为什么uploadFile好像传不了文件到后台？

前端调用代码

selectImg: function(e){    var that=this    wx.chooseImage({      count: 3,      sizeType: ['original', 'compressed'],      sourceType: ['album', 'camera'],      success(res) {        const tempFilePaths = res.tempFilePaths        console.log(tempFilePaths)        that.setData({          imgUrl: tempFilePaths        })        wx.uploadFile({          url: app.serverUrl+"/upload/XZImg?openid="+app.openID, //仅为示例，非真实的接口地址          filePath: tempFilePaths[0],          name: 'files',          success(res) {            const data = res.data            //do something            console.log(data)          },        })             }    })

后端代码

@RestController @RequestMapping("/upload") public class uploadImage {       @PostMapping("/XZImg")     public void uploadFace(String openid, @RequestParam("files") MultipartFile[] files ) throws Exception {         System.out.println(openid);           if (StringUtils.isNotBlank(openid)) {             // 文件保存的命名空间             String fileSpace = "C:/Users/Administrator/ssm_images";             // 保存到数据库中的相对路径             String uploadPathDB = "/" + openid;             System.out.println(uploadPathDB);             FileOutputStream fileOutputStream = null;             InputStream inputStream = null;             try {                 if (files != null &&files.length>0) {                     System.out.println(files);                     String fileName = files[0].getOriginalFilename();                     if (StringUtils.isNotBlank(fileName)) {                         // 文件上传的最终保存路径                         String finalFacePath = fileSpace + uploadPathDB + "/" + fileName;                         // 设置数据库保存的路径                         uploadPathDB += ("/" + fileName);                           File outFile = new File(finalFacePath);                         if (outFile.getParentFile() != null || !outFile.getParentFile().isDirectory()) {                             // 创建父文件夹                             outFile.getParentFile().mkdirs();                         }                           fileOutputStream = new FileOutputStream(outFile);                         inputStream = files[0].getInputStream();                         IOUtils.copy(inputStream, fileOutputStream);                     }                   }             } catch (Exception e) {                 e.printStackTrace();             } finally {                 if (fileOutputStream != null) {                     fileOutputStream.flush();                     fileOutputStream.close();                 }             }         }       } }

一直进不去啊，用HttpServltRequest看请求体参数files是null。是哪里出问题了呢？好像文件根本就没传过去，都是null