Struts is a java JSP/servlet MVC (Model-View-Controller) framework from Apache.org.
It is wise to avoid creating lengthy and complex Action classes. If you start to embed too much logic in the Action class itself, you will begin to find the Action class hard to understand, maintain, and impossible to reuse. Rather than creating overly complex Action classes, it is generally a good practice to move most of the persistence, and "business logic" to a separate application layer. When an Action class becomes lengthy and procedural, it may be a good time to refactor your application architecture and move some of this logic to another conceptual layer; otherwise, you may be left with an inflexible application which can only be accessed in a web-application environment. Struts should be viewed as simply the foundation for implementing MVC in your applications. Struts provides you with a useful control layer, but it is not a fully featured platform for building MVC applications, soup to nuts. from http://struts.apache.org/userGuide/building_controller.html#action_classes
Migrating to Struts 2