springmvc实现异步上传文件

<div>                               <div class="file" style="float: left;">                                                  <input type="file" name="file"id="file" runat="server" >                                     <input type="hidden" name='expoid'id="expoid" value="${expoid}" class="form-control">                               </div>                               <div>                                     <button type="button" class="btn btn-info" id="btnUpload"  onclick="uploadImage()" value="上传">上传</button>                               </div>                                   </div>

 function uploadImage() { var input = $("#file");        //判断是否有选择上传文件            var file = $("#file").val();            if (file == "") {                alert("请选择上传。doc文档文件！");                return;            }            //判断上传文件的后缀名            var strExtension = file.substr(file.lastIndexOf('.') + 1);            if (strExtension != 'doc') {                alert("请选择word文档文件");                return;            }            //上传文件                var formData = new FormData();                formData.append('expoid',$("#expoid").val());                formData.append('file',input[0].files[0]);                layer.load(1, {                      shade: [0.1,'#fff'] //0.1透明度的白色背景                });                $.ajax({                    type: "POST", // 上传文件要用POST                    url: "${ctx}/expo/exhibitionpo/uploadfile",                    dataType : "json",                    crossDomain: true, // 如果用到跨域，需要后台开启CORS                    processData: false,  // 注意：不要 process data                    contentType: false,  // 注意：不设置 contentType                    data: formData                }).success(function(data) {                    $("#fileName").innerHTML=data.fileName;                    $("#timeDate").innerHTML =data.timeDate;                    $("#userName").innerHTML =data.userName;                    layer.alert("文件上传成功！",{icon:1});                    layer.closeAll('loading');                }).fail(function(data) {                    layer.alert("网络错误，请刷新后重试！",{icon:2});                });        }

// 附件上传@RequestMapping(value = "/uploadfile", method = RequestMethod.POST)@ResponseBodypublic Object uploadTest(@RequestParam(required = false, value = "file") MultipartFile file,@RequestParam(required = false, value = "expoid") String expoid, HttpServletRequest request, HttpServletResponse response)throws IOException {Map<String, String> reMap = new HashMap<String, String>();User user = UserUtils.getUser();String path = request.getSession().getServletContext().getRealPath("fujianTemplate");String fileName = file.getOriginalFilename();System.out.println(fileName);System.out.println(path);String newFileName = expoid + "_fujian.doc";System.out.println(newFileName);File targetFile = new File(path, newFileName);if (!targetFile.exists()) {targetFile.mkdirs();}// 保存try {file.transferTo(targetFile);Date d = new Date();SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String dateNowStr = sdf.format(d);reMap.put("fileName", newFileName);reMap.put("timeDate", dateNowStr);reMap.put("userName", user.getName());} catch (Exception e) {e.printStackTrace();}return reMap;}