Spring-context-SimpleApplicationEventMulticaster

Multicaster：组播，广播

把事件和时间类型传递进去，然后找到所有订阅该时间的监听器（ApplicationListener接口的实例），然后循环调用

@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 {
			invokeListener(listener, event);
		}
	}
}