为什么我在Spring上传文件时会出现400错误？

Question

上传文件时出现400错误。 Chrome开发者日志也只告诉我有400错误。我有一种感觉错误源自我的控制器，但由于它没有发现错误，我很难跟踪错误是否正确。堆栈日志告诉我java.lang.NullPointerException: null

Chrome错误

Object {readyState: 4, responseText: "", status: 400, statusText: "error"}

Stack的错误

 null
2017-03-28 08:38:51.322 ERROR 14332 --- [nio-8080-exec-7] g.g.m.a.web.controller.ExamsController   : null

java.lang.NullPointerException: null
    at gh.gov.moh.admissionsportal.web.controller.ExamsController.uploadFile(ExamsController.java:254) ~[main/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_65]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_65]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_65]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_65]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
2017-03-28 08:38:51.353 DEBUG 14332 --- [nio-8080-exec-7] o.s.web.servlet.DispatcherServlet        : Null ModelAndView returned to DispatcherServlet with name 'dispatcherServlet': assuming HandlerAdapter completed request handling
2017-03-28 08:38:51.353 DEBUG 14332 --- [nio-8080-exec-7] o.s.web.servlet.DispatcherServlet        : Successfully completed request

上传课程

private BufferedImage cropImageSquare(byte[] image) {
        // Get a BufferedImage object from a byte array
        BufferedImage croppedImage = null;
        try {
            InputStream in = new ByteArrayInputStream(image);
            BufferedImage originalImage = ImageIO.read(in);

            // Get image dimensions
            int height = originalImage.getHeight();
            int width = originalImage.getWidth();

            // The image is already a square
            if (height == width) {
                return originalImage;
            }

            // Compute the size of the square
            int squareSize = (height > width ? width : height);

            // Coordinates of the image's middle
            int xc = width / 2;
            int yc = height / 2;

            // Crop
            croppedImage = originalImage.getSubimage(
                    xc - (squareSize / 2), // x coordinate of the upper-left corner
                    yc - (squareSize / 2), // y coordinate of the upper-left corner
                    squareSize,            // widht
                    squareSize             // height
            );
        } catch (IOException e) {
            System.out.println(e.getMessage());
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }

        return croppedImage;
    }

控制器

@PostMapping(value = "/uploadFile")
    @ResponseBody
    public ResponseEntity<?> uploadFile( MultipartFile uploadfile, Picture picture, Principal principal, MultipartHttpServletRequest request) {
        User user = (User) ((UsernamePasswordAuthenticationToken) principal).getPrincipal();
        picture.setUser(user);
        try {
            //Null Error here
            MultipartFile multiFile = request.getFile(uploadfile.getOriginalFilename());
            System.out.println("File Length:" + multiFile.getBytes().length);
            System.out.println("File Type:" + multiFile.getContentType());
            // Crop the image (uploadfile is an object of type MultipartFile)
            BufferedImage croppedImage = cropImageSquare(multiFile.getBytes());
            String fileName=multiFile.getOriginalFilename();
            System.out.println("File Name:" +fileName);
            String path=request.getServletContext().getRealPath("/");
            // Get the filename and build the local file path
            File directory=    new File(path+ "/uploads");
            directory.mkdirs();
            String filename = uploadfile.getOriginalFilename();
            String ext = FilenameUtils.getExtension(filename);
            File outPutFile = new File(directory.getAbsolutePath()+System.getProperty("file.separator")+picture.getUploadfile());
            ImageIO.write(croppedImage, ext, outPutFile);
        } catch (Exception e) {
            System.out.println(e.getMessage());
            return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
        }
        //pictureService.save(picture, uploadfile);
        return new ResponseEntity<>(HttpStatus.ACCEPTED);
    }

JS FILE

var $formUploader = $("#upload-file-input");
  $formUploader.on("submit", function(e){
   e.preventDefault();

   var data1 = new FormData(this);
   $.each($formUploader.serializeArray(), function(i, field) {
          data1[field.name] = field.value;
   });
   //next line will add content of file
   data1.append('uploadfile', $('#file')[0].files[0]);
   for(var i of data1.entries()){
        console.log(i[0] + ' '+ i[1]);
   }
$.ajax({
           //dataType: 'json',
           url: $formUploader.prop('action'),
           type: "POST",
           data: data1,
           enctype: 'multipart/form-data',
           processData: false,
           contentType: false,
           cache: false,
           timeout: 10000,
           success: function (data) {
           console.log(data);
             // Handle upload success
             $("#upload-file-message").text("File succesfully uploaded");
           },
           error: function (response) {
             console.log(response);
             // Handle upload error
             $("#upload-file-message").text("File not uploaded (File might be big, size needed.)");
           }
         });
});

上传表格

 <form  id="upload-file-input" th:action="@{/uploadFile}" method="post" th:object="${picture}"
      enctype="multipart/form-data" class="form-inline inline new-item">
    <div th:replace="common/layout :: flash"></div>
    <fieldset>
        <legend> Upload Picture</legend>
        <label class="btn btn-default btn-file">
            Browse
            <input type="file" id="file" name="uploadfile" onchange="$('#custom-file-control').html($(this).val());"/>
            <span id="custom-file-control"></span>
        </label>
        <span id="upload-file-message"></span>
        <button type="submit" class="btn btn-primary">Upload Picture</button>
    </fieldset>
    <div class="style16"></div>
</form>