【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
@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;
}
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
@Override
public 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 {
@Override
public 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;
}
@Override
public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {
}
}
将其添加到容器中：
@Configuration
public class MyMvcConfig extends WebMvcConfigurerAdapter {
@Bean
public 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 4071298
return defaultLocale;
}
