This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
If you define interceptors for an action you must define *all* of the interceptors for an action. So currently, when you configure the interceptor in your action config, you're running only the single interceptor--meaning the "params" interceptor isn't running, so no parameters are set.