Java/Design Pattern/Proxy Pattern
Another Proxy Pattern
<source lang="java">
/* Software Architecture Design Patterns in Java by Partha Kuchana Auerbach Publications
- /
import java.io.BufferedReader; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.util.Vector; public class MainProxyApp {
public static void main(String[] args) {
OrderIF order = new OrderProxy();
Vector v = order.getAllOrders();
v = order.getAllOrders();
v = order.getAllOrders();
v = order.getAllOrders();
}
} class OrderProxy implements OrderIF {
private int counter = 0;
public Vector getAllOrders() {
Order order = new Order();
counter++;
long t1 = System.currentTimeMillis();
Vector v = order.getAllOrders();
long t2 = System.currentTimeMillis();
long timeDiff = t2 - t1;
String msg = "Iteration=" + counter + "::Time=" + timeDiff + "ms";
//log the message
FileUtil fileUtil = new FileUtil();
fileUtil.writeToFile("log.txt", msg, true, true);
return v;
}
} interface OrderIF {
public Vector getAllOrders();
} class Order implements OrderIF {
public Vector getAllOrders() {
FileUtil fileUtil = new FileUtil();
Vector v = fileUtil.fileToVector("orders.txt");
return v;
}
} class MiscUtil {
public static boolean hasDuplicates(Vector v) {
int i = 0;
int j = 0;
boolean duplicates = false;
for (i = 0; i < v.size() - 1; i++) {
for (j = (i + 1); j < v.size(); j++) {
if (v.elementAt(i).toString().equalsIgnoreCase(
v.elementAt(j).toString())) {
duplicates = true;
}
}
}
return duplicates;
}
public static Vector removeDuplicates(Vector s) {
int i = 0;
int j = 0;
boolean duplicates = false;
Vector v = new Vector();
for (i = 0; i < s.size(); i++) {
duplicates = false;
for (j = (i + 1); j < s.size(); j++) {
if (s.elementAt(i).toString().equalsIgnoreCase(
s.elementAt(j).toString())) {
duplicates = true;
}
}
if (duplicates == false) {
v.addElement(s.elementAt(i).toString().trim());
}
}
return v;
}
public static Vector removeDuplicateDomains(Vector s) {
int i = 0;
int j = 0;
boolean duplicates = false;
String str1 = "";
String str2 = "";
Vector v = new Vector();
for (i = 0; i < s.size(); i++) {
duplicates = false;
for (j = (i + 1); j < s.size(); j++) {
str1 = "";
str2 = "";
str1 = s.elementAt(i).toString().trim();
str2 = s.elementAt(j).toString().trim();
if (str1.indexOf("@") > -1) {
str1 = str1.substring(str1.indexOf("@"));
}
if (str2.indexOf("@") > -1) {
str2 = str2.substring(str2.indexOf("@"));
}
if (str1.equalsIgnoreCase(str2)) {
duplicates = true;
}
}
if (duplicates == false) {
v.addElement(s.elementAt(i).toString().trim());
}
}
return v;
}
public static boolean areVectorsEqual(Vector a, Vector b) {
if (a.size() != b.size()) {
return false;
}
int i = 0;
int vectorSize = a.size();
boolean identical = true;
for (i = 0; i < vectorSize; i++) {
if (!(a.elementAt(i).toString().equalsIgnoreCase(b.elementAt(i)
.toString()))) {
identical = false;
}
}
return identical;
}
public static Vector removeDuplicates(Vector a, Vector b) {
int i = 0;
int j = 0;
boolean present = true;
Vector v = new Vector();
for (i = 0; i < a.size(); i++) {
present = false;
for (j = 0; j < b.size(); j++) {
if (a.elementAt(i).toString().equalsIgnoreCase(
b.elementAt(j).toString())) {
present = true;
}
}
if (!(present)) {
v.addElement(a.elementAt(i));
}
}
return v;
}
}// end of class class FileUtil {
DataOutputStream dos;
/*
* Utility method to write a given text to a file
*/
public boolean writeToFile(String fileName, String dataLine,
boolean isAppendMode, boolean isNewLine) {
if (isNewLine) {
dataLine = "\n" + dataLine;
}
try {
File outFile = new File(fileName);
if (isAppendMode) {
dos = new DataOutputStream(new FileOutputStream(fileName, true));
} else {
dos = new DataOutputStream(new FileOutputStream(outFile));
}
dos.writeBytes(dataLine);
dos.close();
} catch (FileNotFoundException ex) {
return (false);
} catch (IOException ex) {
return (false);
}
return (true);
}
/*
* Reads data from a given file
*/
public String readFromFile(String fileName) {
String DataLine = "";
try {
File inFile = new File(fileName);
