Spring中ApplicationEventPublisher发布订阅模式的实现

public class LogEvent extends ApplicationEvent {
    public LogEvent(Object message) {
        super(message);
    }
}

@Slf4j
@RestController
@RequestMapping("/log")
public class LogController {
    @Autowired
    private ApplicationEventPublisher publisher;
    @GetMapping("/publisher")
    public void log() {
        log.info("进入到log方法,开始发送事件");
        publisher.publishEvent(new LogEvent("log方法生成事件信息"));
        log.info("log方法发送事件完毕");
    }
}

/**
 * 管理员日志监听器
 */
@Slf4j
@Component
public class AdminListener {
    @EventListener(LogEvent.class)
    public void adminListen(LogEvent logEvent) {
        try {
            log.info("管理员监听到的日志信息为,{}", logEvent);
            Thread.sleep(5000); // 睡眠5s
            log.info("管理员监听完毕");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

/**
 * 用户日志事件监听器
 */
@Slf4j
@Component
public class UserListener {
    @EventListener(LogEvent.class)
    public void userListen(LogEvent logEvent) {
        try {
            log.info("用户监听到的日志信息为,{}", logEvent);
            Thread.sleep(10000); // 睡眠10s
            log.info("用户监听完毕");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

protected void publishEvent(Object event, @Nullable ResolvableType eventType) {
        Assert.notNull(event, "Event must not be null");
        Object applicationEvent;
        if (event instanceof ApplicationEvent) {
            applicationEvent = (ApplicationEvent)event;
        } else {
            applicationEvent = new PayloadApplicationEvent(this, event);
            if (eventType == null) {
                eventType = ((PayloadApplicationEvent)applicationEvent).getResolvableType();
            }
        }
        if (this.earlyApplicationEvents != null) {
            this.earlyApplicationEvents.add(applicationEvent);
        } else {
            // 在这步完成真正的发布订阅 只有监听完才会向下继续执行
            this.getApplicationEventMulticaster().multicastEvent((ApplicationEvent)applicationEvent, eventType);
        }
        if (this.parent != null) {
            if (this.parent instanceof AbstractApplicationContext) {
                ((AbstractApplicationContext)this.parent).publishEvent(event, eventType);
            } else {
                this.parent.publishEvent(event);
            }
        }