Retaining Client and State Information
All but very simple Web applications are likely to require that information of some kind about the client be retained between different page requests. As has been stated, HTTP is stateless and does not provide a mechanism to ascertain that a series of requests have come from the same client.
There are a number of ways of retaining information about clients, such as hidden fields, cookies, and sessions (all described in this section). HTTP sessions are by far the simplest to use and are the recommended approach for Web Applications. Other techniques such as using HTTP cookies or hidden form fields belong to older, non servlet, technologies such as CGI scripts.
Using Session Objects
Sessions identify page ...