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With the DCM_ThrowMessageEvent service call, you can throw Message event towards the process engine. You can select a message event which you have previously defined in the process module. For every defined data field, you can define an expression to fill the field with information. The context of this expression is the module in which you place this service.
How the process engine behaves when receiving a message event is completely dependent on what was modeled in the process module. There is no default action executed when receiving a message event. Examples of behavior that you can model include: Starting a new case or making a task available to the worklist, canceling a case, or placing information in the domain of the case.
Parameters
| Name | Description | Type | Required | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Send to specific Case Ids | The id(s) of the receiving case(s). The specific caseId(s) do not have to be part of the message, but could be.
| Expression | No | ||||||||||||
| Case Ids Target Attribute | The case ids of the case affected by the message event are placed in the selected attribute. This attribute must be multivalued and of the type integer. | Multivalued integer | No | ||||||||||||
| Message event | The name of the message event that will be triggered. | Message event | Yes | ||||||||||||
| Values | These elements represent the content of the message. You have to specify what the result attributes will be. | Elements | No |
DCM_ThrowMessageEvent vs DCM_ThrowAsyncMessageEvent
The DCM_ThrowAsyncMessageEvent is also available. As the name suggests, that service works asynchronously as opposed to this service which is synchronous. The benefit of using the asynchronous service is that a user does not have to wait for the message event to be processed, which could take some time if the message event is broadcast to a lot of cases. The downside of the asynchronous service is that you no longer receive the affected case ids, as you do not have to wait. So consider carefully which service you need for your use case. It's also possible to broadcast a message event to all listening cases using the DCM_ThrowAsyncMessageEvent, this is not possible using the synchronous service call.
When sending a message to a specific case it is not necessary to have a catching condition on the receiving message node.
A combination of a catching condition and specific case Id is possible. You can send a message to a select number of cases and still use the catching condition to decide to process the message or not.
If you have created a process and you want to extract its Id and save it in an aggregate then extract the value returned from the Case Ids Target Attribute. For example use the AQ_InstanceUpdate service to unpack the multivalued attribute by using an expression like this: UNPACK(Control.ProcessIds).
When sending a message that is used as an event to create a process, then only the new process is created. The event is not broadcasted to all other cases. So if you use an event as ProcessStartNode you should not reuse it as an Adhoc event or inline event inside processes.
Non-existing processess
When the message is sent to specific processes, and some of these do not exist any more, the service ends with a FAIL exit IdError. You have to map this exit to an event in your model in order to catch this. In this case, no processes will receive the message.
Inner workings
The service sends a request to the Case Engine which will in turn ask the Process Engine to which cases it should send the Message event. The case engine will then throw the Message Event to each case. It will add the affected cases to the Case Ids Target Attribute.
If an event fails to be processed, it will be added to the queue and handled asynchronously, the caseId will still be returned.
Overview
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