javax.el.PropertyNotFoundException : Target Unreachable, identifier 'comp' resolved to null

We got a requirement in our project to add a panel with some configuration (like header, collapsed) dynamically using prime faces 5.0. We went ahead with bellow code to implement this.

Implementation with problem

	<p:panel header="#{comp.name}" toggleable="true" closable="true" toggleSpeed="500" closeSpeed="500" collapsed="#{comp.collapsed}">
	<p:outputLabel value="#{comp.component.description}" escape="false" />
	</p:panel>

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Property Not Found Exception

As soon as we wrote this code it started giving us javax.el.PropertyNotFoundException: index.xhtml @33,55 collapsed="#{comp.collapsed}": Target Unreachable, identifier 'comp' resolved to null.

Exception Trace

	javax.el.PropertyNotFoundException: /index.xhtml @33,55 collapsed="#{comp.collapsed}": Target Unreachable, identifier 'comp' resolved to null
	at com.sun.faces.facelets.el.TagValueExpression.isReadOnly(TagValueExpression.java:122)
	at org.primefaces.component.panel.Panel.processUpdates(Panel.java:301)
	....
	....
	Caused by: javax.el.PropertyNotFoundException: Target Unreachable, identifier 'comp' resolved to null
	at com.sun.el.parser.AstValue.getTarget(AstValue.java:131)
	at com.sun.el.parser.AstValue.isReadOnly(AstValue.java:170)
	at com.sun.el.ValueExpressionImpl.isReadOnly(ValueExpressionImpl.java:261)
	at com.sun.faces.facelets.el.TagValueExpression.isReadOnly(TagValueExpression.java:120)
	... 47 more

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Solution

After couple of investigation using Google and Forums, there is no luck to find proper solution for this problem. Another surprising piece in this code is #{comp.name} resolves properly in the header section. As we could not find any solution I went ahead and wrote an hack to solve this problem.

Implementation with hack using JSTL

	<c:set var="collapsedComp" value="false" />
	<c:if test="#{comp.collapsed}">
	<c:set var="collapsedComp" value="true" />
	</c:if>
	<p:panel header="#{comp.name}" toggleable="true" closable="true" toggleSpeed="500" closeSpeed="500" collapsed="#{collapsedComp}">
	<p:outputLabel value="#{comp.component.description}" escape="false" />
	</p:panel>

view raw solution.xhtml hosted with ❤ by GitHub

This solution is a hack using JSTL, once I come up with proper solution will write back.