Java Web Services in a Nutshell

SOAP Headers

So far, we have only concerned ourselves with the body of a SOAP message and its attachments, both of which are intended solely for the ultimate destination of the message. A message can also include headers, which contain information that is related to the routing or processing of the message, but which are not part of the payload itself. SOAP itself does not define any standard headers, but there are specific uses of SOAP that do, some of which are discussed in Chapter 4. In this section, we’ll look in a generic way at the facilities provided by SAAJ for creating and handling headers, and defer detailed discussion of real-world uses of this facility until Chapter 4.

SOAP Actors and the mustUnderstand Attribute

Although the examples that we have shown so far involve only a client and a web service to which the client sends a SOAP message, in practice, a SOAP message may pass through one or more intermediate systems before reaching its ultimate destination. For the purposes of this discussion, an intermediate system is not like a network router, which is concerned only with passing a transport-level packet from node to node until it reaches a destination, but an application-level entity that receives a SOAP message, examines it, and either handles it or forwards it to another SOAP receiver for further processing.

As an example of the use of an intermediate system, suppose that a business wants to make it possible for other businesses to place stock orders by building a ...