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 that we have used HttpSessionBindingEvent class as a parameter to the above methods. This class is a event class which is used for notifications when the changes are made to the attributes of in a session.
The class HttpSessionBindingEvent has two methods: