public class HttpMultipartUpload {
String lineEnd = "rn";
String twoHyphens = "--";
String boundary = "AaB03x87yxdkjnxvi7";

public String upload(URL url, File file, String fileParameterName, HashMap<String, String> parameters) throws IOException {
    HttpURLConnection conn = null;
    DataOutputStream dos = null;
    DataInputStream dis = null;
    FileInputStream fileInputStream = null;

    byte[] buffer;
    int maxBufferSize = 20 * 1024;
    try {
        // ------------------ CLIENT REQUEST
        fileInputStream = new FileInputStream(file);

        // open a URL connection to the Servlet
        // Open a HTTP connection to the URL
        conn = (HttpURLConnection) url.openConnection();
        // Allow Inputs
        conn.setDoInput(true);
        // Allow Outputs
        conn.setDoOutput(true);
        // Don't use a cached copy.
        conn.setUseCaches(false);
        // Use a post method.
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type",
                "multipart/form-data;boundary=" + boundary);

        dos = new DataOutputStream(conn.getOutputStream());

        dos.writeBytes(twoHyphens + boundary + lineEnd);
        dos.writeBytes("Content-Disposition: form-data; name=""
                + fileParameterName + ""; filename="" + mFileName
                + ".jpg" + """ + lineEnd);
        dos.writeBytes("Content-Type:image/jpg" + lineEnd);
        dos.writeBytes(lineEnd);

        // create a buffer of maximum size
        buffer = new byte[Math.min((int) file.length(), maxBufferSize)];
        int length;
        // read file and write it into form...
        while ((length = fileInputStream.read(buffer)) != -1) {
            dos.write(buffer, 0, length);
        }

        for (String name : parameters.keySet()) {
            dos.writeBytes(lineEnd);
            dos.writeBytes(twoHyphens + boundary + lineEnd);
            dos.writeBytes("Content-Disposition: form-data; name=""
                    + name + """ + lineEnd);
            dos.writeBytes(lineEnd);
            dos.writeBytes(parameters.get(name));
        }

        // send multipart form data necessary after file data...
        dos.writeBytes(lineEnd);
        dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
        dos.flush();
    } finally {
        if (fileInputStream != null)
            fileInputStream.close();
        if (dos != null)
            dos.close();
    }

    // ------------------ read the SERVER RESPONSE
    try {
        dis = new DataInputStream(conn.getInputStream());
        StringBuilder response = new StringBuilder();

        String line;
        while ((line = dis.readLine()) != null) {
            response.append(line).append('n');
        }

        System.out.println("Upload file response:" + response.toString());
        return response.toString();

    } finally {
        if (dis != null)
            dis.close();
    }
}
}