How Web Services Function 

The Central Concepts

The SAP NW Application Server supports the providing and consuming of Web Services. It does this using Web Services standards: XML, SOAP, the Web Service Definition Language (WSDL), and Universal Description, Discovery, and Integration (UDDI).

SOAP is a general format for XML messages. Different transport protocols can be included in this format. Using WSDL, you describe the actual interface of your Web service, which consists of method names and input and output messages. At runtime, the message are packed using SOAP and transferred in this form.

UDDI is a type of address service for Web Services. There you will find published the basic data you need to call a Web service. As a Web service provider, you can publish your services there.

 

Providing and Consuming Functions as Web Services

If you wish to provide a certain function written in ABAP as a Web service, you can wrap this using a Web service. This is the so-called inside-out approach. With it, you can make an existing standard interface (for example, a function module) accessible as a Web service using tools and wizards.

If you wish to call a Web service from within an ABAP program, you can also have a proxy class created using the tools on the basis of the WSDL description of the respective Web service. It is of no significance how the Web service was implemented on the server side. The client proxy takes care of the technical aspects – such as creating a SOAP message, the transport layer, or security settings. It encapsulates the communication therefore. The developer of the client application can thus concentrate on the creation of business functions.

Here you can provide one and the same function in different Web services. Web services provide an implementation abstraction. This means that. for a Web service, you fill certain input parameters of a function with default values and, in another Web service, provide the same function with all its parameters. For example, the customer of a Web shop for a textile manufacturer does not wish to be bothered with internal posting details for his or her order. In such a case, the Web service solution would be to fill certain parameters – for example, the company code – with default values already on the Web service provider side, and to provide the Web service client only with parameters that he or she can actually specify. A department store, on the other hand, would like to provide its order with the same manufacturer with a wider range of business posting data. The Web service with all input values for the function behind it has been designed for this purpose.

 

More information:

Web Services