Java Web Services: Up and Running, 2nd Edition

What’s Next?

The focus in the first three chapters has been on RESTful web services and their clients. The next chapter turns to SOAP-based services delivered over HTTP(S), which can be viewed as a special case of RESTful services. The normal request and response payloads in a SOAP-based service are SOAP envelopes, XML documents whose root element has a tag with Envelope as the local name. An example is:

<soap:Envelope xmlns:soap = '...'>
  ...
</soap:Envelope>

In a typical SOAP-based exchange, a client sends an Envelope to a service and gets an Envelope in return. SOAP, like XML in general, is programming-language neutral, and any language with the appropriate libraries can support SOAP-based services and clients. At present, however, only Java and DotNet have strong support for SOAP; the other language systems have spotty support at best.

There is much to be said for SOAP over HTTP. The HTTP handles the transport and, in the case of HTTPS, addresses major wire-level security concerns. The SOAP libraries on the service and the client side typically hide the SOAP, although the SOAP is available to inspect or even manipulate if a service or a client requires this. Chapter 4 looks at the service and the client sides of SOAP-based services; this look includes two SOAP-based clients against the Amazon E-Commerce service. Chapter 5 then examines the handler level in SOAP-based services. At the application level in SOAP-based services, the SOAP itself is transparent; at the handler level, ...