Introduction
I encountered a situation the other day where I need to include a JSF page based on a parameter passed in via a<f:viewParam>. This seems like a very reasonable kind of idea. I expected to be able to make the <ui:include/> use a dynamically set src parameter using EL from the <f:viewParam>. This is where I went wrong (the idea was good...). The <ui:include/> is a tag handler. It is evaluated on Restore View Phase. The value processing does not take place until the Apply Request Values Phase. This presents a problem since the EL binding for my <ui:include/> is based on the <f:viewParam> which is a UIInput object. So we are out of phase. The page will display the results, but all the AJAX will not work.
A Solution
A solution to the problem involves using static<ui:include/> elements wrapped in <ui:fragment/> elements. This allows the tag handler to resolve the page to include, and then the fragment determines (via late binding) whether to display the page based on the <f:viewParam> passed. The page is supported by a @ViewScoped bean to keep the page in scope.
Code
Here is an example of how to do it.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | <?xml version='1.0' encoding='UTF-8' ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> > <h:head> <title>Index</title> <f:metadata> <f:viewParam name="page" value="#{index.page}"/> </f:metadata> </h:head> <h:body> <p>These examples use static binding on the <ui:include/> and use the the <ui:fragment/> <code>rendered</code> attribute to determine which page to display. Since these elements are evaluated after the component tree is restored, the AJAX will work. </p><ui:fragment rendered="#{index.page eq 'page1'}"> <ui:include src="page1.xhtml"/> </ui:fragment> <ui:fragment rendered="#{index.page eq 'page2'}"> <ui:include src="page2.xhtml"/> </ui:fragment> <h:button id="button1" value="Page 1" outcome="good.xhtml?page=page1" includeViewParams="true"/> <h:button id="button2" value="Page 2" outcome="good.xhtml?page=page2" includeViewParams="true"/> <h:button outcome="index" value="Home"/> </h:body></html> |
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