How to retrieve a file from a server via SFTP?

Question

I'm trying to retrieve a file from a server using SFTP (as opposed to FTPS) using Java. How can I do this?

Answer 1

Another option is to consider looking at the JSch library. JSch seems to be the preferred library for a few large open source projects, including Eclipse, Ant and Apache Commons HttpClient, amongst others.

It supports both user/pass and certificate-based logins nicely, as well as all a whole host of other yummy SSH2 features.

Here's a simple remote file retrieve over SFTP. Error handling is left as an exercise for the reader :-)

JSch jsch = new JSch();

String knownHostsFilename = "/home/username/.ssh/known_hosts";
jsch.setKnownHosts( knownHostsFilename );

Session session = jsch.getSession( "remote-username", "remote-host" );    
{
  // "interactive" version
  // can selectively update specified known_hosts file 
  // need to implement UserInfo interface
  // MyUserInfo is a swing implementation provided in 
  //  examples/Sftp.java in the JSch dist
  UserInfo ui = new MyUserInfo();
  session.setUserInfo(ui);

  // OR non-interactive version. Relies in host key being in known-hosts file
  session.setPassword( "remote-password" );
}

session.connect();

Channel channel = session.openChannel( "sftp" );
channel.connect();

ChannelSftp sftpChannel = (ChannelSftp) channel;

sftpChannel.get("remote-file", "local-file" );
// OR
InputStream in = sftpChannel.get( "remote-file" );
  // process inputstream as needed

sftpChannel.exit();
session.disconnect();

Answer 2

Here is the complete source code of an example using JSch without having to worry about the ssh key checking.

import com.jcraft.jsch.*;

public class TestJSch {
    public static void main(String args[]) {
        JSch jsch = new JSch();
        Session session = null;
        try {
            session = jsch.getSession("username", "127.0.0.1", 22);
            session.setConfig("StrictHostKeyChecking", "no");
            session.setPassword("password");
            session.connect();

            Channel channel = session.openChannel("sftp");
            channel.connect();
            ChannelSftp sftpChannel = (ChannelSftp) channel;
            sftpChannel.get("remotefile.txt", "localfile.txt");
            sftpChannel.exit();
            session.disconnect();
        } catch (JSchException e) {
            e.printStackTrace();  
        } catch (SftpException e) {
            e.printStackTrace();
        }
    }
}

Answer 3

Below is an example using Apache Common VFS:

FileSystemOptions fsOptions = new FileSystemOptions();
SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(fsOptions, "no");
FileSystemManager fsManager = VFS.getManager();
String uri = "sftp://user:password@host:port/absolute-path";
FileObject fo = fsManager.resolveFile(uri, fsOptions);

Answer 4

This was the solution I came up with http://sourceforge.net/projects/sshtools/ (most error handling omitted for clarity). This is an excerpt from my blog

SshClient ssh = new SshClient();
ssh.connect(host, port);
//Authenticate
PasswordAuthenticationClient passwordAuthenticationClient = new PasswordAuthenticationClient();
passwordAuthenticationClient.setUsername(userName);
passwordAuthenticationClient.setPassword(password);
int result = ssh.authenticate(passwordAuthenticationClient);
if(result != AuthenticationProtocolState.COMPLETE){
     throw new SFTPException("Login to " + host + ":" + port + " " + userName + "/" + password + " failed");
}
//Open the SFTP channel
SftpClient client = ssh.openSftpClient();
//Send the file
client.put(filePath);
//disconnect
client.quit();
ssh.disconnect();

Answer 5

A nice abstraction on top of Jsch is Apache commons-vfs which offers a virtual filesystem API that makes accessing and writing SFTP files almost transparent. Worked well for us.

Answer 6

There is a nice comparison of the 3 mature Java libraries for SFTP: Commons VFS, SSHJ and JSch

To sum up SSHJ has the clearest API and it's the best out of them if you don't need other storages support provided by Commons VFS.

Here is edited SSHJ example from github:

final SSHClient ssh = new SSHClient();
ssh.loadKnownHosts(); // or, to skip host verification: ssh.addHostKeyVerifier(new PromiscuousVerifier())
ssh.connect("localhost");
try {
    ssh.authPassword("user", "password"); // or ssh.authPublickey(System.getProperty("user.name"))
    final SFTPClient sftp = ssh.newSFTPClient();
    try {
        sftp.get("test_file", "/tmp/test.tmp");
    } finally {
        sftp.close();
    }
} finally {
    ssh.disconnect();
}

