Creating an Identity management framework
I ask - how many times have I written a login screen for any application? I have lost count. I did it when I started programming with the tools that support GUI. List includes - Foxbase, VB, Web Forms, and later Java Swing and now portal pages.
The options to store the credentials remain pretty much the same - RDBMS and a Directory server for more sophisticated implementations.
Frameworks like JAAS provide ability to plug-in implementations for login modules. Is it enough just to authenticate the user? Applications of course want to retrieve details of the logged-in user that includes the standard identifying information and minimal data that can relate a user with a business entity - one of importance in your domain model.
This trail is a thought process and implementation approach for an Identity management framework that may be extended to support authorization.