RequestDispatcher does not help your control by exiting from the servlet (it does NOT exit from the servlet and return the control back to the point of invocation). Since, you are not writing anything to the response object, the ideal solution is to 'return' after forward has been executed. [ December 15, 2008: Message edited by: Nitin Pathak ]
Joined: Sep 25, 2006
I am not aware whether you managed to solve your problem, but here is JavaRanch faq for your beloved exception.
Hope this would make things clearer!
subject: IllegalStateException error come on servlet side