Providing and Consuming Web Services

To a great extent, communication between B2B and e-Commerce applications is based on manually declared interfaces, message formats, and arrangements between business partners. Using Web services, this process can be simplified. Web services are Web-based interfaces that can be integrated into business scenarios of a company based on open and commonly accepted standards. Using Web services enables you to combine functions implemented on different software components into a single process.

Web services are self-contained, modularized, executable entities that can be published, searched for, and accessed across a network. For a caller or sender, a Web service is a black box that may require input and delivers a result.

Introductory Notes
In the following chapters, we assume that the reader is familiar with Web service techniques.



Features
The SAP Web Application Server allows companies to extend their solutions by exposing and integrating Web services. The SAP NetWeaver Developer Studio provides an environment for publishing, discovering, and accessing Web services. Therefore, it allows the SAP Web Application Server to act both as a “server” and as a “client” for Web services.

The Java Web Service Infrastructure allows developers to:

·        Display all self-contained, modularized functions implemented as Enterprise Java Bean (session bean) or as a Java class in a Web service. This includes functions provided by SAP as part of mySAP solutions or developed by the customer or partner. The Web service can be used across the Internet through standard protocols and can easily be integrated in any development framework. Displaying a Java class as a Web service is also possible.

·        Integrate Web services, irrespective of where they reside or how they are implemented. Therefore, business processes spanning different systems, both intra-company and cross-company, can be implemented.

The following triangle shows the basic architecture of the Web services framework:



Service Provider
Within the SAP Web AS, the inside-out approach is used to develop the functions that can be made available as a Web service. After the functions have been implemented, a Web service interface, which is visible to the Web service consumer, has to be created. This interface provides an abstraction layer and consequently independence from the specific implementation. Based on this interface, the Web service is configured and can be accessed during runtime. Full UDDI client capabilities can be used to publish the Web Services to a UDDI registry.

Service Directory
Web service definitions and deployed Web services can be stored in a UDDI registry. WSDL documents provide the basis for the Web service client and can be found in the UDDI using a browser or the standard UDDI API’s. In the SAP Web AS, UDDI client and server functions are provided. You can search in all, and publish to all, registries that conform to the standard. A full-blown UDDI server is shipped as part of the SAP Web AS so customers can create their own registries. SAP also provides a public UDDI Business Registry under uddi.sap.com.

Service Requestor
The SAP Web AS allows you to integrate Web services using the WSDL file as input for generating a Web service client.

Web services and Open Standards
Open integration can only be achieved if it is based on generally accepted standards. The SAP Web Application Server implements the basic Web services standards eXtensible Markup Language (XML), SOAP, Web Service Definition Language (WSDL) and Universal Description, Discovery, and Integration (UDDI).