1. What?
Spring的ApplicationEventPublisher拥有事件发布并且注册事件监听器的能力，拥有一套完整的事件发布与监听机制，类似于Guava的EventBus。
2. Why?
事件处理机制，是设计模式中的观察者模式（生产/消费者编程模型）的优雅实现，高类聚低耦合，降低业务代码的耦合度，支持异步操作。
3. How?
核心类：
a. 事件ApplicationEvent;
b. 事件发布者ApplicationEventPublisher;
c. 事件监听器ApplicationListener或注解@EventListener
步骤：
1.创建自定义的事件模型
@Data
public class Something {
// 自定义字段
private String id;
private String type;
private String name;
// ...
}
2.自定义事件继承ApplicationEvent
public class SomethingRegisterEvent extends ApplicationEvent{
public SomethingRegisterEvent(Something something) {
super(something);
}
}
3.创建事件发布者
@Service
@Slf4j
public class EventService {
@Autowired
private ApplicationEventPublisher publisher;
public void publishSomething(Something something) {
publisher.publishEvent(new SomethingRegisterEvent(something));
log.info("EventService->publishSomething publish success,something:{}", something);
}
}
4.添加事件监听器
a.实现接口方式
@Component
@Slf4j
public class SomethingAsyncEventListener implements ApplicationListener<SomethingRegisterEvent> {
@Override
// 通过自定义线程池实现异步
@Async("commonExecutorPool")
public void onApplicationEvent(@NonNull SomethingRegisterEvent somethingRegisterEvent) {
Something something = (Something) somethingRegisterEvent.getSource();
handlerSomething(something);
log.info("SomethingAsyncEventListener->onApplicationEvent success");
}
private void handlerSomething(Something something) {
log.info("SomethingAsyncEventListener->handler something:{}", something);
}
}
b.通过注解实现
@Component
@Slf4j
public class SomethingEventOneListener {
@EventListener(value = SomethingRegisterEvent.class, condition = "#event.source.type=='opt'")
public void firstHandler(SomethingRegisterEvent event) {
log.info("SomethingEventOneListener->firstHandler success,event:{}", event);
}
@EventListener(value = SomethingRegisterEvent.class, condition = "#event.source.type=='opt'")
// 通过自定义线程池实现异步
@Async("commonExecutorPool")
public void secondHandler(SomethingRegisterEvent event) {
log.info("SomethingEventOneListener->secondHandler success,event:{}", event);
}
}
可通过自定义状态机实现策略模式；线程池实现：传送门
5.测试
@SpringBootTest(classes = {SpringBootDemoApplication.class})
@RunWith(SpringRunner.class)
public class EventServiceTest {
@Autowired
private EventService eventService;
@Test
public void test() {
Something something = new Something();
something.setId("0");
something.setName("test");
something.setType("opt");
eventService.publishSomething(something);
}
}
