Passing EL method expression as attribute of custom Facelets tagfile

Question

I created a custom JSF tag:

Answer 1

My questions are: is this the best way to do this?

That's the only way anyway, provided that you can only use standard JSF/EL facilities and you cannot create a custom taghandler.

You could however create a custom taghandler to convert the value expression to a method expression. The OmniFaces JSF utility library has a <o:methodParam> for exactly this purpose. See also the <o:methodParam> demo page.

You could then end up like:

<my:dataScroller ... scrollListener="#{bean.aMethod}" />

and

<o:methodParam name="scrollListenerMethod" value="#{scrollListener}" />
<rich:dataScroller ... scrollListener="#{scrollListenerMethod}" />

See also:

• Dynamic ui include and commandButton

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How can I make the method optional?

Theoretically, you could use JSTL tags to build the view conditionally. Something like:

<h:someComponent>
    <c:if test="#{not empty fooAttribute}">
        <f:attribute name="foo" value="#{fooAttriubte}" />
    </c:if>
</h:someComponent>

But that's in the particular case of a special method expression listener attribute unfortunately not possible. There's no such thing as <rich:scrollListener> or something which allows you binding a RichFaces specific scrollListener as a separate tag to the <rich:dataScroller>. Best what you could do without creating custom taghandlers is duplicating the whole <rich:dataScroller> in two <c:if>s (or a <c:choose>); one with and other without scrollListener. This is too clumsy. You'd really better create a custom <my:richScrollListener> taghandler for this which you could then place in a <c:if>.