <jsp:setProperty name="entry"name="entry" property="numItems"property="numItems" param="numItems"param="numItems" /> /><jsp:setProperty <jsp:setProperty name="entry"name="entry" property="discountCode"property="discountCode" param="discountCode"param="discountCode" /> />
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Case 3: Associating Case 3: Associating AllAll Properties with Input Properties with Input ParametersParameters
<jsp:useBean id="entry" <jsp:useBean id="entry" class="cwp.SaleEntry" />class="cwp.SaleEntry" /><jsp:setProperty name="entry" <jsp:setProperty name="entry" property="*"property="*" /> />
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Sharing BeansSharing Beans
You can use scope attribute to specify You can use scope attribute to specify where bean is storedwhere bean is stored– <jsp:useBean id="<jsp:useBean id="……" class="" class="……" "
scope="scope="……"" /> />– Bean still also bound to local variable in Bean still also bound to local variable in
_jspService _jspService Lets multiple servlets or JSP pages share Lets multiple servlets or JSP pages share
datadata Also permits conditional bean creationAlso permits conditional bean creation
– Create new object only if you can't find Create new object only if you can't find existing oneexisting one
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Values of the scope Values of the scope AttributeAttribute pagepage
– Default value. Bean object should be placed Default value. Bean object should be placed in the PageContext object for the duration of in the PageContext object for the duration of the current request. Lets methods in same the current request. Lets methods in same servlet access beanservlet access bean
applicationapplication– Bean will be stored in ServletContext Bean will be stored in ServletContext
(available through the application variable or (available through the application variable or by call to getServletContext()). ServletContext by call to getServletContext()). ServletContext is shared by all servlets in the same Web is shared by all servlets in the same Web application (or all servlets on server if no application (or all servlets on server if no explicit Web applications are defined).explicit Web applications are defined).
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Values of the scope Values of the scope AttributeAttribute sessionsession
– Bean will be stored in the HttpSession object Bean will be stored in the HttpSession object associated with the current request, where it associated with the current request, where it can be accessed from regular servlet code can be accessed from regular servlet code with getAttribute and setAttribute, as with with getAttribute and setAttribute, as with normal session objects.normal session objects.
requestrequest– Bean object should be placed in the Bean object should be placed in the
ServletRequest object for the duration of the ServletRequest object for the duration of the current request, where it is available by current request, where it is available by means of getAttributemeans of getAttribute