Listeners

There are several approaches to handle process engine events like task creation, activity completion, and so on.

Execution Listeners

Task Listeners

Spring Events for BPM

BPM add-on additionally introduces a set of Spring application events. The following events are published:

UserTaskAssignedEvent
UserTaskCreatedEvent
UserTaskCompletedEvent
ActivityStartedEvent
ActivityCompletedEvent
ProcessStartedEvent
ProcessCompletedEvent

Here is an example of an event listener that sends an email notification each time a user task is assigned to a user:

@Component("smpl_TaskAssignedNotificationSender")
public class TaskAssignedNotificationSender {

    @Autowired
    private Emailer emailer;

    @Autowired
    private DataManager dataManager;

    @EventListener (1)
    public void onTaskAssigned(UserTaskAssignedEvent event) { (2)
        User user = dataManager.load(User.class) (3)
                .query("select u from smpl_User u where u.username = :username")
                .parameter("username", event.getUsername())
                .one();
        Task task = event.getTask(); (4)
        String emailTitle = "New process task " + task.getName();
        String emailBody = "Hi " + user.getFirstName() + "\n" +
                "The task " + task.getName() + " has been assigned.";
        EmailInfo emailInfo = EmailInfoBuilder.create()
                .setAddresses(user.getEmail())
                .setSubject(emailTitle)
                .setFrom(null)
                .setBody(emailBody)
                .build();
        emailer.sendEmailAsync(emailInfo); (5)
    }
}

1	Declares that the method is an event listener.
2	The listener is fired each time the `UserTaskAssignedEvent` is published.
3	Gets `User` entity to receive a user first name and email address.The `UserTaskAssignedEvent` contains a `username` of a user who is the task assigned to.
4	The `UserTaskAssignedEvent` contains a `Task` object which holds information about the user task.
5	Creates and sends email. See the Email Sending Guide for details.

If you need to get a process variable value in the listener, you can do it this way:

@Autowired
private RuntimeService runtimeService;

@EventListener
public void onOtherProcessTaskAssigned(UserTaskAssignedEvent event) {
    Order order = (Order) runtimeService.getVariable(event.getTask().getExecutionId(), "order");
    // ...
}

By default, a listener is fired when the user task is assigned in any process. If you want to send notifications only for specific process definition, you can check the process definition in the listener method body:

@EventListener
protected void onOtherProcessTaskAssigned(UserTaskAssignedEvent event) {
    if ("order-approval".equals(event.getProcessDefinition().getKey())) {
        // ...
    }
}

or you can define a SpEL (Spring Expression Language) expression that should match in order to handle the event:

@EventListener(condition = "#event.processDefinitionData.key == 'order-approval'")
protected void onOtherProcessTaskAssigned(UserTaskAssignedEvent event) {
    // ...
}