承接前文Spring源码情操陶冶-AbstractApplicationContext#initMessageSource

约定web.xml配置的contextClass为默认值XmlWebApplicationContext

瞧瞧官方注释

	/**

	 * Initialize the ApplicationEventMulticaster.

	 * Uses SimpleApplicationEventMulticaster if none defined in the context.

	 * @see org.springframework.context.event.SimpleApplicationEventMulticaster

	 */

初始化ApplicationEventMulticaster事件，默认使用SimpleApplicationEventMulticaster事件

直接源码

protected void initApplicationEventMulticaster() {

		ConfigurableListableBeanFactory beanFactory = getBeanFactory();

		//查找是否存在id为applicationEventMulticaster的bean对象

		if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {

			this.applicationEventMulticaster =

					beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);

			if (logger.isDebugEnabled()) {

				logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");

			}

		}

		else {

			//默认使用SimpleApplicationEventMulticaster，并注册为单例

			this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);

			beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);

			if (logger.isDebugEnabled()) {

				logger.debug("Unable to locate ApplicationEventMulticaster with name '" +

						APPLICATION_EVENT_MULTICASTER_BEAN_NAME +

						"': using default [" + this.applicationEventMulticaster + "]");

			}

		}

	}

小结

此节内容跟前文initMessageSource类似

下节预告

Spring源码情操陶冶-AbstractApplicationContext#onRefresh