Processing of SOAP Messages - XML

SOAP is used to transfer data across applications on the network. These applications are called SOAP nodes. A SOAP message is sent from an application, called the sender application in the form of a SOAP request, to a receiving application called the receiver application. The data is then processed, and the receiver application returns the response to the sender application. The response is also in the form of a SOAP message. The SOAP Message Exchange Model defines the mechanism in which the messages are transferred using SOAP.

The SOAP Message Exchange Model

The SOAP Message Exchange Model defines the manner in which a SOAP message is transferred from a sender node to a receiver node. When a sender node sends a SOAP request, the request might need to pass through one or more intermediate applications called the intermediate nodes. The path that a SOAP message follows to reach the final node is called the message path. Therefore, when a SOAP message reaches a node that is following the message path, the receiver application processes the SOAP request. The procedure for processing the SOAP request is described in the following list:

  1. The receiver node first identifies the components of a SOAP message. These components include envelope, header, and body. You have learned about the components of a SOAP message in the preceding sections.
  2. After identifying the SOAP components, the receiver application verifies that all components of the SOAP message are supported by the application and then processes the request if the components are verified. However, if the components are not verified, the receiving application discards the request.
  3. If the receiving application is an intermediate application and not the final application (called the ultimate SOAP receiver), the optional components are removed and the final SOAP message is forwarded to the next application, as defined in the message path.

As you can see, an application can act as a sending node, an intermediate node, or a receiver node. The role of the application is specified in the SOAP Header element. The processing of a SOAP message is explained in Figure.

SOAP Message Exchange Model

SOAP Message Exchange Model

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