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 libraries. None of these solutions seem to have an easy answer.

Answer 1

I ended up using Jsch- it was pretty straightforward, and seemed to scale up pretty well (I was grabbing a few thousand files every few minutes).

Answer 2

plug: sshj is the only sane choice! See these examples to get started: download, upload.

Answer 3

Take a look here

That is the source code for Ants' SCP task. The code in the "execute" method is where the nuts and bolts of it are. This should give you a fair idea of what is required. It uses JSch i believe.

Alternatively you could also directly execute this Ant task from your java code.

Answer 4

I wrapped Jsch with some utility methods to make it a bit friendlier and called it

Jscp

Available here: https://github.com/willwarren/jscp

SCP utility to tar a folder, zip it, and scp it somewhere, then unzip it.

Usage:

// create secure context
SecureContext context = new SecureContext("userName", "localhost");

// set optional security configurations.
context.setTrustAllHosts(true);
context.setPrivateKeyFile(new File("private/key"));

// Console requires JDK 1.7
// System.out.println("enter password:");
// context.setPassword(System.console().readPassword());

Jscp.exec(context, 
           "src/dir",
           "destination/path",
           // regex ignore list 
           Arrays.asList("logs/log[0-9]*.txt",
           "backups") 
           );

Also includes useful classes - Scp and Exec, and a TarAndGzip, which work in pretty much the same way.

Answer 5

This is high-level solution, no need to reinvent. Quick and dirty!

1) First, go to http://ant.apache.org/bindownload.cgi and download latest Apache Ant binary. (nowadays, apache-ant-1.9.4-bin.zip).

2) Extract the downloaded file and find the JAR ant-jsch.jar ("apache-ant-1.9.4/lib/ant-jsch.jar"). Add this JAR in your project. Also ant-launcher.jar and ant.jar.

3) Go to Jcraft jsch SouceForge Project and download the jar. Nowadays, jsch-0.1.52.jar. Also Add this JAR in your project.

Now, can you easyly use into java code the Ant Classes Scp for copy files over network or SSHExec for commands in SSH servers.

4) Code Example Scp:

// This make scp copy of 
// one local file to remote dir

org.apache.tools.ant.taskdefs.optional.ssh.Scp scp = new Scp();
int portSSH = 22;
String srvrSSH = "ssh.your.domain";
String userSSH = "anyuser"; 
String pswdSSH = new String ( jPasswordField1.getPassword() );
String localFile = "C:\\localfile.txt";
String remoteDir = "/uploads/";

scp.setPort( portSSH );
scp.setLocalFile( localFile );
scp.setTodir( userSSH + ":" + pswdSSH + "@" + srvrSSH + ":" + remoteDir );
scp.setProject( new Project() );
scp.setTrust( true );
scp.execute();

Answer 6

The openssh project lists several Java alternatives, Trilead SSH for Java seems to fit what you're asking for.

Answer 7

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();
    }
}