Answer 7

Apache Commons SFTP library

Common java properties file for all the examples

serverAddress=111.222.333.444

userId=myUserId

password=myPassword

remoteDirectory=products/

localDirectory=import/

Upload file to remote server using SFTP

import java.io.File;
import java.io.FileInputStream;
import java.util.Properties;

import org.apache.commons.vfs2.FileObject;
import org.apache.commons.vfs2.FileSystemOptions;
import org.apache.commons.vfs2.Selectors;
import org.apache.commons.vfs2.impl.StandardFileSystemManager;
import org.apache.commons.vfs2.provider.sftp.SftpFileSystemConfigBuilder;

public class SendMyFiles {

 static Properties props;

 public static void main(String[] args) {

  SendMyFiles sendMyFiles = new SendMyFiles();
  if (args.length < 1)
  {
   System.err.println("Usage: java " + sendMyFiles.getClass().getName()+
     " Properties_file File_To_FTP ");
   System.exit(1);
  }

  String propertiesFile = args[0].trim();
  String fileToFTP = args[1].trim();
  sendMyFiles.startFTP(propertiesFile, fileToFTP);

 }

 public boolean startFTP(String propertiesFilename, String fileToFTP){

  props = new Properties();
  StandardFileSystemManager manager = new StandardFileSystemManager();

  try {

   props.load(new FileInputStream("properties/" + propertiesFilename));
   String serverAddress = props.getProperty("serverAddress").trim();
   String userId = props.getProperty("userId").trim();
   String password = props.getProperty("password").trim();
   String remoteDirectory = props.getProperty("remoteDirectory").trim();
   String localDirectory = props.getProperty("localDirectory").trim();

   //check if the file exists
   String filepath = localDirectory +  fileToFTP;
   File file = new File(filepath);
   if (!file.exists())
    throw new RuntimeException("Error. Local file not found");

   //Initializes the file manager
   manager.init();

   //Setup our SFTP configuration
   FileSystemOptions opts = new FileSystemOptions();
   SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(
     opts, "no");
   SftpFileSystemConfigBuilder.getInstance().setUserDirIsRoot(opts, true);
   SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, 10000);

   //Create the SFTP URI using the host name, userid, password,  remote path and file name
   String sftpUri = "sftp://" + userId + ":" + password +  "@" + serverAddress + "/" + 
     remoteDirectory + fileToFTP;

   // Create local file object
   FileObject localFile = manager.resolveFile(file.getAbsolutePath());

   // Create remote file object
   FileObject remoteFile = manager.resolveFile(sftpUri, opts);

   // Copy local file to sftp server
   remoteFile.copyFrom(localFile, Selectors.SELECT_SELF);
   System.out.println("File upload successful");

  }
  catch (Exception ex) {
   ex.printStackTrace();
   return false;
  }
  finally {
   manager.close();
  }

  return true;
 }


}

Download file from remote server using SFTP

import java.io.File;
import java.io.FileInputStream;
import java.util.Properties;

import org.apache.commons.vfs2.FileObject;
import org.apache.commons.vfs2.FileSystemOptions;
import org.apache.commons.vfs2.Selectors;
import org.apache.commons.vfs2.impl.StandardFileSystemManager;
import org.apache.commons.vfs2.provider.sftp.SftpFileSystemConfigBuilder;

public class GetMyFiles {

 static Properties props;

 public static void main(String[] args) {

  GetMyFiles getMyFiles = new GetMyFiles();
  if (args.length < 1)
  {
   System.err.println("Usage: java " + getMyFiles.getClass().getName()+
   " Properties_filename File_To_Download ");
   System.exit(1);
  }

  String propertiesFilename = args[0].trim();
  String fileToDownload = args[1].trim();
  getMyFiles.startFTP(propertiesFilename, fileToDownload);

 }

 public boolean startFTP(String propertiesFilename, String fileToDownload){

  props = new Properties();
  StandardFileSystemManager manager = new StandardFileSystemManager();

  try {

   props.load(new FileInputStream("properties/" + propertiesFilename));
   String serverAddress = props.getProperty("serverAddress").trim();
   String userId = props.getProperty("userId").trim();
   String password = props.getProperty("password").trim();
   String remoteDirectory = props.getProperty("remoteDirectory").trim();
   String localDirectory = props.getProperty("localDirectory").trim();


   //Initializes the file manager
   manager.init();

   //Setup our SFTP configuration
   FileSystemOptions opts = new FileSystemOptions();
   SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(
     opts, "no");
   SftpFileSystemConfigBuilder.getInstance().setUserDirIsRoot(opts, true);
   SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, 10000);

   //Create the SFTP URI using the host name, userid, password,  remote path and file name
   String sftpUri = "sftp://" + userId + ":" + password +  "@" + serverAddress + "/" + 
     remoteDirectory + fileToDownload;

