spring事件发布

1.事件管理初始化

    // Initialize event multicaster for this context.
    //初始化事件传播
    initApplicationEventMulticaster();

        a.初始化详解

protected void initApplicationEventMulticaster() {
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		//判断容器中是否有applicationEventMulticaster事件传播
		if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
			this.applicationEventMulticaster =
					beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
			if (logger.isTraceEnabled()) {
				logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
			}
		}
		else {
			//new 一个时间传播并注册到容器中
			this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
			beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
			if (logger.isTraceEnabled()) {
				logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
						"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
			}
		}
	}

2.添加监听器及发布（监听器必须实现ApplicationListener接口）         a.事件传播管理初始化后会扫描容器中实现了ApplicationListener接口的bean并注入到ApplicationEventMulticaster类中的applicationListeners容器中

	// Check for listener beans and register them.
	//注册监听器
	registerListeners();

protected void registerListeners() {
		// Register statically specified listeners first.
		for (ApplicationListener listener : getApplicationListeners()) {
			getApplicationEventMulticaster().addApplicationListener(listener);
		}

		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let post-processors apply to them!
		String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
		for (String listenerBeanName : listenerBeanNames) {
			getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
		}

		// Publish early application events now that we finally have a multicaster...
		Set earlyEventsToProcess = this.earlyApplicationEvents;
		this.earlyApplicationEvents = null;
		if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
			for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
				getApplicationEventMulticaster().multicastEvent(earlyEvent);
			}
		}
	}

    b.bean实例化时，属性注入之后调用ApplicationListenerDetector的postProcessAfterInitialization方法来添加实现了ApplicationListener接口的漏网之鱼

@Override
	public Object postProcessAfterInitialization(Object bean, String beanName) {
		if (bean instanceof ApplicationListener) {
			// potentially not detected as a listener by getBeanNamesForType retrieval
			Boolean flag = this.singletonNames.get(beanName);
			if (Boolean.TRUE.equals(flag)) {
				// singleton bean (top-level or inner): register on the fly
				this.applicationContext.addApplicationListener((ApplicationListener) bean);
			}
			else if (Boolean.FALSE.equals(flag)) {
				if (logger.isWarnEnabled() && !this.applicationContext.containsBean(beanName)) {
					// inner bean with other scope - can't reliably process events
					logger.warn("Inner bean '" + beanName + "' implements ApplicationListener interface " +
							"but is not reachable for event multicasting by its containing ApplicationContext " +
							"because it does not have singleton scope. Only top-level listener beans are allowed " +
							"to be of non-singleton scope.");
				}
				this.singletonNames.remove(beanName);
			}
		}
		return bean;
	}

         c.手动添加及发布事件

 @org.junit.Test
    public void test1(){


        ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        //1.无需注入直接new
        ClassPathXmlApplicationContext classPathXmlApplicationContext =(ClassPathXmlApplicationContext)context;
        classPathXmlApplicationContext.addApplicationListener(new ApplicationDemoListener());
       
        SimpleApplicationEventMulticaster applicationEventMulticaster = (SimpleApplicationEventMulticaster)context.getBean("applicationEventMulticaster");
        //2.手动添加，通过beanName的方式添加
        applicationEventMulticaster.addApplicationListenerBean("ApplicationDemoListener");
        //3.发布事件，在该方法中会获取listener,并调用
        context.publishEvent(new ApplicationDemoEvent(""));
    

@Override
public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
   ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
   Executor executor = getTaskExecutor();
   for (ApplicationListener listener : getApplicationListeners(event, type)) {
      if (executor != null) {
         executor.execute(() -> invokeListener(listener, event));
      }
      else {
         //调用listener的onApplicationEvent（）
         invokeListener(listener, event);
      }
   }
}

 

        c.spring内部事件的发布会调用以下方法：

          入口：

	// Last step: publish corresponding event.
				finishRefresh();

protected void finishRefresh() {
		// Clear context-level resource caches (such as ASM metadata from scanning).
		clearResourceCaches();

		// Initialize lifecycle processor for this context.
		initLifecycleProcessor();

		// Propagate refresh to lifecycle processor first.
		getLifecycleProcessor().onRefresh();

		// Publish the final event.
        //实际仍然调用的是publishEvent（）方法
		publishEvent(new ContextRefreshedEvent(this));

		// Participate in LiveBeansView MBean, if active.
		LiveBeansView.registerApplicationContext(this);
	}