Java Web Services: Up and Running, 2nd Edition

Handlers and Faults in the predictionsSOAP Service

This section ports the various REST-style versions of the predictions web service to a SOAP-based version. The new version is predictionsSOAP, whose structure can be summarized as follows:

• There is a service client and a client-side message handler. The handler inserts an HMAC hash into every client request against the predictionsSOAP service. However, the handler departs from the Amazon practice by inserting the hash into the SOAP header rather than the SOAP body.
• The client, built atop wsimport-generated classes, invokes various CRUD operations in the predictionsSOAP service.
• There is a service-side message handler whose job is to verify the HMAC hash from the client.
• The service implements the standard CRUD operations.
• The service throws SOAP faults from both the handler and the application level in order to contrast the two different APIs. As the name suggests, a SOAP fault signals an error condition; the fault is a special message sent back to the client in place of an error-free SOAP response. The service WSDL indicates, in the portType section, that a client request may result in a fault message rather than a standard response. The architecture of the predictionsSOAP service is sketched in Figure 5-5.

Figure 5-5. The architecture of the predictionsSOAP service

The predictionsSOAP service mirrors, in its structure, the SOAP-based ...