Java/Design Pattern/Facade Pattern
Facade Pattern
<source lang="java">
/* Software Architecture Design Patterns in Java by Partha Kuchana Auerbach Publications
- /
</source>
Facade Pattern 2 in Java
<source lang="java">
//[C] 2002 Sun Microsystems, Inc.--- import java.awt.Container; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.text.NumberFormat; import java.util.HashMap; import java.util.Locale; import java.util.Properties; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextField; public class RunFacadePattern {
public static void main(String [] arguments){
System.out.println("Example for the Facade pattern");
System.out.println();
System.out.println("This code sample uses an InternationalizatgionWizard (a Facade)");
System.out.println(" to manage communication between the rest of the application and");
System.out.println(" a series of other classes.");
System.out.println();
System.out.println("The InternationalizatgionWizard maintains a colleciton of Nation");
System.out.println(" objects. When the setNation method is called, the wizard sets the");
System.out.println(" default nation, updating the Currency, PhoneNumber and localized");
System.out.println(" String resources (InternationalizedText) available.");
System.out.println();
System.out.println("Calls to get Strings for the GUI, the currency symbol or the dialing");
System.out.println(" prefix are routed through the Facade, the InternationalizationWizard.");
System.out.println();
if (!(new File("data.ser").exists())){
DataCreator.serialize("data.ser");
}
System.out.println("Creating the InternationalizationWizard and setting the nation to US.");
System.out.println();
InternationalizationWizard wizard = new InternationalizationWizard();
wizard.setNation("US");
System.out.println("Creating the FacadeGui.");
System.out.println();
FacadeGui application = new FacadeGui(wizard);
application.createGui();
application.setNation(wizard.getNation("US"));
}
} class FacadeGui implements ActionListener, ItemListener{
private static final String GUI_TITLE = "title";
private static final String EXIT_CAPTION = "exit";
private static final String COUNTRY_LABEL = "country";
private static final String CURRENCY_LABEL = "currency";
private static final String PHONE_LABEL = "phone";
private JFrame mainFrame;
private JButton exit;
private JComboBox countryChooser;
private JPanel controlPanel, displayPanel;
private JLabel countryLabel, currencyLabel, phoneLabel;
private JTextField currencyTextField, phoneTextField;
private InternationalizationWizard nationalityFacade;
public FacadeGui(InternationalizationWizard wizard){
nationalityFacade = wizard;
}
public void createGui(){
mainFrame = new JFrame(nationalityFacade.getProperty(GUI_TITLE));
Container content = mainFrame.getContentPane();
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
displayPanel = new JPanel();
displayPanel.setLayout(new GridLayout(3, 2));
countryLabel = new JLabel(nationalityFacade.getProperty(COUNTRY_LABEL));
countryChooser = new JComboBox(nationalityFacade.getNations());
currencyLabel = new JLabel(nationalityFacade.getProperty(CURRENCY_LABEL));
currencyTextField = new JTextField();
phoneLabel = new JLabel(nationalityFacade.getProperty(PHONE_LABEL));
phoneTextField = new JTextField();
currencyTextField.setEditable(false);
phoneTextField.setEditable(false);
displayPanel.add(countryLabel);
displayPanel.add(countryChooser);
displayPanel.add(currencyLabel);
displayPanel.add(currencyTextField);
displayPanel.add(phoneLabel);
displayPanel.add(phoneTextField);
content.add(displayPanel);
controlPanel = new JPanel();
exit = new JButton(nationalityFacade.getProperty(EXIT_CAPTION));
controlPanel.add(exit);
content.add(controlPanel);
exit.addActionListener(this);
countryChooser.addItemListener(this);
mainFrame.addWindowListener(new WindowCloseManager());
mainFrame.pack();
mainFrame.setVisible(true);
}
private void updateGui(){
nationalityFacade.setNation(countryChooser.getSelectedItem().toString());
mainFrame.setTitle(nationalityFacade.getProperty(GUI_TITLE));
countryLabel.setText(nationalityFacade.getProperty(COUNTRY_LABEL));
currencyLabel.setText(nationalityFacade.getProperty(CURRENCY_LABEL));
phoneLabel.setText(nationalityFacade.getProperty(PHONE_LABEL));
exit.setText(nationalityFacade.getProperty(EXIT_CAPTION));
currencyTextField.setText(nationalityFacade.getCurrencySymbol() + " " +
nationalityFacade.getNumberFormat().format(5280.50));
