JSch: com.jcraft.jsch.jschexception unknownhostkey: rsa key fingerprint is - resolved

This exception is thrown because for security purpose, it needs to check if the host key you set in the program matches the host key in the ~/.ssh/known_hosts file.

The following code throws such an exception at the marked line.

import com.jcraft.jsch.Channel;
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;


public class FileCopy {
    public static void main(String[] args){
        try{
            JSch jsch=new JSch();
            Session session = jsch.getSession("<username>","<host name or IP address>");
            session.setPassword("<password>");

            session.connect();

            Channel channel = session.openChannel("sftp");
            channel.connect();
            ChannelSftp sftpChannel = (ChannelSftp)channel;
         
            sftpChannel.get("<source file path/file name>", "<destination file path>");
            sftpChannel.disconnect();
            session.disconnect();
        }catch(JSchException e){
            e.printStackTrace();
        }catch(SftpException se){
            se.printStackTrace();
        }
    }
}

To fix it, you may do one of the followings.

1. Add this line of  code before you call session.connect()

          session.setConfig("StrictHostKeyChecking", "no");

2. Copy the ~/.ssh/known_hosts file from the host to your machine, and add the following line of code before you call session.connect().

         jsch.setKnownHosts("<known_hosts>");
          
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