   // Create local file object
   String filepath = localDirectory +  fileToDownload;
   File file = new File(filepath);
   FileObject localFile = manager.resolveFile(file.getAbsolutePath());

   // Create remote file object
   FileObject remoteFile = manager.resolveFile(sftpUri, opts);

   // Copy local file to sftp server
   localFile.copyFrom(remoteFile, Selectors.SELECT_SELF);
   System.out.println("File download successful");

  }
  catch (Exception ex) {
   ex.printStackTrace();
   return false;
  }
  finally {
   manager.close();
  }

  return true;
 }

}

Delete a file on remote server using SFTP

import java.io.FileInputStream;
import java.util.Properties;

import org.apache.commons.vfs2.FileObject;
import org.apache.commons.vfs2.FileSystemOptions;
import org.apache.commons.vfs2.impl.StandardFileSystemManager;
import org.apache.commons.vfs2.provider.sftp.SftpFileSystemConfigBuilder;

public class DeleteRemoteFile {

 static Properties props;

 public static void main(String[] args) {

  DeleteRemoteFile getMyFiles = new DeleteRemoteFile();
  if (args.length < 1)
  {
   System.err.println("Usage: java " + getMyFiles.getClass().getName()+
   " Properties_filename File_To_Delete ");
   System.exit(1);
  }

  String propertiesFilename = args[0].trim();
  String fileToDownload = args[1].trim();
  getMyFiles.startFTP(propertiesFilename, fileToDownload);

 }

 public boolean startFTP(String propertiesFilename, String fileToDownload){

  props = new Properties();
  StandardFileSystemManager manager = new StandardFileSystemManager();

  try {

   props.load(new FileInputStream("properties/" + propertiesFilename));
   String serverAddress = props.getProperty("serverAddress").trim();
   String userId = props.getProperty("userId").trim();
   String password = props.getProperty("password").trim();
   String remoteDirectory = props.getProperty("remoteDirectory").trim();


   //Initializes the file manager
   manager.init();

   //Setup our SFTP configuration
   FileSystemOptions opts = new FileSystemOptions();
   SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(
     opts, "no");
   SftpFileSystemConfigBuilder.getInstance().setUserDirIsRoot(opts, true);
   SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, 10000);

   //Create the SFTP URI using the host name, userid, password,  remote path and file name
   String sftpUri = "sftp://" + userId + ":" + password +  "@" + serverAddress + "/" + 
     remoteDirectory + fileToDownload;

   //Create remote file object
   FileObject remoteFile = manager.resolveFile(sftpUri, opts);

   //Check if the file exists
   if(remoteFile.exists()){
    remoteFile.delete();
    System.out.println("File delete successful");
   }

  }
  catch (Exception ex) {
   ex.printStackTrace();
   return false;
  }
  finally {
   manager.close();
  }

  return true;
 }

}

Answer 8

hierynomus/sshj has a complete implementation of SFTP version 3 (what OpenSSH implements)

Example code from SFTPUpload.java

package net.schmizz.sshj.examples;

import net.schmizz.sshj.SSHClient;
import net.schmizz.sshj.sftp.SFTPClient;
import net.schmizz.sshj.xfer.FileSystemFile;

import java.io.File;
import java.io.IOException;

/** This example demonstrates uploading of a file over SFTP to the SSH server. */
public class SFTPUpload {

    public static void main(String[] args)
            throws IOException {
        final SSHClient ssh = new SSHClient();
        ssh.loadKnownHosts();
        ssh.connect("localhost");
        try {
            ssh.authPublickey(System.getProperty("user.name"));
            final String src = System.getProperty("user.home") + File.separator + "test_file";
            final SFTPClient sftp = ssh.newSFTPClient();
            try {
                sftp.put(new FileSystemFile(src), "/tmp");
            } finally {
                sftp.close();
            }
        } finally {
            ssh.disconnect();
        }
    }

}

Answer 9

JSch library is the powerful library that can be used to read file from SFTP server. Below is the tested code to read file from SFTP location line by line

JSch jsch = new JSch();
        Session session = null;
        try {
            session = jsch.getSession("user", "127.0.0.1", 22);
            session.setConfig("StrictHostKeyChecking", "no");
            session.setPassword("password");
            session.connect();

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

            InputStream stream = sftpChannel.get("/usr/home/testfile.txt");
            try {
                BufferedReader br = new BufferedReader(new InputStreamReader(stream));
                String line;
                while ((line = br.readLine()) != null) {
                    System.out.println(line);
                }

            } catch (IOException io) {
                System.out.println("Exception occurred during reading file from SFTP server due to " + io.getMessage());
                io.getMessage();

            } catch (Exception e) {
                System.out.println("Exception occurred during reading file from SFTP server due to " + e.getMessage());
                e.getMessage();

            }

            sftpChannel.exit();
            session.disconnect();
        } catch (JSchException e) {
            e.printStackTrace();
        } catch (SftpException e) {
            e.printStackTrace();
        }

Please refer the blog for whole program.

