This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I would suggest looking at the source code for the version of Struts that you are using. If that fails, I know that the book "Programming Jakarta Struts" has several pages on this topic. I assume that most other Struts books also cover this topic.