Controller Contexts and Data Binding 

Use

Within a Web Dynpro component, controller contexts are used as storage locations for data with different structures. Each view controller contains its own context. At a superordinate level, the application development can store additional information in the controller context of a Web Dynpro component or in the context of the custom controller.

Controller contexts have a tree structure consisting of context nodes, node elements with different cardinalities, and context attributes of different data types. However, you must differentiate between the abstract level of the context at design time and its concrete definition at runtime.

Context mapping between context nodes allows the shared use of context data. To do this, the context data is stored in the component context, for example, and made available for write and read access using the context mapping definition in the view context and a reference semantics.

Data binding between the UI element properties and data that is stored in the controller context of a view enables you to easily display this data on the user interface. Note that this purely declarative data transfer from the controller layer to the view layer of an application is possible without any programmatic effort.

Activities

Contexts can be used for the following functions:

·        Context design: You define the required context structures in the controllers of a view and in the component controller. This includes value nodes and value attributes, which represent layout-specific data like the visibility of a UI element and pure business data like question-answer pairs.

·        Context mapping: You must define source and target of the mapping. In this example, the data in both views Question and Answer is used. The controller context of a Web Dynpro component (more precisely, a value node contained in it) serves as the data source. In the controller context of the views Question and Answer, you can then define value nodes as the corresponding data drains using context mapping.

·        Data binding: You must connect context-dependent properties of individual UI elements with the value attributes of the corresponding controller contexts of a view using data binding.