SpringMVC3的ResponseBody返回字符串(JSON)乱码问题解决

近日做一个小项目，用spring mvc 做到ajax请求获取jquery ztree 异步获取树返回json对象时出现了乱码，试了各种办法，查了各种资料，一开始以为是数据库的编码有问题，经测试没问题，又以为是jetty需要设置下响 应头，正在查找时突然想到可能是mvc的responseBody的问题，网上一查，果然是，用了一个设置最简单的办法，解决了问题，特将文章转贴于此， 与我一样遇到此问题的朋友们共享。

添加@RequestMapping注解，配置produces的值

@RequestMapping(value = "/add", produces = {"application/json;charset=UTF-8"})

SpringMVC3的ResponseBody返回字符串乱码问题解决

SpringMVC的@ResponseBody注解可以将请求方法返回的对象直接转换成JSON对象，但是当返回值是String的时候，中文会乱码， 原因是因为其中字符串转换和对象转换用的是两个转换器，而String的转换器中固定了转换编码为"ISO-8859-1"，网上也很多种解决方法，有通 过配置Bean编码的，也有自己重写转换器的，我这里多次尝试未果，只能自己解决。

有两种解决办法：

1.返回字符串时，将字符串结果转换

return new String("你好".getBytes(), "ISO-8859-1");

2.添加@RequestMapping注解，配置produces的值

@RequestMapping(value = "/add", params = {"callback"}, produces = {"text/javascript;charset=UTF-8"})

以上提供的方法虽然需要额外配置，但相对灵活，喜欢一次性永久搞定的，还是应该考虑网上的方法，修改源码，或者替换默认的字符串转换器。

但是在使用<mvc:annotation-driven />配置的前提下，貌似网上的方法都不可靠，可能跟版本或者配置有关系 

这边提供一种修改方法，我这边使用的是3.1的mvc

1.参考网上将默认的StringHttpMessageConverter重写一遍，将其中的编码改为UTF-8

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.util.FileCopyUtils;

public class UTF8StringHttpMessageConverter extends AbstractHttpMessageConverter<String> {

    public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

    private final List<Charset> availableCharsets;

    private boolean writeAcceptCharset = true;

    public UTF8StringHttpMessageConverter() {
        super(new MediaType("text", "plain", DEFAULT_CHARSET), MediaType.ALL);
        this.availableCharsets = new ArrayList<Charset>(Charset.availableCharsets().values());
    }

    /**
     * Indicates whether the {@code Accept-Charset} should be written to any outgoing request.
     * <p>Default is {@code true}.
     */
    public void setWriteAcceptCharset(boolean writeAcceptCharset) {
        this.writeAcceptCharset = writeAcceptCharset;
    }

    @Override
    public boolean supports(Class<?> clazz) {
        return String.class.equals(clazz);
    }

    @Override
    protected String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException {
        Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType());
        return FileCopyUtils.copyToString(new InputStreamReader(inputMessage.getBody(), charset));
    }

    @Override
    protected Long getContentLength(String s, MediaType contentType) {
        Charset charset = getContentTypeCharset(contentType);
        try {
            return (long) s.getBytes(charset.name()).length;
        }
        catch (UnsupportedEncodingException ex) {
            // should not occur
            throw new InternalError(ex.getMessage());
        }
    }

    @Override
    protected void writeInternal(String s, HttpOutputMessage outputMessage) throws IOException {
        if (writeAcceptCharset) {
            outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets());
        }
        Charset charset = getContentTypeCharset(outputMessage.getHeaders().getContentType());
        FileCopyUtils.copy(s, new OutputStreamWriter(outputMessage.getBody(), charset));
    }

    /**
     * Return the list of supported {@link Charset}.
     *
     * <p>By default, returns {@link Charset#availableCharsets()}. Can be overridden in subclasses.
     *
     * @return the list of accepted charsets
     */
    protected List<Charset> getAcceptedCharsets() {
        return this.availableCharsets;
    }

    private Charset getContentTypeCharset(MediaType contentType) {
        if (contentType != null && contentType.getCharSet() != null) {
            return contentType.getCharSet();
        }
        else {
            return DEFAULT_CHARSET;
        }
    }

}

2.context配置

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                                                          http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                                                          http://www.springframework.org/schema/context 
                                                          http://www.springframework.org/schema/context/spring-context-3.1.xsd
                                                          http://www.springframework.org/schema/aop 
                                                          http://www.springframework.org/schema/aop/spring-aop-3.1.xsd
                                                          http://www.springframework.org/schema/tx 
                                                          http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
                                                          http://www.springframework.org/schema/mvc 
                                                          http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd
                                                          http://www.springframework.org/schema/context 
                                                          http://www.springframework.org/schema/context/spring-context-3.1.xsd">


    <mvc:annotation-driven>
        <mvc:message-converters>
            <bean class="yourpackage.UTF8StringHttpMessageConverter" />
        </mvc:message-converters>
    </mvc:annotation-driven>

......
    
</beans>