Java Web Services

Chapter 7. JAX-RPC and JAXM

The Java API for XML Messaging (JAXM) and the Java API for XML-based RPC (JAX-RPC) are both part of the Java Web Services Developer Pack, Winter 01 release.^[10] These APIs are a key part of Sun’s plans to integrate web services interfaces into future versions of the J2EE platform. JAXM provides a common set of Java APIs for creating, consuming, and exchanging SOAP envelopes over various transport mechanisms. It is intended mainly for a document-style exchange of information because it requires the use of low-level APIs to manipulate the SOAP envelope directly. JAX-RPC provides a means for performing RMI-like Remote Procedure Calls over SOAP. In addition, JAX-RPC provides rules for such things as client code generation, SOAP bindings, WSDL-to-Java and Java-to-WSDL mappings, and data mappings between Java and SOAP.

Fundamentally, JAXM supports synchronous communications. In fact, if you don’t run your JAXM provider in a J2EE web container (i.e., it is implemented as a message-driven bean or servlet), then it supports only synchronous communications. You don’t get asynchronous exchanges unless you use the connection provider. Don’t get hung up by the “M” versus “RPC” mislabeling. You can use JAXM to exchange document- or RPC-style SOAP messages, just as you can with JAX-RPC. The real distinction between JAXM and JAX-RPC is that JAXM forces the developer to work directly with the SOAP envelope constructs, and JAX-RPC provides a high-level, WSDL-based framework ...