Redirecting System.out to JTextPane

Question

I have a class (shown below) that extends JPanel and contains a JTextPane. I want to redirect System.out and System.err t

Answer 1

Piped streams always confuse me, which is why my Message Console solution doesn't use them. Anyway here is my attempt at a console using piped streams. A couple of differences:

a) it uses a JTextArea because a JTextArea is more efficient than a JTextPane for just displaying text. Of course if you intend to add attributes to the text then you need a text pane.

b) this solution uses Threads. I'm sure I read somewhere that this was necessary to prevent blocking of the output. Anyway it works in my simple test case.

import java.io.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;

public class Console implements Runnable
{
    JTextArea displayPane;
    BufferedReader reader;

    private Console(JTextArea displayPane, PipedOutputStream pos)
    {
        this.displayPane = displayPane;

        try
        {
            PipedInputStream pis = new PipedInputStream( pos );
            reader = new BufferedReader( new InputStreamReader(pis) );
        }
        catch(IOException e) {}
    }

    public void run()
    {
        String line = null;

        try
        {
            while ((line = reader.readLine()) != null)
            {
//              displayPane.replaceSelection( line + "\n" );
                displayPane.append( line + "\n" );
                displayPane.setCaretPosition( displayPane.getDocument().getLength() );
            }

            System.err.println("im here");
        }
        catch (IOException ioe)
        {
            JOptionPane.showMessageDialog(null,
                "Error redirecting output : "+ioe.getMessage());
        }
    }

    public static void redirectOutput(JTextArea displayPane)
    {
        Console.redirectOut(displayPane);
        Console.redirectErr(displayPane);
    }

    public static void redirectOut(JTextArea displayPane)
    {
        PipedOutputStream pos = new PipedOutputStream();
        System.setOut( new PrintStream(pos, true) );

        Console console = new Console(displayPane, pos);
        new Thread(console).start();
    }

    public static void redirectErr(JTextArea displayPane)
    {
        PipedOutputStream pos = new PipedOutputStream();
        System.setErr( new PrintStream(pos, true) );

        Console console = new Console(displayPane, pos);
        new Thread(console).start();
    }

    public static void main(String[] args)
    {
        JTextArea textArea = new JTextArea();
        JScrollPane scrollPane = new JScrollPane( textArea );

        JFrame frame = new JFrame("Redirect Output");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.getContentPane().add( scrollPane );
        frame.setSize(200, 100);
        frame.setVisible(true);

        Console.redirectOutput( textArea );
        final int i = 0;

        Timer timer = new Timer(1000, new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                System.out.println( new java.util.Date().toString() );
                System.err.println( System.currentTimeMillis() );
            }
        });
        timer.start();
    }
}

Answer 2

In the following link you can find the MessageConsole class that someone mentioned. I implemented a software and used this solution and it works perfect for me. I used the Netbeans design tool, so the code regarding the visual appearance of the JTextPane is a bit cumbersome, so I'm not going to place it here.

JTextPane jTextPane = new JTextPane();

MessageConsole console = new MessageConsole(jTextPane);
/*
This parameters are optional, but if you are looking for a solution with JTextPane it is because you need them, at least color.
*/
console.redirectErr(Color.RED, null);
console.redirectOut();

//some event
private void jButton1ActionPerformed(ActionEvent evt) {
    /*
    In this event I execute a function of my business.
    I put it in a thread so that it does not block the graphical interface.
    There are many calls to System.out.println() and System.err.println()
    */
    BusinessClass bc = new BusinessClass();
    Runnable runnable = () -> {
        bc.someBusinessFn();
    };
    thread = new Thread(runnable);
    thread.start();
}

//My main method
public static void main(String args[]) {
        /* Create and display the GUI */
        EventQueue.invokeLater(() -> {
            new MyJFrame().setVisible(true);
        });
}

Edit

Sorry, I did not realize that in the response similar to this, they had put the link to the MessageConsole class. I didn't see it and I also wanted to show my solution.

Answer 3

Message Console class does this for you.

Edit:

Here is a simple test class:

import java.io.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

public class MessageConsoleTest
{
    public static int counter;

    public static void main(String[] args)
        throws Exception
    {
        JTextComponent textComponent = new JTextPane();
        JScrollPane scrollPane = new JScrollPane( textComponent );

        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame("Message Console");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.getContentPane().add( scrollPane );
        frame.setSize(400, 120);
        frame.setVisible(true);

        MessageConsole console = new MessageConsole(textComponent);
        console.redirectOut();
        console.redirectErr(Color.RED, null);

        Timer timer = new Timer(1000, new java.awt.event.ActionListener()
        {
            public void actionPerformed(java.awt.event.ActionEvent e)
            {
                System.out.println( new java.util.Date().toString() );
            }
        });
        timer.start();

        Thread.sleep(750);

        Timer timer2 = new Timer(1000, new java.awt.event.ActionListener()
        {
            public void actionPerformed(java.awt.event.ActionEvent e)
            {
                System.err.println( "Error Message: " + ++counter);
            }
        });
        timer2.start();
    }
}