Message Intermediate Throw Event design

[aravindhrs]

@ilyabr Implementation must be provided for both activity types(intermediate message throw event & send task).

When it comes to configuring message, intermediate throw event allows to configure the message name (can be called as named message) while modeling the bpmn, but in the send task, one must need to explicitly correlate the message name.

A Send Task is used to send a message. In Camunda this is done by calling Java code.

<sendTask id="sendTask" camunda:class="org.camunda.bpm.MySendTaskDelegate" />

Message Intermediate Throwing event sends a message to an external service. This event has the same behavior as a Send Task.

<intermediateThrowEvent id="message">
  <messageEventDefinition camunda:class="org.camunda.bpm.MyMessageServiceDelegate" />
</intermediateThrowEvent>

To correlate the message to the specific process instance waiting for it by matching some properties of the incoming message to some properties of your process instance:

runtimeService
  .createMessageCorrelation("myMessage") 
  .processInstanceBusinessKey(myMessage.getOrderId().toString()) 
  .processInstanceVariableEquals("customerId", myMessage.getCustomerId()) 
  .correlate();

• A process instance matches if it is waiting for a message named myMessage, …​
• if it carries the orderId of the message as its business key , …​
• and if a process variable “customerId” also matches the expectations.

There are other differences can be read from,

Message-events-vs-message-tasks

Difference between Intermediate Throwing message events and Send Task

@Mass_Shake, You can use either of this. But there’s some differences in usability in terms of limitations. If you use Message events, you can’t attach any boundary events to the intermediate events. But incase of SendTask, you can push the message to the queue/topic also provides the ability to attach interrupting/non-interrupting boundary events. So in that case you can add extra features and have better control over it when some event occurs. From below example, i can attach boundary even…

Intermediate and End message throw events

There are indeed 2 main ways of sending messages A Message Send Event and a Message Send Task. from an implementation point of view they would be the same. A java class that does something like this: execution.getProcessEngineServices() .getRuntimeService() .createMessageCorrelation("MessageName") .processInstanceBusinessKey("BusinessKey") .correlate(); One of the differences is indeed the ability to add a multi-instance but more importantly you can add a boundary event… for example …