Decorator Java, Decorator Design, Java Platform

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Decorator design pattern using Java Platform

While designing User interface using Java AWT or Swings components,
Usually developer requires some more controls with features other than
the existing set of components provided by Java in its rich set of APIs.

Using Decorator pattern one can create/modify existing Look and feel of
UI component, such as JButton that is present in Java API.

Suppose I have to use a button which has a crossed red line over it,
across its two opposite corners.

I can use decorator design patterns to create a similar button as desired.

One way is to override paint method from JComponent/Component and provide
some additional graphical touch to the look and feel of this component.

Here is an example that tries to place an inclined red line across 
a JButton, as shown below in this Image:

CustomJFrame is the main client to run with and the CustomJButon.java, 
draws the desired button from scratch.

the source code is self explanatory, the CustoJButton takes the JButton
object in its construtor and adds an inclined red line to its Graphics 
context.



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Similarly we can add images on to Buttons as we might have seen in some advanced
thick clients.

CustomJButton.java

/**
 * This code is provided "AS IS" without any guarantee
 * or waranty of any kind.
 * Use of this code allowed only for educational and learning
 * purpose. Commercial use of this code is strictly prohibited.
 * You cann't publish this code or this writeup in any other site.
 * Author: Amit
 * Contact : usingframeworks@gmail.com
 * Date: 14-June-2009
 */

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

public class CustomJButton extends JButton
{
   public CustomJButton(String name) {
	   super(name);
   }

   public void paint(Graphics g) {
      super.paint(g);
      int height = this.getHeight();
      int width = this.getWidth();
      g.setColor(Color.red);
      g.setFont(new Font("",Font.BOLD,2));
      g.drawLine(0, 0, width, height);

   }
}


CustomJFrame.java

/**
 * This code is provided "AS IS" without any guarantee
 * or waranty of any kind.
 * Use of this code allowed only for educational and learning
 * purpose. Commercial use of this code is strictly prohibited.
 * You cann't publish this code or this writeup in any other site.
 * Author: Amit
 * Contact : usingframeworks@gmail.com
 * Date: 14-June-2009
 */

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class CustomJFrame extends JFrame
{
	public CustomJFrame()
	{
		setSize(150,70);
		getContentPane().setLayout(new FlowLayout());
		getContentPane().add(new CustomJButton("Save"));
		show();
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent we) {
				System.exit(0);
			}

		});
	}
	public static void main(String args[])
	{
		new CustomJFrame();
	}
}



Similarly in case of AWT based screen we can decorate existing AWT
button with an inclined red line across the button as shown in image
below:


Source code for this example is very simple, I just removed Swings 
related API from these class files and added AWT related API
as shown below:

CustomButton.java

/**
 * This code is provided "AS IS" without any guarantee
 * or waranty of any kind.
 * Use of this code allowed only for educational and learning
 * purpose. Commercial use of this code is strictly prohibited.
 * You cann't publish this code or this writeup in any other site.
 * Author: Amit
 * Contact : usingframeworks@gmail.com
 * Date: 14-June-2009
 */

import java.awt.*;
import java.awt.event.*;

public class CustomAWTButton extends Button
{
   public CustomAWTButton(String name) {
	   super(name);
   }

   public void paint(Graphics g) {
      super.paint(g);
      int height = this.getHeight();
      int width = this.getWidth();
      g.setColor(Color.red);
      g.setFont(new Font("",Font.BOLD,2));
      g.drawLine(0, 0, width, height);

   }
}


CustomFrame.java

/**
 * This code is provided "AS IS" without any guarantee
 * or waranty of any kind.
 * Use of this code allowed only for educational and learning
 * purpose. Commercial use of this code is strictly prohibited.
 * You cann't publish this code or this writeup in any other site.
 * Author: Amit
 * Contact : usingframeworks@gmail.com
 * Date: 14-June-2009
 */

import java.awt.*;
import java.awt.event.*;
public class CustomFrame extends Frame
{
	public CustomFrame()
	{
		setSize(150,70);
		setLayout(new FlowLayout());
		add(new CustomAWTButton("Save"));
		show();
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent we) {
				System.exit(0);
			}

		});
	}
	public static void main(String args[])
	{
		new CustomFrame();
	}
}


One can try experiment on these example to come up with some interesting
UI related designs on Java Platform and submit those ideas here in this
Page (if interested).



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