ABAP Web Services

A Web service is an independent, modular, self-describing application function or service. Based on XML and other standards, this application function can be described, made available, located or called using internet protocols. Each Web service therefore encapsulates a piece of functionality that can be used, for example, to forward a price query to a provider, check the availability of an item in an enterprise resource planning system, or locate a telephone number.

The provider of a Web service is generally called a service provider. The service provider will have a corresponding XML-based description of the Web service in the Web Service Description Language (a WSDL document). In principle, any programming language can be used to implement this service. Based on the HTTP transport protocol, Simple Object Access Protocol (SOAP) is now established as the quasi-standard access protocol.

When publishing a Web service, the service provider transmits information about itself and a description of the service it is offering and transfers this to the services registry. A services registry can be described as a type of Yellow Pages for Web services. In addition to other data, it also provides information on calling the Web service, for example. The services registry therefore provides a description of the Web service only. This description forms an abstraction layer and is therefore not dependent on the corresponding implementation.

The standard register used is the UDDI services registry (Universal Description, Discovery and Integration). SAP provides a public UDDI server at http://uddi.sap.com, and any ABAP client can be set up as a services registry.

The user of a Web service is called a service consumer. In most cases, the service consumer is an application that accesses the Web service. The application obtains the necessary information for this from the service description, which is, for example, stored in the services registry.

SAP NetWeaver Application Server for ABAP provides a standardized architecture and a set of tools for creating Web services and related objects. Existing BAPIs or remote-enabled function modules can be used for setting up Web services or you can develop new Web services in the Object Navigator of SAP NetWeaver AS for ABAP. There are predefined settings for securing Web services or the transports being used. ABAP Web services can be used for communication between SAP systems and between SAP and non-SAP systems.