Usage of process var as delegate class for ServiceTask

Camunda 7 Topics Discussion & Questions
1

Hey guys,

I’m a little bit confused about how to use a process var as delegate class in a ServiceTask.

I’m starting my process in the application:

Map<String, Object> processVars = new HashMap<String, Object>();
processVars.put("delegateClazz", "com.test.FooDelegate");
final ProcessInstance instance = runtimeService.startProcessInstanceByKey("simple-timer-task", processVars);

And that’s the corresponding process:

  <bpmn2:process id="simple-timer-task" isExecutable="true">
    <bpmn2:serviceTask id="ServiceTask_1" camunda:class="${delegateClazz}" name="Callback aufrufen">
      <bpmn2:incoming>SequenceFlow_3</bpmn2:incoming>
      <bpmn2:outgoing>SequenceFlow_2</bpmn2:outgoing>
    </bpmn2:serviceTask>
    <bpmn2:sequenceFlow id="SequenceFlow_2" name="" sourceRef="ServiceTask_1" targetRef="EndEvent_1"/>
    <bpmn2:endEvent id="EndEvent_1">
      <bpmn2:incoming>SequenceFlow_2</bpmn2:incoming>
    </bpmn2:endEvent>
    <bpmn2:startEvent id="StartEvent_2">
      <bpmn2:outgoing>SequenceFlow_3</bpmn2:outgoing>
    </bpmn2:startEvent>
    <bpmn2:sequenceFlow id="SequenceFlow_3" name="" sourceRef="StartEvent_2" targetRef="ServiceTask_1"/>
  </bpmn2:process>

And I’m ending up with error:
Caused by: java.lang.ClassNotFoundException: ${delegateClass}

Any solutions for this problem?

2

Hi Wischmopp,

Your problem is that the value of the camunda:class attribute is parsed as a string and not translated to an expression during the parsing of the BPMN.
As a workaround, you could use the camunda:delegateExpression attribute instead and define the value as a process variable like you already did. The process variable must return an instance of a class implementing the JavaDelegate interface.

Cheers,
Christian

1 Like
3

Hi Christian,

thank you very much for the quick response.
I’ve tried to set an ObjectValue instance with an instance of my Delegate Class, but now camunda is complaining about a missing serializer: Cannot find serializer for value 'ObjectValue
According to the docs camunda should be able to de-/serialize java objects out of the box…

Here’s my code:

        ObjectValue customerDataValue = Variables.objectValue(new TestDelegate())
                .serializationDataFormat(Variables.SerializationDataFormats.JAVA)
                .create();
        String instanceId = startProcessForContract(createdBy, "simple-timer-task", contractId, processVars);
        runtimeService.setVariable(instanceId, "delegate", customerDataValue);

Cheers,
Andi

4

Hi Andi,

Does the class TestDelegate implement java.io.Serializable?

Cheers,
Thorben

1 Like
5

Foooo, not my day :wink:
Thanks Thorben, now It’s working!!

6