Interface for receiving notification events about HttpSession lifecycle changes.

In order to receive these notification events, the implementation class must be either declared in the deployment descriptor of the web application, annotated with javax.servlet.annotation.WebListener, or registered via one of the addListener methods defined on javax.servlet.ServletContext.

Implementations of this interface are invoked at their sessionCreated method in the order in which they have been declared, and at their sessionDestroyed method in reverse order.