#4 add chain of responsibility pattern example - logger - into project

Author: ThanhPhiNgo

README.md

@@ -81,3 +81,5 @@ Reference: https://gpcoder.com/4644-huong-dan-java-design-pattern-proxy/
 ### Chain of Responsibility
 
 Reference: https://gpcoder.com/4665-huong-dan-java-design-pattern-chain-of-responsibility/
+
+> Review: Suitable for create and push Alert through applications (tools) by level

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/AppLogger.java

@@ -0,0 +1,12 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+public class AppLogger {
+
+	public static Logger getLogger() {
+
+		Logger consoleLogger = new ConsoleLogger(LogLevel.DEBUG);
+		Logger fileLogger = consoleLogger.setNext(new FileLogger(LogLevel.ERROR));
+		fileLogger.setNext(new MailLogger(LogLevel.FATAL));
+		return consoleLogger;
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/Client.java

@@ -0,0 +1,23 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+/*
+* Chain of Responsibility Pattern Example
+* */
+public class Client {
+
+	public static void main(String[] args) {
+
+		// Build the chain of responsibility
+		Logger logger = AppLogger.getLogger();
+
+		// Handled by ConsoleLogger since the console has a LogLevel of DEBUG
+		logger.log(LogLevel.INFO, "Info message");
+		logger.log(LogLevel.DEBUG, "Debug message");
+
+		// Handled by ConsoleLogger and FileLogger
+		logger.log(LogLevel.ERROR, "Error message");
+
+		// Handled by ConsoleLogger, FileLogger, MailLogger
+		logger.log(LogLevel.FATAL, "Fatal message");
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/ConsoleLogger.java

@@ -0,0 +1,13 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+public class ConsoleLogger extends Logger {
+
+	public ConsoleLogger(LogLevel logLevel) {
+		super(logLevel);
+	}
+
+	@Override
+	protected void writeMessage(String message) {
+		System.out.println("Console logger: " + message);
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/FileLogger.java

@@ -0,0 +1,13 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+public class FileLogger extends Logger {
+
+	public FileLogger(LogLevel logLevel) {
+		super(logLevel);
+	}
+
+	@Override
+	protected void writeMessage(String message) {
+		System.out.println("File logger: " + message);
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/LogLevel.java

@@ -0,0 +1,22 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+public enum LogLevel {
+
+	NONE(0),
+	INFO(1),
+	DEBUG(2),
+	WARNING(4),
+	ERROR(8),
+	FATAL(16),
+	ALL(32);
+
+	private int level;
+
+	private LogLevel(int level) {
+		this.level = level;
+	}
+
+	public int getLevel() {
+		return level;
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/Logger.java

@@ -0,0 +1,28 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+public abstract class Logger {
+
+	protected LogLevel logLevel;
+	protected Logger nextLogger; // The next Handler in the chain
+
+	public Logger(LogLevel logLevel) {
+		this.logLevel = logLevel;
+	}
+
+	// Set the next logger to make a list/chain of Handlers.
+	public Logger setNext(Logger nextLogger) {
+		this.nextLogger = nextLogger;
+		return nextLogger;
+	}
+
+	public void log(LogLevel severity, String message) {
+		if (this.logLevel.getLevel() <= severity.getLevel()) {
+			writeMessage(message);
+		}
+		if (nextLogger != null) {
+			nextLogger.log(severity, message);
+		}
+	}
+
+	protected abstract void writeMessage(String message);
+}

design-pattern/src/main/java/com/phint2/pattern/behavioral/cor/logger/MailLogger.java

@@ -0,0 +1,13 @@
+package com.phint2.pattern.behavioral.cor.logger;
+
+public class MailLogger extends Logger {
+
+	public MailLogger(LogLevel logLevel) {
+		super(logLevel);
+	}
+
+	@Override
+	protected void writeMessage(String message) {
+		System.out.println("Mail logger: " + message);
+	}
+}