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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