What are controller components and RequestProcessor ?

Controller

• responsible for intercepting and translating user input into actions to be performed by the model.
• responsible for selecting the next view based on user input and the outcome of model operations.
• receives the request from the browser, invoke a business operation and coordinating the view to return to the client. 
• implemented by a Java Servlet
• Centralized point of control for the web application

• In struts framework, the controller responsibilities are implemented by several different components like :  
• The ActionServlet Class 
• The RequestProcess or Class 
• The Action Class

 
RequestProcessor

The class org.apache.struts.action.requestProcessor process the request from the controller. You can sublass the RequestProcessor with your own version.

Flow

• Controller receives a client request
• It delegates the handling of the request to a helper class (Action class)
  This helper knows how to execute the business operation associated with the requested action.
  It acts as a bridge between a client-side user action and business operation.
• The Action class decouples the client request from the business model.
  This decoupling allows for more than one-to-one mapping between the user request and an action.
• The Action class also can perform other functions such as authorization, logging before invoking business operation.