Oracle GlassFish Server 3.0.1 Add-On Component Development Guide

Creating Event Listeners

An event listener gathers statistics from events that an event provider sends. To enable an add-on component to gather statistics from events, create listeners to receive events from the event provider. The listener can receive events from the add-on component in which the listener is created and from other components.

To create an event listener, write a Java class to represent the listener. The listener can be any Java object.

An event listener also represents a component's statistics. To enable the Application Server Management Extensions (AMX) to expose the statistics to client applications, annotate the declaration of the class with the org.glassfish.gmbal.ManagedObject annotation.

Ensure that the class that you write meets these requirements:

A listener is called in the same thread as the event method. As a result, the listener can use thread locals. If the monitored system allows access to thread locals, the listener can access thread locals of the monitored system.

Note –

A listener that is not registered to listen for events is never called by the framework. Therefore, unregistered listeners do not consume any computing resources, such as memory or processor cycles.