import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.ToString;

@Data
@AllArgsConstructor
@ToString
public class OrderCompletedEvent {

    int id;
}

import cz.cizek.edu.springevents.event.OrderCompletedEvent;
import lombok.RequiredArgsConstructor;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.stereotype.Service;

@Service
@RequiredArgsConstructor
public class OrderService {

    private final ApplicationEventPublisher eventPublisher;

    public void completeOrder(int id) {

        //here would be the business logic to complete order
        System.out.println("Order " + id + " was completed");

        eventPublisher.publishEvent(new OrderCompletedEvent(id));
    }
}

import cz.cizek.edu.springevents.event.OrderCompletedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Component
public class OrderHandler {

    @EventListener
    public void onOrderCompletedEvent(OrderCompletedEvent orderCompletedEvent) {

        // here would be e.g. sending an e-mail
        System.out.println("OrderCompletedEvent of order " 
           + orderCompletedEvent.getId() + " was processed");
    }
}