Http post from an application with file attachment

Question

Hi ! I didn't know where else to post this message...
I'm trying to make a HTTP POST from an application and upload a file with it. I have no problems with the posting, just that I haven't got any ideas how to get the file uploaded as well. I've been reading loads of examples regarding the topic, and searching older posts the forum here, without any help.
Here's the method i'm using:
               // open connections
              URL url = new URL ("TheURL");
               URLConnection urlConn = url.openConnection();
                          // We do input & output, without caching
               urlConn.setDoInput (true);
               urlConn.setDoOutput (true);
               urlConn.setUseCaches (false);
                          // multipart/form-data because we want to upload a file
                 urlConn.setRequestProperty ("Content-Type", "multipart/form-data");
              // Open output stream
                 DataOutputStream printout = new DataOutputStream (urlConn.getOutputStream ());
              // Set the actual content
                 String content = "upfile=" + System.getProperty("user.dir") + "\\file.ext&";
                   content += "other_key-value_pairs";
              // write the data to stream, and flush it.
                 printout.writeBytes (URLEncoder.encode(content));
               printout.flush ();
               printout.close ();
               // Get the response.
                 DataInputStream input = new DataInputStream (urlConn.getInputStream());
               FileOutputStream fos=new FileOutputStream("postto.txt");
               String str;
                 BufferedReader bufr = new BufferedReader(new InputStreamReader(input));
              // Write response to outputfile
                 while (null != ((str = bufr.readLine()))) {
                     if (str.length() >0) {
                     fos.write(str.getBytes());
                     fos.write(new String("\n").getBytes());
               input.close ();Now, the response here I get from the url i'm posting to is "Failure, no data-file". I've tried many diff methods of writing the file to the stream, but always get the same result.
I need to file attached like it would be when using a HTML form's <input type="file">.
Please help ! This is getting really urgent !

Answer 1

String content = "upfile=" + System.getProperty("user.dir") + "\\file.ext&";
content += "other_key-value_pairs";
printout.writeBytes (URLEncoder.encode(content));
printout.flush ();
printout.close ();Actually, what this does is create a request like:
GET /path/to/file/script.language?upfile=/home/user/file.ext&other=params HTTP/1.1
Content-Type: multipart/form-data
-- And other HTTP params --
The file is not actually appended to the request.
I really don't know how Java handles the file upload, but you could do it by hand, like so:
public static void doFileUpload(String url, String filename, Hashtable params) throws IOException {
    // Construct the request
    String boundary = "----------------------mUlTiPaRtBoUnDaRy";
    String request_head = "POST " + url + " HTTP/1.0\r\n" +
                                     "Content-type: multipart/form-data; boundary=" + boundary + "\r\n";
    String request_body = boundary + "\r\n\r\nContent-disposition: form-data; name=\"upload\"" +
                                     "\r\n\r\n";
    BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(filename)));
    int b = -1;
    while((b = in.read()) != -1) {
         request_body += (char)b;
    in.close();
    Enumeration keys = params.keys();
    while(keys.hasMoreElements()) {
        String key = keys.nextElement();
        requst_body += "\r\n" + boundary + "\r\n\r\nContent-type: form-data; name=\"key\"\r\n" +
                                (String)params.get(key);
    request_body += "\r\n" + boundary + "--\r\n";
    int length = request_head.length() + request_body.length() + "Content-length: \r\n";
    String req_length = "Content-length: " + (length + new String("" + length).length()) + "\r\n";
    Socket socket = new Socket(url,80);
    PrintStream stream = socket.getOutputStream();
    stream.print(request_head + req_length + req_body);
    // And now an option to read the response, I will omit that...   
}Note: I have not tested this code, just wrote it up out of memory. If it does not work, it will propably need some small fixes.
Tuomas Rinta