Application lifecycle listeners and events

Application lifecycle listeners and events, now part of the Servlet API, enable one to notify interested listeners when servlet contexts and sessions change. For example, you can notify users when attributes change and if sessions or servlet contexts are created or destroyed.

The lifecycle listeners give the application developer greater control over interactions with ServletContext and HttpSession objects. Servlet context listeners manage resources at an application level. Session listeners manage resources associated with a series of requests from a single client. Listeners are available for lifecycle events and for attribute modification events. The listener developer creates a class that implements the javax listener interface, corresponding to the desired listener functionality.

At application startup time, the container uses introspection to create an instance of your listener class and registers it with the appropriate event generator.

When a servlet context is created, the contextInitialized method of your listener class is invoked, which creates the database connection for the servlets in your application to use, if this context is for your application.

When the servlet context is destroyed, your contextDestroyed method is invoked, which releases the database connection, if this context is for your application.


See Also

Listener classes for servlet context and session changes
Webapplications: Resources for learning