External Context Mapping 

In normal context mapping, the referenced original data is always within a Web Dynpro component. To be more exact, the original nodes or attributes are either in the component or in a custom controller context, as the global data store of a Web Dynpro component.

Context mapping is usually represented by scenarios where a component is not dependent on external context data, but saves all context data itself in the original instead. This means that at design time, no assumptions are made that context data has to be referred outside of the component limits, that is, context data that belongs to an external user of the component.

In practice, however, there are cases where the assumption is made at design time that a Web Dynpro component should reference external context data in the original. This means that this type of component is developed deliberately so that it cannot run independently, but is dependent on its subsequent user (an embedding component).

Access to the user of a Web Dynpro component cannot be defined until a concrete component usage is defined. If you think of Web Dynpro components as classes, then a component usage corresponds to a variable that references an object instance of this class.

This type of access to an external original context by a used component instance is known as external context mapping.

To clarify this, consider the following graphic:

External Context Mapping

In a view controller context of the Web Dynpro component Child, context data outside of the child component should be referenced using mapping. First of all, normal context mapping is defined for the component interface context. To reference external context data in the component interface context, the context structure that is required in it is defined. At this point, the developer must therefore know the structure of the original context. The context elements involved must also be marked as “can be mapped externally later“, that is, the later and external user of the child component can define the actual context mapping for the known original context. The property “can be mapped externally later“ is defined using the isInputElement = true element property. The Web Dynpro component Parent uses the child component using the definition of a component usage. The child component does not “see“ its concrete user until this point; here it is the Web Dynpro component Parent. Normal mapping can now take place at the level of a concrete instance of the child component (represented by the component usage) within the outer Parent component. As this context mapping takes place outside of the defines component, that is, in the level of a concrete component usage, it is known as external context mapping. The original context to which the external context mapping refers, keeps the original node elements that are referenced at runtime. Its structure must contain those context elements that were previously selected in the component interface context of the used component as externally mappable input elements (isInputElement = true ) (step 2). Moreover, the general rules should be observed on which mapping context nodes and attributes is based.

The following notes should be observed to aid your understanding of external context mapping:

1. If a parent component defines the use of a child component, then it can only be related to the child component by its component interface (for example using context mapping). For this reason, external context mapping only starts from the context elements that belong to the component interface context.
2. External context mapping always occurs in two steps. In the first step, elements are selected in the component interface context as “can be mapped externally later” using the isInputElement = true property. In the second step, the actual context mapping between the component interface context and the external original context is defined for a concrete use of a component.
3. In external context mapping it is possible that mappings to contexts are defined in different controllers. So, with use A of a child component, there could be external mapping to the component controller. With a second use B of the same component, the original context could belong to a custom controller, however. The only condition is that both original contexts contain such context elements that are compatible to the “can be mapped externally later“ context structure that is defined in the component interface.

 

Restriction

 

Note that context attributes cannot be defined as “can be mapped externally later“ directly below the root node (top level context attribute) in the component interface content. External context mapping is possible only for those context attributes that belong to independent or dependent context nodes.