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(inFile)));
DataLine = br.readLine();
br.close();
} catch (FileNotFoundException ex) {
return (null);
} catch (IOException ex) {
return (null);
}
return (DataLine);
}
public boolean isFileExists(String fileName) {
File file = new File(fileName);
return file.exists();
}
public boolean deleteFile(String fileName) {
File file = new File(fileName);
return file.delete();
}
/*
* Reads data from a given file into a Vector
*/
public Vector fileToVector(String fileName) {
Vector v = new Vector();
String inputLine;
try {
File inFile = new File(fileName);
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(inFile)));
while ((inputLine = br.readLine()) != null) {
v.addElement(inputLine.trim());
}
br.close();
} // Try
catch (FileNotFoundException ex) {
//
} catch (IOException ex) {
//
}
return (v);
}
/*
* Writes data from an input vector to a given file
*/
public void vectorToFile(Vector v, String fileName) {
for (int i = 0; i < v.size(); i++) {
writeToFile(fileName, (String) v.elementAt(i), true, true);
}
}
/*
* Copies unique rows from a source file to a destination file
*/
public void copyUniqueElements(String sourceFile, String resultFile) {
Vector v = fileToVector(sourceFile);
v = MiscUtil.removeDuplicates(v);
vectorToFile(v, resultFile);
}
} // end FileUtil
</source>
Proxy Pattern 2
<source lang="java">
//[C] 2002 Sun Microsystems, Inc.---
import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.ArrayList; import java.util.Iterator; public class RunProxyPattern {
public static void main(String[] arguments) {
System.out.println("Example for the Proxy pattern");
System.out.println();
System.out.println("This code will demonstrate the use of a Proxy to");
System.out.println(" provide functionality in place of its underlying");
System.out.println(" class.");
System.out.println();
System.out
.println(" Initially, an AddressBookProxy object will provide");
System.out.println(" address book support without requiring that the");
System.out
.println(" AddressBookImpl be created. This could potentially");
System.out.println(" make the application run much faster, since the");
System.out
.println(" AddressBookImpl would need to read in all addresses");
System.out.println(" from a file when it is first created.");
System.out.println();
if (!(new File("data.ser").exists())) {
DataCreator.serialize("data.ser");
}
System.out.println("Creating the AddressBookProxy");
AddressBookProxy proxy = new AddressBookProxy("data.ser");
System.out.println("Adding entries to the AddressBookProxy");
System.out.println("(this operation can be done by the Proxy, without");
System.out.println(" creating an AddressBookImpl object)");
proxy.add(new AddressImpl("Sun Education [CO]", "500 El Dorado Blvd.",
"Broomfield", "CO", "80020"));
proxy.add(new AddressImpl("Apple Inc.", "1 Infinite Loop",
"Redwood City", "CA", "93741"));
System.out.println("Addresses created. Retrieving an address");
System.out
.println("(since the address is stored by the Proxy, there is");
System.out
.println(" still no need to create an AddressBookImpl object)");
System.out.println();
System.out.println(proxy.getAddress("Sun Education [CO]").getAddress());
System.out.println();
System.out
.println("So far, all operations have been handled by the Proxy,");
System.out
.println(" without any involvement from the AddressBookImpl.");
System.out.println(" Now, a call to the method getAllAddresses will");
System.out.println(" force instantiation of AddressBookImpl, and will");
System.out.println(" retrieve ALL addresses that are stored.");
System.out.println();
ArrayList addresses = proxy.getAllAddresses();
System.out.println("Addresses retrieved. Addresses currently stored:");
System.out.println(addresses);
}
} interface Address extends Serializable {
public static final String EOL_STRING = System
.getProperty("line.separator");
public static final String SPACE = " ";
public static final String COMMA = ",";
public String getAddress();
