Java or Groovy file to check Multipart/form-data opload protocol.

multipart.groovy

/**
 * This utility class provides an abstraction layer for sending multipart HTTP
 * POST requests to a web server. 
 * @author www.codejava.net
 *
 */
public class MultipartUtility {
    private final String boundary;
    private static final String LINE_FEED = "\r\n";
    private HttpURLConnection httpConn;
    private String charset;
    private OutputStream outputStream;
    private PrintWriter writer;

    /**
     * This constructor initializes a new HTTP POST request with content type is set to multipart/form-data
     * @param requestURL
     * @param charset
     * @throws IOException
     */
    public MultipartUtility(String requestURL, String charset) throws IOException {
        this.charset = charset;

        // creates a unique boundary based on time stamp
        boundary = "===" + System.currentTimeMillis() + "===";

        URL url = new URL(requestURL);
        httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setDoOutput(true); // indicates POST method
        httpConn.setDoInput(true);
        httpConn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
        outputStream = httpConn.getOutputStream();
        writer = new PrintWriter(new OutputStreamWriter(outputStream, charset), true);
    }
 
    /**
     * Adds a form field to the request
     * @param name field name
     * @param value field value
     */
    public void addFormField(String name, String value) {
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append("Content-Disposition: form-data; name=\"" + name + "\"").append(LINE_FEED);
        writer.append("Content-Type: text/plain; charset=" + charset).append(LINE_FEED);
        writer.append(LINE_FEED);
        writer.append(value).append(LINE_FEED);
        writer.flush();
    }

    /**
     * Adds a upload file section to the request 
     * @param fieldName name attribute in <input type="file" name="..." />
     * @param uploadFile a File to be uploaded 
     * @throws IOException
     */
    public void addFilePart(String fieldName, File uploadFile) throws IOException {
        String fileName = uploadFile.getName();
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append( "Content-Disposition: form-data; name=\"" + fieldName + "\"; filename=\"" + fileName + "\"").append(LINE_FEED);
        writer.append( "Content-Type: " + URLConnection.guessContentTypeFromName(fileName)).append(LINE_FEED);
        writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
        writer.append(LINE_FEED);
        writer.flush();

        FileInputStream inputStream = new FileInputStream(uploadFile);
        byte[] buffer = new byte[4096];
        int bytesRead = -1;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead);
        }
        outputStream.flush();
        inputStream.close();

        writer.append(LINE_FEED);
        writer.flush();
    }

    /**
     * Completes the request and receives response from the server.
     * @return a list of Strings as response in case the server returned
     * status OK, otherwise an exception is thrown.
     * @throws IOException
     */
    public List<String> finish() throws IOException {
        List<String> response = new ArrayList<String>();

        writer.append(LINE_FEED).flush();
        writer.append("--" + boundary + "--").append(LINE_FEED);
        writer.close();

        // checks server's status code first
        int status = httpConn.getResponseCode();
        println status
        if (status == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(new InputStreamReader( httpConn.getInputStream()));
            String line = null;
            while ((line = reader.readLine()) != null) {
                response.add(line);
            }
            reader.close();
            httpConn.disconnect();
        } else {
            throw new IOException("Server returned non-OK status: " + status);
        }
        return response;
    }
}

 public static void main(String[] args) {
        String charset = "ISO-8859-1";
        File   uploadFile1 = new File("server/file");
        String requestURL = "http://api/rpc/bulk/";

        try {
            MultipartUtility multipart = new MultipartUtility(requestURL, charset);
            multipart.addFormField("description", "phones");
            multipart.addFormField("username", "******");
            multipart.addFormField("password", "******");

            multipart.addFilePart("fileUpload", uploadFile1);

            List<String> response = multipart.finish();
            System.out.println("SERVER REPLIED:");
            for (String line : response) {
                System.out.println(line);
            }
        } catch (IOException ex) {
            System.out.println("ERROR: " + ex.getMessage());
            ex.printStackTrace();
        }
    }

Thanks for the script - helped me a lot. I'm not sure what the use case is for https://gist.github.com/frankvilhelmsen/5212452#file-multipart-groovy-L74 though - in my case it breaks uploaded files since adding 2 additional bytes.