If you use Delegation Code, you can access the BPMN model instance and current element of the executed process. If a BPMN model is accessed, it will be cached to avoid redundant database queries.

Java Delegate

If your class implements the org.camunda.bpm.engine.delegate.JavaDelegate interface, you can access the BPMN model instanceand the current flow element. In the following example the JavaDelegate was added to a service task in the BPMN model.Therefore the returned flow element can be cast to a ServiceTask.

public class ExampleServiceTask implements JavaDelegate {
  public void execute(DelegateExecution execution) throws Exception {
    BpmnModelInstance modelInstance = execution.getBpmnModelInstance();
    ServiceTask serviceTask = (ServiceTask) execution.getBpmnModelElementInstance();
  }
}

Execution Listener

If your class implements the org.camunda.bpm.engine.delegate.ExecutionListener interface, you can access the BPMN model instanceand the current flow element. As an Execution Listener can be added to several elements like process, events, tasks, gatewaysand sequence flows, it can not be guaranteed which type the flow element will be.

public class ExampleExecutionListener implements ExecutionListener {
  public void notify(DelegateExecution execution) throws Exception {
    BpmnModelInstance modelInstance = execution.getBpmnModelInstance();
    FlowElement flowElement = execution.getBpmnModelElementInstance();
  }
}

Task Listener

If your class implements the org.camunda.bpm.engine.delegate.TaskListener interface, you can access the BPMN model instanceand the current user task since a Task Listener can only be added to a user task.

public class ExampleTaskListener implements TaskListener {
  public void notify(DelegateTask delegateTask) {
    BpmnModelInstance modelInstance = delegateTask.getBpmnModelInstance();
    UserTask userTask = delegateTask.getBpmnModelElementInstance();
  }
}

原文: https://docs.camunda.org/manual/7.9/user-guide/model-api/bpmn-model-api/delegation-code/