Java EE (Java Enterprise Edition) General Discussion

I've been searching on google for more than an hour on how to do this, but I can't find it anywhere. Basically, I'm calling the servlet as a <form> action from a jsp page having the URL like http://localhost/ps/viewpic.jsp?cat=1&pid=5. The servlet updates a database. After it finishes updating, I would like to reload the page to reflect the changes. How on Earth do I do that, 'cause it's driving me mad? I tried using sendRedirect() with various strings, but to no avail. How can I retrieve the page's URL?