How can I make a default border for a JWindow?

Question

I have a JWindow object that is created when a button is pressed in a JFrame. I want the JWindow to have the same type of border as the JFrame from which it's created. However, the JWindow is not created automatically with a border as the JFrame is, so I don't know how to set the border abstractly so that whatever border is used for the JFrame, per he default L&F, will also be used for the JWindow.
I tried grabbing the border object from the JFame instance itself, but there is no such field in JFrame or any of its ancestor classes. I looked at UIDefaults, but I have no idea how this class can be used to get what I want. For example, if I use UIDefaults.getBorder(Object obj), what do I specify for the argument?
I'd be happy with an abstract or a concrete solution. That is, either using the default Border for top level containers in the current L&F, or by grabbing an actual Border instance from a JFrame object.
-Mark

Answer 1

Also, I'm curious why you said that JFrame is not a swing component.A Swing component extends JComponent. Basically this means that all the painting of the component is done in Java. You can add Borders to any Swing component. It is called a light weight component. A light weight component cannot exist by itself on the window desktop.
JFrame, JDialog and JWindow are top level components. They can exist on their own on the windows desktop because essentially they are Windows native components. They have been fancied up to make it easy for you to access and add other Swing components to it which is why they are found in the swing package.
A Windows border is not the same thing as a Swing Border and there is no way to access the native windows border and use it in a Swing application (that I know of anyway). Swing Borders are not used in a normal JFrame, the Windows border is used. You can however, turn off the use of Windows decorations and use Swing painted decorations. Read the tutorial on [url http://java.sun.com/docs/books/tutorial/uiswing/components/frame.html#setDefaultLookAndFeelDecorated]Specifying Windows Decorations. However, this doesn't really help you with your Border problem. If you look at the source code for the FrameBorder, you will find that the "blue" color of the Border is only painted for "active" windows and a JWindow can never be the active window, only the parent JFrame or JDialog is considered active.
Here is a simple program for you to play around with:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class FrameDecorated
     public static void main(String[] args)
          JFrame.setDefaultLookAndFeelDecorated(true);
          JFrame frame = new JFrame();
          frame.setDefaultCloseOperation( JFrame.DISPOSE_ON_CLOSE );
          frame.setSize(300, 300);
          frame.setVisible(true);
          Border border = frame.getRootPane().getBorder();
//          Border border = UIManager.getBorder( "RootPane.frameBorder" );
          System.out.println( border );
          JWindow window = new JWindow(frame);
          JPanel contentPane = (JPanel)window.getContentPane();
          contentPane.add(new JTextField(), BorderLayout.NORTH);
          contentPane.setBorder( border );
          window.setSize(300, 300);
          window.setLocationRelativeTo( null );
          window.setVisible( true );
          System.out.println("Window:" + window);
          Window ancestor = SwingUtilities.getWindowAncestor(contentPane);
          System.out.println("Ancestor:" + ancestor);
          System.out.println(ancestor.isActive());
          System.out.println(frame.isActive());
}