I am training in web developement and am learning about JSP & Servlets. I have some knowledge of HttpSession - I have used it in some of my sample projects.
In browsers I have seen the option to "delete cookies". If I delete the cookies it deletes the HttpSession also.
Are cookies and session the same? What are the differences between them?
A cookie is simply a short text string that is sent back and forth between the client and the server. You could store name=bob; password=asdfas in a cookie and send that back and forth to identify the client on the server side. You could think of this as carrying on an exchange with a bank teller who has no short term memory, and needs you to identify yourself for each and every transaction. Of course using a cookie to store this kind information is horrible insecure. Cookies are also limited in size.
Now, when the bank teller knows about his/her memory problem, He/She can write down your information on a piece of paper and assign you a short id number. Then, instead of giving your account number and driver's license for each transaction, you can just say "I'm client 12"
Translating that to Web Servers: The server will store the pertinent information in the session object, and create a session ID which it will send back to the client in a cookie. When the client sends back the cookie, the server can simply look up the session object using the ID. So, if you delete the cookie, the session will be lost.
One other alternative is for the server to use URL rewriting to exchange the session id.
Suppose you had a link - www.myserver.com/myApp.jsp You could go through the page and rewrite every URL as www.myserver.com/myApp.jsp?sessionID=asdf or even www.myserver.com/asdf/myApp.jsp and exchange the identifier that way. This technique is handled by the web application container and is usually turned on by setting the configuration to use cookieless sessions.
Sessions are server-side files that contain user information, while Cookies are client-side files that contain user information. Sessions have a unique identifier that maps them to specific users. This identifier can be passed in the URL or saved into a session cookie.
Most modern sites use the second approach, saving the identifier in a Cookie instead of passing it in a URL (which poses a security risk). You are probably using this approach without knowing it, and by deleting the cookies you effectively erase their matching sessions as you remove the unique session identifier contained in the cookies.
A lot contributions on this thread already, just summarize a sequence diagram to illustrate it in another way.
The is also a good link about this topic, https://web.stanford.edu/~ouster/cgi-bin/cs142-fall10/lecture.php?topic=cookie
Google JSESSIONID. This will explain how the Servlet API initially uses URL re-writing and then, if cookies are enabled, cookies to manage sessions.
HTTP is stateless so the client browser must send the id of its session to the server with each request. The server, through whatever means, uses this id to retrieve any data for that session making it available for the lifetime of the request.
