Visitor Pattern - Example : Visitor Pattern « Design Pattern « Java

1. Java
2. Design Pattern
3. Visitor Pattern

Visitor Pattern - Example

/*

Software Architecture Design Patterns in Java
by Partha Kuchana 

Auerbach Publications


*/


import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

import com.sun.java.swing.plaf.windows.WindowsLookAndFeel;

public class OrderManager extends JFrame {
  public static final String newline = "\n";

  public static final String GET_TOTAL = "Get Total";

  public static final String CREATE_ORDER = "Create Order";

  public static final String EXIT = "Exit";

  public static final String CA_ORDER = "California Order";

  public static final String NON_CA_ORDER = "Non-California Order";

  public static final String OVERSEAS_ORDER = "Overseas Order";

  private JComboBox cmbOrderType;

  private JTextField txtOrderAmount, txtAdditionalTax, txtAdditionalSH;

  private JLabel lblOrderType, lblOrderAmount;

  private JLabel lblAdditionalTax, lblAdditionalSH;

  private JLabel lblTotal, lblTotalValue;

  private OrderVisitor objVisitor;

  public OrderManager() {
    super("Visitor Pattern - Example");

    //Create the visitor instance
    objVisitor = new OrderVisitor();

    cmbOrderType = new JComboBox();
    cmbOrderType.addItem(OrderManager.CA_ORDER);
    cmbOrderType.addItem(OrderManager.NON_CA_ORDER);
    cmbOrderType.addItem(OrderManager.OVERSEAS_ORDER);

    txtOrderAmount = new JTextField(10);
    txtAdditionalTax = new JTextField(10);
    txtAdditionalSH = new JTextField(10);

    lblOrderType = new JLabel("Order Type:");
    lblOrderAmount = new JLabel("Order Amount:");
    lblAdditionalTax = new JLabel("Additional Tax(CA Orders Only):");
    lblAdditionalSH = new JLabel("Additional S & H(Overseas Orders Only):");

    lblTotal = new JLabel("Result:");
    lblTotalValue = new JLabel("Click Create or GetTotal Button");

    //Create the open button
    JButton getTotalButton = new JButton(OrderManager.GET_TOTAL);
    getTotalButton.setMnemonic(KeyEvent.VK_G);
    JButton createOrderButton = new JButton(OrderManager.CREATE_ORDER);
    getTotalButton.setMnemonic(KeyEvent.VK_C);
    JButton exitButton = new JButton(OrderManager.EXIT);
    exitButton.setMnemonic(KeyEvent.VK_X);
    ButtonHandler objButtonHandler = new ButtonHandler(this);

    getTotalButton.addActionListener(objButtonHandler);
    createOrderButton.addActionListener(objButtonHandler);
    exitButton.addActionListener(new ButtonHandler());

    //For layout purposes, put the buttons in a separate panel
    JPanel buttonPanel = new JPanel();

    JPanel panel = new JPanel();
    GridBagLayout gridbag2 = new GridBagLayout();
    panel.setLayout(gridbag2);
    GridBagConstraints gbc2 = new GridBagConstraints();
    panel.add(getTotalButton);
    panel.add(createOrderButton);
    panel.add(exitButton);
    gbc2.anchor = GridBagConstraints.EAST;
    gbc2.gridx = 0;
    gbc2.gridy = 0;
    gridbag2.setConstraints(createOrderButton, gbc2);
    gbc2.gridx = 1;
    gbc2.gridy = 0;
    gridbag2.setConstraints(getTotalButton, gbc2);
    gbc2.gridx = 2;
    gbc2.gridy = 0;
    gridbag2.setConstraints(exitButton, gbc2);

