HttpURLConnection PUT 到谷歌云存储给出错误 403

I tried to upload a file to Google Cloud Storage using XML API. I have the right GoogleAccessId, expiry date and signature generated for each upload. The strange thing is that I can PUT file using Postman (application for Chrome), so I'm sure that the URL is ok. I just cannot PUT it using my Android Java program (it returns to me 403 error). The source code performing upload is here (it base on this one: https://cloud.google.com/storage/docs/access-control#Signing-Strings):

    URL url;
    HttpURLConnection connection;

    try {
        url = new URL("http://google-testbucket.storage.googleapis.com/testdata.txt?GoogleAccessId=1234567890123@developer.gserviceaccount.com&Expires=1331155464&Signature=BClz9e4UA2MRRDX62TPd8sNpUCxVsqUDG3YGPWvPcwN%2BmWBPqwgUYcOSszCPlgWREeF7oPGowkeKk7J4WApzkzxERdOQmAdrvshKSzUHg8Jqp1lw9tbiJfE2ExdOOIoJVmGLoDeAGnfzCd4fTsWcLbal9sFpqXsQI8IQi1493mw%3D");
        connection = (HttpURLConnection) url.openConnection();
        connection.setDoOutput(true);
        connection.setRequestMethod("PUT");

        OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream());
        out.write("Test");
        out.close();

        Log.i("TAG", "PUT Response code: " + connection.getResponseCode());

    } catch (MalformedURLException e) {
        e.printStackTrace();
        Log.e("TAG", "MalformedURLException");
    } catch (ProtocolException e) {
        e.printStackTrace();
        Log.e("TAG", "ProtocolException");
    } catch (IOException e) {
        e.printStackTrace();
        Log.e("TAG", "IOException");
    }

PUT 对象的文档:https://cloud.google.com/storage/docs/xml-api/put-object-upload

任何人都可以调查这个问题并给我提示这个问题可能出了什么问题吗?