JSF Ajax addClientBehavior gives null.pointer.exception - ajax

Question

I'm trying to add programatically an Ajax client behavior to a custom component but when I do I get a null.pointer.exception (as an Alert in the browser no error in the logs), if I add the behavior in the .xhtml it works fine but I really need to add them programatically (actually the component is going to be rendered dinamically from a top component (dashboard -> N columns -> N widgets per column all from a Database)
I have tested this creating a simple DataList component
Here is the relevant code...
DataListRenderer
#Override
public void encodeEnd(FacesContext context, UIComponent component) throws IOException{
DataList datalist = (DataList)component;
ResponseWriter writer = context.getResponseWriter();
.. bunch of rendering options....
// If sortable then we add the sortable script.
// This basically ends up generating a call to jsf.ajax.request(source,event,params);
if (sortable != null && sortable.equalsIgnoreCase("true")) {
ScriptUtils.startScript(writer, clientId);
writer.write("$(function() {");
writer.write("$(EasyFaces.escapeId('" + clientId + "')).sortable({");
writer.write("update: function (event, ui) { ");
writer.write(new AjaxRequest().addEvent(StringUtils.addSingleQuotes("update"))
.addExecute(StringUtils.addSingleQuotes(datalist.getClientId()))
.addSource(StringUtils.addSingleQuotes(datalist.getClientId()))
.addOther("sourceId", "ui.item.attr('id')")
.addOther("dataValue", "ui.item.attr('data-value')")
.addOther("dropedPosition", "ui.item.index()")
.getAjaxCall());
writer.write(" } ");
encodeClientBehaviors(context, datalist);
writer.write("});");
writer.write("});");
ScriptUtils.endScript(writer);
}
// This is where I add the behavior
AjaxBehavior ajaxBehavior = (AjaxBehavior) FacesContext.getCurrentInstance().getApplication().createBehavior(AjaxBehavior.BEHAVIOR_ID);
ajaxBehavior.setRender(Arrays.asList("#form"));
ajaxBehavior.setExecute(Arrays.asList("#form"));
MethodExpression listener = FacesContext.getCurrentInstance().getApplication()
.getExpressionFactory().createMethodExpression(context.getELContext(),"#{dataListManager.updateModel}", null,
new Class[] { AjaxBehaviorEvent.class });
ajaxBehavior.addAjaxBehaviorListener(new AjaxBehaviorListenerImpl(listener));
datalist.addClientBehavior(datalist.getDefaultEventName(), ajaxBehavior);
}
... rest of the code
Now the .xhtml is as follows:
...
h:form>
<et:dataList id="dl" value="#{easyfacesBean.data}" itemValue="foo" var="xx" sortable="true">
<h:outputText id="txt" value="#{xx}" />
</et:dataList>
</h:form>
...
This renders the code Ok, the list actually can be ordered but when re-ordered it gives me the null.pointer.exception error
This is what comes back from the server:
<?xml version='1.0' encoding='UTF-8'?>
<partial-response><error><error-name>class java.lang.NullPointerException</error-name><error-message><![CDATA[]]></error-message></error></partial-response>
Now, If I comment this line
datalist.addClientBehavior(datalist.getDefaultEventName(), ajaxBehavior);
And simply add the tag like so:
<h:form>
<et:dataList id="dl" value="#{easyfacesBean.data}" itemValue="foo" var="xx" sortable="true">
<f:ajax />
<h:outputText id="txt" value="#{xx}" />
</et:dataList>
</h:form>
Everything works fine.. any ideas? I would settle for a way to actually know where the null.point.exception is ..
BTW if I don't comment the line that actually add's the behavior and add the < f:ajax > tag the error changes to java.lang.IndexOutOfBoundsException
<?xml version='1.0' encoding='UTF-8'?>
<partial-response><error><error-name>class java.lang.IndexOutOfBoundsException</error-name><error-message><![CDATA[Index: 1, Size: 1]]></error-message>
Regards!