    //****************************************************
    GridBagLayout gridbag = new GridBagLayout();
    buttonPanel.setLayout(gridbag);
    GridBagConstraints gbc = new GridBagConstraints();

    buttonPanel.add(lblOrderType);
    buttonPanel.add(cmbOrderType);
    buttonPanel.add(lblOrderAmount);
    buttonPanel.add(txtOrderAmount);
    buttonPanel.add(lblAdditionalTax);
    buttonPanel.add(txtAdditionalTax);
    buttonPanel.add(lblAdditionalSH);
    buttonPanel.add(txtAdditionalSH);
    buttonPanel.add(lblTotal);
    buttonPanel.add(lblTotalValue);

    gbc.insets.top = 5;
    gbc.insets.bottom = 5;
    gbc.insets.left = 5;
    gbc.insets.right = 5;

    gbc.anchor = GridBagConstraints.EAST;
    gbc.gridx = 0;
    gbc.gridy = 0;
    gridbag.setConstraints(lblOrderType, gbc);
    gbc.anchor = GridBagConstraints.WEST;
    gbc.gridx = 1;
    gbc.gridy = 0;
    gridbag.setConstraints(cmbOrderType, gbc);

    gbc.anchor = GridBagConstraints.EAST;
    gbc.gridx = 0;
    gbc.gridy = 1;
    gridbag.setConstraints(lblOrderAmount, gbc);
    gbc.anchor = GridBagConstraints.WEST;
    gbc.gridx = 1;
    gbc.gridy = 1;
    gridbag.setConstraints(txtOrderAmount, gbc);

    gbc.anchor = GridBagConstraints.EAST;
    gbc.gridx = 0;
    gbc.gridy = 2;
    gridbag.setConstraints(lblAdditionalTax, gbc);
    gbc.anchor = GridBagConstraints.WEST;
    gbc.gridx = 1;
    gbc.gridy = 2;
    gridbag.setConstraints(txtAdditionalTax, gbc);

    gbc.anchor = GridBagConstraints.EAST;
    gbc.gridx = 0;
    gbc.gridy = 3;
    gridbag.setConstraints(lblAdditionalSH, gbc);
    gbc.anchor = GridBagConstraints.WEST;
    gbc.gridx = 1;
    gbc.gridy = 3;
    gridbag.setConstraints(txtAdditionalSH, gbc);

    gbc.anchor = GridBagConstraints.EAST;
    gbc.gridx = 0;
    gbc.gridy = 4;
    gridbag.setConstraints(lblTotal, gbc);
    gbc.anchor = GridBagConstraints.WEST;
    gbc.gridx = 1;
    gbc.gridy = 4;
    gridbag.setConstraints(lblTotalValue, gbc);

    gbc.insets.left = 2;
    gbc.insets.right = 2;
    gbc.insets.top = 40;

    //****************************************************

    //Add the buttons and the log to the frame
    Container contentPane = getContentPane();

    contentPane.add(buttonPanel, BorderLayout.NORTH);
    contentPane.add(panel, BorderLayout.CENTER);
    try {
      UIManager.setLookAndFeel(new WindowsLookAndFeel());
      SwingUtilities.updateComponentTreeUI(OrderManager.this);
    } catch (Exception ex) {
      System.out.println(ex);
    }

  }

  public static void main(String[] args) {
    JFrame frame = new OrderManager();

    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });

    //frame.pack();
    frame.setSize(500, 400);
    frame.setVisible(true);
  }

  public void setTotalValue(String msg) {
    lblTotalValue.setText(msg);
  }

  public OrderVisitor getOrderVisitor() {
    return objVisitor;
  }

  public String getOrderType() {
    return (String) cmbOrderType.getSelectedItem();
  }

  public String getOrderAmount() {
    return txtOrderAmount.getText();
  }

  public String getTax() {
    return txtAdditionalTax.getText();
  }

  public String getSH() {
    return txtAdditionalSH.getText();
  }

} // End of class OrderManager

class ButtonHandler implements ActionListener {
  OrderManager objOrderManager;

  public void actionPerformed(ActionEvent e) {
    String totalResult = null;

    if (e.getActionCommand().equals(OrderManager.EXIT)) {
      System.exit(1);
    }
    if (e.getActionCommand().equals(OrderManager.CREATE_ORDER)) {
      //get input values
      String orderType = objOrderManager.getOrderType();
      String strOrderAmount = objOrderManager.getOrderAmount();
      String strTax = objOrderManager.getTax();
      String strSH = objOrderManager.getSH();

      double dblOrderAmount = 0.0;
      double dblTax = 0.0;
      double dblSH = 0.0;

      if (strOrderAmount.trim().length() == 0) {
        strOrderAmount = "0.0";
      }
      if (strTax.trim().length() == 0) {
        strTax = "0.0";
      }
      if (strSH.trim().length() == 0) {
        strSH = "0.0";
      }

      dblOrderAmount = new Double(strOrderAmount).doubleValue();
      dblTax = new Double(strTax).doubleValue();
      dblSH = new Double(strSH).doubleValue();

