src/main/java/org/efaps/ui/wicket/behaviors/dojo/MessageListenerBehavior.java
@Override
    public void renderHead(final Component _component,
                           final IHeaderResponse _response)
    {
        super.renderHead(_component, _response);
        _response.render(JavaScriptHeaderItem.forScript(MessageListenerBehavior.getScript(_component),
                            _component.getClass().getName() + "_MessageListener"));

    }
@Override
    public void renderHead(final Component _component,
                           final IHeaderResponse _response)
    {
        super.renderHead(_component, _response);
        _response.render(JavaScriptHeaderItem.forScript(MessageListenerBehavior.getScript(_component),
                            _component.getClass().getName() + "_MessageListener"));

    }
Render to the web response whatever the component wants to contribute to
the head section.

@param _component    Component this behavior belongs to
@param _response     Response object