ajax 上传文件

var formData = new FormData($("#form")[0]);
                    $.ajax({
                        url : "/xx/xx",
                        type : "POST",
                        data : formData,
                        async : true,
                        cache : false,
                        contentType : false,
                        processData : false,
                        success : function(returnData) {
                            //..
                        },
                        error : function(returnData) {
                            //..
                        }
                    });

@RequestMapping("/xx")
    public String showExcel(HttpServletRequest request, MultipartFile importExcel) {
  //...
)