Decorator Design Pattern in 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.Properties;
import java.util.Vector;
public class DecoratorClient {
public static void main(String[] args) {
LoggerFactory factory = new LoggerFactory();
Logger logger = factory.getLogger();
HTMLLogger hLogger = new HTMLLogger(logger);
//the decorator object provides the same interface.
hLogger.log("A Message to Log");
EncryptLogger eLogger = new EncryptLogger(logger);
eLogger.log("A Message to Log");
}
} // End of class
class ConsoleLogger implements Logger {
public void log(String msg) {
System.out.println(msg);
}
}
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 LoggerDecorator implements Logger {
Logger logger;
public LoggerDecorator(Logger inp_logger) {
logger = inp_logger;
}
public void log(String DataLine) {
/*
* Default implementation to be overriden by subclasses.
*/
logger.log(DataLine);
}
}// end of class
interface Logger {
public void log(String msg);
}
class HTMLLogger extends LoggerDecorator {
public HTMLLogger(Logger inp_logger) {
super(inp_logger);
}
public void log(String DataLine) {
/*
* Added functionality
*/
DataLine = makeHTML(DataLine);
/*
* Now forward the encrypted text to the FileLogger for storage
*/
logger.log(DataLine);
}
public String makeHTML(String DataLine) {
/*
* Make it into an HTML document.
*/
DataLine = "<HTML><BODY>" + "<b>" + DataLine + "</b>"
+ "</BODY></HTML>";
return DataLine;
}
}// 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
class FileLogger implements Logger {
private static FileLogger logger;
//Prevent clients from using the constructor
private FileLogger() {
}
public static FileLogger getFileLogger() {
if (logger == null) {
logger = new FileLogger();
}
return logger;
}
public synchronized void log(String msg) {
FileUtil futil = new FileUtil();
futil.writeToFile("log.txt", msg, true, true);
}
}
class EncryptLogger extends LoggerDecorator {
public EncryptLogger(Logger inp_logger) {
super(inp_logger);
}
public void log(String DataLine) {
/*
* Added functionality
*/
DataLine = encrypt(DataLine);
/*
* Now forward the encrypted text to the FileLogger for storage
*/
logger.log(DataLine);
}
public String encrypt(String DataLine) {
/*
* Apply simple encryption by Transposition... Shift all characters by
* one position.
*/
DataLine = DataLine.substring(DataLine.length() - 1)
+ DataLine.substring(0, DataLine.length() - 1);
return DataLine;
}
}// end of class
class LoggerFactory {
public boolean isFileLoggingEnabled() {
Properties p = new Properties();
try {
p.load(ClassLoader.getSystemResourceAsStream("Logger.properties"));
String fileLoggingValue = p.getProperty("FileLogging");
if (fileLoggingValue.equalsIgnoreCase("ON") == true)
return true;
else
return false;
} catch (IOException e) {
return false;
}
}
public Logger getLogger() {
if (isFileLoggingEnabled()) {
return FileLogger.getFileLogger();
} else {
return new ConsoleLogger();
}
}
}
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