Java Web Services

Chapter 4. SOAP-RPC, SOAP-Faults, and Misunderstandings

SOAP-RPC

SOAP-RPC defines a model for representing an RPC and an RPC response using the SOAP infrastructure. It is not necessarily bound tightly to a synchronous request/reply model, or to the HTTP protocol. In fact, both the SOAP 1.1 and 1.2 specifications explicitly state that the use of SOAP-RPC is orthogonal to the protocol binding. The specifications do concede that when SOAP-RPC is bound to HTTP, an RPC invocation maps naturally to an HTTP request, and an RPC return maps naturally to an HTTP response, but this natural mapping is purely coincidental. One of the goals of the SOAP 1.2 effort was to distance itself from the point of view that SOAP is inherently an RPC mechanism. As a result, SOAP-RPC was moved into the optional “Adjuncts” portion of the specification.

That said, what’s really important is that SOAP defines a uniform model for representing an RPC and its return value or values. The fundamental requirements for an RPC call are that the body element contains the method name and the parameters and that the parameters are accessible via accessors.^[5] In addition, SOAP has provisions for encoding the method signature, header data, and the URI that represents the destination.

In the next example, we’ll look at a SOAP-RPC client that calls a remote service that returns the value of a book at Barnes & Noble. The service is hosted and available at http://www.xmethods.net. Let’s start by running the client and examining ...