JSP EL is a simple expression language for accessing data.

JSP EL variables

EL Variables come from one of two places:

1. implicit variable

   pageContext
   pageScope
   requestScope
   sessionScope
   applicationScope
   param
   paramValues
   header
   headerValues
   cookie
   initParam

2. pageContext.findAttribute(varname)

   which is like getting the first of:

   • page.getAttribute(varname)
   • request.getAttribute(varname)
   • session.getAttribute(varname)
   • application.getAttribute(varname)

So if you have a variable like:

<% boolean a = true; %>

you have to store it as an attribute to make it available as an EL variable:

<% boolean b = true; pageContext.setAttribute("b",new Boolean(b)); %> <c:if test=""> b is TRUE </c:if>

Here is an example that shows this a bit more:

Making values available as JSP EL variables

<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <% boolean a = true; boolean b = true; pageContext.setAttribute("b",new Boolean(b)); boolean c = false; pageContext.setAttribute("c",new Boolean(c)); boolean param = true; pageContext.setAttribute("param",new Boolean(param)); %> <%-- this is false because 'a' is not findable by pageContext.findAttribute(varname) --%> <c:if test="${a}"> a is TRUE </c:if> <c:if test="${b}"> b is TRUE </c:if> <%-- this is false because 'c' was set to false --%> <c:if test="${c}"> c is TRUE </c:if> <%-- This is false because 'param' is an implicit variable which is used instead of pageContext.findAttribute("param") --%> <c:if test="${param}"> param is TRUE </c:if>

b is TRUE

Copyright © 1998-2005 Caucho Technology, Inc. All rights reserved. Resin® is a registered trademark, and HardCoretm and Quercustm are trademarks of Caucho Technology, Inc.