Java WindowClosing event not called when jFrame.setUndecorated(true) is set

Question

In the following snippet the WindowClosing event is not called except if you remove one line of code to the snippet. The line of code to be removed is:

jFrame.setUndecorated(true);

Apparently this setUndecorated(true) method disables the WindowListener/WindowAdapter functionality. Is this normal?

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.HeadlessException;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.File;
import java.io.IOException;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import org.apache.commons.io.FileUtils;

public class WindowClosing extends JFrame {

    private static WindowClosing jFrame;
    private static Container contentPane;

    public WindowClosing() throws HeadlessException {
        super();
        setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        addWindowListener(new WindowAdapter() {
                @Override
                public void windowClosing(WindowEvent e) {
                    JOptionPane.showMessageDialog(null, "closing" ,"Cookie", JOptionPane.INFORMATION_MESSAGE);
                    try {
                        FileUtils.cleanDirectory(new File("./temp/"));
                    } catch (IOException e1) {
                        e1.printStackTrace();
                    }
                    e.getWindow().dispose();
                    System.exit(0);
                    }
            });
    }

    public static void main(String[] args)  {
        jFrame = new WindowClosing();
        jFrame.setUndecorated(true);
        jFrame.pack();
        contentPane = jFrame.getContentPane();
        contentPane.setLayout(new BorderLayout());
        jFrame.setVisible(true);
    }
}

Answer 1

The reason WindowListener is not called when closing the frame is due to: the window is not closed with the closing icon of the frame, which are disabled by jFrame.setUndecorated(true);. Even if the system icons (close, maximize, minimize) are present and the user close the frame with a menu item, the WindowListener is not called.