@RequestBody 异常：Required request body is missing

一、异常信息：

"exception": "org.springframework.http.converter.HttpMessageNotReadableException",
"message": "Required request body is missing: public 
com.game.manager.security.web.vo.response.Responsecom.game.manager.security.web.controller.RoleCont
roller.listRole(com.game.manager.security.web.vo.request.ListRoleReq)"

Controller代码:

@ApiOperation(tags="获取所有角色信息",value="获取所有角色信息")
@GetMapping("/listRole")
@ResponseBody
public Response listRole(@RequestBody ListRoleReq listRoleReq){
    return    Response.success("");
}

三、源码分析：

异常的抛出点在RequestResponseBodyMethodProcessor的readWithMessageConverters方法，

@Override
    protected  Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter parameter,
            Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {

        HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
        ServletServerHttpRequest inputMessage = new ServletServerHttpRequest(servletRequest);

        Object arg = readWithMessageConverters(inputMessage, parameter, paramType);
        if (arg == null) {
            if (checkRequired(parameter)) {
                throw new HttpMessageNotReadableException("Required request body is missing: " +
                        parameter.getMethod().toGenericString());
            }
        }
        return arg;
    }

而arg 的返回时在AbstractMessageConverterMethodArgumentResolver的readWithMessageConverters进行。

    @SuppressWarnings("unchecked")
    protected  Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter parameter,
            Type targetType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {

        MediaType contentType;
        boolean noContentType = false;
        try {
            contentType = inputMessage.getHeaders().getContentType();
        }
        catch (InvalidMediaTypeException ex) {
            throw new HttpMediaTypeNotSupportedException(ex.getMessage());
        }
        if (contentType == null) {
            noContentType = true;
            contentType = MediaType.APPLICATION_OCTET_STREAM;
        }

        Class contextClass = (parameter != null ? parameter.getContainingClass() : null);
        Class targetClass = (targetType instanceof Class ? (Class) targetType : null);
        if (targetClass == null) {
            ResolvableType resolvableType = (parameter != null ?
                    ResolvableType.forMethodParameter(parameter) : ResolvableType.forType(targetType));
            targetClass = (Class) resolvableType.resolve();
        }

        HttpMethod httpMethod = ((HttpRequest) inputMessage).getMethod();
        Object body = NO_VALUE;

        try {
            inputMessage = new EmptyBodyCheckingHttpInputMessage(inputMessage);

            for (HttpMessageConverter converter : this.messageConverters) {
                Class> converterType = (Class>) converter.getClass();
                if (converter instanceof GenericHttpMessageConverter) {
                    GenericHttpMessageConverter genericConverter = (GenericHttpMessageConverter) converter;
                    if (genericConverter.canRead(targetType, contextClass, contentType)) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("Read [" + targetType + "] as \"" + contentType + "\" with [" + converter + "]");
                        }
                        if (inputMessage.getBody() != null) {
                            inputMessage = getAdvice().beforeBodyRead(inputMessage, parameter, targetType, converterType);
                            body = genericConverter.read(targetType, contextClass, inputMessage);
                            body = getAdvice().afterBodyRead(body, inputMessage, parameter, targetType, converterType);
                        }
                        else {
                            body = getAdvice().handleEmptyBody(null, inputMessage, parameter, targetType, converterType);
                        }
                        break;
                    }
                }
                else if (targetClass != null) {
                    if (converter.canRead(targetClass, contentType)) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("Read [" + targetType + "] as \"" + contentType + "\" with [" + converter + "]");
                        }
                        if (inputMessage.getBody() != null) {
                            inputMessage = getAdvice().beforeBodyRead(inputMessage, parameter, targetType, converterType);
                            body = ((HttpMessageConverter) converter).read(targetClass, inputMessage);
                            body = getAdvice().afterBodyRead(body, inputMessage, parameter, targetType, converterType);
                        }
                        else {
                            body = getAdvice().handleEmptyBody(null, inputMessage, parameter, targetType, converterType);
                        }
                        break;
                    }
                }
            }
        }
        catch (IOException ex) {
            throw new HttpMessageNotReadableException("I/O error while reading input message", ex);
        }

        if (body == NO_VALUE) {
            if (httpMethod == null || !SUPPORTED_METHODS.contains(httpMethod) ||
                    (noContentType && inputMessage.getBody() == null)) {
                return null;
            }
            throw new HttpMediaTypeNotSupportedException(contentType, this.allSupportedMediaTypes);
        }

        return body;
    }

由于我们的ContenType是Json格式，因此由JsonConvert进行处理。而GET方法请求试没有传输body因此无法获取body信息。导出返回的body为null，因此抛出异常。

二、导致原因

通过源码的分析我们得出。因为GET方法请求试没有传输body信息。导致Spring处理body的时候为null，抛出异常。只用我们将GET方法修改成POST方法即可访问。