Answer 10

Andy, to delete file on remote system you need to use (channelExec) of JSch and pass unix/linux commands to delete it.

Answer 11

Try edtFTPj/PRO, a mature, robust SFTP client library that supports connection pools and asynchronous operations. Also supports FTP and FTPS so all bases for secure file transfer are covered.

Answer 12

I found complete working example for SFTP in java using JSCH API http://kodehelp.com/java-program-for-uploading-file-to-sftp-server/

Answer 13

Though answers above were very helpful, I've spent a day to make them work, facing various exceptions like "broken channel", "rsa key unknown" and "packet corrupt".

Below is a working reusable class for SFTP FILES UPLOAD/DOWNLOAD using JSch library.

Upload usage:

SFTPFileCopy upload = new SFTPFileCopy(true, /path/to/sourcefile.png", /path/to/destinationfile.png");

Download usage:

SFTPFileCopy download = new SFTPFileCopy(false, "/path/to/sourcefile.png", "/path/to/destinationfile.png");

The class code:

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.UIKeyboardInteractive;
import com.jcraft.jsch.UserInfo;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.swing.JOptionPane;
import menue.Menue;

public class SFTPFileCopy1 {

    public SFTPFileCopy1(boolean upload, String sourcePath, String destPath) throws FileNotFoundException, IOException {
        Session session = null;
        Channel channel = null;
        ChannelSftp sftpChannel = null;
        try {
            JSch jsch = new JSch();
            //jsch.setKnownHosts("/home/user/.putty/sshhostkeys");
            session = jsch.getSession("login", "mysite.com", 22);
            session.setPassword("password");

            UserInfo ui = new MyUserInfo() {
                public void showMessage(String message) {

                    JOptionPane.showMessageDialog(null, message);

                }

                public boolean promptYesNo(String message) {

                    Object[] options = {"yes", "no"};

                    int foo = JOptionPane.showOptionDialog(null,
                            message,
                            "Warning",
                            JOptionPane.DEFAULT_OPTION,
                            JOptionPane.WARNING_MESSAGE,
                            null, options, options[0]);

                    return foo == 0;

                }
            };
            session.setUserInfo(ui);

            session.setConfig("StrictHostKeyChecking", "no");
            session.connect();
            channel = session.openChannel("sftp");
            channel.setInputStream(System.in);
            channel.setOutputStream(System.out);
            channel.connect();
            sftpChannel = (ChannelSftp) channel;

            if (upload) { // File upload.
                byte[] bufr = new byte[(int) new File(sourcePath).length()];
                FileInputStream fis = new FileInputStream(new File(sourcePath));
                fis.read(bufr);
                ByteArrayInputStream fileStream = new ByteArrayInputStream(bufr);
                sftpChannel.put(fileStream, destPath);
                fileStream.close();
            } else { // File download.
                byte[] buffer = new byte[1024];
                BufferedInputStream bis = new BufferedInputStream(sftpChannel.get(sourcePath));
                OutputStream os = new FileOutputStream(new File(destPath));
                BufferedOutputStream bos = new BufferedOutputStream(os);
                int readCount;
                while ((readCount = bis.read(buffer)) > 0) {
                    bos.write(buffer, 0, readCount);
                }
                bis.close();
                bos.close();
            }
        } catch (Exception e) {
            System.out.println(e);
        } finally {
            if (sftpChannel != null) {
                sftpChannel.exit();
            }
            if (channel != null) {
                channel.disconnect();
            }
            if (session != null) {
                session.disconnect();
            }
        }
    }

    public static abstract class MyUserInfo
            implements UserInfo, UIKeyboardInteractive {

        public String getPassword() {
            return null;
        }

        public boolean promptYesNo(String str) {
            return false;
        }

        public String getPassphrase() {
            return null;
        }

        public boolean promptPassphrase(String message) {
            return false;
        }

        public boolean promptPassword(String message) {
            return false;
        }

        public void showMessage(String message) {
        }

        public String[] promptKeyboardInteractive(String destination,
                String name,
                String instruction,
                String[] prompt,
                boolean[] echo) {

            return null;
        }
    }
}

Answer 14

You also have JFileUpload with SFTP add-on (Java too): http://www.jfileupload.com/products/sftp/index.html

Answer 15

I use this SFTP API called Zehon, it's great, so easy to use with a lot of sample code. Here is the site http://www.zehon.com

Answer 16

The best solution I've found is Paramiko. There's a Java version.