Unlike developing a web service provider, creating a web service client application always starts with an existing WSDL file. This process is similar to the process you use to build a service from an existing WSDL file. The WSDL file that the client consumes already contains the WS-* policy assertions (and, in some cases, any value-added WSIT policy assertions that augment Sun's implementation, but can safely be ignored by other implementations). Most of the policy assertions are defined in the WS-* specifications. Sun's implementation processes these standard policy assertions.
The policy assertions describe any requirements from the server as well as any optional features the client may use. The WSIT build tools and run-time environment detect the WSDL's policy assertions and configure themselves appropriately, if possible. If an unsupported assertion is found, an error message describing the problem will be displayed.
Typically, you retrieve the WSDL directly from a web service provider using the wsimport tool. The wsimport tool then generates the corresponding Java source code for the interface described by the WSDL. The Java compiler, javac, is then called to compile the source into class files. The programming code uses the generated classes to access the web service.