scp via java

Question

What is the best method of performing an scp transfer via the Java programming language? It seems I may be able to perform this via JSSE, JSch or the bouncy castle java libr

Answer 1

Here is an example to upload a file using JSch:

ScpUploader.java:

import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.SftpException;

import java.io.ByteArrayInputStream;
import java.util.Properties;

public final class ScpUploader
{
    public static ScpUploader newInstance()
    {
        return new ScpUploader();
    }

    private volatile Session session;
    private volatile ChannelSftp channel;

    private ScpUploader(){}

    public synchronized void connect(String host, int port, String username, String password) throws JSchException
    {
        JSch jsch = new JSch();

        Properties config = new Properties();
        config.put("StrictHostKeyChecking", "no");

        session = jsch.getSession(username, host, port);
        session.setPassword(password);
        session.setConfig(config);
        session.setInputStream(System.in);
        session.connect();

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

    public synchronized void uploadFile(String directoryPath, String fileName, byte[] fileBytes, boolean overwrite) throws SftpException
    {
        if(session == null || channel == null)
        {
            System.err.println("No open session!");
            return;
        }

        // a workaround to check if the directory exists. Otherwise, create it
        channel.cd("/");
        String[] directories = directoryPath.split("/");
        for(String directory : directories)
        {
            if(directory.length() > 0)
            {
                try
                {
                    channel.cd(directory);
                }
                catch(SftpException e)
                {
                    // swallowed exception

                    System.out.println("The directory (" + directory + ") seems to be not exist. We will try to create it.");

                    try
                    {
                        channel.mkdir(directory);
                        channel.cd(directory);
                        System.out.println("The directory (" + directory + ") is created successfully!");
                    }
                    catch(SftpException e1)
                    {
                        System.err.println("The directory (" + directory + ") is failed to be created!");
                        e1.printStackTrace();
                        return;
                    }

                }
            }
        }

        channel.put(new ByteArrayInputStream(fileBytes), directoryPath + "/" + fileName, overwrite ? ChannelSftp.OVERWRITE : ChannelSftp.RESUME);
    }

    public synchronized void disconnect()
    {
        if(session == null || channel == null)
        {
            System.err.println("No open session!");
            return;
        }

        channel.exit();
        channel.disconnect();
        session.disconnect();

        channel = null;
        session = null;
    }
}

AppEntryPoint.java:

import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.SftpException;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public final class AppEntryPoint
{
    private static final String HOST = "192.168.1.1";
    private static final int PORT = 22;
    private static final String USERNAME = "root";
    private static final String PASSWORD = "root";

    public static void main(String[] args) throws IOException
    {
        ScpUploader scpUploader = ScpUploader.newInstance();

        try
        {
            scpUploader.connect(HOST, PORT, USERNAME, PASSWORD);
        }
        catch(JSchException e)
        {
            System.err.println("Failed to connect the server!");
            e.printStackTrace();
            return;
        }

        System.out.println("Successfully connected to the server!");

        byte[] fileBytes = Files.readAllBytes(Paths.get("C:/file.zip"));

        try
        {
            scpUploader.uploadFile("/test/files", "file.zip", fileBytes, true); // if overwrite == false, it won't throw exception if the file exists
            System.out.println("Successfully uploaded the file!");
        }
        catch(SftpException e)
        {
            System.err.println("Failed to upload the file!");
            e.printStackTrace();
        }

        scpUploader.disconnect();
    }
}