Message Delegates

Message Delegates

Message Delegates are the Java representation of the Message Events in your BPMN model. You link a Message Delegate to a certain Message Event by selecting the Message Event in the Camunda Modeler and adding a Java class to the Implementation field. Make sure you use the fully qualified class name. Like this:

org.package.myClass

You will only need Message Delegates for Message Send Events. Incoming messages will be resolved to the correct BPMN process execution automatically using Message Correlation and the message inputs will be added to that execution's process variables.

To make a Message Delegate for Message Send Events, your Java class needs to extend AbstractTaskMessageSend. Most of the time, you will not be adding any processing logic to your Message Delegates, therefore you usually won't be overwriting the doExecute method like with Service Delegates. Instead, you most likely want to aggregate the information you processed in earlier steps and attach it to a message. For this you need to overwrite the getAdditionalInputParamters method. The DSF translates BPMN messages into FHIR Task resources to execute the communication modeled by your BPMN diagrams. The information you are sending to another BPMN process is specified in the Task.input elements a.k.a. Input Parameters, hence the name of the method. The constructor of your delegate class should also forward a ProcessPluginApi instance to its superclass constructor. You can learn more about the ProcessPluginApi here.