问题：
在前端通过get请求服务端返回String类型的服务时，会出现中文乱码问题
原因：
由于spring默认对String类型的返回的编码采用的是 StringHttpMessageConverter
>>> spring mvc的一个bug，spring MVC有一系列HttpMessageConverter去处理用@ResponseBody注解的返回值，如返回list则使用MappingJacksonHttpMessageConverter，返回string，则使用StringHttpMessageConverter，这个convert使用的是字符集是iso-8859-1,而且是final的：
public static final Charset DEFAULT_CHARSET = Charset.forName("ISO-8859-1");
解决办法：
方案一：
对于需要返回字符串的方法添加注解，如下：只针对单个方法生效，不全局生效
public String getAllUser()throws JsonGenerationException, JsonMappingException, IOException{
List < User > users = userService.getAll();
ObjectMapper om = new ObjectMapper();
System.out.println(om.writeValueAsString(users));
DataGrid dg = new DataGrid();
dg.setData(users);
return om.writeValueAsString(dg);
}
方案二：
在spring-servlet.xml中加入：
<mvc:annotation-driven> <mvc:message-converters register-defaults="true"> <bean class="org.springframework.http.converter.StringHttpMessageConverter"> <property name="supportedMediaTypes" value = "text/plain;charset=UTF-8" /> </bean> </mvc:message-converters> </mvc:annotation-driven>
方案三：
重写一个MessageConverter，然后注册到AnnotationMethodHandlerAdapter
package com.h5.common.converter;
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.StreamUtils;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
public class EncodingAdapter extends AbstractHttpMessageConverter < String > {
public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
private final Charset defaultCharset;
private final List < Charset > availableCharsets;
private boolean writeAcceptCharset;
public EncodingAdapter() {
this(DEFAULT_CHARSET);
}
public EncodingAdapter(Charset defaultCharset) {
super(new MediaType[]{
new MediaType("text", "plain", defaultCharset),
MediaType.ALL
});
this.writeAcceptCharset = true;
this.defaultCharset = defaultCharset;
this.availableCharsets = new ArrayList(Charset.availableCharsets().values());
}
public void setWriteAcceptCharset(boolean writeAcceptCharset) {
this.writeAcceptCharset = writeAcceptCharset;
}
public boolean supports(Class < ? > clazz) {
return String.class == clazz;
}
protected String readInternal(Class < ? extends String > clazz, HttpInputMessage inputMessage)throws IOException {
Charset charset = this.getContentTypeCharset(inputMessage.getHeaders().getContentType());
return StreamUtils.copyToString(inputMessage.getBody(), charset);
}
protected Long getContentLength(String str, MediaType contentType) {
Charset charset = this.getContentTypeCharset(contentType);
try {
return Long.valueOf((long)str.getBytes(charset.name()).length);
} catch (UnsupportedEncodingException var5) {
throw new IllegalStateException(var5);
}
}
protected 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 < Charset > getAcceptedCharsets() {
return this.availableCharsets;
}
private Charset getContentTypeCharset(MediaType contentType) {
return contentType != null && contentType.getCharSet() != null ? contentType.getCharSet() : this.defaultCharset;
}
}
//注册方法一：
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> <property name="messageConverters"> <util:list> <bean class="com.ctrip.hotel.h5.common.converter.EncodingAdapter "> <constructor-arg index="0" value="UTF-8"/> </bean> </util:list> </property> </bean>
//注册方法二：
在webconfig.java中：
@Override
public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
EncodingAdapter stringConverter = new EncodingAdapter();
converters.add(0, stringConverter);
}
方案四：
直接新建一个如下的类，放入代码即可。
package com.h5.common.encode;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
import org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.List;
/**
* Created by xingyuzhu on 2017/2/27.
* 解决@ResponseBody返回的响应中中文乱码问题.
*/
@Component
public class EncodingPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException{
if (bean instanceof RequestMappingHandlerAdapter) {
List < HttpMessageConverter < ? >> convs = ((RequestMappingHandlerAdapter)bean).getMessageConverters();
for (HttpMessageConverter < ? > conv : convs) {
if (conv instanceof StringHttpMessageConverter) {
((StringHttpMessageConverter)conv).setSupportedMediaTypes(
Arrays.asList(new MediaType("text", "html",
Charset.forName("UTF-8"))));
}
}
}
if (bean instanceof RequestResponseBodyMethodProcessor) {
List < HttpMessageConverter < ? >> convs = ((RequestMappingHandlerAdapter)bean).getMessageConverters();
for (HttpMessageConverter < ? > conv : convs) {
if (conv instanceof StringHttpMessageConverter) {
((StringHttpMessageConverter)conv).setSupportedMediaTypes(
Arrays.asList(new MediaType("text", "html",
Charset.forName("UTF-8"))));
}
}
}
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException{
return bean;
}
}
方案五：
在我们的webconfig.java中，注册一个bean：该方法有缺陷RequestMappingHandlerAdapter中的其他messageconverter丢失，导致其他问题，比如返回的是一个jsp页面，就会挂掉
@Bean
public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
RequestMappingHandlerAdapter reqMapHAdapter = new RequestMappingHandlerAdapter();
ArrayList < HttpMessageConverter < ? >> msgConvs = new ArrayList < > ();
StringHttpMessageConverter stringConverter = new
StringHttpMessageConverter(Charset.forName("UTF-8"));
stringConverter.setSupportedMediaTypes(Arrays.asList(MediaType.TEXT_PLAIN));
msgConvs.add(stringConverter);
reqMapHAdapter.setMessageConverters(msgConvs);
return reqMapHAdapter;
}
方案六：
在webconfig.java中：
@Override
public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
StringHttpMessageConverter stringConverter = new StringHttpMessageConverter(Charset.forName("UTF-8"));
converters.add(0, stringConverter);
}
方案七：（篡改框架的编码，推荐使用）
在webconfig.java中，篡改一下StringHttpMessageConverter的编码方式
@Override
public void extendMessageConverters(List < HttpMessageConverter < ? >> converters) {
HttpMessageConverter converter = Iterables.find(converters, new Predicate < HttpMessageConverter < ? >> () {
@ Override
public boolean apply( @ Nullable HttpMessageConverter < ? > input) {
return input != null && input instanceof StringHttpMessageConverter;
}
}, null);
if (converter == null) {
StringHttpMessageConverter stringConverter = new StringHttpMessageConverter();
stringConverter.setSupportedMediaTypes(Arrays.asList(new MediaType("text", "html", Charset.forName(UTF8))));
converters.add(1, stringConverter); //默认的StringHttpMessageConverter在第二个位置
return;
}
StringHttpMessageConverter stringHttpMessageConverter = (StringHttpMessageConverter)converter;
stringHttpMessageConverter.setSupportedMediaTypes(Arrays.asList(new MediaType("text", "html", Charset.forName(UTF8))));
}