From a web server's perspective, a web application is a series of unrelated server hits. There is no automatic recognition if a user has visited the site before, even if their last interaction was seconds before. A session provides a context between multiple user interactions by remembering the application state. Clients identify themselves during each interaction by a cookie, or, in the case of a cookie-less browser, by placing the session identifier in the URL.
A session object can store objects, such as tabular data, information about the application's current state, and information about the current user. Objects bound to a session are available to other components that use the same session.
For more information, see Chapter 5, Session Managers.
After a successful login, you should direct a servlet to establish the user's identity in a standard object called a session object. This object holds information about the current session, including the user's login name and any additional information to retain. Application components can then query the session object to obtain user authentication.
For more information about providing a secure user session for your application, see Chapter 6, Securing Web Applications.