Using subflows

You can include subflows in your message flows in exactly the same way as you include built-in or user-defined nodes.

You can also connect them to other nodes in the same way. Because you can define a subflow once, and use it in more than one message flow (and even in more than one message flow project), a subflow can provide benefits:

However, you must remember that a subflow is not a single node, and its inclusion increases the number of nodes in the message flow, which might affect its performance.

Consider these examples of subflow use:

Start of changeUse the Passthrough node to enable versioning of a subflow at run time. The Passthrough node allows you to add a label to your message flow or subflow. By combining this label with keyword replacement from your version control system, you can identify which version of a subflow is included in a deployed message flow. You can use this label for your own purposes. If you have included the correct version keywords in the label, you can see the value of the label:
  • Stored in the broker archive (BAR) file, using the mqsireadbar command
  • As last deployed to a particular broker, on the properties of a deployed message flow in the Message Brokers Toolkit
  • In the run time, if you enable user trace for that message flow.
The message that it propagates on its out terminal is the same message that it received on its in terminal. For example, if you develop an error processing subflow to include in several message flows, you might want to modify that subflow. However, you might want to introduce the modified version initially to just a subset of the message flows in which it is included. Set a value for the instance of the Passthrough node that identifies which version of the subflow you have included.End of change

The use of subflows is demonstrated in the Error Handler sample and the Coordinated Request Reply sample. The Error Handler sample uses a subflow to trap information about errors and store the information in a database. The Coordinated Request Reply sample uses a subflow to encapsulate the storage of the ReplyToQ and ReplyToQMgr values in a WebSphere MQ message so that the processing logic can be easily reused in other message flows and to allow alternative implementations to be substituted.

Related concepts
Message flows overview
Promoted properties
Related tasks
Designing a message flow
Defining a promoted property
Creating a message flow
Defining message flow content
Related reference
Built-in nodes