/IWBEP/CL_MGW_ABS_MODEL

This is the abstract class for a model provider class (MPC).

This is the abstract class for a model provider class (MPC). Every concrete implementation of a model provider class shall be derived from this class.

Several constants are defined for this class.

Constant	Description
GCS_SAP_TEXT_OBJECT_TYPES	Constants can be use to address the kind of text which can be used, for example a text symbol of a class in the backend. The structure contains a list of the possible text object types. This text object should be used to create text with method SET_TEXT_KEY for a field label. TEXT_SYMBOL_CLASS uses a text element of a class in the backend system.
CARDINALITY_FEED	Value=* for multiplicity / cardinality of an association end type, for example.
CARDINALITY_ENTITY	Value=1 for multiplicity / cardinality of an association end type, for example.
CARDINALITY_ENTITY_0	Value=0..1 for multiplicity / cardinality of an association end type, for example.
GCS_SAP_SEMANTIC	All possible values as constants for annotation sap:semantics.
GCS_FC_TARGET_PATH	Values for target path of feed customization, for example for content source and type of a Media Links entry.

There is only one member, that is the MODEL which is the starting object to define the OData Channel data model.

Methods

Method DEFINE

This method needs to be implemented by an application to define its metadata. The entry point is the member data model.

Method GET_LAST_MODIFIED

Based on the implementation of this method a time stamp is sent in the HTTP response header of every metadata request to give the Web infrastructure the ability to cache the metadata document.

Note

The default implementation of this method derives the last modified time stamp based on the changed time stamp of the model provider class (MPC). The application can overwrite the logic if it does not fit.

Parameter	Description
RV_LAST_MODIFIED	Time stamp which is set as Last-Modified in the HTTP response header.

Starting with SAP Gateway 2.0 SP06 (IW_BEP and IF_FND) the result of GET_LAST_MODIFIED also controls the cache on the SAP Gateway server for service document and service metadata document requests. If the SAP Gateway metadata cache is active, then the SAP Gateway server performs a handshake with the backend, based on the GET_LAST_MODIFIED result and compares the timestamp from the cached metadata on the SAP Gateway server with the one returned by the GET_LAST_MODIFIED implementation of the Model Provider on the backend.

If the cache is outdated on the SAP Gateway server, then the new metadata is sent from the backend and the cache is updated with the new metadata on the SAP Gateway server. As a result, the latest changes of your metadata is always reflected when requesting a service and a service metadata document.

If the cache is not outdated on the SAP Gateway server, then the backend does not send any metadata back to the SAP Gateway server, because the cached metadata is still up-to-date.

Note

As a result, the latest changes of your metadata is always reflected when requesting a service and a service metadata document.

Caution

With this behavior the following setup will lead to a performance bottleneck for service and service metadata document requests, because the cache is in this case refreshed in every request for metadata:

Method GET_LAST_MODIFIED is overwritten with coding like GET TIME STAMP FIELD rv_last_modified.
The SAP Gateway metadata cache is active.

In order to always have the latest metadata present on your client applications, it is recommended to perform a request to the service metadata document as a very first call of your client application choreography (for example when starting the application) to the SAP Gateway server.

Method GET_VOCAN_TEXTS

The method is called with a table of all annotation text keys that have been defined in the corresponding model.

The framework implementation does the following:

It loads the corresponding texts for all referenced data elements and referenced text elements.
It calls method GET_VOCAN_PROVIDER_TEXTS to retrieve the provider texts in a second step.

As a rule there is no need to overwrite this method.

Parameter	Description
IV_LANGUAGE	The current language.
IT_VOCAN_TEXT_KEYS	Table of all annotation text keys that have been defined in the corresponding model.
CT_VOCAN_TEXTS_OBJ	Table containing the actual annotation texts.

Method GET_VOCAN_PROVIDER_TEXTS

The method is called with a table of annotation text keys that have been defined in the corresponding model, but only for the text type "provider text".

The framework implementation simply throws a NOT-IMPLEMENTED exception. A provider using its own text repository must overwrite this method and return the texts for all provider texts that have been defined in the model and which are also provided via import parameter IT_VOCAN_TEXT_KEYS.

Parameter	Description
IV_LANGUAGE	The current language.
IT_VOCAN_TEXT_KEYS	Table of annotation text keys, of the type "provider text".
CT_VOCAN_TEXTS_OBJ	Table containing the actual annotation texts.