Show TOC

/IWBEP/CL_MGW_ABS_MODELLocate this document in the navigation structure

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

Use

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 NetWeaver Gateway 2.0 SP06 (IW_BEP and IF_FND) the result of GET_LAST_MODIFIED also controls the cache on the SAP NetWeaver Gateway server for service document and service metadata document requests. If the SAP NetWeaver Gateway metadata cache is active, then the SAP NetWeaver 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 NetWeaver 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 NetWeaver Gateway server, then the new metadata is sent from the backend and the cache is updated with the new metadata on the SAP NetWeaver 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 NetWeaver Gateway server, then the backend does not send any metadata back to the SAP NetWeaver 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 NetWeaver 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 NetWeaver Gateway server.