动态 ui:include 和 ui:fragment: 渲染为 false 的组件仍然在组件树内部

Question

I am force to use a very old version of MyFaces 2.0.5 I think, and dynamic include with EL cause so much problem, so I switch to static include with ui:fragment

<ui:fragment rendered="#{filtersPopup.filterFileName == 'checkBoxFilters'}">
    checkBoxFilters
    <ui:include src="/analytics/checkBoxFilters.xhtml" rendered="#{filtersPopup.filter != null}"/>
</ui:fragment>
<ui:fragment rendered="#{filtersPopup.filterFileName == 'DateRelativeFilter'}">
    DateRelativeFilter
    <ui:include src="/analytics/DateRelativeFilter.xhtml" rendered="#{filtersPopup.filter != null}"/>
</ui:fragment>
<ui:fragment rendered="#{filtersPopup.filterFileName == 'listboxFilter'}">
    listboxFilter
    <ui:include src="/analytics/listboxFilter.xhtml" rendered="#{filtersPopup.filter != null}"/>
</ui:fragment>

With this, it still complain about duplicate id because I use same id on couples of these source file. So it seems that even rendered should be false , it still make it to the component tree. However duplicate id is fine. I can fix that easy, so now when I submit form, I got this exception

 /analytics/checkBoxFilters.xhtml at line 24 and column 118 value="#{filtersPopup.filter.groups}": Property 'groups' not found on type ListBoxFilter

so as you can see from the exception, it ListBoxFilter is the object I want, so only include ListBoxFilter.xhtml, but is being accessed checkBoxFilters.xhtml hence the error. Any idea how to fix this issue please?

Answer 1

The <ui:include> doesn't extend from UIComponent . It's a tag handler. It does thus not support the rendered attribute at all. It's also nowhere listed in the tag documentation .

<ui:fragment> is indeed an UIComponent . So basically you end up with all those 3 include files being included during view build time and thus all 3 physically end up in JSF component tree. It's only the HTML output which is conditionally rendered via <ui:fragment rendered> . You still end up with duplicate component IDs from those includes because they all end up in JSF component tree.

You should be using a taghandler like <c:if> instead of <ui:fragment> to conditionally build the JSF component tree.

So, theoretically, this should do for each of them:

<c:if test="#{filtersPopup.filterFileName == 'checkBoxFilters'}">
    checkBoxFilters
    <c:if test="#{filtersPopup.filter != null}">
        <ui:include src="/analytics/checkBoxFilters.xhtml" />
    </c:if>
</c:if>

... etc

This has however some caveats when #{filtersPopup} is a view scoped bean and/or when you're using <f:viewParam> :

1. This requires minimum Mojarra 2.1.18, otherwise JSF view scoped beans will fail to restore.

2. Taghandlers run during view build time. So things which runs thereafter like <f:viewParam> won't work at all. You'd need to fall back to manually grabbing HTTP request parameters via ExternalContext .

See also:

• JSTL in JSF2 Facelets... makes sense?