Question :How can I enable session tracking for JSP pages if the browser has
disabled cookies? (JSP)
Answer :We know that session tracking uses cookies by default to associate a
session identifier with a unique user. If the browser does not support
cookies, or if cookies are disabled, you can still enable session tracking
using URL rewriting.
URL rewriting essentially includes the session ID within the link itself as a
name/value pair. However, for this to be effective, you need to append the
session ID for each and every link that is part of your servlet response.
Adding the session ID to a link is greatly simplified by means of of a couple
of methods: response.encodeURL() associates a session ID with a given
URL, and if you are using redirection, response.encodeRedirectURL() can
be used by giving the redirected URL as input.
Both encodeURL() and encodeRedirectedURL() first determine whether
cookies are supported by the browser; if so, the input URL is returned
unchanged since the session ID will be persisted as a cookie.
Consider the following example, in which two JSP files, say hello1.jsp and
hello2.jsp, interact with each other. Basically, we create a new session
within hello1.jsp and place an object within this session. The user can then
traverse to hello2.jsp by clicking on the link present within the page.Within
hello2.jsp, we simply extract the object that was earlier placed in the
session and display its contents. Notice that we invoke the encodeURL()
within hello1.jsp on the link used to invoke hello2.jsp; if cookies are
disabled, the session ID is automatically appended to the URL, allowing
hello2.jsp to still retrieve the session object.
Try this example first with cookies enabled. Then disable cookie support,
restart the brower, and try again. Each time you should see the
maintenance of the session across pages.
Do note that to get this example to work with cookies disabled at the
browser, your JSP engine has to support URL rewriting.
hello1.jsp
<%@ page session="true" %>
<%
Integer num = new Integer(100);
session.putValue("num",num);
String url =response.encodeURL("hello2.jsp");
%>
hello2.jsp
hello2.jsp
<%@ page session="true" %>
<%
Integer i= (Integer )session.getValue("num");
out.println("Num value in session is "+i.intValue());
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Friday, March 13, 2009
How can I enable session tracking for JSP pages if the browser has
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