国际化主要是引入了MessageSource，我们简单看下如何使用，以及其原理。
1.1 设置资源文件
在 properties新建i18n目录
新建message文件：
messages.properties
error.title=Your request cannot be processed
messages_zh_CN.properties
error.title=您的请求无法处理
1.2 配置
修改properties文件的目录：在application.yml或者application.properties中配置 spring.message.basename
spring:
application:
name: test-worklog
messages:
basename: i18n/messages
encoding: UTF-8
1.3 使用
引用自动注解的MessageSource,调用messageSource.getMessage即可，注意，需要通过 LocaleContextHolder.getLocale()获取当前的地区。
@Autowired
private MessageSource messageSource;
/**
* 国际化
*
* @param result
* @return
*/
public String getMessage(String result, Object[] params) {
String message = "";
try {
Locale locale = LocaleContextHolder.getLocale();
message = messageSource.getMessage(result, params, locale);
} catch (Exception e) {
LOGGER.error("parse message error! ", e);
}
return message;
}
如何设置个性化的地区呢? forLanguageTag 即可
Locale locale = Locale.forLanguageTag(user.getLangKey());
1.4 原理分析
MessageSourceAutoConfiguration中，实现了autoconfig
@Configuration
@ConditionalOnMissingBean(value = MessageSource.class, search = SearchStrategy.CURRENT)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Conditional(ResourceBundleCondition.class)
@EnableConfigurationProperties
@ConfigurationProperties(prefix = "spring.messages")
public class MessageSourceAutoConfiguration {
该类一方面读取配置文件，一方面创建了MessageSource的实例:
@Bean
public MessageSource messageSource() {
ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
if (StringUtils.hasText(this.basename)) {
messageSource.setBasenames(StringUtils.commaDelimitedListToStringArray(
StringUtils.trimAllWhitespace(this.basename)));
}
if (this.encoding != null) {
messageSource.setDefaultEncoding(this.encoding.name());
}
messageSource.setFallbackToSystemLocale(this.fallbackToSystemLocale);
messageSource.setCacheSeconds(this.cacheSeconds);
messageSource.setAlwaysUseMessageFormat(this.alwaysUseMessageFormat);
return messageSource;
}
因此，默认是加载的ResourceBundleMessageSource，该类派生与于AbstractResourceBasedMessageSource
@Override
public final String getMessage(String code, Object[] args, String defaultMessage, Locale locale) {
String msg = getMessageInternal(code, args, locale);
if (msg != null) {
return msg;
}
if (defaultMessage == null) {
String fallback = getDefaultMessage(code);
if (fallback != null) {
return fallback;
}
}
return renderDefaultMessage(defaultMessage, args, locale);
}
最终是调用resolveCode来获取message，通过ResourceBundle来获取message
@Override
protected MessageFormat resolveCode(String code, Locale locale) {
// 遍历语言文件路径
Set<String> basenames = getBasenameSet();
for (String basename : basenames) {
ResourceBundle bundle = getResourceBundle(basename, locale);
if (bundle != null) {
MessageFormat messageFormat = getMessageFormat(bundle, code, locale);
if (messageFormat != null) {
return messageFormat;
}
}
}
return null;
}
// 获取ResourceBundle
protected ResourceBundle getResourceBundle(String basename, Locale locale) {
if (getCacheMillis() >= 0) {
// Fresh ResourceBundle.getBundle call in order to let ResourceBundle
// do its native caching, at the expense of more extensive lookup steps.
return doGetBundle(basename, locale);
}
else {
// Cache forever: prefer locale cache over repeated getBundle calls.
synchronized (this.cachedResourceBundles) {
Map<Locale, ResourceBundle> localeMap = this.cachedResourceBundles.get(basename);
if (localeMap != null) {
ResourceBundle bundle = localeMap.get(locale);
if (bundle != null) {
return bundle;
}
}
try {
ResourceBundle bundle = doGetBundle(basename, locale);
if (localeMap == null) {
localeMap = new HashMap<Locale, ResourceBundle>();
this.cachedResourceBundles.put(basename, localeMap);
}
localeMap.put(locale, bundle);
return bundle;
}
catch (MissingResourceException ex) {
if (logger.isWarnEnabled()) {
logger.warn("ResourceBundle [" + basename + "] not found for MessageSource: " + ex.getMessage());
}
// Assume bundle not found
// -> do NOT throw the exception to allow for checking parent message source.
return null;
}
}
}
}
// ResourceBundle
protected ResourceBundle doGetBundle(String basename, Locale locale) throws MissingResourceException {
return ResourceBundle.getBundle(basename, locale, getBundleClassLoader(), new MessageSourceControl());
}
最后来看getMessageFormat：
/**
* Return a MessageFormat for the given bundle and code,
* fetching already generated MessageFormats from the cache.
* @param bundle the ResourceBundle to work on
* @param code the message code to retrieve
* @param locale the Locale to use to build the MessageFormat
* @return the resulting MessageFormat, or {@code null} if no message
* defined for the given code
* @throws MissingResourceException if thrown by the ResourceBundle
*/
protected MessageFormat getMessageFormat(ResourceBundle bundle, String code, Locale locale)
throws MissingResourceException {
synchronized (this.cachedBundleMessageFormats) {
// 从缓存读取
Map<String, Map<Locale, MessageFormat>> codeMap = this.cachedBundleMessageFormats.get(bundle);
Map<Locale, MessageFormat> localeMap = null;
if (codeMap != null) {
localeMap = codeMap.get(code);
if (localeMap != null) {
MessageFormat result = localeMap.get(locale);
if (result != null) {
return result;
}
}
}
// 缓存miss，从bundle读取
String msg = getStringOrNull(bundle, code);
if (msg != null) {
if (codeMap == null) {
codeMap = new HashMap<String, Map<Locale, MessageFormat>>();
this.cachedBundleMessageFormats.put(bundle, codeMap);
}
if (localeMap == null) {
localeMap = new HashMap<Locale, MessageFormat>();
codeMap.put(code, localeMap);
}
MessageFormat result = createMessageFormat(msg, locale);
localeMap.put(locale, result);
return result;
}
return null;
}
}
作者：Jadepeng
出处：jqpeng的技术记事本--http://www.cnblogs.com/xiaoqi
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