Schedule a method to refresh a TextArea that receives the result via ssh every x minutes

Question

In order to realize a small supervisor of a server, I would like to know how to relaunch the ask(...) method in my code below. The goal is to query the server via SSH with the JSch library, and to return the result, in the JTextArea every x minutes.

The code works fine for me, I want just add the refresh option in the JTextArea, which receives the result via SSH every x minutes.

public class Test1 {
    public static void main(String args[]) throws Exception {
        final JFrame frame = new JFrame("Superviser SRV");
        frame.setLayout(new FlowLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(600, 500);

        JLabel label1 = new JLabel("Informations of SRV",JLabel.CENTER);            
        frame.getContentPane().add(label1);
        
        JTextArea ta11 = new JTextArea(1,50);
        JScrollPane sp11 = new JScrollPane(ta11);

        Border border = BorderFactory.createLineBorder(Color.BLACK);
        ta11.setBorder(BorderFactory.createCompoundBorder(border,
                BorderFactory.createEmptyBorder(10, 10, 10, 10)));

        frame.getContentPane().add(sp11);
        frame.setVisible(true);   
    
        int Port=22;
        String usernam ="usernam";
        String passwd ="passwd";
        String host ="192.168.10.1";      
        String msg = " Check Procs = ";     
        String com = " /usr/local/nagios/libexec/check_procs -w 200 -c 300 && exit \n";
        ask(ta11, Port, usernam, host, passwd, msg, com);
    }

    public static void ask(JTextArea ta, int port, String name, String ip, String password, String msg, String com)
            throws JSchException, IOException {
        JSch jsch = new JSch();
        Session session = jsch.getSession(name, ip, port);
        session.setPassword(password);
        session.setConfig("StrictHostKeyChecking", "no");
        System.out.println("Establishing Connection...");
        session.connect();
        System.out.println("Connection established.");

        ChannelExec channelExec = (ChannelExec)session.openChannel("exec");
        InputStream in = channelExec.getInputStream();
        channelExec.setCommand("sudo su - root");     
        channelExec.connect();
        OutputStream out = channelExec.getOutputStream();   
        out.write((com).getBytes());
        out.flush();
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String line= reader.readLine();  
        ta.append(msg+" = "+line);

        out.close();
        reader.close();
        channelExec.disconnect();
        session.disconnect();
    } 
}

Answer 1

You can use a timer to run the task every so many minutes.

int minutes = 2;
Timer timer = new Timer("query timer", true);
//it is daemon so it doesn't prevent the app from exiting.

timer.schedule( 
    new TimerTask(){
        public void run(){
            ask(ta11, Port, usernam, host, passwd, msg, com);
        }
    }, minutes * 60 * 1000 );

That will run the code every 2 minutes.

This performs the work on a separate thread, so when you update your text area you should post it to the EDT.

EventQueue.invokeLater( () -> {
    ta.append(msg+" = "+line);
});

As a side note, I would set this up via linux/server to run the privileged task on cron that updates a file in an less secure area. Then just use ssh to access the file without ever needing to sudo/su with a password stored as plain text in a java program.

Answer 2

You may use a Thread and in the overridden method public void run() you can create a try-catch block which would call the method ask(...).

Then you can do Thread.currentThread().wait(int millis , int nanoseconds) to pause the thread for 1 minute, then you may fetch new data in 1 minute and then you can rerun the ask method.

NOTE: This can be implemented in a forever loop but taking into consideration,the wastage that may happen , you can run this entire thread in a for-loop. In this way you can run this ask(...) method for x hours(say) and refresh it each minute.

Hope this helps :)