As we know that the Session is used to maintain the session
between request. Session object is responsible to hold the
conversational state across multiple requests. The listener
HttpSessionAttributeListener is an interface and extends the
java.util.EventListener class. This listener will be called by
the container whenever there there will be change to the
attribute list on the servlet session of a web application. This
listener is used when we want to know when a attribute has been
added in a session, when a attribute has been removed and when
it is replaced by another attribute. We can also say that this
attribute is used when the developer is interested to be
notified when the session attribute changes. Now you may be
wondering what is an attribute. An attribute is an object set or
you can simply say that it is name/value pair where the name
refers to a String and a value refers to the Object.
javax.servlet.http.HttpSessionAttributeListener interface has
following methods: In the above methods you can see