Multipart getParameter问题

Question

我从客户端向servlet发送此请求：

在客户端我正在做：                  img = Capture.capturePhoto（200,200）;

        InfiniteProgress inf = new InfiniteProgress();            
        Dialog progress = inf.showInifiniteBlocking(); 
        MultipartRequest request = new MultipartRequest();

        request.setUrl("http://localhost:8080/Test/Test");//calling servlet

          request.addData("ImageName.jpg", img, "image/jpeg");
          request.addArgument("imgname", "image1");


        request.setDisposeOnCompletion(progress);
        NetworkManager.getInstance().addToQueue(request);

在服务器端，我正在使用它：

a = req.getParameter("imgname");// but value I'm getting is null 
File repository = new File ("F:/SERVLET images");
System.out.println(repository);
DiskFileItemFactory factory = new DiskFileItemFactory(1024, repository);
((DiskFileItemFactory) factory).setRepository(repository);
ServletFileUpload upload = new ServletFileUpload(factory);

try
{
    items = upload.parseRequest(req);
}
catch (FileUploadException e)
{
    // TODO Auto-generated catch block
    e.printStackTrace();
}
Iterator<FileItem> iter = items.iterator();
while (iter.hasNext())
{
    FileItem item = iter.next();
    File f1 = new File ("F:/SERVLET images/pics/'"+a+"'.jpg");
    // 'null'.jpg is Printing and image is not displaying   
    try
    {
        item.write(f1);
        System.out.print(f1);
    }
}

我出错了什么？