SecondCut++

SecondCut++

module/README.md

@@ -4,26 +4,22 @@ title: Module
 folder: module
 permalink: /patterns/module/
 pumlid: JShB3OGm303HLg20nFVjnYGM1CN6ycTfVtFSsnjfzY5jPgUqkLqHwXy0mxUU8wuyqidQ8q4IjJqCO-QBWGOtVh5qyd5AKOmW4mT6Nu2-ZiAekapH_hkcSTNa-GC0
-categories: Persistence Tier
+categories: Creational Pattern
 tags:
  - Java
  - Difficulty-Beginner
 ---
 
 ## Intent
-A layer of mappers that moves data between objects and a database while keeping them independent of each other and the mapper itself
+Module pattern is used to implement the concept of software modules, defined by modular programming, in a programming language with incomplete direct support for the concept.
 
 ![alt text](./etc/module.png "Module")
 
 ## Applicability
-The module pattern is a design pattern used to implement the concept of software modules, defined by modular programming, in a programming language with incomplete direct support for the concept.
-
 The Module pattern can be considered a creational pattern and a structural pattern. It manages the creation and organization of other elements, and groups them as the structural pattern does.
 
 An object that applies this pattern can provide the equivalent of a namespace, providing the initialization and finalization process of a static class or a class with static members with cleaner, more concise syntax and semantics.
 
-It supports specific cases where a class or object can be considered structured, procedural data. And, vice versa, migrate structured, procedural data, and considered as object-oriented.
-
 ## Credits
 
 * [Module](https://en.wikipedia.org/wiki/Module_pattern)

module/etc/module.ucls

@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.1.9" icons="true" always-add-relationships="false" generalizations="true" realizations="true" 
+  associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.module.FileLoggerModule" project="module" 
+    file="/module/src/main/java/com/iluwatar/module/FileLoggerModule.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="401" y="190"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="2" language="java" name="com.iluwatar.module.ConsoleLoggerModule" project="module" 
+    file="/module/src/main/java/com/iluwatar/module/ConsoleLoggerModule.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="686" y="176"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="3" language="java" name="com.iluwatar.module.App" project="module" 
+    file="/module/src/main/java/com/iluwatar/module/App.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="558" y="501"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <association id="4">    
+    <end type="SOURCE" refId="1" navigable="false">      
+      <attribute id="5" name="singleton"/>      
+      <multiplicity id="6" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="1" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="7">    
+    <end type="SOURCE" refId="2" navigable="false">      
+      <attribute id="8" name="singleton"/>      
+      <multiplicity id="9" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="2" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="10">    
+    <end type="SOURCE" refId="3" navigable="false">      
+      <attribute id="11" name="consoleLoggerModule"/>      
+      <multiplicity id="12" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="2" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="13">    
+    <end type="SOURCE" refId="3" navigable="false">      
+      <attribute id="14" name="fileLoggerModule"/>      
+      <multiplicity id="15" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="1" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

module/src/main/java/com/iluwatar/module/App.java

@@ -35,23 +35,35 @@ import java.io.FileNotFoundException;
  */
 public final class App {
 
-	private static final String OUTPUT_FILE = "output.txt";
-	private static final String ERROR_FILE = "error.txt";
-
-	public static FilePrinterModule filePrinterModule = null;
+	public static FileLoggerModule fileLoggerModule = null;
+	public static ConsoleLoggerModule consoleLoggerModule = null;
 
 	public static void prepare() throws FileNotFoundException {
-		filePrinterModule = FilePrinterModule.getSingleton();
+		
+		fileLoggerModule = FileLoggerModule.getSingleton();
+		consoleLoggerModule = ConsoleLoggerModule.getSingleton();
 