      //Create the order
      Order order = createOrder(orderType, dblOrderAmount, dblTax, dblSH);

      //Get the Visitor
      OrderVisitor visitor = objOrderManager.getOrderVisitor();

      // accept the visitor instance
      order.accept(visitor);

      objOrderManager.setTotalValue(" Order Created Successfully");
    }

    if (e.getActionCommand().equals(OrderManager.GET_TOTAL)) {
      //Get the Visitor
      OrderVisitor visitor = objOrderManager.getOrderVisitor();
      totalResult = new Double(visitor.getOrderTotal()).toString();
      totalResult = " Orders Total = " + totalResult;
      objOrderManager.setTotalValue(totalResult);
    }
  }

  public Order createOrder(String orderType, double orderAmount, double tax,
      double SH) {
    if (orderType.equalsIgnoreCase(OrderManager.CA_ORDER)) {
      return new CaliforniaOrder(orderAmount, tax);
    }
    if (orderType.equalsIgnoreCase(OrderManager.NON_CA_ORDER)) {
      return new NonCaliforniaOrder(orderAmount);
    }
    if (orderType.equalsIgnoreCase(OrderManager.OVERSEAS_ORDER)) {
      return new OverseasOrder(orderAmount, SH);
    }
    return null;
  }

  public ButtonHandler() {
  }

  public ButtonHandler(OrderManager inObjOrderManager) {
    objOrderManager = inObjOrderManager;
  }

} // End of class ButtonHandler

class NonCaliforniaOrder implements Order {
  private double orderAmount;

  public NonCaliforniaOrder() {
  }

  public NonCaliforniaOrder(double inp_orderAmount) {
    orderAmount = inp_orderAmount;
  }

  public double getOrderAmount() {
    return orderAmount;
  }

  public void accept(OrderVisitor v) {
    v.visit(this);
  }
}

class CaliforniaOrder implements Order {
  private double orderAmount;

  private double additionalTax;

  public CaliforniaOrder() {
  }

  public CaliforniaOrder(double inp_orderAmount, double inp_additionalTax) {
    orderAmount = inp_orderAmount;
    additionalTax = inp_additionalTax;
  }

  public double getOrderAmount() {
    return orderAmount;
  }

  public double getAdditionalTax() {
    return additionalTax;
  }

  public void accept(OrderVisitor v) {
    v.visit(this);
  }
}

interface VisitorInterface {
  public void visit(NonCaliforniaOrder nco);

  public void visit(CaliforniaOrder co);

  public void visit(OverseasOrder oo);
}

class OverseasOrder implements Order {
  private double orderAmount;

  private double additionalSH;

  public OverseasOrder() {
  }

  public OverseasOrder(double inp_orderAmount, double inp_additionalSH) {
    orderAmount = inp_orderAmount;
    additionalSH = inp_additionalSH;
  }

  public double getOrderAmount() {
    return orderAmount;
  }

  public double getAdditionalSH() {
    return additionalSH;
  }

  public void accept(OrderVisitor v) {
    v.visit(this);
  }
}

class OrderVisitor implements VisitorInterface {
  private Vector orderObjList;

  private double orderTotal;

  public OrderVisitor() {
    orderObjList = new Vector();
  }

  public void visit(NonCaliforniaOrder inp_order) {
    orderTotal = orderTotal + inp_order.getOrderAmount();
  }

  public void visit(CaliforniaOrder inp_order) {
    orderTotal = orderTotal + inp_order.getOrderAmount()
        + inp_order.getAdditionalTax();
  }

  public void visit(OverseasOrder inp_order) {
    orderTotal = orderTotal + inp_order.getOrderAmount()
        + inp_order.getAdditionalSH();
  }

  public double getOrderTotal() {
    return orderTotal;
  }
}

interface Order {
  public void accept(OrderVisitor v);
}

           
       

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