How to open any command line program through a swing GUI and pass commands to it?

Question

I basically want to convert a command line program into a gui program using Swing. As soon as the user presses an appropriate button, a corresponding command should be passed by the GUI to the command line program. If we can do this without showing the command line program then it would be a complete replacement of that program.

I have been trying to search this on the internet for the past two days now and I only found the Runtime.getRuntime().exec(cmd) command useful to open the command prompt and open that command line program, but as the commands can't be further passed on to the prompt, no further action can be performed on that program. Please Help.

Answer 1

I would actually avoid passing through the command prompt and directly invoke your command line program. All you have to do is to find where your program is located.

A few things to take into consideration:

• You should execute your command outside the EDT (Event dispatching thread) to avoid GUI-freeze (SwingWorker will do a very good job at it)
• Rather use ProcessBuilder than RuntimeExec

Here is an example of such code which invokes the command java -version (this is only for the example of using the ProcessBuilder API):

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;
import java.util.concurrent.ExecutionException;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.UIManager;

public class TestRuntimeExec {

    private JButton executeButton;

    protected void initUI() {
        final JFrame frame = new JFrame();
        frame.setTitle(TestRuntimeExec.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        executeButton = new JButton("Clik me to execute command");
        executeButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                doWork();
            }
        });
        frame.add(executeButton, BorderLayout.SOUTH);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    protected void doWork() {
        SwingWorker<String, Void> worker = new SwingWorker<String, Void>() {
            @Override
            protected String doInBackground() throws Exception {
                ProcessBuilder builder = new ProcessBuilder(System.getProperty("java.home") + "/bin/java", "-version");
                builder.redirectErrorStream(true);
                Process process = builder.start();
                ConsoleReader consoleReader = new ConsoleReader(process.getInputStream());
                consoleReader.start();
                int waitFor = process.waitFor();
                consoleReader.join();
                switch (waitFor) {
                case 0:
                    return consoleReader.getResult();
                default:
                    throw new RuntimeException("Failed to execute " + builder.command() + " \nReturned message: "
                            + consoleReader.getResult());
                }
            }

            @Override
            protected void done() {
                try {
                    showCommandResult(get());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                    showCommandError(e);
                }
            }
        };
        worker.execute();
    }

    protected void showCommandError(ExecutionException e) {
        JOptionPane.showMessageDialog(executeButton, e.getMessage(), "An error has occured", JOptionPane.ERROR_MESSAGE);
    }

    protected void showCommandResult(String commandResult) {
        JOptionPane.showMessageDialog(executeButton, commandResult);
    }

    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception e) {
            e.printStackTrace();
        }
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TestRuntimeExec().initUI();
            }
        });
    }

    public static class ConsoleReader extends Thread {
        private InputStream is;

        private StringWriter sw;

        ConsoleReader(InputStream is) {
            this.is = is;
            sw = new StringWriter();
        }

        @Override
        public void run() {
            try {
                int c;
                while ((c = is.read()) != -1) {
                    sw.write(c);
                }
            } catch (IOException e) {
                ;
            }
        }

        String getResult() {
            return sw.toString();
        }
    }
}