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。
@Data
public 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<MyEvent> {
@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
@Slf4j
public 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
@Slf4j
public 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);
}
}
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
@Slf4j
public 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：
