multipartfile如何转成File

我是这样写的： MultipartFile multipartFile = multiRequest.getFile(iter.next());

CommonsMultipartFile cf= (CommonsMultipartFile)multipartFile;
DiskFileItem fi = (DiskFileItem)cf.getFileItem();

File file = fi.getStoreLocation();
但是报错说找不到文件：java.io.FileNotFoundException

有什么解决办法啊 急需！！

@RequestMapping("/up2.do")
public String up2(HttpServletRequest request,@RequestParam("file")MultipartFile file) {
    String path=request.getSession().getServletContext().getRealPath("/upload/");
    String suffix = file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf("."));     
    String fileName = UUID.randomUUID().toString()+ suffix; 
    File f=new File(path,fileName);
    file.transferTo(f);
}