WAS v8.5 > WebSphere applications > Messaging resources > Interoperation with WebSphere MQ > How messages are passed between service integration and a WebSphere MQ network
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
Usually, we do not have to be aware of conversion between message formats to exchange JMS messages between service integration and WebSphere MQ, because service integration performs the appropriate conversion automatically, including character and numeric encoding. However, you might have 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 have to specify a non-default map message encoding format.
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 we 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 containing an MQRFH2. To simplify interoperation, we can configure service integration to omit the MQRFH2 from messages for applications that cannot process the MQRFH2. However, be aware 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.
- If the message contains other headers, instead of, or as well as, the MQRFH2 header, those headers are treated as part of the JMS message body and the JMS message becomes a bytes message.
Figure 1. Message conversion to and from WebSphere MQ format
For reference information about the mappings for specific message header fields and properties between a service integration bus and WebSphere MQ, see the topics listed in the related reference. To help you program applications that interoperate with WebSphere MQ, these topics describe how the message formats are mapped between service integration messages and WebSphere MQ messages.
Reference:
Map the message body to and from WebSphere MQ format
Map the message header fields and properties to and from WebSphere MQ format
Map MQMD Report fields to JMS provider-specific properties
Map additional MQRFH2 header fields in service integration
Map the JMS delivery option and message reliability to and from the WebSphere MQ persistence value
Map destinations to and from WebSphere MQ queues, topics, and destinations
How to process WebSphere MQ message headers