transfer files from unix to windows using java

Question

I want to get a file from unix system to my local system which is on windows using java. I'm very much new to this concept. Any ideas on how it could be done? Which is the best java API for this task?

Answer 1

I have found JSch to be very useful and straight foreword. Below is a snippet of code written to put all .txt files in a given folder on the sftp server.

public static void sftpConnection() {

    // Object Declaration.
    JSch jsch = new JSch();
    Session session = null;
    Channel channel = null;

    // Variable Declaration.
    String user = "foo";
    String host = "10.9.8.7";
    Integer port = 22;
    String password = "test123";
    String watchFolder = "\\localhost\textfiles";
    String outputDir = "/remote/textFolder/";
    String filemask = "*.txt";


   try {
        session = jsch.getSession(user, host, port);

        /*
         * StrictHostKeyChecking Indicates what to do if the server's host 
         * key changed or the server is unknown. One of yes (refuse connection), 
         * ask (ask the user whether to add/change the key) and no 
         * (always insert the new key).
         */
        session.setConfig("StrictHostKeyChecking", "no");
        session.setPassword(password);

        session.connect();

        channel = session.openChannel("sftp");
        channel.connect();
        ChannelSftp sftpChannel = (ChannelSftp)channel;

        // Go through watch folder looking for files.
        File[] files = findFile(watchFolder, filemask);
        for(File file : files) {
            // Upload file.
            putFile(file, sftpChannel, outputDir);            
        }                 
    } finally {
        sftpChannel.exit();
        session.disconnect();
    }
}

public static void putFile(File file, ChannelSftp sftpChannel, String outputDir) {

    FileInputStream fis = null;

    try {
        // Change to output directory.
        sftpChannel.cd(outputDir);

        // Upload file.

        fis = new FileInputStream(file);
        sftpChannel.put(fis, file.getName());
        fis.close();

    } catch{}
}

public static File[] findFile(String dirName, final String mask) {
    File dir = new File(dirName);

    return dir.listFiles(new FilenameFilter() {
        public boolean accept(File dir, String filename)
            { return filename.endsWith(mask); }
    } );
}

Answer 2

If the Unix machine supports SFTP, JSch is an option. You could adapt the following code to meet your needs:

private static final String USER_PROMPT = "Enter username@hostname:port";
private static final boolean USE_GUI = true;

public static void main(final String[] arg) {
  Session session = null;
  ChannelSftp channelSftp = null;
  try {
    final JSch jsch = new JSch();

    final String defaultInput = System.getProperty("user.name") + "@localhost:22";
    String input = (USE_GUI) ? JOptionPane.showInputDialog(USER_PROMPT, defaultInput) : System.console().readLine("%s (%s): ", USER_PROMPT, defaultInput);
    if (input == null || input.trim().length() == 0) {
      input = defaultInput;
    }
    final int indexOfAt = input.indexOf('@');
    final int indexOfColon = input.indexOf(':');
    final String user = input.substring(0, indexOfAt);
    final String host = input.substring(indexOfAt + 1, indexOfColon);
    final int port = Integer.parseInt(input.substring(indexOfColon + 1));

    jsch.setKnownHosts("/path/to/known_hosts");
    // if you have set up authorized_keys on the server, using that identitiy
    // with the code on the next line allows for password-free, trusted connections
    // jsch.addIdentity("/path/to/id_rsa", "id_rsa_password");

    session = jsch.getSession(user, host, 22);

    final UserInfo ui = new MyUserInfo();
    session.setUserInfo(ui);
    session.connect();
    channelSftp = (ChannelSftp) session.openChannel("sftp");
    channelSftp.connect();
    channelSftp.get("/remotepath/remotefile.txt", "/localpath/localfile.txt");
  } finally {
    if (channelSftp != null) {
      channelSftp.exit();
    }
    if (session != null) {
      session.disconnect();
    } 
  }
}

public static class MyUserInfo implements UserInfo {
  private String password;

  @Override
  public String getPassword() {
    return password;
  }

  @Override
  public boolean promptYesNo(final String str) {
    final Object[] options = {"yes", "no"};
    final boolean yesNo = (USE_GUI) ? JOptionPane.showOptionDialog(null, str, "Warning", JOptionPane.DEFAULT_OPTION, JOptionPane.WARNING_MESSAGE, null, options, options[0]) == 0 : System.console().readLine("Enter y or n: ").equals("y");
    return yesNo;
  }

  @Override
  public String getPassphrase() {
    return null;
  }

  @Override
  public boolean promptPassphrase(final String message) {
    return true;
  }

  @Override
  public boolean promptPassword(final String message) {
    if (!USE_GUI) {
      password = new String(System.console().readPassword("Password: "));
      return true;
    } else {
      final JTextField passwordField = new JPasswordField(20);
      final Object[] ob = {passwordField};
      final int result = JOptionPane.showConfirmDialog(null, ob, message, JOptionPane.OK_CANCEL_OPTION);
      if (result == JOptionPane.OK_OPTION) {
        password = passwordField.getText();
        return true;
      } else {
        return false;
      }
    }
  }

  @Override
  public void showMessage(final String message) {
    if (!USE_GUI) {
      System.console().printf(message);
    } else {
      JOptionPane.showMessageDialog(null, message);
    }
  }
}

Answer 3

There are multiple choices to do that. First one simple socket communication between a java client and a server. If you want to go with this approach then follow this:

http://mrbool.com/file-transfer-between-2-computers-with-java/24516

Then there are other high level protocols implementations that can be used such as FTP, HTTP, etc

Follow a related SO post for java FTP client server: FTP client server model for file transfer in Java

Answer 4

First thing that goes into my mind is FTP.