This solution is basically a 'static' wait page. It's better than a blank screen, right??
This is just one of many posts, but I suck at choosing the right keywords when using UBB search. I'm sure this has been discussed a lot more on here, it's a common request.
People have talked about using threads to spin off the long-process. Then you do all sorts of things.
Like... have a single page refresh using meta tags, and checking the 'done pile' (the session, for example) for the expected message ("I am done this long process"), and if it's there, use sendRedirect to get them off that 'wait' page.