EasyUI中使用Ajax提交文件表单

HTML代码：

<form id="fileForm" enctype="multipart/form-data" method="post">
     <input type="file" id="file" name="file" style="width: 200px">
 </form>

jquery代码：

$('#fileForm').form('submit',{
   url:"········",success:function(data){
     // change the JSON string to javascript object
     var msg = eval('(' + data + ')');
     if (msg.success) {
       alert(1);
     }else{
       alert(2);
     }
   }
 });

java代码：

@RequestMapping(params = "addFile")
@ResponseBody
public SuccessMsg addFile(MultipartFile numFile){
    SuccessMsg msg = new SuccessMsg();
    return msg;
}