How to logout from Tomcat using Spring and JAAS form based authentication?

[voorth]

I've written a JAAS LoginModule to handle authentication. Login works
exactly as I expected, but there seems to be no way to logout again.
I'm using Form Based Authentication.

Searching the web seems to tell me that I need to use Tomcats
LoginContext.logout() for that, but I have been unable to find a way to
access the LoginContext from Spring.

Any pointer would be appreciated.

Henk van Voorthuijsen