Intro

This is a simple synchronous event handling system, for use in Spring based applications.

Rationale

Using domain events to notify other components that something of interest happened encourages loose-coupling of components and (among other things) makes it easier to satisfy the Single Responsibility Principle.

Usage

First, include in the event sender an instance of the Spring's ApplicationEventPublisher:

@Autowired
private ApplicationEventPublisher eventPublisher;

Then, publish your Event, which should extend AbstractDomainEvent:

eventPublisher.publishEvent(new MyCustomEvent(loggedInUser, dataOfInterest));

To get this event handled, you then create a listener class. This must be a Spring @Component and have a void single-argument method with a type of your event (or a superclass):

@Component
public class MyEventsListener implements DomainEventListener {
    
    ...
    @EventHandler(MyCustomEvent.class)
    public void handleMyCustomEvent(MyCustomEvent event) {
        ...
    }
    ...
}