JSP Tutorials - Herong's Tutorial Examples - Version 4.03, by Dr. Herong Yang
EL Variables Are pageContext Attributes
This section provides a tutorial example to prove that EL variables are 'pageContext' attributes.
Based the rules and the examples in the previous sections, we can easily conclude that:
Here is an example JSP page to show you that you can mix variables and pageContext attributes any way you want:
<?xml version="1.0"?> <jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" xmlns:c="http://java.sun.com/jsp/jstl/core" version="2.1"> <!-- ExpVariable.jspx - Copyright (c) 2012, HerongYang.com, All Rights Reserved. --> <jsp:directive.page contentType="text/html"/> <html><body> <c:set var="message" value="Hi there!"/> 1. ${message}<br/> 2. <jsp:expression>pageContext.findAttribute("message") </jsp:expression><br/> <jsp:scriptlet><![CDATA[ String s = "Hello world!"; pageContext.setAttribute("hello", s, PageContext.PAGE_SCOPE); ]]></jsp:scriptlet> 3. ${hello}<br/> <jsp:useBean id="today" class="java.util.Date"/> 4. ${today}<br/> <jsp:scriptlet><![CDATA[ java.util.Date d = new java.util.Date(); d.setTime(d.getTime()+24*60*60*1000); pageContext.setAttribute("tomorrow", d, PageContext.PAGE_SCOPE); ]]></jsp:scriptlet> 5. ${tomorrow}<br/> <jsp:setProperty name="today" property="time" value="1000000000000"/> 6. ${today}<br/> 7. ${today.time}<br/> </body></html> </jsp:root>
Here is the output this page:
1. Hi there! 2. Hi there! 3. Hello world! 4. Sun Jul 01 13:20:19 EST 2012 5. Mon Jul 02 13:20:19 EST 2012 6. Sat Sep 08 21:46:40 EDT 2001 7. 1000000000000
Note that:
Exercise: Since there many methods to add an attribute to pageContext, useBean, c:set, and pageContext.setAttribute, write a simple program to show what happens if the same attribute name is used by different methods.
Last update: 2012.
Table of Contents
JSP (JavaServer Pages) Overview
Tomcat 7 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
What is EL (Expression Language)?
Literal Data and Named Variables
Basic Operators and Operations
Collection Elements and Object Properties
Expression Examples in Static Text
Expression Examples in Static Text - Result
►EL Variables Are pageContext Attributes
Overview of JSTL (JSP Standard Tag Libraries)