JSP Tutorials - Herong's Tutorial Examples - v5.11, by Herong Yang
c:out Action Tag with EL Expressions
This section provides a tutorial example of using EL expressions in the c:out JSTL Core tag.
The <c:out> action tag is probably the best tag to show how EL (Expression Language) expression can be used in JSTL tags. Here is a JSP page example, ExpExampleTag.jspx:
<?xml version="1.0"?> <jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" xmlns:c="http://java.sun.com/jsp/jstl/core" version="2.3"> <!-- ExpExampleTag.jspx - Copyright (c) 2006 HerongYang.com. All Rights Reserved. --> <jsp:directive.page contentType="text/html"/> <html><body> <p>JSTL EL Expression Examples:</p> <c:out value="1. ${1+1==2}"/><br/> <c:out value="2. ${1+1}"/><br/> <c:out value="3. ${1/3}"/><br/> <c:out value="4. ${1.0/3.0}"/><br/> <c:out value="5. ${quantity*price lt 100.0 and country=='USA'}"/><br/> <c:set var="message" value="Hi there!"/> <c:out value="6. ${message}"/><br/> <c:out value="7. ${'message'}"/><br/> <c:out value="10. ${pageContext.request.method}"/><br/> <c:out value="11. ${pageContext.request[method]}"/><br/> <c:out value="12. ${pageContext.request['method']}"/><br/> <!-- c:out value="13. ${pageContext.request.'method'}"/><br/ --> <!-- c:out value="14. ${pageContext.'request'.method}"/><br/ --> <c:out value="15. ${pageContext['request']['method']}"/><br/> <c:out value="16. ${pageContext['request'].method}"/><br/> <!-- c:out value="20. ${pageContext.request.cookies.length}"/><br/ --> <c:out value="21. ${pageContext.request.cookies[0].name}"/><br/> <c:out value="22. ${pageContext.request.cookies[0].value}"/><br/> <c:out value="23. ${pageContext.request.cookies[0]}"/><br/> <!-- c:out value="24. ${pageContext.request.cookies.0}"/><br/ --> <!-- c:out value="25. ${pageContext.request.cookies.0.name}"/><br/ --> <c:out value="26. ${pageContext.request.cookies['0']}"/><br/> <jsp:scriptlet>double pi = 3.14159;</jsp:scriptlet> <c:out value="30. ${pi}"/><br/> <jsp:scriptlet> double[] list = new double[3]; list[0] = 9.99; </jsp:scriptlet> <c:out value="31. ${list[0]}"/><br/> <!-- c:out value="32. ${pageContext.request.class.name}"/><br/ --> <!-- c:out value="33. ${pageContext[request[class[name]]]}"/><br/ --> <!-- c:out value="34. ${out.class.name}"/><br/ --> <!-- c:out value="35. ${pageContext.out.class.name}"/><br/ --> <c:out value="36. ${sessionScope.now}"/><br/> <jsp:scriptlet> session.setAttribute("now", new java.util.Date()); </jsp:scriptlet> <c:out value="37. ${sessionScope.now.time}"/><br/> </body></html> </jsp:root>
Note that:
If you visit the ExpExampleTag.jspx page for the first time, you will get:
JSTL EL Expression Examples: 1. true 2. 2 3. 0.3333333333333333 4. 0.3333333333333333 5. false 6. Hi there! 7. message 10. GET 11. 12. GET 15. GET 16. GET 21. 22. 23. 26. 30. 31. 36. 37. 1353078652164
If you visit the ExpExampleTag.jspx page again, you will get:
JSTL EL Expression Examples: 1. true 2. 2 3. 0.3333333333333333 4. 0.3333333333333333 5. false 6. Hi there! 7. message 10. GET 11. 12. GET 15. GET 16. GET 21. JSESSIONID 22. 669C0B7624702AF8209AF2B672ED9BFA 23. javax.servlet.http.Cookie@4c2b5e 26. javax.servlet.http.Cookie@4c2b5e 30. 31. 36. Sun Jul 1 10:10:52 EST 2012 37. 1152816698019
Note that:
Table of Contents
JSP (JavaServer Pages) Overview
Tomcat Installation on Windows Systems
Syntax of JSP Pages and JSP Documents
JavaBean Objects and "useBean" Action Elements
Managing HTTP Response Header Lines
Non-ASCII Characters Support in JSP Pages
Overview of JSTL (JSP Standard Tag Libraries)
►c:out Action Tag with EL Expressions
Example - Dumping EL Implicit Objects
Example - Calculating Prime Numbers
Multiple Tags Working Together
Using Tomcat on CentOS Systems
Connecting to SQL Server from Servlet