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copied!<p>HTTP is stateless. Meaning that the data returned by the server does not depend on any previous actions by the user. Cookies and other non-HTTP methods is what makes the web appear to be stateful, enabling user to for example log-in and out on websites.</p> <p>Check out: <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html" rel="nofollow">http://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html</a></p> <p>For an application developers, it IS stateless always. </p> <p>For end users it is appears to be statefull</p> <p>Now,</p> <p>Each HTTP request results in a new invocation of a servlet (i.e., a thread calling the servlet’s service and doXxx methods), regardless of whether the connection is keep-alive or not. </p> <p><strong>EDIT:</strong></p> <p>HttpSession object is used to set information related to a specific session say, the number of products in a cart for the current session. Note that session gets closed if the browser is closed or if you clear the cookies.</p> <p>How does the webserver know that its the same session?</p> <p>Webservers sends a sessionId to the browser in the form of cookie. And, the browser sends the cookie having sessionId back to the server for subsequent requests.</p> <p>How does the browser identifies which cookies to send for a link/request? </p> <p>It is based on the these parameters. If the request matches these parameters the browser sends that particular cookie:</p> <p>Domain: The domain name to which the request is made. </p> <p>Path: If the context root path name is same. </p> <p>Secure: Server sends if the given cookie if it can be sent on this non-secure channel</p> <p>If cookies are disabled then it uses URL-rewriting. </p> <p>Is it possible to retain the session even after the browser is closed and opened? Yes. The answer is cookie + DB + Googling :)</p>

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