-		filePrinterModule.prepare(OUTPUT_FILE, ERROR_FILE);
+		/* Prepare modules */
+		fileLoggerModule.prepare();
+		consoleLoggerModule.prepare();
 	}
 
 	public static void unprepare() {
-		filePrinterModule.unprepare();
+
+		/* Close all resources */
+		fileLoggerModule.unprepare();
+		consoleLoggerModule.unprepare();
 	}
 
 	public static final void execute(final String... args) {
-		filePrinterModule.printString("Hello World");
+
+		/* Send logs on file system */
+		fileLoggerModule.printString("Message");
+		fileLoggerModule.printErrorString("Error");
+
+		/* Send logs on console */
+		consoleLoggerModule.printString("Message");
+		consoleLoggerModule.printErrorString("Error");
 	}
 
 	/**

module/src/main/java/com/iluwatar/module/ConsoleLoggerModule.java

@@ -0,0 +1,106 @@
+/**
+ * The MIT License Copyright (c) 2016 Amit Dixit
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+ * associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+ * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.iluwatar.module;
+
+import java.io.FileNotFoundException;
+import java.io.PrintStream;
+
+import org.apache.log4j.Logger;
+
+/**
+ * The Module pattern can be considered a Creational pattern and a Structural
+ * pattern. It manages the creation and organization of other elements, and
+ * groups them as the structural pattern does. An object that applies this
+ * pattern can provide the equivalent of a namespace, providing the
+ * initialization and finalization process of a static class or a class with
+ * static members with cleaner, more concise syntax and semantics.
+ * <p>
+ * The below example demonstrates a Console logger module, which can print
+ * simple and error messages in two designated formats
+ */
+public class ConsoleLoggerModule {
+
+	private static final Logger logger = Logger
+			.getLogger(ConsoleLoggerModule.class);
+
+	private static ConsoleLoggerModule singleton = null;
+
+	public PrintStream output = null;
+	public PrintStream error = null;
+
+	private ConsoleLoggerModule() {
+	}
+
+	public static final ConsoleLoggerModule getSingleton() {
+
+		if (ConsoleLoggerModule.singleton == null) {
+			ConsoleLoggerModule.singleton = new ConsoleLoggerModule();
+		}
+
+		return ConsoleLoggerModule.singleton;
+	}
+
+	/**
+	 * 
+	 * @throws FileNotFoundException
+	 */
+	public final void prepare() {
+
+		logger.debug("ConsoleLoggerModule::prepare();");
+
+		this.output = new PrintStream(System.out);
+		this.error = new PrintStream(System.err);
+	}
+
+	/**
+	 * 
+	 */
+	public final void unprepare() {
+
+		if (this.output != null) {
+
+			this.output.flush();
+			this.output.close();
+		}
+
+		if (this.error != null) {
+
+			this.error.flush();
+			this.error.close();
+		}
+
+		logger.debug("ConsoleLoggerModule::unprepare();");
+	}
+
+	/**
+	 * 
+	 * @param value
+	 */
+	public final void printString(final String value) {
+		this.output.println(value);
+	}
+
+	/**
+	 * 
+	 * @param value
+	 */
+	public final void printErrorString(final String value) {
+		this.error.println(value);
+	}
+}

module/src/main/java/com/iluwatar/module/FileLoggerModule.java

@@ -1,11 +1,3 @@
-package com.iluwatar.module;
-
-import java.io.FileNotFoundException;
-import java.io.FileOutputStream;
-import java.io.PrintStream;
-
-import org.apache.log4j.Logger;
-
 /**
  * The MIT License Copyright (c) 2016 Amit Dixit
  *
@@ -27,39 +19,60 @@ import org.apache.log4j.Logger;
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-public final class FilePrinterModule {
+package com.iluwatar.module;
+
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.PrintStream;
+
+import org.apache.log4j.Logger;
+
+/**
+ * The Module pattern can be considered a Creational pattern and a Structural
+ * pattern. It manages the creation and organization of other elements, and
+ * groups them as the structural pattern does. An object that applies this
+ * pattern can provide the equivalent of a namespace, providing the
+ * initialization and finalization process of a static class or a class with
+ * static members with cleaner, more concise syntax and semantics.
+ * <p>
+ * The below example demonstrates a File logger module, which can print simple
+ * and error messages in two designated files
+ */
+public final class FileLoggerModule {
 
 	private static final Logger logger = Logger
-			.getLogger(FilePrinterModule.class);
+			.getLogger(FileLoggerModule.class);
 
