How service integration converts messages to and from WebSphere MQ format

Messages are converted between WebSphere® MQ format and service integration format as they flow between the two systems.

Exchanging messages between JMS programs through service integration and WebSphere MQ

In general, you do not need to be aware of conversion between message formats to exchange JMS messages between service integration and WebSphere MQ. However, you might need to learn about message conversion if your JMS applications do not behave as expected or if your service integration configuration includes JMS programs or mediations that process messages to or from non-JMS WebSphere MQ programs.

If your service integration applications exchange MapMessage objects with WebSphere MQ applications, you might need to specify a non-default map message encoding format. For more information, see Setting the WebSphere MQ encoding format for JMS Map entries.

When service integration converts messages to and from WebSphere MQ format

Service integration converts a service integration message into a WebSphere MQ message in the following circumstances:
  • When service integration sends a message to WebSphere MQ using a WebSphere MQ link.
  • When a service integration mediation places the message on a queue point that is a WebSphere MQ queue.
  • When a service integration application sends the message to a destination where the mediation point (if any) or the queue point (if there is no mediation) is a WebSphere MQ queue.
Service integration converts a WebSphere MQ message into a service integration message in the following circumstances:
  • When WebSphere MQ sends the message to a service integration bus using a WebSphere MQ link.
  • When a service integration mediation receives the message from a mediation point that is a WebSphere MQ queue.
  • When a service integration application receives the message from a destination where the queue point is a WebSphere MQ queue.
When you use the WebSphere MQ messaging provider, there is no conversion between WebSphere MQ format and service integration format.

Overview of message conversion

When service integration converts a message to WebSphere MQ format, it usually constructs a WebSphere MQ message descriptor (MQMD), a rules and formatting header 2 (MQRFH2), and a message payload:
  • Message descriptor (MQMD): Service integration sets fields in the MQMD based on the service integration message header fields and properties; these include JMS message header fields and properties applicable to the message. Service integration always constructs an MQMD.
  • Rules and formatting header 2 (MQRFH2): Service integration sets fields in the MQRFH2 based on the service integration message header fields and properties. Some WebSphere MQ applications cannot process messages that contain an MQRFH2. To simplify interoperation, you can configure service integration to omit the MQRFH2 from messages for applications that cannot process the MQRFH2. Note that when service integration omits the MQRFH2, it discards the corresponding service integration header fields and properties.
  • Message payload: Service integration uses the body of the service integration message (if any) as the payload of the WebSphere MQ message.
When service integration converts a message from WebSphere MQ format:
  • It sets the service integration message header fields and properties from the MQMD and (if present) the MQRFH2 in the WebSphere MQ message.
  • It sets the service integration message body to the contents (if any) of the WebSphere MQ message that immediately follow the MQRFH2.

In the following figure there is a service integration message and a WebSphere MQ message. The service integration message is encapsulated by the JMS message implementation for service integration. The service integration message contains "header fields", "Properties" and a "Body". The WebSphere MQ message contains a "MQMD", a "MQRFH2" and a "Payload". There is a two-way conversion flows between each of the "header fields" and "Properties" boxes, each of the "MQMD" and "MQRFH2" boxes, and also between the "Body" and the "Payload" boxes.

Figure 1. Message conversion to and from WebSphere MQ format
This figure is described in the surrounding text.



Subtopics
How message properties and reliability levels are mapped between service integration and WebSphere MQ
Related concepts
Learning about interoperating with a WebSphere MQ network
Concept topic    

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Last updated: Feb 19, 2011 5:25:36 AM CST
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