phoneTextField.setText(nationalityFacade.getPhonePrefix());
mainFrame.invalidate();
countryLabel.invalidate();
currencyLabel.invalidate();
phoneLabel.invalidate();
exit.invalidate();
mainFrame.validate();
}
public void actionPerformed(ActionEvent evt){
Object originator = evt.getSource();
if (originator == exit){
exitApplication();
}
}
public void itemStateChanged(ItemEvent evt){
Object originator = evt.getSource();
if (originator == countryChooser){
updateGui();
}
}
public void setNation(Nation nation){
countryChooser.setSelectedItem(nation);
}
private class WindowCloseManager extends WindowAdapter{
public void windowClosing(WindowEvent evt){
exitApplication();
}
}
private void exitApplication(){
System.exit(0);
}
} class Nation {
private char symbol;
private String name;
private String dialingPrefix;
private String propertyFileName;
private NumberFormat numberFormat;
public Nation(String newName, char newSymbol, String newDialingPrefix,
String newPropertyFileName, NumberFormat newNumberFormat) {
name = newName;
symbol = newSymbol;
dialingPrefix = newDialingPrefix;
propertyFileName = newPropertyFileName;
numberFormat = newNumberFormat;
}
public String getName(){ return name; }
public char getSymbol(){ return symbol; }
public String getDialingPrefix(){ return dialingPrefix; }
public String getPropertyFileName(){ return propertyFileName; }
public NumberFormat getNumberFormat(){ return numberFormat; }
public String toString(){ return name; }
} class Currency{
private char currencySymbol;
private NumberFormat numberFormat;
public void setCurrencySymbol(char newCurrencySymbol){ currencySymbol = newCurrencySymbol; }
public void setNumberFormat(NumberFormat newNumberFormat){ numberFormat = newNumberFormat; }
public char getCurrencySymbol(){ return currencySymbol; }
public NumberFormat getNumberFormat(){ return numberFormat; }
} class DataCreator{
private static final String GUI_TITLE = "title";
private static final String EXIT_CAPTION = "exit";
private static final String COUNTRY_LABEL = "country";
private static final String CURRENCY_LABEL = "currency";
private static final String PHONE_LABEL = "phone";
public static void serialize(String fileName){
saveFrData();
saveUsData();
saveNlData();
}
private static void saveFrData(){
try{
Properties textSettings = new Properties();
textSettings.setProperty(GUI_TITLE, "Demonstration du Pattern Facade");
textSettings.setProperty(EXIT_CAPTION, "Sortir");
textSettings.setProperty(COUNTRY_LABEL, "Pays");
textSettings.setProperty(CURRENCY_LABEL, "Monnaie");
textSettings.setProperty(PHONE_LABEL, "Numero de Telephone");
textSettings.store(new FileOutputStream("french.properties"), "French Settings");
}
catch (IOException exc){
System.err.println("Error storing settings to output");
exc.printStackTrace();
}
}
private static void saveUsData(){
try{
Properties textSettings = new Properties();
textSettings.setProperty(GUI_TITLE, "Facade Pattern Demonstration");
textSettings.setProperty(EXIT_CAPTION, "Exit");
textSettings.setProperty(COUNTRY_LABEL, "Country");
textSettings.setProperty(CURRENCY_LABEL, "Currency");
textSettings.setProperty(PHONE_LABEL, "Phone Number");
textSettings.store(new FileOutputStream("us.properties"), "US Settings");
}
catch (IOException exc){
System.err.println("Error storing settings to output");
exc.printStackTrace();
}
}
private static void saveNlData(){
try{
Properties textSettings = new Properties();
textSettings.setProperty(GUI_TITLE, "Facade Pattern voorbeeld");
textSettings.setProperty(EXIT_CAPTION, "Exit");
textSettings.setProperty(COUNTRY_LABEL, "Land");
textSettings.setProperty(CURRENCY_LABEL, "Munt eenheid");
textSettings.setProperty(PHONE_LABEL, "Telefoonnummer");
textSettings.store(new FileOutputStream("dutch.properties"), "Dutch Settings");
}
catch (IOException exc){
System.err.println("Error storing settings to output");
exc.printStackTrace();
}
}
} class PhoneNumber {
private static String selectedInterPrefix;
private String internationalPrefix;
private String areaNumber;
private String netNumber;
public PhoneNumber(String intPrefix, String areaNumber, String netNumber) {
this.internationalPrefix = intPrefix;
this.areaNumber = areaNumber;
this.netNumber = netNumber;
}
public String getInternationalPrefix(){ return internationalPrefix; }
public String getAreaNumber(){ return areaNumber; }
public String getNetNumber(){ return netNumber; }
