Nandhini Arumugam and Jeyarani Venkatasamy have written an article for Developer.com called "Processing Request/Response Messages of a Web Service Using the Handler Chain," which explains how handler chains work and what they can do for web services.

In a nutshell, they're web service analogs to the Servlet filter mechanism, and present an ideal layer to implement the various web service APIs without requiring the service developer to understand or manage the entire Web Service specification stack.

For example, there are specifications for authentication, encryption, transaction participation, routing, and a number of other things, all which can be understandably daunting to an individual developer. With the handler chain, however, most of these specifications can be managed in a filter (a handler) such that the developer has much less awareness and coupling to the specifications. Some coupling might still be necessary, for various reasons.

Tools should be able to manage handler chain configuration, which means that they soon might be very common in web service development in Java.

What do you think?

The descriptor file web-service.xml does not seem to be the same as in ref-impl provided by Sun for JAX-RPC! What implementation of JAX-RPC is the example using?

Here is what the sun JAX-RPC RI descriptor looks like


    <handlerChains>
      <chain runAt="server">
        <handler className="service.ServerHandler1"
            headers="ns1:loginfo"
            xmlns:ns1="http://example.com/headerprops">
          <property name="name" value="server1"/>
        </handler>

        <handler className="service.ServerHandler2">
          <property name="name" value="server2"/>
        </handler>
      </chain>
    </handlerChains>
    </endpoint>

In the DOS days we just used to save interrupt vector, and then jump to it. Did not have cool XML configuration files, though ;)

Where's the news? Another lousy attempt of gaining fame with another flavour of well-known design patterns.

Not quite: it's a detail of how you can actually see the WS-* specs being used.

This looks like plain old SOAP with Axis. Where's the WS-* connection?

everything possible out of the box with WebSphere. why even bother coding what you already paid for?

Looking for a new prospect on development is not the issue here. As the title of the article clearly states it is about understanding how this handler chain works. Nothing more, nothing less. So do not expect any new ideas in that article.

Jan