事件监听器

案例：主线业务做完之后，执行发送短信，发送邮件事件，且能实现事件解耦；

方法一：实现ApplicationListener

@Configuration
public class Demo {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(Demo.class);
        context.getBean(MyService.class).doBusiness();
        context.close();
    }

    static class MyEvent extends ApplicationEvent {
        public MyEvent(Object source) {
            super(source);
        }
    }

    @Component
    static class MyService {
        private static final Logger log = LoggerFactory.getLogger(MyService.class);
        @Autowired
        private ApplicationEventPublisher publisher; 
        public void doBusiness() {
            log.debug("主线业务");
            // 主线业务完成后需要做一些支线业务
            publisher.publishEvent(new MyEvent("MyService.doBusiness()"));
        }
    }

    @Component
    static class SmsApplicationListener implements ApplicationListener<MyEvent> {
        private static final Logger log = LoggerFactory.getLogger(SmsApplicationListener.class);
        @Override
        public void onApplicationEvent(MyEvent event) {
            log.debug("发送短信");
        }
    }

    @Component
    static class EmailApplicationListener implements ApplicationListener<MyEvent> {
        private static final Logger log = LoggerFactory.getLogger(EmailApplicationListener.class);
        @Override
        public void onApplicationEvent(MyEvent event) {
            log.debug("发送邮件");
        }
    }

}

方法二：@EventListener

@Configuration
public class Demo {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(Demo.class);
        context.getBean(MyService.class).doBusiness();
        context.close();
    }

    static class MyEvent extends ApplicationEvent {
        public MyEvent(Object source) {
            super(source);
        }
    }

    @Component
    static class MyService {
        private static final Logger log = LoggerFactory.getLogger(MyService.class);
        @Autowired
        private ApplicationEventPublisher publisher;
        public void doBusiness() {
            log.debug("主线业务");
            publisher.publishEvent(new MyEvent("MyService.doBusiness()"));
        }
    }

    @Component
    static class SmsService {
        private static final Logger log = LoggerFactory.getLogger(SmsService.class);
        @EventListener
        public void listener(MyEvent myEvent) {
            log.debug("发送短信");
        }
    }

    @Component
    static class EmailService {
        private static final Logger log = LoggerFactory.getLogger(EmailService.class);
        @EventListener
        public void listener(MyEvent myEvent) {
            log.debug("发送邮件");
        }
    }

    //将主线任务与支线任务异步执行
    @Bean
    public ThreadPoolTaskExecutor executor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(3);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(100);
        return executor;
    }

    @Bean
    public SimpleApplicationEventMulticaster applicationEventMulticaster(ThreadPoolTaskExecutor executor) {
        SimpleApplicationEventMulticaster multicaster = new SimpleApplicationEventMulticaster();
        multicaster.setTaskExecutor(executor);
        return multicaster;
    }

}