A new class called RequestProcessor was added to the framework in Struts 1.1. This class takes over much of the work that the ActionServlet class performed in previous versions. With 1.1, you can still configure the class name of the ActionServlet that you want to use for an application in the web.xml file, but the RequestProcessor now carries out much of the real request-processing work.
By default, applications use the org.apache.struts.action.RequestProcessor class to handle all incoming requests. You are not required to do anything if the default behavior suits your requirements. You can, however, choose to override the default implementation with one of your own. You can switch implementations by configuring the controller element in the Struts configuration file. See Chapter 4 for more details on configuring the controller element.