Looking for JSP login open source application

I'm wondering if there is any open source login application (JSP based) that you guys could recommend.

I found this one below but it doesn't seem to provide any documentation. So it's very hard for me to understand how to use it.
http://sourceforge.net/projects/modauthmd5/

Thanks in advance for the help.

What functions should this module perform? The one you linked to is an Apache module, so it goes beyond Java and installation in a servlet container.

I'm looking for something really simple, basically just:

- Ability for user to sign up, login to JSP pages, change their profile (username and password).
- Ability for administrator to manage users.