WebSphere Message Brokers
File: ac00455_
Writer: Kate Hostler

Concept topic

This build: July 31, 2007 21:16:42

Application programming interfaces

WebSphere Message Broker does not provide any unique programming interfaces, but supports several programming interfaces that are already in use by messaging applications today.

If you have existing end-user applications that are written to these interfaces, they can typically run unchanged in a broker environment. You must create the message flows to interact with these applications across the supported protocols, using the appropriate input and output nodes. WebSphere Message Broker provides built-in input and output nodes for its supported protocols and you can create your own user-defined nodes to support additional protocols if you choose.

You can also create new end-user applications to interact with the broker.

Message headers

WebSphere Message Broker provides parsers for a large number of WebSphere MQ headers, and can therefore accept messages that contain these headers across the WebSphere MQ Enterprise Transport, WebSphere MQ Mobile Transport, and WebSphere MQ Telemetry Transport protocols.

Messages must include a WebSphere MQ Message Descriptor (MQMD) as the first header, which must precede user or application data in every message. The MQMD contains basic control information that must travel with the message, including:

When a message is processed by a WebSphere Message Broker broker, it typically (but not necessarily) has one or more additional headers. The header following the MQMD is always identified in the format field within the MQMD, and itself contains another format field to identify either the header that follows, or the format of the user data.

The additional headers can include:

MQRFH
The Rules and Formatting header is used by WebSphere MQ Publish/Subscribe.
MQRFH2
The MQRFH2 is an updated version of MQRFH and allows Unicode strings to be transported without translation, and it can carry numeric data types. The MQRFH2 header carries a description of the message contents, so that WebSphere Message Broker can select the correct message parser when content-based processing is carried out on the message. In addition, this header contains publish/subscribe command messages. Messages created by the SCADAInput node always include and MQRFH2 header.

Use the MQRFH2 header in all new applications written for the WebSphere Message Broker environment that use a supported protocol based on WebSphere MQ technology. The MQRFH2 header should be immediately before the body of the message (that is, the last header).

If an MQRFH2 header is not included (which is normally the case of the application uses a supported protocol that is not based on WebSphere MQ technology), you must configure the message flow that processes its messages to specify the message characteristics (by setting the input node properties).

Related concepts
Publish/Subscribe
Message flows overview
Related tasks
Developing publish/subscribe applications
Developing message flows
Related reference
Publish/subscribe
MQRFH2 header
Built-in nodes
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This build: July 31, 2007 21:16:42

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