JSch库是一个功能强大的库，可以用来从SFTP服务器读取文件。下面是逐行从SFTP位置读取文件的测试代码

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();
        }

整个节目请参考博客。

虽然上面的答案很有帮助，但我花了一天时间让它们工作，面对各种异常，如“中断通道”，“rsa密钥未知”和“数据包损坏”。

下面是一个工作的可重用类SFTP文件上传/下载使用JSch库。

上传用法:

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

下载使用:

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

类代码:

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;
        }
    }
}

这就是我想到的解决办法 http://sourceforge.net/projects/sshtools/(为了清晰起见，省略了大多数错误处理)。这是我博客的节选

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();

另一种选择是考虑查看JSch库。JSch似乎是一些大型开源项目的首选库，包括Eclipse、Ant和Apache Commons HttpClient等等。

它很好地支持用户/通行证和基于证书的登录，以及所有其他漂亮的SSH2特性。

这是一个简单的远程文件检索SFTP。错误处理留给读者练习:-)

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();

下面是使用JSch的示例的完整源代码，无需担心ssh密钥检查。

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();
        }
    }
}

在Jsch之上的一个很好的抽象是Apache common -vfs，它提供了一个虚拟文件系统API，使得SFTP文件的访问和写入几乎是透明的。这对我们来说很有效。