Add something like @Observes from CDI

[SentryMan]

So there I am looking at the Jakarta CDI spec, and I find out about this useful technique available to them.

We could define an SPI for an event manager and an interface for sending events.

interface ObserverManager {
   <T> void registerEventListener(Consumer<T> observer, Type eventType);
   List<Consumer<T>> getObservers(Type eventType);
}

interface Event<T> {
  void fire(T);
  void fireAsync(T);
}

@interface EventType {
}

Here's how I'm thinking a user would go about it.

Publishing

Annotate an event class:

@EventType
class MyEvent  {
//contents...
}

And we'd generate the impl:

@Generated
@Component
class MyEventPublisher implements Event<MyEvent>  {
//inject the Observer Manager and implement publishing methods...
}

The user can then inject this class and publish an event.

Observing

The user can add @Observes to a bean method to signify this should be registered in the manager.

@Singleton
class MyObserver  {
//contents...
 void observeMyEvent(@Observes MyEvent) {
  //contents...
  }
}

We'd then generate the DI class to also register this method to the ObserverManager.

Thoughts?