JSF Expression Language: scope for expression language syntax

[Tim Wise]

Hi all,

I have a simple question: what is the scope where I can use JSF EL?

The point is that I need to use a value from a backing bean in the JSTL tag even before I use <f:view>. Here is an example:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>

<c:set var="title" value='Details for "#{detailsController.entity.name}"'/>
<%@ include file="/header.jsp" %> <%-- header.jsp uses ${title} to set HTML page title --%>
<f:view>
    <h:form>
    <%-- uses detailsController to populate form with data, etc. --%>
...

But surely it doesn't work. It results to exactly "Details for "#{detailsController.entity.name}"" in page title, #{} syntax doesn't work there. I've tried to envelope the <c:set ...> with <f:view>...</f:view> but it didn't work either. So, the question is why? Should the syntax #{} work only in some specific context?

[Shasi Mitra]

Any jsf tag/EL has to be used inside <f:view> only.

[Tim Holloway]

You'd be better off using Facelets. It does a very civilized approach to page tiling and you don't need JSTL or other kludges.

[Tim Wise]

Thanks for your answers. Actually I finally found why it didn't work. I've been using a JST 1.1.2 which doesn't use the unified EL. Now I'm using JSTL 1.2, and my backing bean gets invoked, but I still don't get the desired result. The value from a backing bean property is not actually used. Given my previous example:

<c:set var="title" value="Details for '#{detailsController.entity.name}'"/>

the value "Details for ''" is set to "title" variable. Getters getEntity() and getName() are invoked and return correct value (I've checked this in debugger).

I assume this behavior may be caused by the declaration of "value" attribute for <c:set ...> tag:

<attribute>
  <description>Expression to be evaluated.</description>
  <name>value</name>
  <required>false</required>
  <rtexprvalue>true</rtexprvalue>
  <deferred-value>
    <type>java.lang.Object</type>
  </deferred-value>
</attribute>

As seen here, the deferred value has Object type. Could it be the reason of this behavior? How could I overcome this and finally get my String value returned from a backing bean used in the <c:set ...> correctly? Or, if it is not the reason, why doesn't it work now?

Many thanks for your help and any ideas.

P.S. Tim, I already consider using Facelets indeed, thanks for hint

[Tim Wise]

Well, so as to close the topic... I've found what was wrong: it occurs that only ${} syntax should be used if the attribute is declared as rtexprvalue=true, which is the case for c:set's value attribute. So, finally, this works fine with JSTL 1.2 unified EL:

<c:set var="title" value="Details for '${detailsController.entity.name}'"/>

BTW, it even can be used outside of the <f:view>...