public static String getSelectedInterPrefix(){ return selectedInterPrefix; }
public void setInternationalPrefix(String newPrefix){ internationalPrefix = newPrefix; }
public void setAreaNumber(String newAreaNumber){ areaNumber = newAreaNumber; }
public void setNetNumber(String newNetNumber){ netNumber = newNetNumber; }
public static void setSelectedInterPrefix(String prefix) { selectedInterPrefix = prefix; }
public String toString(){
return internationalPrefix + areaNumber + netNumber;
}
} class InternationalizedText{
private static final String DEFAULT_FILE_NAME = "";
private Properties textProperties = new Properties();
public InternationalizedText(){
this(DEFAULT_FILE_NAME);
}
public InternationalizedText(String fileName){
loadProperties(fileName);
}
public void setFileName(String newFileName){
if (newFileName != null){
loadProperties(newFileName);
}
}
public String getProperty(String key){
return getProperty(key, "");
}
public String getProperty(String key, String defaultValue){
return textProperties.getProperty(key, defaultValue);
}
private void loadProperties(String fileName){
try{
FileInputStream input = new FileInputStream(fileName);
textProperties.load(input);
}
catch (IOException exc){
textProperties = new Properties();
}
}
} class InternationalizationWizard{
private HashMap map;
private Currency currency = new Currency();
private InternationalizedText propertyFile = new InternationalizedText();
public InternationalizationWizard() {
map = new HashMap();
Nation[] nations = {
new Nation("US", "$", "+1", "us.properties", NumberFormat.getInstance(Locale.US)),
new Nation("The Netherlands", "f", "+31", "dutch.properties", NumberFormat.getInstance(Locale.GERMANY)),
new Nation("France", "f", "+33", "french.properties", NumberFormat.getInstance(Locale.FRANCE))
};
for (int i = 0; i < nations.length; i++) {
map.put(nations[i].getName(), nations[i]);
}
}
public void setNation(String name) {
Nation nation = (Nation)map.get(name);
if (nation != null) {
currency.setCurrencySymbol(nation.getSymbol());
currency.setNumberFormat(nation.getNumberFormat());
PhoneNumber.setSelectedInterPrefix(nation.getDialingPrefix());
propertyFile.setFileName(nation.getPropertyFileName());
}
}
public Object[] getNations(){
return map.values().toArray();
}
public Nation getNation(String name){
return (Nation)map.get(name);
}
public char getCurrencySymbol(){
return currency.getCurrencySymbol();
}
public NumberFormat getNumberFormat(){
return currency.getNumberFormat();
}
public String getPhonePrefix(){
return PhoneNumber.getSelectedInterPrefix();
}
public String getProperty(String key){
return propertyFile.getProperty(key);
}
public String getProperty(String key, String defaultValue){
return propertyFile.getProperty(key, defaultValue);
}
}
</source>
Facade pattern in Java
<source lang="java">
/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center
- /
import java.awt.BorderLayout; import java.awt.Button; import java.awt.Color; import java.awt.ruponent; import java.awt.Dialog; import java.awt.Frame; import java.awt.Graphics; import java.awt.GridLayout; import java.awt.Label; import java.awt.List; import java.awt.Panel; import java.awt.TextArea; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import java.sql.Connection; import java.sql.DatabaseMetaData; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; import java.util.Vector; public class DatabaseFrame extends Frame implements ActionListener,
ItemListener {
Database db;
List Tables, Columns, Data;
TextArea query;
Button Search, Quit;
public DatabaseFrame() {
super("Database demonstration");
setGUI();
db = new Database("sun.jdbc.odbc.JdbcOdbcDriver");
db.Open("jdbc:odbc:Grocery prices", null);
String tnames[] = db.getTableNames();
loadList(Tables, tnames);
String queryText = "SELECT * from yourTableName";
query.setText(queryText);
}
//------------------------------------
private void setGUI() {
setBackground(Color.lightGray);
setLayout(new BorderLayout());
Panel pn = new Panel();
add("North", pn);
pn.setLayout(new GridLayout(1, 3));
pn.add(new Label("Tables"));
pn.add(new Label("Columns"));
pn.add(new Label("Data"));
Panel pc = new Panel();
add("Center", pc);
pc.setLayout(new GridLayout(1, 3));
pc.add(Tables = new List(15));
pc.add(Columns = new List(15));
pc.add(Data = new List(15));
Tables.addItemListener(this);
Columns.addItemListener(this);
Panel ps = new Panel();
add("South", ps);
ps.add(query = new TextArea("", 3, 40));