-	private static FilePrinterModule singleton = null;
+	private static FileLoggerModule singleton = null;
+
+	private static final String OUTPUT_FILE = "output.txt";
+	private static final String ERROR_FILE = "error.txt";
 
 	public PrintStream output = null;
 	public PrintStream error = null;
 
-	private FilePrinterModule() {
+	private FileLoggerModule() {
 	}
 
-	public static final FilePrinterModule getSingleton() {
+	public static final FileLoggerModule getSingleton() {
 
-		if (FilePrinterModule.singleton == null) {
-			FilePrinterModule.singleton = new FilePrinterModule();
+		if (FileLoggerModule.singleton == null) {
+			FileLoggerModule.singleton = new FileLoggerModule();
 		}
 
-		return FilePrinterModule.singleton;
+		return FileLoggerModule.singleton;
 	}
 
 	/**
 	 * 
 	 * @throws FileNotFoundException
 	 */
-	public final void prepare(final String outputFile, final String errorFile)
-			throws FileNotFoundException {
+	public final void prepare() throws FileNotFoundException {
 
-		logger.debug("MainModule::prepare();");
+		logger.debug("FileLoggerModule::prepare();");
 
-		this.output = new PrintStream(new FileOutputStream(outputFile));
-		this.error = new PrintStream(new FileOutputStream(errorFile));
+		this.output = new PrintStream(new FileOutputStream(OUTPUT_FILE));
+		this.error = new PrintStream(new FileOutputStream(ERROR_FILE));
 	}
 
 	/**
@@ -79,7 +92,7 @@ public final class FilePrinterModule {
 			this.error.close();
 		}
 
-		logger.debug("MainModule::unprepare();");
+		logger.debug("FileLoggerModule::unprepare();");
 	}
 
 	/**
@@ -87,7 +100,7 @@ public final class FilePrinterModule {
 	 * @param value
 	 */
 	public final void printString(final String value) {
-		this.output.print(value);
+		this.output.println(value);
 	}
 
 	/**
@@ -95,6 +108,6 @@ public final class FilePrinterModule {
 	 * @param value
 	 */
 	public final void printErrorString(final String value) {
-		this.error.print(value);
+		this.error.println(value);
 	}
 }

module/src/test/java/com/iluwatar/module/ModuleTest.java

@@ -24,19 +24,21 @@ import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
+import java.io.InputStreamReader;
 
 import org.apache.log4j.Logger;
 import org.junit.Test;
 
 /**
- * The Data Mapper (DM) is a layer of software that separates the in-memory
- * objects from the database. Its responsibility is to transfer data between the
- * two and also to isolate them from each other. With Data Mapper the in-memory
- * objects needn't know even that there's a database present; they need no SQL
- * interface code, and certainly no knowledge of the database schema. (The
- * database schema is always ignorant of the objects that use it.) Since it's a
- * form of Mapper , Data Mapper itself is even unknown to the domain layer.
+ * The Module pattern can be considered a Creational pattern and a Structural
+ * pattern. It manages the creation and organization of other elements, and
+ * groups them as the structural pattern does. An object that applies this
+ * pattern can provide the equivalent of a namespace, providing the
+ * initialization and finalization process of a static class or a class with
+ * static members with cleaner, more concise syntax and semantics.
  * <p>
+ * The below example demonstrates a JUnit test for testing two different
+ * modules: File Logger and Console Logger
  */
 public class ModuleTest {
 
@@ -54,23 +56,23 @@ public class ModuleTest {
 	 * @throws IOException
 	 */
 	@Test
-	public void testPositiveMessage() throws IOException {
+	public void positiveTestConsoleMessage() throws IOException {
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		final FilePrinterModule filePrinterModule = FilePrinterModule
+		final FileLoggerModule fileLoggerModule = FileLoggerModule
 				.getSingleton();
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		filePrinterModule.prepare(OUTPUT_FILE, ERROR_FILE);
+		fileLoggerModule.prepare();
 
