JSF 2 - How can I add an Ajax listener method to composite component interface?

If you can get rid of the AjaxBehaviorEvent argument,

public void genericAjaxEventLogger() {    // ...}

then you can use

<cc:attribute name="ajaxEventListener" method-signature="void listener()" />

If the argument is mandatory (for logging?), then you need to re-specify the attribute as follows

<cc:attribute name="ajaxEventListener" method-signature="void listener(javax.faces.event.AjaxBehaviorEvent)" />

However, this does here not work as expected with

<f:ajax listener="#{cc.attrs.ajaxEventListener}" />

on GF 3.1 + Mojarra 2.1.1:

SEVERE: javax.faces.FacesException: wrong number of arguments    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:89)    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:409)    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1534)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:326)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:227)    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:170)    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:822)    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:719)    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1013)    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)    at java.lang.Thread.run(Unknown Source)Caused by: java.lang.IllegalArgumentException: wrong number of arguments    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)    at java.lang.reflect.Method.invoke(Unknown Source)    at com.sun.el.parser.AstValue.invoke(AstValue.java:234)    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297)    at com.sun.faces.facelets.el.ContextualCompositeMethodExpression.invoke(ContextualCompositeMethodExpression.java:177)    at com.sun.faces.facelets.tag.TagAttributeImpl$AttributeLookupMethodExpression.invoke(TagAttributeImpl.java:450)    at com.sun.faces.facelets.tag.jsf.core.AjaxBehaviorListenerImpl.processAjaxBehavior(AjaxHandler.java:447)    at javax.faces.event.AjaxBehaviorEvent.processListener(AjaxBehaviorEvent.java:113)    at javax.faces.component.behavior.BehaviorBase.broadcast(BehaviorBase.java:102)    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:760)    at javax.faces.component.UICommand.broadcast(UICommand.java:300)    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)    ... 28 more

I'm not sure if this is a bug or not. For that I'd need to invest some more time to naildown it. However, it was workaroundable by creating a backing component which gets the MethodExpression from the attributes and invokes with the right number of arguments. Here's a complete kickoff example:

<ui:component     xmlns:f="http://java.sun.com/jsf/core"    xmlns:h="http://java.sun.com/jsf/html"    xmlns:cc="http://java.sun.com/jsf/composite"    xmlns:ui="http://java.sun.com/jsf/facelets">    <cc:interface componentType="testCC">        <cc:attribute name="ajaxEventListener" method-signature="void listener(javax.faces.event.AjaxBehaviorEvent)" />    </cc:interface>    <cc:implementation>        <h:commandButton value="Submit">            <f:ajax listener="#{cc.ajaxEventListener}" />        </h:commandButton>    </cc:implementation></ui:component>

with

package com.example;import javax.el.MethodExpression;import javax.faces.component.FacesComponent;import javax.faces.component.UINamingContainer;import javax.faces.context.FacesContext;import javax.faces.event.AjaxBehaviorEvent;@FacesComponent(value="testCC")public class TestCC extends UINamingContainer {    public void ajaxEventListener(AjaxBehaviorEvent event) {        FacesContext context = FacesContext.getCurrentInstance();        MethodExpression ajaxEventListener = (MethodExpression) getAttributes().get("ajaxEventListener");        ajaxEventListener.invoke(context.getELContext(), new Object[] { event });    }}

Regardless, I believe that the backing component puts doors open for new ways to achieve the functional requirement you have had in mind anyway ;)

Here is an example on how to use the interface to set an attribute and reference it within the implementation. You must define the method-signature of the method that will be called. This informs the composite component handler that there is a method value, rather than a value expression, contained in the #{cc.attrs.ajaxEventListener} expression.

<cc:interface name="composite-comp"    <cc:attribute required="true" name="ajaxEventListener"                   method-signature="void f1(javax.faces.event.AjaxBehaviorEvent)" />    <cc:attribute required="true" name="ajaxRenderTargets" /></cc:interface><cc:implementation>    .    .    .    <f:ajax event="valueChange" execute="@this"        listener="#{cc.attrs.ajaxEventListener}"        render="#{cc.attrs.ajaxRenderTargets}" /></cc:implementation>