Sure. I have a post.POST.jsp which takes the XML submitted from the client, makes decisions, and checks for errors.
If there are no errors, it generates a PDF using the pdf generator service.
If there are errors, it uses the GuideSubmitServlet to redirect back to the URL the client came from, with the submitted document included with the errors in the redirectParams, so the user can see the data they submitted to give context to the errors.
We want to use a POST rather than a GET, because there are limits to a GET.