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Most messaging systems divide the message data into a header and a body. The header contains fields that are used by the messaging infrastructure to manage the flow of messages. However, most endpoint systems that participate in the integration solution generally are not aware of these extra data elements. In some cases, systems may even consider these fields as erroneous because they do not match the message format used by the application. On the other hand, the messaging components that route the messages between the applications may require the header fields and would consider a message invalid if it does not contain the proper header fields.

How can existing systems participate in a messaging exchange that places specific requirements on the message format, such as message header fields or encryption?

Use a Envelope Wrapper to wrap application data inside an envelope that is compliant with the messaging infrastructure. Unwrap the message when it arrives at the destination.

The process of wrapping and unwrapping a message consists of five steps:

Related patterns: Messaging Bridge

Find the full description of this pattern in: Enterprise Integration Patterns Gregor Hohpe and Bobby Woolf ISBN 0321200683 650 pages Addison-Wesley

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