Types of controller in webdynpro abap

Controllers are the entry point into a webdynpro application. User can instruct the application via this controller only. Controllers holds all the logic and flow of the application and context hold the data. In an application there are 5 types of controller.

• Component controller: This is the main controller and the only one for the application. You can also call it as a global controller. Whenever webdynpro application is called this controller instantiated first. All the major logic is hold by the this controller ans it is also visible to other controllers of that application.
• Custom controllers: As the name suggests if the requirement need some extra functionality which component controller can not serve, then you can create a custom controller. Its completely optional. Generally if your component have many views and windows, then you can create multiple custom controllers to split the load. This is similar to modularisation technique in ABAP report.
• Interface controller: This is also a default controller which creates in the webdynpro framework automatically. This controller is mainly use in-case you are importing some existing components functionality. This is called component usage. 
• View controllers: Every view is having a controller to collect data from component controller based on user request. That is view controller. 
• Window controllers: Similar to views every window is also have a controller to get data via inbound or outbound plugs.

The major data is always retrieved in the component controller context and later on with the help of view and window controller passes to views and windows.