案例1：自定义多播器和多线程有什么关系？
自定义多播器
自定义多播器如下所示，其实和我们自定义其他的不太一样，因为其他的自定义不会有value值，为什么此处必须要有value = "applicationEventMulticaster"？？？
@Component(value = "applicationEventMulticaster") public class Myulticaster extends SimpleApplicationEventMulticaster{ public MyMulticaster () { setTaskExecutor(Executors.newSingleThreadExecutor()); } }
答案在源码中
AbstractApplicationContext的initApplicationEventMulticaster()方法用于初始化Multicaster，Spring已经把多播器的名字写在源码中
public static final String APPLICATION_EVENT_MULTICASTER_BEAN_NAME = "applicationEventMulticaster"; protected void initApplicationEventMulticaster() { ConfigurableListableBeanFactory beanFactory = getBeanFactory(); //如果beanFactory中有applicationEventMulticaster的bean,就把该Bean赋值给this.applicationEventMulticaster if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) { this.applicationEventMulticaster = beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class); } } else { //否则就创建一个SimpleApplicationEventMulticaster this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory); beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster); } }
案例
下面是自定义的listener
@Component public class MyApplicationListener implements ApplicationListener<ApplicationEvent> { @Override public void onApplicationEvent(ApplicationEvent event) { System.out.println("-----------MyApplicationListener-------------"); try { TimeUnit.SECONDS.sleep(3); } catch (Exception e) { e.printStackTrace(); } finally { } System.out.println("-----------MyApplicationListener over-------------"); } }
当不不自定义多播器的时候，上面listener是同步执行的，如果定义了多波器，是异步执行的。
源码
https://github.com/cbeann/Demooo/blob/master/spring-demo/src/main/java/ioc/AppMyulticasterDemo.java
案例2:异步@Async
@Service public class EmailService { @Async public void sendEmail() { System.out.println("---start--"); try { TimeUnit.SECONDS.sleep(5); } catch (Exception e) { e.printStackTrace(); } finally { } System.out.println("---end--"); } }
调用EmailService.sendEmail（）的时候是异步，也是用了线程池
源码
https://github.com/cbeann/Demooo/blob/master/springboot-demo/src/main/java/com/example/theadpool/App.java
