Spring Boot的消息事件机制 顶
Spring Boot自带了消息机制，可以让我们在一个地方发布消息，多个地方同时接收消息并处理消息，当然这是在同一个JVM内存下进行的，不同的进程还需要使用MQ来实现。我觉得该消息模式跟观察者模式有一定的区别，观察者模式一般观察的是一个对象内部属性发生变化的时候使用。而该消息机制可以在任意地方使用。
消息事件本身是一个对象，继承于ApplicationEvent
@Data
public class DemoEvent extends ApplicationEvent {
private String type;
private List<Map> msg;
public DemoEvent(Object source,String type,List<Map> msg) {
super(source);
this.type = type;
this.msg = msg;
}
}还需要有一个消息事件发布者，将这个消息事件给发布出去
@Component
public class DemoPublisher {
@Autowired
ApplicationContext applicationContext;
public void publish(DemoEvent demoEvent) {
applicationContext.publishEvent(demoEvent);
}
}然后就是我们的侦听者，侦听者可以有任意个根据业务不同做不同的处理，他的写法分两种，一个是实现了ApplicationListener接口，一个是在方法上打上@EventListener标签
@Component
@Slf4j
public class DemoListener implements ApplicationListener<DemoEvent> {
@Override
@Async
public void onApplicationEvent(DemoEvent demoEvent) {
log.info("接收到publisher发送到消息，时间" + Time.getTime());
List<Map> msg = demoEvent.getMsg();
String type = demoEvent.getType();
try {
Thread.sleep(3000);
}catch (Exception e) {
e.printStackTrace();
}
log.info("类型" + type + ",消息内容:" + msg);
}
}@Component
@Slf4j
public class DemoListener1 {
@EventListener
public void onDemoEvent(DemoEvent demoEvent) {
log.info("listener1通过注解接收到了publisher发送的消息，时间" + Time.getTime());
String type = demoEvent.getType();
List<Map> msg = demoEvent.getMsg();
try {
Thread.sleep(2000);
}catch (Exception e) {
e.printStackTrace();
}
log.info("listener1:类型" + type + ",消息内容：" + msg);
}
}但是我们需要知道的是，多个消息监听是同步执行的，他们会发生阻塞，所以我们需要进行异步监听，实现异步监听只需要在方法上打上@Async标签，同时在Springboot主程序中开启允许异步
@EnableAsync
@SpringBootApplication
public class LanmdaApplication {
public static void main(String[] args) {
SpringApplication.run(LanmdaApplication.class, args);
}
}最后写一个测试的Controller
@Slf4j
@RestController
public class TestController {
@Autowired
private DemoPublisher publisher;
@GetMapping("/test")
public String testListener() {
List<Map> list = new ArrayList<>();
Map<String,String> m1 = new HashMap<>();
m1.put("1","2");
Map<String,String> m2 = new HashMap<>();
m2.put("3","4");
Map<String,String> m3 = new HashMap<>();
m3.put("5","6");
list.add(m1);
list.add(m2);
list.add(m3);
log.info("开始发布消息:" + Time.getTime());
publisher.publish(new DemoEvent(this,"测试消息",list));
log.info("消息发布结束:" + Time.getTime());
return "消息发布成功";
}
}执行后，日志如下
2019-07-21 10:42:39.686 INFO 1756 --- [nio-8080-exec-1] c.g.lanmda.controller.TestController : 开始发布消息:10:42:39 2019-07-21 10:42:39.687 INFO 1756 --- [nio-8080-exec-1] com.guanjian.lanmda.event.DemoListener1 : listener1通过注解接收到了publisher发送的消息，时间10:42:39 2019-07-21 10:42:41.690 INFO 1756 --- [nio-8080-exec-1] com.guanjian.lanmda.event.DemoListener1 : listener1:类型测试消息,消息内容：[{1=2}, {3=4}, {5=6}] 2019-07-21 10:42:41.695 INFO 1756 --- [nio-8080-exec-1] .s.a.AnnotationAsyncExecutionInterceptor : No task executor bean found for async processing: no bean of type TaskExecutor and no bean named 'taskExecutor' either 2019-07-21 10:42:41.697 INFO 1756 --- [nio-8080-exec-1] c.g.lanmda.controller.TestController : 消息发布结束:10:42:41 2019-07-21 10:42:41.697 INFO 1756 --- [cTaskExecutor-1] com.guanjian.lanmda.event.DemoListener : 接收到publisher发送到消息，时间10:42:41 2019-07-21 10:42:44.701 INFO 1756 --- [cTaskExecutor-1] com.guanjian.lanmda.event.DemoListener : 类型测试消息,消息内容:[{1=2}, {3=4}, {5=6}]