SpringMVC 返回 json 字符串中文乱码

原因

最近在写一些小的Demo案例，但是被AJAX的 json 返回乱码折磨了好久。最后通过研究StringHttpMessageConverter源代码发现，开发者很坑的使用了”ISO-8859-1”作为默认编码。经过代码测试，下面给出四种方法解决SpringMVC 返回 json 字符串中文乱码。（本文spring版本4.3.11.RELEASE）

public class StringHttpMessageConverter extends AbstractHttpMessageConverter {public static final Charset DEFAULT_CHARSET = Charset.forName("ISO-8859-1");private volatile List availableCharsets;private boolean writeAcceptCharset;// 后面省略

方法一：自己编写一个工具类

学过servlet我们可以知道，可以通过HttpServletResponse设置返回编码。

工具类

public class ResponseTool {public static void write(HttpServletResponse response,Object o)throws Exception{response.setContentType("text/html;charset=utf-8");PrintWriter out=response.getWriter();out.println(o.toString());out.flush();out.close();}
 }

测试方法

@RequestMapping(value = "/toolToJson")
 public void toolToJson(HttpServletResponse response) throws Exception {Map map = new HashMap();map.put("code", "200");map.put("msg", "这是一句话，测试返回json是否乱码。");ResponseTool.write(response,new Gson().toJson(map));
 }

方法二：使用produces属性

在RequestMapping使用（produces = “text/html; charset=utf-8”）produces 作用根据请求头中的Accept进行匹配，如请求头“Accept:text/html”时即可匹配。

如果类型是：application/json ，设置为：produces = “application/json; charset=utf-8”
测试方法

@RequestMapping(value = "/producesToJson", method = RequestMethod.GET, produces="text/html;charset=UTF-8")
 @ResponseBody
 public String producesToJson() {Map map = new HashMap();map.put("code", "200");map.put("msg", "这是一句话，测试返回json是否乱码。");return new Gson().toJson(map);
 }

方法三：通过配置spring-mvc.xml

在spring-mvc.xml添加配置

text/html;charset=UTF-8application/json;charset=UTF-8text/plain;charset=UTF-8application/xml;charset=UTF-8
 

测试方法

@RequestMapping(value = "/json")
 @ResponseBody
 public String json() {Map map = new HashMap();map.put("code", "200");map.put("msg", "这是一句话，测试返回json是否乱码。");return new Gson().toJson(map);
 }

方法四：完成自己的AbstractHttpMessageConverter

分析源码可以看出StringHttpMessageConverter继承与AbstractHttpMessageConverter，分析该抽象类得，相关的操作字符编码的方法可以重写，于是我们可以自定义一个类继承StringHttpMessageConverter，然后重写相关的方法。这里我们只需要把ISO-8859-1改成UTF-8，并修改构造方法。

UTF8StringHttpMessageConverter 类

package com.javazhan.controller;import org.springframework.http.HttpInputMessage;
 import org.springframework.http.HttpOutputMessage;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.AbstractHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.http.converter.HttpMessageNotWritableException;
 import org.springframework.util.StreamUtils;import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.List;/*** @Author: yandq* @Description:* @Date: Create in 11:50 2018/4/3* @Modified By:*/
 public class UTF8StringHttpMessageConverter extends AbstractHttpMessageConverter {public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");private volatile List availableCharsets;private boolean writeAcceptCharset;public UTF8StringHttpMessageConverter() {this(DEFAULT_CHARSET);}public UTF8StringHttpMessageConverter(Charset defaultCharset) {super(defaultCharset, new MediaType[]{MediaType.TEXT_PLAIN, MediaType.ALL});this.writeAcceptCharset = true;}public void setWriteAcceptCharset(boolean writeAcceptCharset) {this.writeAcceptCharset = writeAcceptCharset;}@Overridepublic boolean supports(Class clazz) {return String.class == clazz;}@Overrideprotected String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException {Charset charset = this.getContentTypeCharset(inputMessage.getHeaders().getContentType());return StreamUtils.copyToString(inputMessage.getBody(), charset);}@Overrideprotected Long getContentLength(String str, MediaType contentType) {Charset charset = this.getContentTypeCharset(contentType);try {return (long)str.getBytes(charset.name()).length;} catch (UnsupportedEncodingException var5) {throw new IllegalStateException(var5);}}@Overrideprotected void writeInternal(String str, HttpOutputMessage outputMessage) throws IOException {if (this.writeAcceptCharset) {outputMessage.getHeaders().setAcceptCharset(this.getAcceptedCharsets());}Charset charset = this.getContentTypeCharset(outputMessage.getHeaders().getContentType());StreamUtils.copy(str, charset, outputMessage.getBody());}protected List getAcceptedCharsets() {if (this.availableCharsets == null) {this.availableCharsets = new ArrayList(Charset.availableCharsets().values());}return this.availableCharsets;}private Charset getContentTypeCharset(MediaType contentType) {return contentType != null && contentType.getCharset() != null ? contentType.getCharset() : this.getDefaultCharset();}
 }
 

定义好上面的类后，只需要将该类注册到Spring的annotaion 处理序列中即可，当加上@ResponseBody时，Spring将会调用上面自定义类中复写的方法，从而返回UTF-8的编码：

测试方法

@RequestMapping(value = "/json")
 @ResponseBody
 public String json() {Map map = new HashMap();map.put("code", "200");map.put("msg", "这是一句话，测试返回json是否乱码。");return new Gson().toJson(map);
 }

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