DaBlick February 2016

Why are validations from my JSF composite facet being done when the facet is not rendered

I have a problem that validations from a composite's facet are being fired even when I do not render the composite.

I stripped the problem down to the following barebones code.

Here is the composite entityDetailPanel:

<ui:composition xmlns="http://www.w3.org/1999/xhtml"

    <composite:attribute name="prefix" required="true" />
    <composite:facet name="lowerPanel"/>


    <h:form id="#{cc.attrs.prefix}entityDetailForm2" 
            styleClass="#{cc.attrs.prefix}EntityDetailPanelForm #{cc.attrs.prefix}Listener" >

        <p:messages id="#{cc.attrs.prefix}messages" autoUpdate="true" closable="true"/>

            update="@(.#{cc.attrs.prefix}Listener), @(.#{cc.attrs.prefix}EntityDetailPanelForm}"/>

        <composite:renderFacet name="lowerPanel" rendered="false"/>


And here is the invocation:

<?xml version="1.0" encoding="UTF-8"?>
<ui:composition xmlns="http://www.w3.org/1999/xhtml"

    <common:entityDetailPanel id="foo" prefix="Instruments">

        <f:facet name="lowerPanel">
            <!--  <p:inputText id="assetClassPrompt" required="true"  requiredMessage="Why do we get this message?"        


BalusC February 2016

This problem is two-fold.

First, the <cc:renderFacet> is never designed to work this way. It does not support the rendered attribute. That it somehow works is because the facet is internally re-interpreted as an UIPanel component and all attributes are (incorrectly) automatically inherited from the tag. You should not rely on that. The rendered attribute is incorrectly considered during render response, causing confusing behavior that it "works". This is technically a bug in the JSF implementation. The attributes are (correctly) not inherited during the postback, causing the trouble you observed. The components are still decoded and validated "in spite of" that they are not rendered.

Second, the <p:inputText> extends from UIInput which checks before validation if there's any submitted value. A submitted value of null is interpreted as complete absence of the input field in the form, so it's skipped. A submitted value of an empty string is interpeted as an empty value, so it's validated. The <p:selectOneMenu>, however, has overriden the standard UIInput behavior and considers null the same way as an empty string. Even when the submitted value is null (which means that the input field wasn't in the form at all), it's still being validated. This is technically a bug in PrimeFaces side.

Your intent is at least clear: conditionally render a facet. The <cc:xxx> tags are evaluated during Facelets compile time (which is a step before view build time), so conditionally building the <cc:renderFacet> using JSTL <c:if> will also not ever work.

Your best bet is redefining "render lower

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Asked in February 2016
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