Spring MVC RestTemplate文件上传报401错误求助及代码排查

我需要通过Spring MVC RestTemplate按照下图所示的参数上传文件。

我尝试了多种实现方式，但均报错401 Unauthorized。我需要一份可通过Spring MVC RestTemplate实现文件上传的代码，现将自己无法正常运行的代码附上，请帮忙排查问题。

@RequestMapping(value = "/uploadPEFile", method = { RequestMethod.POST}, 
            produces = "application/json")
    @ResponseBody
    public String uploadPEFile(@RequestParam(value = "file", required = false) MultipartFile file,
            HttpServletRequest request, HttpServletResponse httpResponse) {
        JsonResponse objResponse = null;
        String enterpriseId = "";
        String enterpriseName = "";
        String type = "";
        String productId = "";
        String userIds = "";
        String title = "";
        String description = "";
        String date = "";
        String externalUrl = "";
        String presenterName = "";
        try {

            enterpriseId = request.getParameter("enterpriseId");
            enterpriseName = request.getParameter("enterpriseName");
            type = request.getParameter("type");
            productId = request.getParameter("productId");
            userIds = request.getParameter("userIds");
            title = request.getParameter("title");
            description = request.getParameter("description");
            date = request.getParameter("date");
            if(date != null && !date.isEmpty())
            {
                String [] dateArray = date.split(" ");
                date = dateArray[2]+" "+getMonth(dateArray[1])+", "+dateArray[3];
            }
            externalUrl = request.getParameter("externalURL");
            presenterName = request.getParameter("presenterName");
            JsonObject jsonBody = new JsonObject();
            jsonBody.addProperty("title", title);
            jsonBody.addProperty("description", description);
            jsonBody.addProperty("date", date);
            jsonBody.addProperty("external_url", externalUrl);
            jsonBody.addProperty("presenter_name", presenterName);
            String cmsDeviceId = PortalUtil.getPropertyValue("cms.device.id");
        
                    if (file != null) {
                final String filename = file.getOriginalFilename();
                
                ByteArrayResource fileAsResource = new ByteArrayResource(file.getBytes()) {
                    @Override
                    public String getFilename() {
                        return filename;
                    }
                };
                String filePath = "/persivia edge/"+type+"/"+filename;
                File userFile = new File(System.getProperty(PortalConstants.cdnPath) + filePath);
                if(!userFile.exists()) {
                    userFile.mkdirs();
                }
                file.transferTo(userFile);
                HttpHeaders headers = new HttpHeaders();
                headers.setContentType(MediaType.MULTIPART_FORM_DATA);
                MultiValueMap<String, Object> body = new LinkedMultiValueMap<>();
                body.add("device_id",cmsDeviceId);
//              body.add("attachment",fileAsResource);
//              body.add("attachment",new MultipartInputStreamFileResource(file.getInputStream(), file.getOriginalFilename()));
                body.add("attachment",new FileSystemResource(filePath));
                
                body.add("source", "web");
                body.add("filename", filename);
                body.add("enterprise_id", enterpriseId);
                body.add("enterpriseName", enterpriseName);
                body.add("type", type);
                body.add("product_id",productId);
                body.add("userIds",userIds);
                body.add("body", jsonBody.toString());
                
                HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(body, headers);
                RestTemplate restTemplate = new RestTemplate();
                String requestUrl = PortalUtil.getPropertyValue("cms.api.url")+"wp-json/wp/v2/upload_content";
                String response = restTemplate.postForObject(requestUrl, requestEntity, String.class);
                httpResponse.setStatus(HttpServletResponse.SC_OK);
                JsonObject data = new JsonObject();
                objResponse = JsonResponse.build(ResponseStatus.status200, ResponseStatus.message200,
                        "Logo info updated successfully", data);
            }

        } catch (Exception e) {
            e.printStackTrace();
            logger.error(e.getMessage(), e.getCause());

            objResponse = JsonResponse.build(ResponseStatus.status500, ResponseStatus.message500,
                    e.getMessage(), null);

            httpResponse.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        }
        return new Gson().toJson(objResponse);
    }

内容的提问来源于stack exchange，提问作者Majid Khakwani