0 Session Tracking in Java Tutorial

• Session objects live on the server
• Sessions automatically associated with client via cookies or URL-rewriting
– Use request.getSession to get session
• Behind the scenes, the system looks at cookie or URL extra info and sees if it matches the key to some previously stored session object. If so, it returns that object. If not, it creates a new one, assigns a cookie or URL info as its key, and returns that new session object.
• Hashtable-like mechanism lets you store arbitrary objects inside session
– setAttribute stores values
– getAttribute retrieves values
• Access the session object
– Call request.getSession to get HttpSession object
• This is a hashtable associated with the user
• Look up information associated with a session.
– Call getAttribute on the HttpSession object, cast the return value to the appropriate type, and check whether the result is null.
• Store information in a session.
– Use setAttribute with a key and a value.
• Discard session data.
– Call removeAttribute discards a specific value.
– Call invalidate to discard an entire session