六、Spring Boot 国际化

1. SpringBoot的自动配置
   SpringBoot自动配置好了管理国际化资源文件的组件：

   @Configuration
   @ConditionalOnMissingBean(value = MessageSource.class, search = SearchStrategy.CURRENT)
   @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
   @Conditional(ResourceBundleCondition.class)
   @EnableConfigurationProperties
   @ConfigurationProperties(prefix = "spring.messages")
   public class MessageSourceAutoConfiguration {
   
       private static final Resource[] NO_RESOURCES = {};
   
       /**
        * Comma-separated list of basenames (essentially a fully-qualified classpath
        * location), each following the ResourceBundle convention with relaxed support for
        * slash based locations. If it doesn't contain a package qualifier (such as
        * "org.mypackage"), it will be resolved from the classpath root.
        */
       //我们的配置文件可以直接放在类路径下叫messages.properties；
       private String basename = "messages";
      
       /**
        * Message bundles encoding.
        */
       private Charset encoding = Charset.forName("UTF-8");
   
       /**
        * Loaded resource bundle files cache expiration, in seconds. When set to -1, bundles
        * are cached forever.
        */
       private int cacheSeconds = -1;
   
       /**
        * Set whether to fall back to the system Locale if no files for a specific Locale
        * have been found. if this is turned off, the only fallback will be the default file
        * (e.g. "messages.properties" for basename "messages").
        */
       private boolean fallbackToSystemLocale = true;
   
       /**
        * Set whether to always apply the MessageFormat rules, parsing even messages without
        * arguments.
        */
       private boolean alwaysUseMessageFormat = false;
       //为容器添加了ResourceBundleMessageSource 组件
       @Bean
       public MessageSource messageSource() {
           ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
           if (StringUtils.hasText(this.basename)) {
               //设置国际化资源文件的基础名（去掉语言国家代码的）
               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;
       }
   
   

2. 国际化

   1. 编写国际化配置文件，抽取页面需要显示的国际化消息
      

   2. 在SpringBoot的配置文件中使用spring.messages前缀配置国际化：

        spring:
       	 messages:
          	basename: i18n.login
      

   3. 页面示例

      
      
      
          
          
          
          
          
          
          
          
          
      
      
      
      	
      
      	    
      	    
      Please sign in
      	    Username
      	    
      	    Password
      	    
      	    
      
      	        
      	             [[#{login.remember}]]
      	        
      	    
      	    Sign in
      	    
      © 2017-2018
      	    中文
      	    English
      	
      
      
      

      注意实例中的国际化引入语法:
      使用的是#{…}语法，可以参考Thymeleaf中第四章Standard Expression Syntax中4.1Messages讲解，如下图.
      

   4. 启动项目测试效果, 效果图如下
      浏览器中文状态下：
      
      浏览器英文状态下(浏览器切换语言为英语)
      

   5. 如果在浏览器为中文状态下中文乱码了，可以进行下图设置(这种方式仅对当前项目有效，如想对所有项目有效，请进行如下操作： file --> Other Srttings --> default Setting… 在进行下图设置)：
      

3. 如何通过按钮进行国际化转换？
   

   1. SpringBoot对资源国际化解析原理

      @Bean
      @ConditionalOnMissingBean
      @ConditionalOnProperty(prefix = "spring.mvc", name = "locale")
      public LocaleResolver localeResolver() {
      	//如果指定了spring.mvc.locale，就返回FixedLocaleResolver。如果 spring.mvc.locale没有指定，那么就返回一个AcceptHeaderLocaleResolver 。
      	//AcceptHeaderLocaleResolver 的作用就是根据请求头 带来的 区域信息 进行国际化
      	if (this.mvcProperties.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {
      		return new FixedLocaleResolver(this.mvcProperties.getLocale());
      	}
      	AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();
      	localeResolver.setDefaultLocale(this.mvcProperties.getLocale());
      	return localeResolver;
      }
      

      AcceptHeaderLocaleResolver 中的 resolveLocale()方法

      public Locale resolveLocale(HttpServletRequest request) {
              Locale defaultLocale = this.getDefaultLocale();
              if (defaultLocale != null && request.getHeader("Accept-Language") == null) {
                  return defaultLocale;
              } else {
              	//从请求头重获取区域信息
                  Locale requestLocale = request.getLocale();
                  List supportedLocales = this.getSupportedLocales();
                  if (!supportedLocales.isEmpty() && !supportedLocales.contains(requestLocale)) {
                      Locale supportedLocale = this.findSupportedLocale(request, supportedLocales);
                      if (supportedLocale != null) {
                          return supportedLocale;
                      } else {
                          return defaultLocale != null ? defaultLocale : requestLocale;
                      }
                  } else {
                      return requestLocale;
                  }
              }
          }
      

      之前实例(浏览器语言为中文的情况下)发出去的请求信息：
      
      (浏览器语言为中文的情况下)发出去的请求信息：
      

      2. 编辑 LocaleResolver

         import org.springframework.util.StringUtils;
         import org.springframework.web.servlet.LocaleResolver;
         
         import javax.servlet.http.HttpServletRequest;
         import javax.servlet.http.HttpServletResponse;
         import java.util.Locale;
         
         /**
          * Created by RM on 2018/9/30.
          *
          * 可以在链接上携带区域信息
          */
         public class MyLocalResolver implements LocaleResolver{
         
             //解析区域信息
             @Override
             public Locale resolveLocale(HttpServletRequest httpServletRequest) {
                 String l = httpServletRequest.getParameter("l");
                 //默认使用系统的区域信息
                 Locale Locale = java.util.Locale.getDefault();
                 //如果请求中有设置, 就用设置请求中的区域信息
                 if(!StringUtils.isEmpty(l)){
                     String[] split = l.split("_");
                     Locale = new Locale(split[0],split[1]);
                 }
                 return Locale;
             }
         
             //设置区域信息
             @Override
             public void setLocale(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Locale locale) {
         
             }
         }
         

      3. 容器中添加 编辑的 LocaleResolver组件

         @Configuration
         public class MyMvcConfig extends WebMvcConfigurerAdapter {
          	@Bean
             public LocaleResolver localeResolver(){
                 return new MyLocalResolver();
             }
         }