eventStore.java

Class Clientservice implements Service {
	
	public Object serviceMethod() {

		businessLogic.execute();
		db.save();

		externalApi1.call();
		
		try {
			externalApi2.call(request); //with circuit breaker or make very first call async
		} catch (HttpClientErrorException ex) { 
			eventStore.submit("dead_letter_queue", request, correlationId, request.Class);
		}
		catch (Exception ex) {
			eventStore.submit("event_name",request, correlationId, request.Class)
		}
	}
}


Class EventStoreImpl implements EventStore {
	
	public Object submit(String eventName, Request request, String correlationId, Class clazz  ) {
		messageQueue.push(eventName, request, correlationId)

	}

	public void listen(String eventName, Callback<RequestClass> callback) {


		//eventName is the name of queue in message broker
		messageQueue.listen(eventName, new DefaultConsumer() {
			public void HandleDelivery(byte[] body) {
				callback.call(body);
			}
		});

	}
}

Class TargetService implements Service {
	
	public Object serviceMethod() {
		businessLogic.apply();
	}
}



Class TargetServiceIntegration{
	
	@Autowire
	Service TargetService;

	public Object serviceMethodInt() {

		eventStore.listen("TargetServiceIntegration.serviceMethodInt", new Callback() {
			public void call(byte[] body) {
				System.out.println(body);
			}
		})
		
		targetService.serviceMethod();
	}
}