J2EE™ and JAX™: Developing Web Applications and Web Services

13.1. SOAP

Nothing prevents us from passing XML messages in middleware such as JMS, or even across a simple socket connection we manage ourselves. But in these cases, it is only the message content itself—the payload—that is formatted in XML. Information used to get the message to its destination—such as routing information, priority, and any other message options—is specified in a different manner, typically as parameters to API calls.

The standard for XML messaging is something known as SOAP, for Simple Object Access Protocol. It is yet another W3C standard, which originated from Microsoft. In a SOAP message, not just the payload but everything about the message is in XML. SOAP messages comprise an envelope part and a body part, both of which ...