spring mvc 上传图片问题

Question

后台：
@RequestMapping(method = RequestMethod.POST,params="picture")
public @ResponseBody String updateLoad(@RequestParam(value = "file") MultipartFile file) {
String filePath = request.getSession().getServletContext().getRealPath("/") + java.io.File.separator + AppConstants.PICTURE_PLACE;

    String name = FileUtil.saveFile(file, filePath);
    return name;
}

前台：

  <form id="imageUploadForm"  action='coupon?picture' method="post" enctype='multipart/form-data'>
                                <input type="file" name="file" class="default" />
                                <input type="submit" value="upload" />
            </form>    

报错：Required MultipartFile parameter 'file' is not present,怎么改能不报错，并且传过来的file 不为null

Answer 1