public String getType();
public String getDescription();
public String getStreet();
public String getCity();
public String getState();
public String getZipCode();
public void setType(String newType);
public void setDescription(String newDescription);
public void setStreet(String newStreet);
public void setCity(String newCity);
public void setState(String newState);
public void setZipCode(String newZip);
} interface AddressBook {
public void add(Address address); public ArrayList getAllAddresses(); public Address getAddress(String description); public void open(); public void save();
} class FileLoader {
public static Object loadData(File inputFile) {
Object returnValue = null;
try {
if (inputFile.exists()) {
if (inputFile.isFile()) {
ObjectInputStream readIn = new ObjectInputStream(
new FileInputStream(inputFile));
returnValue = readIn.readObject();
readIn.close();
} else {
System.err.println(inputFile + " is a directory.");
}
} else {
System.err.println("File " + inputFile + " does not exist.");
}
} catch (ClassNotFoundException exc) {
exc.printStackTrace();
} catch (IOException exc) {
exc.printStackTrace();
}
return returnValue;
}
public static void storeData(File outputFile, Serializable data) {
try {
ObjectOutputStream writeOut = new ObjectOutputStream(
new FileOutputStream(outputFile));
writeOut.writeObject(data);
writeOut.close();
} catch (IOException exc) {
exc.printStackTrace();
}
}
} class DataCreator {
private static final String DEFAULT_FILE = "data.ser";
public static void main(String[] args) {
String fileName;
if (args.length == 1) {
fileName = args[0];
} else {
fileName = DEFAULT_FILE;
}
serialize(fileName);
}
public static void serialize(String fileName) {
try {
serializeToFile(createData(), fileName);
} catch (IOException exc) {
exc.printStackTrace();
}
}
private static Serializable createData() {
ArrayList items = new ArrayList();
items.add(new AddressImpl("Home address", "1418 Appian Way",
"Pleasantville", "NH", "27415"));
items.add(new AddressImpl("Resort", "711 Casino Ave.", "Atlantic City",
"NJ", "91720"));
items.add(new AddressImpl("Vacation spot", "90 Ka"ahanau Cir.",
"Haleiwa", "HI", "41720"));
return items;
}
private static void serializeToFile(Serializable data, String fileName)
throws IOException {
ObjectOutputStream serOut = new ObjectOutputStream(
new FileOutputStream(fileName));
serOut.writeObject(data);
serOut.close();
}
} class AddressImpl implements Address {
private String type;
private String description;
private String street;
private String city;
private String state;
private String zipCode;
public static final String HOME = "home";
public static final String WORK = "work";
public AddressImpl() {
}
public AddressImpl(String newDescription, String newStreet, String newCity,
String newState, String newZipCode) {
description = newDescription;
street = newStreet;
city = newCity;
state = newState;
zipCode = newZipCode;
}
public String getType() {
return type;
}
public String getDescription() {
return description;
}
public String getStreet() {
return street;
}
public String getCity() {
return city;
}
public String getState() {
return state;
}
public String getZipCode() {
return zipCode;
}
public void setType(String newType) {
type = newType;
}
public void setDescription(String newDescription) {
description = newDescription;
}
public void setStreet(String newStreet) {
street = newStreet;
}
public void setCity(String newCity) {
city = newCity;
}
public void setState(String newState) {
state = newState;
}
public void setZipCode(String newZip) {
zipCode = newZip;
}
public String toString() {
return description;
}
public String getAddress() {
return description + EOL_STRING + street + EOL_STRING + city + COMMA
+ SPACE + state + SPACE + zipCode + EOL_STRING;
}
} class AddressBookProxy implements AddressBook {
private File file;
private AddressBookImpl addressBook;
private ArrayList localAddresses = new ArrayList();
public AddressBookProxy(String filename) {
file = new File(filename);
}
