I am currently in the process of learning Struts 2 and I am currently building a simple application where unverified users are redirected to a login form.
I have a login
You can find the complete example of struts2 with a custom Login Interceptor here
http://sandeepbhardwaj.github.io/2010/12/01/struts2-with-login-interceptor.html
great tutorial.