文件上传 struct中 注入的file属性获取不到

public static File getTempFile(HttpServletRequest request, String name){
        try
        {
            Part part = request.getPart("file");
            InputStream is = part.getInputStream();
            FileOutputStream fos = new FileOutputStream(getRequest().getRealPath("/") + name);
            byte[]buff=new byte[1024];
            int len=0;
            while((len=is.read(buff))>0){
                fos.write(buff);
            }
            is.close();
            fos.close();
            File fileTemp = new File(getRequest().getRealPath("/") + name);
            return fileTemp;
        }
        catch(Exception e)
        {
            System.err.println("上传文件错误："+e);
        }
        return null;
    }