关于Springboot LocaleResolver 国际化的实现方式

第一种方式

package com.wuhao.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {

    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("index");
        registry.addViewController("/index.html").setViewName("index");
        registry.addViewController("/main.html").setViewName("dashboard");
    }

    @Bean
    public LocaleResolver localeResolver(){
        return new MyLocalResolver();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginHandlerInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/index.html","/","/user/login");
    }

}

package com.wuhao.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.thymeleaf.util.StringUtils;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Locale;


public class MyLocalResolver implements LocaleResolver, WebMvcConfigurer {
    //解析请求
    @Override
    public Locale resolveLocale(HttpServletRequest request) {
        String language = request.getParameter("l");
        Locale defaultLanguage = Locale.getDefault();
        if(!StringUtils.isEmpty(language)){
            String[] split = language.split("_");
            defaultLanguage = new Locale(split[0], split[1]);
        }
        return defaultLanguage;
    }

    @Override
    public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {

    }
}

第二种方式

package com.wuhao.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.thymeleaf.util.StringUtils;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Locale;

@Component("localeResolver")
public class MyLocalResolver implements LocaleResolver, WebMvcConfigurer {
    //解析请求
    @Override
    public Locale resolveLocale(HttpServletRequest request) {
        String language = request.getParameter("l");
        Locale defaultLanguage = Locale.getDefault();
        if(!StringUtils.isEmpty(language)){
            String[] split = language.split("_");
            defaultLanguage = new Locale(split[0], split[1]);
        }
        return defaultLanguage;
    }

    @Override
    public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {

    }
}

区别就在于 一种是用@bean注解去实现， @bean注解声明的方法 会返回当前声明方法的类型 

也就是说@bean声明以后 ioc注册时，会注册 LocaleResolver 类型。 

第二种方式 如果我只是用@Component 而不是@Component("localeResolver")。一样会失败 

因为DispatcherServlet在执行注册的时候， 只会去找

protected void initStrategies(ApplicationContext context) {
    this.initMultipartResolver(context);
    this.initLocaleResolver(context);
    this.initThemeResolver(context);
    this.initHandlerMappings(context);
    this.initHandlerAdapters(context);
    this.initHandlerExceptionResolvers(context);
    this.initRequestToViewNameTranslator(context);
    this.initViewResolvers(context);
    this.initFlashMapManager(context);
}

initLocaleResolver 这个方法里的

private void initLocaleResolver(ApplicationContext context) {
    try {
        this.localeResolver = (LocaleResolver)context.getBean("localeResolver", LocaleResolver.class);
        if (this.logger.isTraceEnabled()) {
            this.logger.trace("Detected " + this.localeResolver);
        } else if (this.logger.isDebugEnabled()) {
            this.logger.debug("Detected " + this.localeResolver.getClass().getSimpleName());
        }
    } catch (NoSuchBeanDefinitionException var3) {
        this.localeResolver = (LocaleResolver)this.getDefaultStrategy(context, LocaleResolver.class);
        if (this.logger.isTraceEnabled()) {
            this.logger.trace("No LocaleResolver 'localeResolver': using default [" + this.localeResolver.getClass().getSimpleName() + "]");
        }
    }

}
这个变量。
所以自己