addPanel(ps, Search = new Button("Run Query"));
addPanel(ps, Quit = new Button("Quit"));
Search.addActionListener(this);
Quit.addActionListener(this);
setBounds(100, 100, 500, 300);
setVisible(true);
}
//------------------------------------
private void addPanel(Panel ps, Component c) {
Panel p = new Panel();
ps.add(p);
p.add(c);
}
//------------------------------------
private void loadList(List list, String[] s) {
list.removeAll();
for (int i = 0; i < s.length; i++)
list.add(s[i]);
}
//------------------------------------
public void actionPerformed(ActionEvent e) {
Object obj = e.getSource();
if (obj == Quit)
System.exit(0);
if (obj == Search)
clickedSearch();
}
//------------------------------------
public void itemStateChanged(ItemEvent e) {
Object obj = e.getSource();
if (obj == Tables)
showColumns();
if (obj == Columns)
showData();
}
//------------------------------------
private void showColumns() {
String cnames[] = db.getColumnNames(Tables.getSelectedItem());
loadList(Columns, cnames);
}
//------------------------------------
private void showData() {
String colname = Columns.getSelectedItem();
String colval = db.getColumnValue(Tables.getSelectedItem(), colname);
Data.setVisible(false);
Data.removeAll();
Data.setVisible(true);
colval = db.getNextValue(Columns.getSelectedItem());
while (colval.length() > 0) {
Data.add(colval);
colval = db.getNextValue(Columns.getSelectedItem());
}
}
//------------------------------------
private void clickedSearch() {
resultSet rs = db.Execute(query.getText());
String cnames[] = rs.getMetaData();
Columns.removeAll();
queryDialog q = new queryDialog(this, rs);
q.show();
}
//------------------------------------
static public void main(String argv[]) {
new DatabaseFrame();
}
} class queryDialog extends Dialog implements ActionListener {
resultSet results;
Button OK;
textPanel pc;
Vector tables;
public queryDialog(Frame f, resultSet r) {
super(f, "Query Result");
results = r;
setLayout(new BorderLayout());
OK = new Button("OK");
Panel p = new Panel();
add("South", p);
p.add(OK);
OK.addActionListener(this);
pc = new textPanel();
pc.setBackground(Color.white);
add("Center", pc);
makeTables();
setBounds(100, 100, 500, 300);
setVisible(true);
repaint();
}
//-------------------------------------
private void makeTables() {
tables = new Vector();
String t[] = results.getMetaData();
tables.addElement(t);
while (results.hasMoreElements()) {
tables.addElement(results.nextElement());
}
}
//-------------------------------------
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
//-------------------------------------
class textPanel extends Panel {
public void paint(Graphics g) {
String s[];
int x = 0;
int y = g.getFontMetrics().getHeight();
int deltaX = (int) 1.5f
* (g.getFontMetrics().stringWidth("wwwwwwwwwwwwww"));
for (int i = 0; i < tables.size(); i++) {
s = (String[]) tables.elementAt(i);
for (int j = 0; j < s.length; j++) {
String st = s[j];
g.drawString(st, x, y);
x += deltaX;
}
x = 0;
y += g.getFontMetrics().getHeight();
if (i == 0)
y += g.getFontMetrics().getHeight();
}
}
}
} class Database {
Connection con;
resultSet results;
ResultSetMetaData rsmd;
DatabaseMetaData dma;
String catalog;
String types[];
String database_url;
public Database(String driver) {
types = new String[1];
types[0] = "TABLES"; //initialize type array
try {
Class.forName(driver);
} //load the Bridge driver
catch (Exception e) {
System.out.println(e.getMessage());
}
}
//-----------------------------------
public void close() {
try {
con.close();
} catch (Exception e) {
System.out.println("close error");
}
}
//-----------------------------------
public void Open(String url, String cat) {
catalog = cat;
database_url = url;
try {
con = DriverManager.getConnection(url);
dma = con.getMetaData(); //get the meta data
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
//-----------------------------------
public void reOpen() {
try {
con = DriverManager.getConnection(database_url);
dma = con.getMetaData(); //get the meta data
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
//-----------------------------------
public String[] getTableNames() {
String[] tbnames = null;
Vector tname = new Vector();
//add the table names to a Vector
//since we don"t know how many there are
try {
results = new resultSet(dma.getTables(catalog, null, "%", types));
} catch (Exception e) {
System.out.println(e);
}
