I have the following composite component:

<?xml version="1.0" encoding="UTF-8"?>
<ui:component xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:c="http://java.sun.com/jsp/jstl/core"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.org/ui"
    xmlns:fn="http://java.sun.com/jsp/jstl/functions"
    xmlns:composite="http://java.sun.com/jsf/composite">

    <composite:interface>
        <composite:attribute required="true" name="field" />
        <composite:attribute required="true" name="value" />
        <composite:attribute required="false" name="size"/>
    </composite:interface>

    <composite:implementation>
    ...
            <div class="wrapper">
                <h:inputText value="#{cc.attrs.value}"
                    id="#{field.id}" 
                    rendered="#{field.rendered}" 
                    size="#{cc.attrs.size}">
                </h:inputText>
                <h:messages for="#{field.id}" styleClass="errorMessage"/>
            </div>
    ...
    </composite:implementation>
</ui:component>

The problem is that when I'm using this component without setting its size attribute, it still gets rendered as size=0 in the html input element.

What I want is to render the nested h:inputText's attribute only if it has a valid value (eg. not empty). Alternatively, I'd like to expose all attributes of the nested element if they are not overridden explicitly.

How would it be possible?

You can use JSTL <c:if> to build the view conditionally and <f:attribute> to specify an attribute separately:

<h:inputText ...>
    <c:if test="#{not empty cc.attrs.size}">
        <f:attribute name="size" value="#{cc.attrs.size}" />
    </c:if>
</h:inputText>

An alternative is to specify a default for the composite component attribute:

<cc:attribute name="size" required="false" default="10" />

Additional to BalusC's post:

You must use

type="int" in the cc:attribute-tag :

cc:attribute name="maxlength" type="int"

I believe there is an alternate method for accessing attributes. I've used this with JSF 2 when accessing an attribute named with a java reserved keyword.

{cc.attrs['size']}

来源：https://stackoverflow.com/questions/12897202/conditionally-render-elements-attribute-in-a-composite-component

标签

jsf

composite-component

Conditionally render element's attribute in a composite component

{cc.attrs['size']}