Spring源码(4)Context篇之AbstractApplicationContext（下）

上一篇讲解了Spring的AbstractApplicationContext类refresh()方法，前六步（其中五步）都是针对BeanFactory的处理…

下面接着讲其七：initMessageSource();

/**
* Initialize the MessageSource.
 * Use parent's if none defined in this context.
 */
protected void initMessageSource() {
	ConfigurableListableBeanFactory beanFactory = getBeanFactory();
	if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
		this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
		// Make MessageSource aware of parent MessageSource.
		if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
			HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
			if (hms.getParentMessageSource() == null) {
				// Only set parent context as parent MessageSource if no parent MessageSource
				// registered already.
				hms.setParentMessageSource(getInternalParentMessageSource());
			}
		}
		if (logger.isDebugEnabled()) {
			logger.debug("Using MessageSource [" + this.messageSource + "]");
		}
	}
	else {	//如果工程里没有配置messageSource的bean，则走默认的处理逻辑
		// Use empty MessageSource to be able to accept getMessage calls.
		DelegatingMessageSource dms = new DelegatingMessageSource();
		dms.setParentMessageSource(getInternalParentMessageSource());
		this.messageSource = dms;
		beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
		if (logger.isDebugEnabled()) {
			logger.debug("Unable to locate MessageSource with name '" + MESSAGE_SOURCE_BEAN_NAME +
					"': using default [" + this.messageSource + "]");
		}
	}
}

该方法主要是关于MessageSource的处理，MessageSource是Spring处理国际化配置的资源类，一般项目会有关于MessageSource的配置：

Boot项目的配置

/**
 * 描述 : <注册消息资源处理器>. <br>
 */
@Bean
public MessageSource messageSource() {
	ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
	messageSource.setBasename("config.messages.messages");
	messageSource.setCacheSeconds(10); //reload messages every 10 seconds
	messageSource.setDefaultEncoding("UTF-8");
	messageSource.setUseCodeAsDefaultMessage(true);
	return messageSource;
}

或传统web项目的配置（xml配置）：

<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
　　<property name="basenames">
　　　　<list>
　　　　　　<value>resources/messages</value>
　　　　</list>
　　</property>
</bean>

如果工程里有上面的关于messageSource的配置，则工程会走if 代码块，否则走else代码块（意思是即使我们没有配置国际化相关类，spring会采用默认的国际化处理）

其八initApplicationEventMulticaster();

/**
 * Initialize the ApplicationEventMulticaster.
 * Uses SimpleApplicationEventMulticaster if none defined in the context.
 * @see org.springframework.context.event.SimpleApplicationEventMulticaster
 */
protected void initApplicationEventMulticaster() {
	ConfigurableListableBeanFactory beanFactory = getBeanFactory();
	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 {
		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 + "]");
		}
	}
}

这里是实例化事件传播的类，ApplicationContext容器提供了容器内部事件发布功能，ApplicationContext基于Observer模式，提供了针对Bean的事件传播功能。通过Application. publishEvent方法，我们可以将事件通知系统内所有的
ApplicationListener。

Spring源码(4)Context篇之AbstractApplicationContext（下）

其九onRefresh(); 调用的是AbstractRefreshableWebApplicationContext类的onRefresh()方法

/**
 * Initialize the theme capability.
 */
@Override
protected void onRefresh() {
	this.themeSource = UiApplicationContextUtils.initThemeSource(this);
}

这里实例化的是TimeSource类，解读为主题资源类，一般工程是这样配置主题资源的（工程用不到时，可缺省配置）：

<bean id="themeSource" class="org.springframework.ui.context.support.ResourceBundleThemeSource"/>

其十registerListeners();

/**
* Add beans that implement ApplicationListener as listeners.
 * Doesn't affect other listeners, which can be added without being beans.
 */
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<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
	this.earlyApplicationEvents = null;
	if (earlyEventsToProcess != null) {
		for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
			getApplicationEventMulticaster().multicastEvent(earlyEvent);
		}
	}
}

休息一下，再接着写…

Spring源码(4)Context篇之AbstractApplicationContext（下）

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