SpringBoot - 资源国际化

2018年06月19日 11:00:31 流烟默阅读数：344

【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.*/private String basename = "messages";//我们的配置文件可以直接放在类路径下叫messages.properties；/*** 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@Beanpublic 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;}

还可以在SpringBoot的配置文件中使用spring.messages前缀配置国际化：

# 国际化配置文件（包名.基础名）
spring.messages.basename=i18n.login

【2】编写国际化资源文件

抽取页面需要显示的国际化消息，编写国际化资源文件。

login.properties

如图所示，idea会自动切换到国际化视图。另外，在编写properties时，除了传统的使用key:value在properties中编写外，还可以如下所示：

【3】页面示例

如下所示，在页面中使用properties的属性：


<label class="sr-only" th:text="#{login.username}">Username</label>
<input type="text"  name="username" class="form-control" placeholder="Username" th:placeholder="#{login.username}" required="" autofocus="">
<label class="sr-only" th:text="#{login.password}">Password</label>
<input type="password" name="password" class="form-control" placeholder="Password" th:placeholder="#{login.password}" required="">
<div class="checkbox mb-3">
<label>
<input type="checkbox" value="remember-me"/> [[#{login.remember}]]
//这里使用行内写法，input是自结束标签，没有标签体
</label>
</div>
<button class="btn btn-lg btn-primary btn-block" type="submit" th:text="#{login.btn}">Sign in</button>

注意这里使用的是#{…}语法，可以参考Thymeleaf中第四章Standard Expression Syntax中4.1Messages讲解，如下图.

测试结果：

浏览器设置英文：

浏览器设置中文：

【4】SpringBoot对资源国际化解析原理

首先明白两个组件：国际化Locale（区域信息对象）；LocaleResolver（获取区域信息对象）。

① WebMVCAutoConfiguration中对LocaleResolver 配置

@Bean
@ConditionalOnMissingBean
@ConditionalOnProperty(prefix = "spring.mvc", name = "locale")
public LocaleResolver localeResolver() {if (this.mvcProperties.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {return new FixedLocaleResolver(this.mvcProperties.getLocale());}AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();localeResolver.setDefaultLocale(this.mvcProperties.getLocale());return localeResolver;
}

如果spring.mvc.locale没有指定，那么就返回一个AcceptHeaderLocaleResolver 。如果指定了spring.mvc.locale，那么就返回FixedLocaleResolver。

② 查看AcceptHeaderLocaleResolver

@Overridepublic Locale resolveLocale(HttpServletRequest request) {Locale defaultLocale = getDefaultLocale();if (defaultLocale != null && request.getHeader("Accept-Language") == null) {return defaultLocale;}Locale requestLocale = request.getLocale();if (isSupportedLocale(requestLocale)) {return requestLocale;}Locale supportedLocale = findSupportedLocale(request);if (supportedLocale != null) {return supportedLocale;}return (defaultLocale != null ? defaultLocale : requestLocale);}

从请求头里面解析Locale！这也就是为什么浏览器切换语言显示不同资源的原理。

【5】中英切换

如下图所示，通过点击中文英文按钮切换不同资源显示：

① 页面修改如下：

<a class="btn btn-sm" th:href="@{/index.html(l='zh_CN')}">中文</a>
<a class="btn btn-sm" th:href="@{/index.html(l='en_US')}">English</a>

这里使用的是Thymeleaf模板引擎中链接参数的写法(key=value)，也可以使用原始写法如下：

<a class="btn btn-sm" th:href="@{/index.html?l=zh_CN}">中文</a>
<a class="btn btn-sm" th:href="@{/index.html?l=en_US}">English</a>

② 编写自定义区域信息解析器

/*** 可以在连接上携带区域信息*/
public class MyLocaleResolver implements LocaleResolver {@Overridepublic Locale resolveLocale(HttpServletRequest request) {String l = request.getParameter("l");Locale locale = Locale.getDefault();if(!StringUtils.isEmpty(l)){String[] split = l.split("_");locale = new Locale(split[0],split[1]);}return locale;}@Overridepublic void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {}
}

将其添加到容器中：

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

③ Locale.getDefault()

该方法根据系统环境拿到Locale，如本机上如果没有传 l 参数，那么就会返回defaultLocale。此时无论浏览器语言设置什么，都显示中文。

 /*** Gets the current value of the default locale for this instance* of the Java Virtual Machine.* <p>* The Java Virtual Machine sets the default locale during startup* based on the host environment. It is used by many locale-sensitive* methods if no locale is explicitly specified.* It can be changed using the* {@link #setDefault(java.util.Locale) setDefault} method.** @return the default locale for this instance of the Java Virtual Machine*/public static Locale getDefault() {// do not synchronize this method - see 4071298return defaultLocale;}