component controller and view controller methods

   Depending on the controller type,additional hook methods are available.For the component controller,there are three additional standard methods.Two are of importance:
   1. wddobeforenavigation()
   Whenever a client event is raised,the corresponding action method in the view controller is processed.The method wddobeforenavigation() is called after the action method has been processed and just before the Web Dynpro framwork processes the events in the navigation queue.
   2. wddopostprocessing()
   In complex Web Dynpro applications,it is possible that the data from multiple components must be validated before the next step in the business process can be taken.This method has been impplemented so that cross-component validation can take place.It is the last controller method that is processed before the UI is sent to the client.

   For view controllers,there are two additional hook methods:
   1.wddobeforeaction()
   After the Web Dynpro application has been started and the user has raised a client event,the first methods to be processed in the Web Dynpro application are the wddobeforeaction() methods of all view controllers of the previous rendered view assembly.This happens even before the action handler method related to the client event is processed.
   2. wddomodifyview()
   The only method that allows to access the UI element hierarchy is the view's wddomodifyview() method.The interface parameter VIEW is a reference to the UI element hierarchy;the FIRST_TIME parameer can be used to find out if this method has been previously processed in the view controller's life cycle.This method can be used to manipulate the UI element hierarchy dynamically.