Ajaxファイルアップロード機能(Spring MVC)

<script src="static/js/jquery-3.4.1.js"></script>

<form id="form-avatar" enctype="multipart/form-data">
 <p>Please select the file to upload: </p>
 
 <p><input type="file" name="file" /></p>
 <p><input id="btn-avatar" type="button" value="upload" /></p>
</form>

<script>
 function uploadfile(){
  $.ajax({
   url : "/url/upload",
   data: new FormData($("#form-avatar")[0]),
   type : "POST",
   // Tell jQuery not to process the data sent, for serialization of data parameters.
   processData : false,
   // Tell jQuery not to set the Content-Type request header
   contentType : false,

   success : function(json) {
    alert("Execution successful");
   },
   error : function(json) {
    alert("Failed");

   }
  });
 }
 $("#btn-avatar").on("click",uploadfile);
</script>

@PostMapping("/upload")
 public void fileUpload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
  System.out.println("gone");
  // upload path save settings
  String path = request.getServletContext().getRealPath("/upload");
  File realPath = new File(path);
  if (!realPath.exists()) {
   realPath.mkdir();
  }
  //Upload file address
  System.out.println("Upload file save address: " + realPath);

  // write the file directly via CommonsMultipartFile's method (note this time)
  file.transferTo(new File(realPath + "/" + file.getOriginalFilename()));

 }