HttpServletResponse - does sendError terminate request stream?

[Tim]

I'm looking for a way to terminate an http request file upload from
within a filter.

It appears that the servlet container starts a seperate thread for
handling the request, so simply doing a response.sendRedirect will not
terminate the upload. It waits until after the upload is complete and
then redirects. Not so good when a 40MB file is coming your way!

What I need to know is whether or not a response.sendError will
immediately send the error to the client browser. It appears that
this is the case, but I'm having a difficult time finding in-depth
documentation on the inner workings of JBoss Tomcat engine.

Thanks.