Using JSch to download files.

JSch is a popular java library to connect to SSHD server.

Here is the code listing which connects to the SSHD server to download and upload files.

package com.mm.ftpclient;

import java.io.Closeable;
import java.io.FileInputStream;
import java.util.List;

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.ChannelSftp.LsEntry;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;

public class SftpUtil {

// can be used to filter the files, not implemented here.
public interface LsEntryFilter{
boolean accept(LsEntry e);
}

public static Session getSession(String hostIp, String username, String password)
        throws Exception {
log("SFTPUtil : entering getSession....");
JSch jsch = new JSch();
Session session = jsch.getSession(username, hostIp);
session.setPassword(password);
session.setConfig("StrictHostKeyChecking", "no");
log("SFTPUtil : exiting getSession....");
return session;
}

public static ChannelSftp getChannelSftp(Session session) throws Exception {
Channel channel = session.openChannel("sftp");
channel.setInputStream(System.in);
channel.setOutputStream(System.out);
channel.connect();

ChannelSftp sftpChannel = (ChannelSftp) channel;
return sftpChannel;
}


// updloads the src file to remote server.
public static void uploadFile(Session session, String srcFile, String destFile)
        throws Exception {
log("SFTPUtil : Entering uploadFile.....");

ChannelSftp sftpChannel = getChannelSftp(session);
FileInputStream is = new FileInputStream(srcFile);

try {
sftpChannel.put(is, destFile);
} finally {
close(is);
if (sftpChannel != null)
sftpChannel.disconnect();
}
log("SFTPUtil : Exiting uploadFile.....");
}

public static void downloadFile(Session session, String srcDir, String destDir,
        String fileName) throws Exception {
ChannelSftp sftpChannel = getChannelSftp(session);
List<ChannelSftp.LsEntry> list = getFiles(sftpChannel, srcDir, destDir);
try {
log("SFTPUtil : ls command output is :" + list);
for (ChannelSftp.LsEntry file : list) {
if (!file.getAttrs().isDir() && file.getFilename().equals(fileName)) {
log("SFTPUtil : downloading file to local working dir, filename is : [" +                                                      file.getFilename() + "]");
sftpChannel.get(file.getFilename(), file.getFilename());
}
}
} finally {
if (sftpChannel != null)
sftpChannel.disconnect();
}
}


public static List<ChannelSftp.LsEntry> getFiles(ChannelSftp sftpChannel, String srcDir,
        String destDir) throws Exception {

sftpChannel.lcd(destDir);
log("SFTPUtil : local working dir: " + sftpChannel.lpwd());

sftpChannel.cd(srcDir);
log("SFTPUtil : remote working dir: " + sftpChannel.pwd());

// Get a listing of the remote directory
@SuppressWarnings("unchecked")
List<ChannelSftp.LsEntry> list = sftpChannel.ls(".");
log("SFTPUtil : running command 'ls .' on remote server : ");

return list;
}



private static void log(String msg) {
System.out.println(msg);
}

private static void close(Closeable is) {
try {
if (is != null)
is.close();
} catch (Exception e) {
}
}

}

Here is the driver code to test

public static void test() throws Exception{
Session session = SftpUtil.getSession("127.0.0.1", "demo", "demo");
session.connect();
try{
List<LsEntry> files = SftpUtil.getFiles(getChannelSftp(session), "/test", "c:/test");
for(LsEntry  file : files){
System.out.println(file.getFilename());
}
}finally{
session.disconnect();
}
}