[Jboss-dev-forums] [Design of JBoss jBPM] - Re: Web Services for jBPM (cnt'd)

[aguizar <nu...@jb...>]

Anil, thanks for your suggestions! The timing was excellent as we're about to start the implementation of service invocation. I spent some time reading the public review draft of the JAX-WS 2.0 specification, so I'm now able to expand Tom's questions :-)

Referred as "a follow-on to JAX-RPC 1.1" (1), the name change reflects the new direction of this technology. Among other goals, "JAX-WS 2.0 will improve support for document/message centric usage" (2). 

The client deployment model defined in WS4EE did not address standalone (JSE) clients, as opposed to application (JEE) clients. On the other hand, JAX-WS will be prepared for inclusion in a future version of JSE and "will define mechanisms to produce fully portable clients".

JAX-RPC defined its own data binding facilities, but it did not define a way to turn them off. Conversely, "JAX-WS describes the WSDL<->Java mapping, but data binding is delegated to JAXB" (3).

JAX-RPC spared a programmer the details of converting between Java method invocations and the corresponding XML messages. In some cases, tough, operating at the XML message level is desirable. Under JAX-RPC the only way to do it was indirectly via handlers. In JAX-WS, "the Dispatch interface provides support for this mode of interaction" (4). 

Dispatch supports two usages: 'Message' and 'Message Payload'. In the latter, a client application would work with the contents of the SOAP Body rather than the SOAP message as a whole. We would like this usage for jBPM as the framework still deals with overall message assembly/disassembly.

JAX-WS provides the features we traded off from JAX-RPC (optional WSDL support, pluggable message handlers), presents a modular design and still lets us work at the message level. I still have not taken a look at the deployment model; will do asap. Annotations, while making web services in java as easy to code as in .net, are not useful as stated earlier. I will be more interested in the model if there something in the direction of "fully portable clients".

References
The Java API for XML Web Services 2.0: http://jcp.org/en/jsr/detail?id=224 
(1) Introduction
(2) Section 1.1
(3) Section 1.3.1
(3) Section 4.4

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