Correlating an external message to an Execution

[ktm]

I have a simple process with an eventBasedGateway.  I have 2 intermediateCatchEvents after the gateway; one has a timer and the other has a messageEventDefinition ("userCallback").  I have a test; the test works.  However, it seems wrong.

In my test, I create a process instance:

      Map<String, Object> variables = new HashMap<String, Object>();
      variables.put("tempId", "ktm099");
ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("createUser", "bizKey", variables);

I query the Execution and apply the message, and this works.  But I think my query is wrong.  I expect to query for businessKey and messageEventSubscriptionName.  But this does not work.  I get null for my query.  This does work:

        Execution execution = runtimeService.createExecutionQuery()
         .messageEventSubscriptionName("callbackMessage")
         .processVariableValueEquals("tempId", "ktm099")
         .singleResult();

Digging into this, I find that the engine holds 2 executions.  The first has the businesKey but no messageEventSubscription.  The second has the messageEventSubscription but businessKey is null.

I don't understand how Executions are related to process instances, so I am writing to ask if there is a pattern for this kind of correlation.

Thanks.
Kit

[ronald_van_kuij]

I don't understand how Executions are related to process instances,

Here is the answer

[ktm]

These 2 queries get me to the Execution I want:
      Execution processEx = runtimeService.createExecutionQuery()
              .processInstanceBusinessKey("abc")
              .singleResult();

      Execution messageListener = runtimeService.createExecutionQuery()
              .processInstanceId(processEx.getProcessInstanceId())
              .messageEventSubscriptionName("callbackMessage")
              .singleResult();

I was expecting the following to work, but it does not:
      Execution messageListener = runtimeService.createExecutionQuery()
              .processInstanceBusinessKey("abc")
              .messageEventSubscriptionName("callbackMessage")
              .singleResult();

It seems to me that there is a kind of parent/child relationship here and I feel as though an ExecutionQuery on business key should return all Executions which are associated with the ProcessInstance which was created with said business key.

I'm just complaining, when you get down to it.

[jbarrez]

Indeed, the executions are actually a tree of executions:

http://nurkiewicz.blogspot.be/2011/01/activiti-processes-and-executions.html