承接前文

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