核心子方法10: registerListeners()方法详解

先总结: 该方法主要用于注册监听器, 在所有注册的bean中查找listener监听器bean, 注册到消息广播器中

1.遍历应用程序中存在的监听器集合，并将对应的监听器添加到监听器的多路广播器中

for (ApplicationListener<?> listener : getApplicationListeners()) {          
     getApplicationEventMulticaster().addApplicationListener(listener);
}

2.从容器中获取所有实现了ApplicationListener接口的bd的bdName, 放入ApplicationListenerBeans集合中

1 String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
2 for (String listenerBeanName : listenerBeanNames) {             
3 　　getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
4 }

3.发布早期应用程序事件

1 Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
2         this.earlyApplicationEvents = null;
3         if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
4             for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
5                 getApplicationEventMulticaster().multicastEvent(earlyEvent);
6         }
7 }