springboot参数传中文乱码的解决方案

前言

本文案例来自业务部门的一个业务场景。他们的业务场景是他们部门研发了一个微服务上下文透传组件，其透传原理也挺简单的，就是通过springboot拦截器把请求参数塞进threadlocal，然后下游通过threadlocal取到值，服务之间进行feign调用时，再把threadlocal的参数塞到header头里面。这个组件一直用得好好的，突然有一天因为传的参数值是中文，导致乱码。他们通过尝试下面的各种方案，都无法解决。最后就让我们部门排查处理。

业务部门的实现思路

他们一开始的思路方向是参数编码不一致导致中文乱码。于是他们就朝这个方向努力着，于是就有了如下方案

方案一：

String value = new String("我是中文乱码".getBytes("ISO-8859-1"),"UTF-8");

这个是常用解决字符串中文乱码的方法之一

方案二：编写字符编码过滤器

@WebFilter(urlPatterns = "/*",filterName = "CharacterEncodingFilter")
public class CharacterEncodingFilter implements Filter{
 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
 }
 
 @Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
 HttpServletRequest request = (HttpServletRequest) servletRequest;
 HttpServletResponse response = (HttpServletResponse) servletResponse;
 request.setCharacterEncoding("UTF-8");
 response.setCharacterEncoding("UTF-8");
 
 filterChain.doFilter(request , response);
 }
 @Override
 public void destroy() {
 }
}

然后启动类上加上@ServletComponentScan。@WebFilter是servlet3.0才有的注解。当然这个过滤器你还可以这么写

public class CharacterEncodingFilter implements Filter{
 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
 }
 
 @Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
 HttpServletRequest request = (HttpServletRequest) servletRequest;
 HttpServletResponse response = (HttpServletResponse) servletResponse;
 request.setCharacterEncoding("UTF-8");
 response.setCharacterEncoding("UTF-8");
 
 filterChain.doFilter(request , response);
 }
 @Override
 public void destroy() {
 }
}

然后启动类上加上@ServletComponentScan。@WebFilter是servlet3.0才有的注解。当然这个过滤器你还可以这么写

public class CharacterEncodingFilter implements Filter{
 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
 }
 
 @Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
 HttpServletRequest request = (HttpServletRequest) servletRequest;
 HttpServletResponse response = (HttpServletResponse) servletResponse;
 request.setCharacterEncoding("UTF-8");
 response.setCharacterEncoding("UTF-8");
 
 filterChain.doFilter(request , response);
 }
 @Override
 public void destroy() {
 }
}

写个bean配置类，如下

 @Bean
 public FilterRegistrationBean registerAuthFilter() {
 FilterRegistrationBean registration = new FilterRegistrationBean();
 registration.setFilter(new CharacterEncodingFilter();
 registration.addUrlPatterns("/*");
 registration.setName("CharacterEncodingFilter");
 registration.setOrder(1); 
 return registration;
 }

方案三：在application.yml指定编码格式为utf-8

spring:
 http:
 encoding:
 charset: utf-8
 enabled: true
 force: true

server:
 tomcat:
 uri-encoding: UTF-8

方案四：写个StringHttpMessageConverter

百度来的基本上都是长这样。不过在spring5版本WebMvcConfigurerAdapter这个类已经过时。其替代方式是实现WebMvcConfigurer接口或者继承WebMvcConfigurationSupport。不过如果使用WebMvcConfigurationSupport，则会使springboot的mvc自动装配失效。失效的原因是

拓展一点小知识，加上@EnableWebMvc同样也会springboot的mvc自动装配失效。其原因是

org.springframework.web.servlet.config.annotation.DelegatingWebMvcConfiguration这个配置类继承WebMvcConfigurationSupport

介绍那么多种方案，并没有解决按例的问题。那问题点出在哪里？前边案例我们提到过，在feign调用时，会把threadlocal的参数塞到header里面。真正乱码的问题点就在这里，header是不支持中文传输的，如果你硬要传输，基本上接收方接到就是???这种看似乱码的符号

破题关键

在把threadlocal的值塞到header里面时，先做下URLEncoder编码，形如

URLEncoder.encode(“我是中文乱码”,"UTF-8")

在接收header参数时，做下URLDecoder.解码，形如下

URLDecoder.decode(header中待解码的参数值, "UTF-8")

总结

方向错了，虽然再怎么努力看似也啥没卵用，不过至少可能会收获其他意想不到的东西

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