 		/* Print 'Message' in file */
-		filePrinterModule.printString(MESSAGE);
+		fileLoggerModule.printString(MESSAGE);
 
-		/* Test if 'Message' is printed in file */
-		assertEquals(readFirstLine(OUTPUT_FILE), MESSAGE);
+		/* Test if 'Message' is printed on console */
+		assertEquals(readFirstLine(), MESSAGE);
 
 		/* Unprepare to cleanup the modules */
-		filePrinterModule.unprepare();
+		fileLoggerModule.unprepare();
 	}
 
 	/**
@@ -79,20 +81,20 @@ public class ModuleTest {
 	 * @throws IOException
 	 */
 	@Test
-	public void testNegativeMessage() throws IOException {
+	public void negativeTestConsoleMessage() throws IOException {
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		final FilePrinterModule filePrinterModule = FilePrinterModule
+		final ConsoleLoggerModule consoleLoggerModule = ConsoleLoggerModule
 				.getSingleton();
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		filePrinterModule.prepare(OUTPUT_FILE, ERROR_FILE);
+		consoleLoggerModule.prepare();
 
-		/* Test if nothing is printed in file */
-		assertEquals(readFirstLine(OUTPUT_FILE), null);
+		/* Test if nothing is printed on console */
+		assertEquals(readFirstLine(), null);
 
 		/* Unprepare to cleanup the modules */
-		filePrinterModule.unprepare();
+		consoleLoggerModule.unprepare();
 	}
 
 	/**
@@ -101,23 +103,23 @@ public class ModuleTest {
 	 * @throws FileNotFoundException
 	 */
 	@Test
-	public void testPositiveErrorMessage() throws FileNotFoundException {
+	public void positiveTestConsoleErrorMessage() {
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		final FilePrinterModule filePrinterModule = FilePrinterModule
+		final ConsoleLoggerModule consoleLoggerModule = ConsoleLoggerModule
 				.getSingleton();
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		filePrinterModule.prepare(OUTPUT_FILE, ERROR_FILE);
+		consoleLoggerModule.prepare();
 
 		/* Print 'Error' in file */
-		filePrinterModule.printErrorString(ERROR);
+		consoleLoggerModule.printErrorString(ERROR);
 
-		/* Test if 'Message' is printed in file */
-		assertEquals(readFirstLine(ERROR_FILE), ERROR);
+		/* Test if 'Message' is printed on console */
+		assertEquals(readFirstLine(), ERROR);
 
 		/* Unprepare to cleanup the modules */
-		filePrinterModule.unprepare();
+		consoleLoggerModule.unprepare();
 	}
 
 	/**
@@ -126,20 +128,152 @@ public class ModuleTest {
 	 * @throws FileNotFoundException
 	 */
 	@Test
-	public void testNegativeErrorMessage() throws FileNotFoundException {
+	public void negativeTestConsoleErrorMessage() {
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		final FilePrinterModule filePrinterModule = FilePrinterModule
+		final ConsoleLoggerModule consoleLoggerModule = ConsoleLoggerModule
 				.getSingleton();
 
