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Introducing JAX-RPC
Build and access Web services based on synchronous RPC-oriented SOAP messaging
by Simon Horrell
May 2002 Issue
The Java API for XML-based remote procedure calls (JAX-RPC) simplifies the process of building Web services that incorporate XML-based RPC. It defines mappings between XML types and Java types that attempt to hide the details of XML and provide a familiar method-call paradigm. This introduction shows how developers can use JAX-RPC to implement and call SOAP-based Web services described by the Web Services Description Language (WSDL). Let's see how it works.
Web services can be document-oriented endpoints or method-oriented endpoints. The XML messages exchanged with a document-oriented Web service contain an XML document, and all message semantics are application-defined. With a method-oriented Web service, a pair of correlated XML messages corresponds to an RPC, and part of the message semantics are predefined. One message passes inbound from caller to Web service and contains the method identifier and any input parameters. The information in this message is used to map to a method call in some native programming language, and to execute it with the supplied input parameters. After the method executes, another message passes outbound from Web service to caller and contains the method identifier, the result of executing the method, and any output parameters (or exception information in the case of an error). The most common XML messaging protocol for representing RPCs in this way is the Simple Object Access Protocol
(SOAP) 1.1.
Most developers don't want to write, transmit, interpret, and correlate XML messages by hand and then map them to and from native programmatic types. The JAX-RPC aims to set a common standard in the Java space for writing and consuming RPC-based Web services. As of this writing, JAX-RPC—the result of work by the Java Community Process under Java Specification Request 101—is at version 0.7 (public draft 2).
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