Not all uses of jstl's fn: function produce an exception. For exemple: | #{fn:length(testFromType)} | works fine. But I get the same exception with | <s:button id="done" | value="Done" | view="/TestList.xhtml" | > | <f:param name="lengthTest" | value="#{fn:length(testFromType)}"/> | </s:button> | and only when I change of tab in a rich:tabPanel (but not when the page is loaded) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4052355#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...