public void open() {
addressBook = new AddressBookImpl(file);
Iterator addressIterator = localAddresses.iterator();
while (addressIterator.hasNext()) {
addressBook.add((Address) addressIterator.next());
}
}
public void save() {
if (addressBook != null) {
addressBook.save();
} else if (!localAddresses.isEmpty()) {
open();
addressBook.save();
}
}
public ArrayList getAllAddresses() {
if (addressBook == null) {
open();
}
return addressBook.getAllAddresses();
}
public Address getAddress(String description) {
if (!localAddresses.isEmpty()) {
Iterator addressIterator = localAddresses.iterator();
while (addressIterator.hasNext()) {
AddressImpl address = (AddressImpl) addressIterator.next();
if (address.getDescription().equalsIgnoreCase(description)) {
return address;
}
}
}
if (addressBook == null) {
open();
}
return addressBook.getAddress(description);
}
public void add(Address address) {
if (addressBook != null) {
addressBook.add(address);
} else if (!localAddresses.contains(address)) {
localAddresses.add(address);
}
}
} class AddressBookImpl implements AddressBook {
private File file;
private ArrayList addresses = new ArrayList();
public AddressBookImpl(File newFile) {
file = newFile;
open();
}
public ArrayList getAllAddresses() {
return addresses;
}
public Address getAddress(String description) {
Iterator addressIterator = addresses.iterator();
while (addressIterator.hasNext()) {
AddressImpl address = (AddressImpl) addressIterator.next();
if (address.getDescription().equalsIgnoreCase(description)) {
return address;
}
}
return null;
}
public void add(Address address) {
if (!addresses.contains(address)) {
addresses.add(address);
}
}
public void open() {
addresses = (ArrayList) FileLoader.loadData(file);
}
public void save() {
FileLoader.storeData(file, addresses);
}
}
</source>
Proxy 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.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Image; import java.awt.Label; import java.awt.MediaTracker; import java.awt.Toolkit; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JFrame; import javax.swing.JPanel; public class ProxyDisplay extends JFrame {
public ProxyDisplay() {
super("Display proxied image");
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
JPanel p = new JPanel();
getContentPane().add(p);
p.setLayout(new BorderLayout());
ImageProxy image = new ImageProxy("elliott.jpg", 321, 271);
p.add("Center", image);
p.add("North", new Label(" "));
p.add("West", new Label(" "));
setSize(370, 350);
setVisible(true);
}
static public void main(String[] argv) {
new ProxyDisplay();
}
} //================================== class ImageProxy extends JPanel implements Runnable {
int height, width;
MediaTracker tracker;
Image img;
JFrame frame;
Thread imageCheck; //to monitor loading
public ImageProxy(String filename, int w, int h) {
height = h;
width = w;
tracker = new MediaTracker(this);
img = Toolkit.getDefaultToolkit().getImage(filename);
tracker.addImage(img, 0); //watch for image loading
imageCheck = new Thread(this);
imageCheck.start(); //start 2nd thread monitor
//this begins actual image loading
try {
tracker.waitForID(0, 1);
} catch (InterruptedException e) {
}
}
public void paint(Graphics g) {
if (tracker.checkID(0)) {
height = img.getHeight(frame); //get height
width = img.getWidth(frame); //and width
g.setColor(Color.lightGray); //erase box
g.fillRect(0, 0, width, height);
g.drawImage(img, 0, 0, this); //draw loaded image
} else {
//draw box outlining image if not loaded yet
g.setColor(Color.black);
g.drawRect(1, 1, width - 2, height - 2);
}
}
public Dimension getPreferredSize() {
return new Dimension(width, height);
}
//public int getWidth() {return width;}
//public int getHeight(){return height;}
public void run() {
//this thread monitors image loading
//and repaints when done
//the 1000 msec is artifically long
//to allow demo to display with delay
try {
Thread.sleep(1000);
while (!tracker.checkID(0))
Thread.sleep(1000);
} catch (Exception e) {
}
repaint();
}
}
</source>
