<form id="uploadForm" enctype="multipart/form-data">
  <input id="file" type="file" name="file"/>
  <button id="upload" type="button">上传</button>
</form>

 var formData = new FormDate($('#uploadForm')[0]);

 $.ajax({
        url: 'http://10.10.2.254:8080/file/associateupload',
        type: 'POST',
        cache: false,
        data: formData,
        processData: false,
        contentType: false,
        success:function(res){
            console.log(res);
        }
    });

<div id="uploadDiv">
  <input id="file" type="file"/>
  <button id="upload" type="button">上传</button>
</div>

var formData = new FormData();
formData.append('file', $('#file')[0].files[0]);
$.ajax({
  url: '/upload',
  type: 'POST',
  cache: false,
  data: formData,
  processData: false,
  contentType: false,
  success:function(res){
     console.log(res);
  }