MQ Header Setter mediation primitive
Use the MQ Header Setter mediation primitive to create, set, copy or delete WebSphere® MQ message headers.
Introduction
You can use the MQ Header Setter mediation primitive to provide a mechanism for managing MQ headers in a message. You can change, copy, add, or delete MQ headers by setting the mediation primitive properties.
If you want multiple header changes you can set multiple actions. Multiple actions are acted on sequentially, in the order you specify; this means that header changes can build on each other.
The MQ Header Setter mediation primitive has one input terminal (in), one output terminal (out) and a fail terminal (fail). The in terminal is wired to accept a message and the other terminals are wired to propagate a message. If the mediation is successful, the out terminal propagates the modified message. If an exception occurs during the transformation, the fail terminal propagates the original message, together with any exception information contained in the failInfo element.
Details
You can create a new MQ header (apart from the MQMD header) and specify the header field values. The new MQ header element is added to the service message object (SMO); if a header of the same type already exists the new header is appended to the end of the header list.
You can also search for MQ headers that already exist in the SMO, by specifying the header type to match on. If matching headers are found, you can set the header fields to the values you specify, or you can delete the headers (other than the MQMD header). Alternatively, you can copy the first matching MQ header to another location in the SMO.
Generally, you specify the field values of MQ headers, using either a literal value or an XPath expression.
Usage
You can use the MQ Header Setter mediation primitive to ensure that when an MQ message is sent to another system, the headers that are sent with the message are correctly set.
Because the operations you define occur sequentially, a later operation can depend on an earlier operation. For example, you could create a new header, copy it to elsewhere in the SMO and then delete it from the list of headers it was initially appended to.
You can also use the MQ Header Setter mediation primitive to help to filter messages, using the Message Filter mediation primitive. You might want to find a particular header and make it available to be used in the filtering. For example, you could copy an MQ header to a more accessible place, and the Message Filter primitive could then use the details inside the header.