How filter posts to j_security_check?

[Robert Paris]

I added a filter and tried two different URL mappings:
/*
and
/j_security_check

When I do the second one ("j_security_check") my filter is never called (even though a form posted to that URL) and if I do the first, it is called but I cannot get the password/username. I want to intercept the request BEFORE it gets to j_security_check. Is there a way to do this?