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 Resin Server | Application Server (Java EE Certified) and Web Server

jsp el

JSP EL is a simple expression language for accessing data.

JSP EL variables

EL Variables come from one of two places:

  1. implicit variable
  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}">
b is TRUE


Here is an example that shows this a bit more:

Making values available as JSP EL variables
<%@ taglib prefix="c" uri="" %>
  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
<c:if test="${'${'}a}">
a is TRUE

<c:if test="${'${'}b}">
b is TRUE

<%-- this is false because 'c' was set to false --%>
<c:if test="${'${'}c}">
c is TRUE

  This is false because 'param' is an implicit variable
  which is used instead of pageContext.findAttribute("param")
<c:if test="${'${'}param}">
param is TRUE
b is TRUE

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