HttpSessionBindingListener interface should be implemented by classes that may be bound into sessions as attributes and if they want to know when they were bound. When an object which implements this interface is bound to a session or unbound from the session, the container will call its valueBound and valueUnbound methods respectively. Since the interface is added by the attributes that are added to the session themselves and cannot listen to any other attributes, you don’t have to mention it in the web.xml file or have the @WebListener annotation.

In Java EE, a session between a client and server may be maintained in three different ways: cookies, url rewriting and SSL sessions. We will see both session management through cookies and URL rewriting here. In both these approaches multiple requests from the client are connected together as a session using an attribute JSESSIONID. In case of session management through cookies, a cookie with name JSESSIONID saves the JSESSIONID at client (browser) side and is sent to client every time a request is made within that session from that same client.

There is a saying that a picture can speak thousand words. UML diagrams are those pictures which can speak all those words about your design. There are many categories of UML diagrams. However this note will contain only those class diagram components that are really required for representing your design decisions, design patterns and principles.

You may use request and response wrappers to extend the functionality of request or response objects. For instance, we can provide an extra layer of buffer using a wrapper with its own internal buffer independent of the output stream supplied by the container. We can pass this to other components and once we finally verify the content, then we can write it into containers output stream and thus actually committing the response. 

You may use request and response wrappers to extend the functionality of request or response objects. We can pass in our custom wrapper to a RequestDispatcher forward and include, and override any default behavior. For instance, we can provide an extra layer of buffer using a wrapper with its own internal buffer independent of the output stream supplied by the container. We can pass this to other components and once we finally verify the content, then we can write it into containers output stream and thus actually committing the response.