spring:refresh方法之initMessageSource

initMessageSource

國際化（Internationalization）簡稱 i18n，簡單來說就是不同國家/地區/語言的用戶，訪問同一個程序，得到對應的本地化資源。

Spring中國際化的支持是AbstractApplicationContext中定義的默認bean(ApplicationContext實現了MessageSource接口)

源碼：

protected void initMessageSource() {
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
//如果有id爲messageSource的bean，就獲取並賦值；如果沒有，則創建默認的。
		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 {
			// 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 + "]");
			}
		}
	}