Hi,
I have a tree with nodeSelectListener like

public void processCurrentSelection(NodeSelectedEvent event){
}

and inside the listener, I am trying to add a request parameter value,so that I can change the contents on one of my view,where selection is done like this using facelets

<ui:composition>
 <c:if test='${param.stage=="one"}'>
 <ui:include src="one-pagejspx"/>
 </c:if>
 <c:if test='${param.stage=="two"}'>
 <ui:include src="two-page.jspx"/>
 </c:if>
 <c:otherwise>
 <ui:include src="default.jspx"/>
 </c:otherwise>
 </ui:composition>

Based upon the type of currently selected node,in the listener I added values to the requestParameter map,like
FaceContext.getCurrentInstance().getExtrenalContext.getRequestParamaterMap.put("stage","one");

But I am getting the following error.

com.sun.faces.lifecycle.UpdateModelValuesPhase execute java.lang.UnsupportedOperationException

Please let me know how can I update the parameter value before it reaches the rendering part for the facelets.

Thanks