Service Types  

Definition

A functional component used to save and access application data, enable systems and applications to exchange data, or maintain the business process logic. In the CAS perspective of NetWeaver Developer Studio you will encounter entity, application, and external services.

See the following for additional information about the services used in the Composite Application Framework Core (CAF Core) application:

○     Entity Services

○     Application Services

○     External Services

Structure

Technically, application and entity services are modeled as a session bean according to the EJB (Enterprise Java Bean) 2.0 specifications. With EJB, the J2EE platform is responsible for handling transactions, persistency, shared data access, and security issues. In this architecture, the session services’ EJBs are independent and reusable components that are completely decoupled from any application or user interface (UI) layer.

While entity and application services are both stateless, application services can also be remotely enabled, for example, as a defined Web service.

Metadata

Information about a service is stored as metadata information. Metadata information describes the attributes and relations a service holds, how it is fed from an underlying application, and the data that is stored (which is read from the backend). From this metadata, Java sources and configuration files (such as table definitions or mappings for JDO [Java Data Objects]) are generated and compiled.

Metadata is stored in the Metadata Model Repository (MMR). The MMR consists of a design time part using local XML (Extensible Markup Language) files to store the metadata and a runtime part storing the metadata in the database of the Web Application Server (WAS).

Integration

Application, entity and external services can be related to other entity services. Relations between entities can only be unidirectional. There can be 0:1 and 0:n relationships.

Example

The following shows an example of an entity service with simple and complex attributes and relations to other entities:

Product

●     ID (String, simple attribute, key)

●     Name (text field, simple attribute)

●     Description (text field, simple attribute)

●     Category (entity service)

●     Vendor (entity service)

●     Weight (double, simple attribute)

●     Document (entity service, points to SAP Knowledge Management)

It is used to attach documents such as product specifications, manuals, or construction plans.

See also:

Designing Services in CAF Core for more information on creating, modeling, and integrating services.