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);@Overridepublic 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 {@Autowiredprivate 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