I would like to put some of our web pages in a password-protected directory.
If a user logs in, then he or she gets access to the directory. We have a
table of users in a database table.

I'm trying to use form-based authentication. I've googled around and read a
handful of articles about it, but the piece they all seem to be missing is
how to use information in the database to tell the container that a
particular user is authorized. There appear to be different servlet
container-specific mechanisms (like Tomcat realms, etc?.) but I need
something which works across containers. How can I tell the container, using
Java code in my JSP, that a particular user is authorized?