resin Resin 3.0

JSP EL is a simple expression language for accessing data.
  • 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:

    <%@ 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 (c) 1998-2009 Caucho Technology, Inc. All rights reserved.
    caucho® , resin® and quercus® are registered trademarks of Caucho Technology, Inc.

    • EL Variables come from one of two places:

    1. implicit variable
    pageContext
    pageScope
    requestScope
    sessionScope
    applicationScope
    param
    paramValues
    header
    headerValues
    cookie
    initParam
    Copyright (c) 1998-2009 Caucho Technology, Inc. All rights reserved.
    caucho® , resin® and quercus® are registered trademarks of Caucho Technology, Inc.