1、定義事件繼承ApplicationEvent

/**
 * 訂單完成事件
 */
@Getter
public class OrderFinishedEvent extends ApplicationEvent {

    private final Order order;

    public OrderFinishedEvent(Object source, Order order) {
        super(source);
        this.order = order;
    }
}

2、發布事件

@Resource
private ApplicationContext applicationContext;

applicationContext.publishEvent(new OrderFinishedEvent(this, order));

3、監聽事件

（1）實現ApplicationListener

@Component
public class FirstOrderFinishedListener implements ApplicationListener<OrderFinishedEvent> {
    @Override
    public void onApplicationEvent(OrderFinishedEvent event) {
        Order order = event.getOrder();
        ...
    }
}

（2）注解@EventListener

// ({可監聽多個事件，逗號分隔})
@EventListener(OrderFinishedEvent.class)
// 參數0或1個，返回類型任意（異步@Async時不能返回原生類型如boolean）
public void onApplicationEvent(OrderFinishedEvent event) {
    logger.info("訂單完成：{}", JSON.toJSONString(event));
    Order order = event.getOrder();
}

備注：監聽事件通常會異步處理，方法加上注解 @Async("threadPoolTaskExecutor")，使用指定線程池異步處理。