Uploading Files to Google App Engine

In previous post we talked about sending emails with attachments from the Google App Engine.

But how do we get files from a client to the cloud?

Here is a sample code in C#:

public static string UploadFilesToRemoteUrl(string url, string[] files, NameValueCollection nvc, string cookie)

{

    string boundary = "----------------------------" +

    DateTime.Now.Ticks.ToString("x");

    HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

    httpWebRequest.ContentType = "multipart/form-data; boundary=" + boundary;

    httpWebRequest.Method = "POST";

    httpWebRequest.KeepAlive = true;

    httpWebRequest.Headers["Cookie"] = cookie;

    httpWebRequest.Credentials = System.Net.CredentialCache.DefaultCredentials;

    Stream memStream = new MemoryStream();

    byte[] boundarybytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

    string formdataTemplate = "\r\n--" + boundary +

        "\r\nContent-Disposition: form-data; name=\"{0}\";\r\n\r\n{1}";

    foreach (string key in nvc.Keys)

    {

        string formitem = string.Format(formdataTemplate, key, nvc[key]);

        byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);

        memStream.Write(formitembytes, 0, formitembytes.Length);

    }

    memStream.Write(boundarybytes, 0, boundarybytes.Length);

    string headerTemplate = "Content-Disposition: form-data; name=\"{0}\";filename=\"{1}\"\r\n\r\n";

    for (int i = 0; i < files.Length; i++)

    {

        string header = string.Format(headerTemplate, "file" + i, files[i]);

        byte[] headerbytes = Encoding.UTF8.GetBytes(header);

        memStream.Write(headerbytes, 0, headerbytes.Length);

        FileStream fileStream = new FileStream(files[i],

            FileMode.Open, FileAccess.Read);

        byte[] buffer = new byte[1024];

        int bytesRead = 0;

        while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)

        {

            memStream.Write(buffer, 0, bytesRead);

        }

        memStream.Write(boundarybytes, 0, boundarybytes.Length);

        fileStream.Close();

    }

    httpWebRequest.ContentLength = memStream.Length;

    Stream requestStream = httpWebRequest.GetRequestStream();

    memStream.Position = 0;

    byte[] tempBuffer = new byte[memStream.Length];

    memStream.Read(tempBuffer, 0, tempBuffer.Length);

    memStream.Close();

    requestStream.Write(tempBuffer, 0, tempBuffer.Length);

    requestStream.Close();

    WebResponse webResponse = httpWebRequest.GetResponse();

    Stream stream = webResponse.GetResponseStream();

    StreamReader reader = new StreamReader(stream);

    string responseFromServer = reader.ReadToEnd();

    webResponse.Close();

    reader.Close();

    stream.Close();

    httpWebRequest = null;

    webResponse = null;

    return responseFromServer;

}

The method above has a cookie as a parameter. Here is an excellent site by Dale Lane where you can see how to access authenticated Google App Engine service from a C# client.