while (results.hasMoreElements())
tname.addElement(results.getColumnValue("TABLE_NAME"));
//copy the table names into a String array
tbnames = new String[tname.size()];
for (int i = 0; i < tname.size(); i++)
tbnames[i] = (String) tname.elementAt(i);
return tbnames;
}
//-----------------------------------
public String[] getTableMetaData() {
// return the table type information
results = null;
try {
results = new resultSet(dma.getTables(catalog, null, "%", types));
} catch (Exception e) {
System.out.println(e.getMessage());
}
return results.getMetaData();
}
//-----------------------------------
public String[] getColumnMetaData(String tablename) {
//return the data on a column
results = null;
try {
results = new resultSet(dma.getColumns(catalog, null, tablename,
null));
} catch (Exception e) {
System.out.println(e.getMessage());
}
return results.getMetaData();
}
//-----------------------------------
public String[] getColumnNames(String table) {
//return an array of Column names
String[] tbnames = null;
Vector tname = new Vector();
try {
results = new resultSet(dma.getColumns(catalog, null, table, null));
while (results.hasMoreElements())
tname.addElement(results.getColumnValue("COLUMN_NAME"));
} catch (Exception e) {
System.out.println(e);
}
tbnames = new String[tname.size()];
for (int i = 0; i < tname.size(); i++)
tbnames[i] = (String) tname.elementAt(i);
return tbnames;
}
//-----------------------------------
public String getColumnValue(String table, String columnName) {
//return the value of a given column
String res = null;
try {
if (table.length() > 0)
results = Execute("Select " + columnName + " from " + table
+ " order by " + columnName);
if (results.hasMoreElements())
res = results.getColumnValue(columnName);
} catch (Exception e) {
System.out.println("Column value error" + columnName
+ e.getMessage());
}
return res;
}
//-----------------------------------
public String getNextValue(String columnName) {
// return the next value in that column
//using the remembered resultSet
String res = "";
try {
if (results.hasMoreElements())
res = results.getColumnValue(columnName);
} catch (Exception e) {
System.out
.println("next value error" + columnName + e.getMessage());
}
return res;
}
//-----------------------------------
public resultSet Execute(String sql) {
//execute an SQL query on this database
results = null;
try {
Statement stmt = con.createStatement();
results = new resultSet(stmt.executeQuery(sql));
} catch (Exception e) {
System.out.println("execute error: " + e.getMessage());
}
return results;
}
} class resultSet {
//this class is a higher level abstraction
//of the JDBC ResultSet object
ResultSet rs;
ResultSetMetaData rsmd;
int numCols;
public resultSet(ResultSet rset) {
rs = rset;
try {
//get the meta data and column count at once
rsmd = rs.getMetaData();
numCols = rsmd.getColumnCount();
} catch (Exception e) {
System.out.println("resultset error" + e.getMessage());
}
}
//-----------------------------------
public String[] getMetaData() {
//returns an array of all the column names
//or other meta data
String md[] = new String[numCols];
try {
for (int i = 1; i <= numCols; i++)
md[i - 1] = rsmd.getColumnName(i);
} catch (Exception e) {
System.out.println("meta data error" + e.getMessage());
}
return md;
}
//-----------------------------------
public boolean hasMoreElements() {
try {
return rs.next();
} catch (Exception e) {
System.out.println("next error " + e.getMessage());
return false;
}
}
//-----------------------------------
public String[] nextElement() {
//copies contents of row into string array
String[] row = new String[numCols];
try {
for (int i = 1; i <= numCols; i++)
row[i - 1] = rs.getString(i);
} catch (Exception e) {
System.out.println("next element error" + e.getMessage());
}
return row;
}
//-------------------------------------
public String getColumnValue(String columnName) {
String res = "";
try {
res = rs.getString(columnName);
} catch (Exception e) {
System.out.println("Column value error:" + columnName
+ e.getMessage());
}
return res;
}
//-------------------------------------
public String getColumnValue(int i) {
String res = "";
try {
res = rs.getString(i);
} catch (Exception e) {
System.out.println("Column value error: " + i + " "
+ e.getMessage());
}
return res;
}
//----------------------------------------------
public void finalize() {
try {
rs.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}
</source>
