参考：Spring事件监听流程分析【源码浅析】_private void processbean(final string beanname, fi-CSDN博客

一、简介

    Spring早期通过实现ApplicationListener接口定义监听事件，Spring 4.2开始通过@EventListener注解实现监听事件

@FunctionalInterface
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {

    /**
     * Handle an application event.
     * @param event the event to respond to
     */
    void onApplicationEvent(E event);


    /**
     * Create a new {@code ApplicationListener} for the given payload consumer.
     * @param consumer the event payload consumer
     * @param <T> the type of the event payload
     * @return a corresponding {@code ApplicationListener} instance
     * @since 5.3
     * @see PayloadApplicationEvent
     */
    static <T> ApplicationListener<PayloadApplicationEvent<T>> forPayload(Consumer<T> consumer) {
       return event -> consumer.accept(event.getPayload());
    }


}

二、示例

    （1）、自定义事件，相当于抽象观察者     

/*
* 系统日志事件，观察者
* */
public class SysLogEvent extends ApplicationEvent {
    public SysLogEvent(SysLog sysLog){
        super(sysLog);
    }
}

    （2）、自定义实现，相当于具体观察者

@Component
public class SysLogListener implements ApplicationListener<SysLogEvent> {
    private final static Logger logger = LoggerFactory.getLogger(SysLogListener.class);

    @Override
    public void onApplicationEvent(SysLogEvent event) {
        logger.info("收到调用日志消息："+ JSON.toJSONString(event));
    }

    /*
    * spring 4.2版本用@EventListener注解
    * */
//    @EventListener(SysLogEvent.class)
    public void saveSysLog(SysLog event){
        logger.info("收到调用日志消息："+ JSON.toJSON(event));
    }
}

    （3）、发布订阅事件

@RestController
@RequestMapping("/event")
public class EventController {

    @Autowired
    private ApplicationContext applicationContext;

    @RequestMapping("public")
    public void event(){
       SysLog sysLog = new SysLog();
       sysLog.setLogId("1");
       sysLog.setCode("2");
       sysLog.setMessage("3");
       applicationContext.publishEvent(new SysLogEvent(sysLog));

    }
}

  （4）、测试