@ExceptionHandler全局异常捕获响应体返回中文乱码

问题现象

在全局异常处理后，发现响应体返回中文的错误信息竟然乱码了，如下：

问题原因

Controller

@RequestMapping(value = "/user/{user_id}", method = RequestMethod.DELETE, consumes =MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
@ResponseStatus(code = HttpStatus.OK)
public String deleteUser(HttpServletRequest request, HttpServletResponse response,@PathVariable(value = "user_id") String userId) {String userName = userService.getUserName(userId);if (userName == null) {// 此处异常被全局异常处理throw new NullPointerException();}// delete userreturn "success";
}

全局异常处理器ControllerAdvice

@Component
@ControllerAdvice
public class GlobalExceptionHandler {@Resourceprivate MessageProcessor messageProcessor;/*** 处理其他未被捕获的异常，返回服务器内部错误，响应500** @param request   http请求* @param exception 参数绑定异常* @return 异常响应国际化信息*/@ExceptionHandler(value = Exception.class)@ResponseBody@ResponseStatus(value = HttpStatus.INTERNAL_SERVER_ERROR)public String handleException(HttpServletRequest request, Exception exception) {return messageProcessor.getMessage(request, INTERNAL_ERROR_DEFAULT_MESSAGE);}
}

国际化资源包

response.500.message.0001=系统错误，请稍后重试。response.500.message.0001=System error, please try again later.

问题分析

分析下原因，是因为触发了全局异常捕获，handleException()方法上标注了@ResponseBody，即返回的message会被放入响应体中返回给前端。和Controller方法不同的是，使用@RequestMapping方法指定了consumes=MediaType.APPLICATION_JSON_VALUE，即响应体会被json处理，但是@ExceptionHandler方法未指定响应体格式Content-Type,可以在postman中查看：

由SpringMVC处理流程可知

6、返回ModelAndView之后仍然是交由HandleAdapter去处理，所以重点分析下Adapter。这里的Adapter实现类为RequestMappingHandlerAdapter,入口为handleInternal方法，调用invokeHandlerMethod()

handleInternal()

@Override
protected ModelAndView handleInternal(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {ModelAndView mav;mav = invokeHandlerMethod(request, response, handlerMethod);return mav;
}

invokeHandlerMethod()

@Nullable
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {// 创建ServletWebRequest对象ServletWebRequest webRequest = new ServletWebRequest(request, response);try {WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);// 设置方法参数解析器if (this.argumentResolvers != null) {invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);}// 设置方法返回值处理器if (this.returnValueHandlers != null) {invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);}invocableMethod.setDataBinderFactory(binderFactory);invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);// ModelAndView容器，将上述参数设置进去并初始化相关配置ModelAndViewContainer mavContainer = new ModelAndViewContainer();mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));modelFactory.initModel(webRequest, mavContainer, invocableMethod);mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);// 异步请求处理AsyncWebRequest，不涉及已忽略// 调用此方法并处理返回值invocableMethod.invokeAndHandle(webRequest, mavContainer);return getModelAndView(mavContainer, modelFactory, webRequest);}finally {webRequest.requestCompleted();}
}

invokeAndHandle()

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer          mavContainer, Object... providedArgs) throws Exception {// 调用方法获取方法返回值，如果发生异常，此时获取的是异常处理的方法的返回值Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);// 根据@ResponseStatus注解设置响应码setResponseStatus(webRequest);// 返回值为null时处理if (returnValue == null) {if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {disableContentCachingIfNecessary(webRequest);mavContainer.setRequestHandled(true);return;}}else if (StringUtils.hasText(getResponseStatusReason())) {// 如果在@ResponseStatus注解设置reason()，则进去此处mavContainer.setRequestHandled(true);return;}mavContainer.setRequestHandled(false);Assert.state(this.returnValueHandlers != null, "No return value handlers");// returnValueHandlers处理返回值try {this.returnValueHandlers.handleReturnValue(returnValue, getReturnValueType(returnValue), mavContainer, webRequest);}catch (Exception ex) {if (logger.isTraceEnabled()) {logger.trace(formatErrorForReturnValue(returnValue), ex);}throw ex;}
}

handleReturnValue()

public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {// 在returnHandler列表中根据supportsReturnType()方法，获取第一个支持的HandlerHandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType);if (handler == null) {throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());}// Handler中有messageConverters列表，根据messageConverter的canWrite()方法选择合适的messageConvert,并将message写入到response中。handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
}

由上分析可知，最终是根据messageConvert将返回值写入到response中。由于返回值是String，而messageConvert所以会使用StringHttpMessageConvert:

而StringHttpMessageConvert的Content-Type默认是text/plain;charset=UTF-8，编码方式是ISO-8859-1，所以产生中文乱码

解决方法

解决方法一：在配置文件中指定StringHttpMessageConverter的字符集，推荐此方案。

<!--开启SpringMVC注解驱动-->
<!--指定validator-->
<mvc:annotation-driven validator="validator"><!--指定StringHttpMessageConverter的字符集--><mvc:message-converters><bean class="org.springframework.http.converter.StringHttpMessageConverter"><property name="supportedMediaTypes"><list><value>text/plain;charset=utf-8</value><value>text/html;charset=UTF-8</value></list></property></bean></mvc:message-converters>
</mvc:annotation-driven>

解决方法二：在bean后处理器中指定StringHttpMessageConverter的字符集，所有的被spring托管的bean都会执行postProcessAfterInitialization方法，建议使用解决方法一。

@Component
public class DefineCharSet implements BeanPostProcessor {//实例化之前调用@Nullablepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {return bean;}//实例化之后调用@Nullablepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {// 指定StringHttpMessageConverter的字符集if(bean instanceof StringHttpMessageConverter){MediaType mediaType = new MediaType("text", "html", Charset.forName("UTF-8"));List<MediaType> types = new ArrayList<MediaType>();types.add(mediaType);((StringHttpMessageConverter) bean).setSupportedMediaTypes(types);}return bean;}
}

测试：