11.6 Service Requester

Oracle Application Server makes creating a Web Services requester, or client program, extremely easy. As mentioned earlier, OC4J Web Services provide a Web Services home page for each deployed Web Service as shown in Figure 11-5. On this home page are links to a WSDL file, and Web Services proxy files generated by the Web Services Assembler program. The Web Services Assembler tool can even generate a Web Service proxy for Web Services not published on Oracle Application Server. In addition to supporting service calls, a proxy generated by the Web Services Assembler also supports SOAP headers.

Oracle Application Server defines two types of clients that can execute a Web Service: a static client and a dynamic client. These clients are described in the next sections.

11.6.1 Static Client

A static client , in Oracle's terminology, is one that is created with all the information necessary to execute a Web Service. To access an OC4J Web Service as a static client, all you need is to create a Java program that makes a copy of the proxy object for the service and then use the proxy to call a method by the same name and with the same parameters as the service.

11.6.2 Dynamic Client

A dynamic client is one that looks up an available Web Service and executes it at runtime. In this case, the client doesn't know the location of the Web Service or may not even know the name of the Web Service until the time that it looks up available Web Services in a UDDI directory. Once it locates a service (either because it's the first service found or because it uses some other type of determination to choose one of multiple services), the dynamic client looks up its specification via a link to a WSDL file and then uses the specifications in the WSDL file to invoke the desired Web Service.

Oracle Application Server provides two Java packages, oracle.j2ee.ws.client and oracle.j2ee.ws.client.wsdl , that work in concert to dynamically invoke a Web Service given the location of a WSDL file. If you combine these with the use of the UDDI API, you can indeed dynamically identify and execute a Web Service at runtime.

11.6.3 Web Services Security

Oracle Application Server supports authentication and authorization for Web Services using the same mechanisms as for other Oracle Application Server applications. Authentication is enabled using JAAS as implemented in OC4J. Web Services can ensure data privacy and integrity by using SSL.

Chapter 4 describes overall Oracle Application Server security.