what is sap webdynpro

What is SAP WebDynpro? Concept of WebDynpro (ABAP centric)

I believe that the concept of WebDynpro is more important than just creating a WebDynpro application. There are enough documents on the net on how to create a WD application. But there are very few documents which will give you the concept of WebDynpro.

I am making an effort here to provide the basics, concept and architecture of WebDynpro, with ABAP in mind.

Pre-requisite assumed: Knowledge of ABAP

What is WebDynpro?
WebDynpro is SAP's model or approach towards web screen design. SAP aims to achieve a clear distinction between UI design and backend code through this model. Dynpro means Dynamic Program, (SAP's terminology for interactive UI). hence Web Dynpro means Web screen. WebDynpro is also a latest model by SAP. Earlier approaches include ITS (Internet Transaction Sever) and BSP (Business Server Pages).

What is the programing language used for WebDynpro?
For the WebDynpro both ABAP and Java can be used. ABAP being the latest and also seems to be the future for WebDynpro. View my WebDynpro articles here.

Future of WebDynpro: ABAP or Java?
Story of WebDynpro. Who is the hero? ABAP or Java ?

What is a View?
View is a layout of UI elements. Example of UI elements is Input field, Output Filed, Radio buttons etc.
View also contains the methods which are local to the view.

What is a Window?
Window is a group of Views. One of the View will be a default View. Navigation to other views of the Window can happen only from the default view.

What is a inbound/Outbound Plug ? 
Plugs are used to navigate between Views. Inbound plugs define inbound connections to a view, and Outbound plugs define subsequent View for a View.

What is a WebDynpro Component ?
WebDynpro Component can contain other WD Component, Windows and Views.
WebDynpro Component is a reusable entity. It can be reused by another component so that re-usability is achieved. 
Hierarchically WD Component is at the highest level within a WD model.

What is a Interface View ? 
Every Window is accessed by an Interface view. 
Name of the Interface View will be same as Window.
Interface View defines inbound and outbound Plugs for a Window.

What is WebDynpro Application?
WebDynpro Application provides a way to use the functionality built using a WebDynpro component. 

A WebDynpro application is defined by following three parameters
1. A WebDynpro application refers to ONE WebDynpro Component,
2. A WebDynpro application refers to ONE Interface View (of the above WebDynpro component),
3. A WebDynpro Application has a URL, so that it can be accessed from a browser.

What is the link from a WebDynpro Application till a view?
A WebDynpro URL points to a WebDynpro Application.
A WebDynpro Application points to an Interface View.
A Interface View points to a Window.
A Window points to its default View.

What is a View Context?
The data used in a View is stored in a object called View Context.

What is an Action?
For certain UI elements like Button, you would want some action to happen when the button is pushed. 
So Action is defined at UI element level.
As soon as a Action gets created, a handler method gets automatically created by name HandleUIEvent_ in the View Controller. In this method you can define the behavior of the action.

What is a Component Context?
The data used in a Component is stored in a object called as Component Context. Component Context is global within a OCmponent.

What is a View Controller?
In SE80, you cannot see any object called as “View Controller”. The code related to View is located in the “Method” tab of the View. This is logically called as a View Controller.

What is a Component Controller?
Component Controller has the Programming part of a Component.
It is an object visible in SE80. It contains the methods which are global within the Component. I.e. These methods can be accessed by all objects within the Component

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