java ssh2连接JumpServer 开源堡垒机，让后访问对应的服务器查看服务器日志

使用Java连接JumpServer并访问对应的服务器有多种方法，其中一种常用的方法是使用JSch库。

以下是一个简单的示例代码，演示如何使用JSch连接JumpServer并访问对应的服务器：

import com.jcraft.jsch.*;

public class SSHConnection {
    public static void main(String[] args) {
        String jumpServerHostname = "jumpServerHostname";
        String jumpServerUsername = "jumpServerUsername";
        String jumpServerPassword = "jumpServerPassword";
        String targetServerHostname = "targetServerHostname";
        String targetServerUsername = "targetServerUsername";
        String targetServerPassword = "targetServerPassword";

        int jumpServerPort = 22;
        int targetServerPort = 22;

        try {
            JSch jsch = new JSch();

            // connect to jump server
            Session jumpServerSession = jsch.getSession(jumpServerUsername, jumpServerHostname, jumpServerPort);
            jumpServerSession.setPassword(jumpServerPassword);
            jumpServerSession.setConfig("StrictHostKeyChecking", "no");
            jumpServerSession.connect();
            System.out.println("Connected to jump server.");

            // create ssh tunnel to target server via jump server
            int assignedPort = jumpServerSession.setPortForwardingL(0, targetServerHostname, targetServerPort);
            System.out.println("SSH tunnel established to target server.");

            // connect to target server via ssh tunnel
            Session targetServerSession = jsch.getSession(targetServerUsername, "localhost", assignedPort);
            targetServerSession.setPassword(targetServerPassword);
            targetServerSession.setConfig("StrictHostKeyChecking", "no");
            targetServerSession.connect();
            System.out.println("Connected to target server.");

            // execute command on target server
            Channel channel = targetServerSession.openChannel("exec");
            ((ChannelExec) channel).setCommand("tail -f /var/log/syslog");
            channel.setInputStream(null);
            ((ChannelExec) channel).setErrStream(System.err);
            InputStream in = channel.getInputStream();
            channel.connect();
            byte[] tmp = new byte[1024];
            while (true) {
                while (in.available() > 0) {
                    int i = in.read(tmp, 0, 1024);
                    if (i < 0) break;
                    System.out.print(new String(tmp, 0, i));
                }
                if (channel.isClosed()) {
                    System.out.println("Exit status: " + channel.getExitStatus());
                    break;
                }
                Thread.sleep(1000);
            }
            channel.disconnect();
            targetServerSession.disconnect();
            jumpServerSession.disconnect();
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
    }
}

这个示例代码中，假设JumpServer的主机名是jumpServerHostname，用户名是jumpServerUsername，密码是jumpServerPassword，目标服务器的主机名是targetServerHostname，用户名是targetServerUsername，密码是targetServerPassword。这个代码通过SSH隧道连接到JumpServer，然后通过JumpServer连接到目标服务器，并在目标服务器上执行“tail -f /var/log/syslog”命令来查看系统日志。

你需要将这个示例代码中的主机名、用户名、密码和端口号替换为你自己的值，以便连接到你想要的JumpServer和目标服务器。