How to stop recursive composite component from including itself recursively

Question

Is it possible to have a JSF component that has ui:repeat and inside the repeat call the same component? It's because I'm building tree of question:

<cc:interface>
    <cc:attribute name="questions" required="true" />
    <cc:attribute name="renderQuestions" required="true" default="true" />
</cc:interface>

<cc:implementation>

    <c:if test="#{cc.attrs.renderQuestions}">
        <ui:repeat value="#{cc.attrs.questions}" var="q">
            <p:panelGrid columns="2">
                <h:outputLabel value="#{q.question}"></h:outputLabel>
                <p:selectBooleanButton onLabel="#{messages['commons.yes']}"
                    offLabel="#{messages['commons.no']}" onIcon="ui-icon-check"
                    offIcon="ui-icon-close" value="#{q.ok}">
                    <p:ajax update="@all"></p:ajax>
                </p:selectBooleanButton>
            </p:panelGrid>

            <cf:question renderQuestions="#{q.ok}" questions="#{q.children}" />

        </ui:repeat>
    </c:if>

</cc:implementation>

Currently I'm having stackoverflow?

Answer 1

Use a view build time tag to stop the recursion instead of a view render time tag. The component tree is built during view build time. The rendered attribute isn't evaluated during view build time, but instead during view render time. So your construct basically keeps including itself in an infinite loop. You should already know that StackOverflowError is caused by a recursion so deep that the memory stack can't handle it anymore (usually around ~1000 iterations).

Replace <h:panelGroup rendered> by a <c:if test> and it'll work as expected. The renderQuestions can by the way be simplified by omitting the check on children. The <ui:repeat> won't render anything anyway if there are no children.

If you happen to use view scoped beans in this construct and you're using Mojarra implementation, then make sure that you upgrade to at least 2.1.18, because binding a view build time tag attribute to a view scoped bean property would in older versions break the view scope.

See also:

• JSTL in JSF2 Facelets... makes sense? - explains "view build time" versus "view render time"

Answer 2

Based on the answer of BalusC I created a solution like this.

<composite:interface>
    [..]
    <composite:attribute name="level" required="true" default="0"/>
</composite:interface>
<composite:implementation>

        <c:if test="#{cc.attrs.level == 0}">
            <a4j:repeat value="#{cc.attrs.list}" var="subList" rendered="#{cc.attrs.list != null}">

                    <xx:recursiveComponent list="#{subList}" id="subComponent" level="1"/>

            </a4j:repeat>   
        </c:if>

</composite:implementation>

The level attribute is used at build time to avoid endless recursion and the renered attribute of the a4j:repeat (or ui:repeat in your case) will be evaluated at render time.