Attaching the undercover agent to the message event

Attach the undercover agent (UCA) to the message event. The event waits for the completion of the UCA. When the UCA completes, the event completes.

1. Open the Process Designer desktop editor.
2. Open a process application that contains a BPD with a message event.
3. Open the BPD that includes the message event.
4. Click the message event in the BPD to select it.
5. Click the Implementation option in the properties.
6. In the Message Trigger section, click the Select button next to the Attached UCA field and pick My UCA that you created in the preceding steps.
7. Ensure that the Consume Message and Durable Subscription check boxes are enabled. (For more information about these options, see Modeling message events.)
   Tip: If you occasionally use inbound messages, consider using durable subscription events. Durable subscriptions are Java Message Service (JMS) subscriptions that persist and store subscribed messages even when the client is not connected. The durable messages accumulate, even if you select the check box to make them consumable. Periodically use the BPMDeleteDurableMessages command for deleting durable subscription events.
8. Click the Data Mapping option in the properties. Notice that the Output correlation key is automatically set to the someString variable from the UCA. The variable is used as a correlation parameter, which allows you to correlate an event recipient with a particular key.
   Note: When an event occurs, that event must be matched against the correct instance of the process for which the event is destined. The ability to match the event against the correct instance is called correlation. You must specify one variable in the message event that has a value that matches the value of the incoming event's UCA payload (the correlation value). If there is such a match, the message is received. If not, the message is not received, and the event continues to wait.
9. In the field next to the variable, type tw.system.process.instanceId. This sets the value of the someString variable to the ID of the running instance, which allows you to test the implementation in the Inspector.

   In this example, you are creating a UCA that uses the current process instance ID as the correlation parameter. For example, if you have a process application with the instance ID of 50 and another process application with the instance ID of 100, if you invoke the UCA passing an ID of 50, only the first process application receives the event.

10. Save your work.