15 | SpringBoot + thymeleaf 的登陆页面如何实现国际化

1、编写国际化配置文件，抽取页面需要显示的国际化消息

（1）在resources文件夹下创建i18n文件夹，用来存放国际化配置文件，为什么是i18n???

i18n（其来源是英文单词 internationalization的首末字符i和n，18为中间的字符数）是“国际化”的简称。

然后任意打开一个配置文件，如login_en_US.properties，点击Resources Bundle，输入你想要国际化的属性

（2）在全局配置文件中绑定这些自定义的国际化配置
SpringBoot自动配置好了管理国际化资源文件的组件

@ConfigurationProperties(prefix = "spring.messages")
public class MessageSourceAutoConfiguration {/*** 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；@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;}

我们的配置文件可以直接放在类路径下叫messages.properties 不用做任何配置就可使用国际化，但我们这里创建了一个i18n文件夹，所以我们要在全局配置文件中通过spring.messages.messages绑定资源文件的基础名（去掉语言国家代码的）

application.properties

spring.messages.basename=i18n.login

2、修改login.html

https://www.webjars.org/
公共资源用webjars提供的东西，自己的资源就用assets文件夹里的

<!--加入Bootstrap依赖--><dependency><groupId>org.webjars</groupId><artifactId>bootstrap</artifactId><version>4.5.0</version></dependency>

<!DOCTYPE html>
<html lang="en"  xmlns:th="http://www.thymeleaf.org">
<head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"><meta name="description" content=""><meta name="author" content=""><title>Signin Template for Bootstrap</title><!-- Bootstrap core CSS --><link href="asserts/css/bootstrap.min.css" th:href="@{/webjars/bootstrap/4.5.0/css/bootstrap.css}" rel="stylesheet"><!-- Custom styles for this template --><link href="asserts/css/signin.css" th:href="@{/asserts/css/signin.css}" rel="stylesheet">
</head><body class="text-center">
<form class="form-signin" action="dashboard.html"><img class="mb-4" th:src="@{/asserts/img/bootstrap-solid.svg}" src="asserts/img/bootstrap-solid.svg" alt="" width="72" height="72"><h1 class="h3 mb-3 font-weight-normal" th:text="#{login.tip}">Please sign in</h1><label class="sr-only" th:text="#{login.username}">Username</label><input type="text" class="form-control" placeholder="Username" th:placeholder="#{login.username}" required="" autofocus=""><label class="sr-only" th:text="#{login.password}">Password</label><input type="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}]]</label></div><button class="btn btn-lg btn-primary btn-block" type="submit" th:text="#{login.btn}">Sign in</button><p class="mt-5 mb-3 text-muted">© 2017-2018</p><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>
</form>
</body>
</html>

3、编写MyLocaleResolver实现LocaleResolver接口

（1）创建MyLocaleResolver类

//可以在连接上携带区域信息
public class MyLocaleResolver implements LocaleResolver {@Overridepublic Locale resolveLocale(HttpServletRequest httpServletRequest) {String l = httpServletRequest.getParameter("l");// 如果没有 l 返回请求头的默认值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 httpServletRequest, HttpServletResponse httpServletResponse, Locale locale) {}
}

为什么要实现LocaleResolver接口呢？？
国际化Locale（区域信息对象）；LocaleResolver（获取区域信息对象）；

         @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;}
默认的就是根据请求头带来的区域信息获取Locale进行国际化

（2）在配置类中注册这个Bean

//使用WebMvcConfigurer可以来扩展SpringMVC的功能
//@EnableWebMvc   不要接管SpringMVC
@Configuration
public class MyMvcConfig implements WebMvcConfigurer {//所有的WebMvcConfigurer组件都会一起起作用@Bean //将组件注册在容器public WebMvcConfigurer webMvcConfigurer(){WebMvcConfigurer webMvcConfigurer = new WebMvcConfigurer() {@Overridepublic void addViewControllers(ViewControllerRegistry registry) {registry.addViewController("/").setViewName("login");registry.addViewController("/index.html").setViewName("login");}};return webMvcConfigurer;}@Beanpublic LocaleResolver localeResolver(){return new MyLocaleResolver();}
}

ok，到登录页面按中/英文按钮可以切换成中英文页面