当把一个事件发布到Spring提供的ApplicationContext中，被监听器侦测到，就会执行对应的处理方法。
事件本身事件是一个自定义的类，需要继承Spring提供的ApplicationEvent。
@Datapublic class MyEvent extends ApplicationEvent { private String msg; public MyEvent(Object source, String msg) { super(source); this.msg = msg;
}
}事件监听基本方法是实现ApplicationListener接口，自定义一个监听器，实现onApplicationEvent()方法，然后添加到ApplicationContext。
比如：
public class MyListener implements ApplicationListener{ @Override public void onApplicationEvent(MyEvent event) { System.out.print("监听到MyEvent事件"); } } ...// SpringBoot的启动类中添加监听器 public static void main(String[] args) { SpringApplication application = new SpringApplication(MyApplication.class); application.addListeners(new MyListener()); application.run(args); }
也可以使用注解@EventListener（推荐）：原理就是通过扫描这个注解，创建监听器并添加到ApplicationContext。
@Component@Slf4jpublic class MyEventHandler { @EventListener
public void handleEvent(MyEvent event) {
log.info("------------处理事件：{}", event.getMsg()); try {
Thread.sleep(5 * 1000L);
log.info("事件1(5s)处理完成");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}事件发布可以通过上下文对象的发布方法ConfigurableApplicationContext::publishEvent()来发布。
也可以实现ApplicationEventPublisherAware接口来发布（推荐）。
@Component@Slf4jpublic class EventService implements ApplicationEventPublisherAware { public ApplicationEventPublisher publisher; @Override
public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) { this.publisher = applicationEventPublisher;
} public String doEventWork(String msg) {
log.info("------------publish event:" + msg);
MyEvent event = new MyEvent(this, msg);
publisher.publishEvent(event); return "OK";
}
}测试代码@SpringBootTest@RunWith(SpringRunner.class)public class EventServiceTest { @Autowired
private EventService service; @Test
public void eventTest() {
String msg="Java Code";
service.doEventWork(msg);
}
}image
注意如果2个事件之间是继承关系，会先监听到子类事件，处理完再监听父类。
// MyEvent2 extends MyEvent@Component@Slf4jpublic class MyEventHandler { @EventListener
public void handleEvent(MyEvent event) {
log.info("------------处理事件：{}", event.getMsg()); try {
Thread.sleep(5 * 1000L);
log.info("事件1(5s)处理完成");
} catch (InterruptedException e) {
e.printStackTrace();
}
} @EventListener
public void handleEvent2(MyEvent2 event) {
log.info("------------处理事件2：{}", event.getMsg()); try {
Thread.sleep(10 * 1000L);
log.info("事件2(10s)处理完成");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}当我publish一个子类事件MyEvent2时，日志如下：
image
作者：Joepis
链接：https://www.jianshu.com/p/47ae0bbdf205
