here how can i get request object so that,i can forward to my jsp page..
You can't - there will never be a request when a session times out and is invalidated by the servlet container because initial processing of a request resets the timer for the matching session.
How will you identify a request as belonging to a recent user whose session timed out versus a request from a brand new user?
There is no way you can do this using ONLY the session mechanism.
I suggest you could use c ookies just like commercial sites do. Amazon recognizes me because my browser has (one or more) long-lived c ookie specific to the Amazon URL.
See the JavaDocs for java.servlet.http.C ookie for an introduction on how to create your own c ookies. Search for RFC 2965 for the complete rules on c ookies.