Factory Design Pattern using Java

We start this demonstation with the goal to make two differnt systems render a button. One system will render simple html text and the other system we create will be for a *java*.awt and *javax*.swing systems. (We call this system a 'windows' system). We start off by creating the Java namespaces we need for this project. We create a package called buttons and another one called factory In the buttons package we create an interface we call Button. Here is the code for the interface:

public interface Button {
    void render();
    void onClick();
}

As you can see, the requirements to use this interface is to include the two methods render and onClick The first button we create will be for Html buttons. The name of this class will be HtmlButton. HtmlButton needs to implement Button. Because it is implementing Button we need to include a render method and an onClick our code looks like:

public class HtmlButton implements Button {

    public void render() {
        System.out.println("");
        onClick();
    }

    public void onClick() {
        System.out.println("Click! Button says - 'Hello World!'");
    }
}

So now let's create the same method using the awt/swing libraries. The code for this version will be:

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

/**
 * Windows button implementation.
 */
public class WindowsButton implements Button {
    JPanel panel = new JPanel();
    JFrame frame = new JFrame();
    JButton button;

    public void render() {
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JLabel label = new JLabel("Hello World!");
        label.setOpaque(true);
        label.setBackground(new Color(235, 233, 126));
        label.setFont(new Font("Dialog", Font.BOLD, 44));
        label.setHorizontalAlignment(SwingConstants.CENTER);
        panel.setLayout(new FlowLayout(FlowLayout.CENTER));
        frame.getContentPane().add(panel);
        panel.add(label);
        onClick();
        panel.add(button);

        frame.setSize(320, 200);
        frame.setVisible(true);
        onClick();
    }

    public void onClick() {
        button = new JButton("Exit");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                frame.setVisible(false);
                System.exit(0);
            }
        });
    }
}

Now let's turn to the factory side of our project. In the factory package we should have some core business that should group together. We create an abstract class we call Dialog this will be our code:

public abstract class Dialog {

    public void renderWindow() {
        Button okButton = createButton();
        okButton.render();
    }

    /**
     * Subclasses will override this method in order to create specific button
     * objects.
     */
    public abstract Button createButton();
}

We now define how our styles run. For the HTML side I write the following:

public class HtmlDialog extends Dialog {

   @Override
   public Button createButton() {
      return new HtmlButton();
   }
}

And for our window side we write:

public class WindowsDialog extends Dialog {

   @Override
   public Button createButton() {
      return new WindowsButton();
   }
}

Now let's put this all together in our Demo.java program. This is the code:

public class Demo {
    private static Dialog dialog;

    public static void main(String[] args) {
        configure();
        runBusinessLogic();
    }

    /**
     * The concrete factory is usually chosen depending on configuration or
     * environment options.
     */


    static void configure() {
    // use 1 or 2 to run

        switch(2) {
            case 1:
                dialog = new WindowsDialog();
                break;
            case 2:
                dialog = new HtmlDialog();
                break;
            default:
                // exit code block
        }
    }

    /**
     * All of the client code should work with factories and products through
     * abstract interfaces. This way it does not care which factory it works
     * with and what kind of product it returns.
     */
    static void runBusinessLogic() {
        dialog.renderWindow();
    }
}

Be good and happy programming
Find Ray on:
facebook.com/TheRayCode/
youTube
The Ray Code
Ray Andrade