 		/* Prepare the essential sub modules, to perform the sequence of jobs */
-		filePrinterModule.prepare(OUTPUT_FILE, ERROR_FILE);
+		consoleLoggerModule.prepare();
+
+		/* Test if nothing is printed on console */
+		assertEquals(readFirstLine(), null);
+
+		/* Unprepare to cleanup the modules */
+		consoleLoggerModule.unprepare();
+	}
+
+	/**
+	 * This test verify that 'MESSAGE' is perfectly printed in output file
+	 * 
+	 * @throws IOException
+	 */
+	@Test
+	public void positiveTestFileMessage() throws IOException {
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		final FileLoggerModule fileLoggerModule = FileLoggerModule
+				.getSingleton();
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		fileLoggerModule.prepare();
+
+		/* Print 'Message' in file */
+		fileLoggerModule.printString(MESSAGE);
+
+		/* Test if 'Message' is printed in file */
+		assertEquals(readFirstLine(OUTPUT_FILE), MESSAGE);
+
+		/* Unprepare to cleanup the modules */
+		fileLoggerModule.unprepare();
+	}
+
+	/**
+	 * This test verify that nothing is printed in output file
+	 * 
+	 * @throws IOException
+	 */
+	@Test
+	public void negativeTestFileMessage() throws IOException {
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		final FileLoggerModule fileLoggerModule = FileLoggerModule
+				.getSingleton();
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		fileLoggerModule.prepare();
+
+		/* Test if nothing is printed in file */
+		assertEquals(readFirstLine(OUTPUT_FILE), null);
+
+		/* Unprepare to cleanup the modules */
+		fileLoggerModule.unprepare();
+	}
+
+	/**
+	 * This test verify that 'ERROR' is perfectly printed in error file
+	 * 
+	 * @throws FileNotFoundException
+	 */
+	@Test
+	public void positiveTestFileErrorMessage() throws FileNotFoundException {
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		final FileLoggerModule fileLoggerModule = FileLoggerModule
+				.getSingleton();
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		fileLoggerModule.prepare();
+
+		/* Print 'Error' in file */
+		fileLoggerModule.printErrorString(ERROR);
+
+		/* Test if 'Message' is printed in file */
+		assertEquals(readFirstLine(ERROR_FILE), ERROR);
+
+		/* Unprepare to cleanup the modules */
+		fileLoggerModule.unprepare();
+	}
+
+	/**
+	 * This test verify that nothing is printed in error file
+	 * 
+	 * @throws FileNotFoundException
+	 */
+	@Test
+	public void negativeTestFileErrorMessage() throws FileNotFoundException {
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		final FileLoggerModule fileLoggerModule = FileLoggerModule
+				.getSingleton();
+
+		/* Prepare the essential sub modules, to perform the sequence of jobs */
+		fileLoggerModule.prepare();
 
 		/* Test if nothing is printed in file */
 		assertEquals(readFirstLine(ERROR_FILE), null);
 
 		/* Unprepare to cleanup the modules */
-		filePrinterModule.unprepare();
+		fileLoggerModule.unprepare();
+	}
+
+	/**
+	 * Utility method to read first line of a file
+	 * 
+	 * @param file
+	 * @return
+	 */
+	private static final String readFirstLine() {
+
+		String firstLine = null;
+		BufferedReader bufferedReader = null;
+		try {
+
+			/* Create a buffered reader */
+			bufferedReader = new BufferedReader(
+					new InputStreamReader(System.in));
+
+			/* Read the line */
+			firstLine = bufferedReader.readLine();
+
+			logger.info("ModuleTest::readFirstLineFromConsole() : firstLine : "
+					+ firstLine);
+
+		} catch (final IOException e) {
+			logger.error("ModuleTest::readFirstLineFromConsole()", e);
+		} finally {
+
+			if (bufferedReader != null) {
+				try {
+					bufferedReader.close();
+				} catch (final IOException e) {
+					logger.error("ModuleTest::readFirstLineFromConsole()", e);
+				}
+			}
+		}
+
+		return firstLine;
 	}
 
 	/**
@@ -160,17 +294,18 @@ public class ModuleTest {
 			/* Read the line */
 			firstLine = bufferedReader.readLine();
 
-			logger.info("ModuleTest::readFile() : firstLine : " + firstLine);
+			logger.info("ModuleTest::readFirstLine() : firstLine : "
+					+ firstLine);
 
 		} catch (final IOException e) {
-			logger.error("ModuleTest::readFile()", e);
+			logger.error("ModuleTest::readFirstLine()", e);
 		} finally {
 
 			if (bufferedReader != null) {
 				try {
 					bufferedReader.close();
 				} catch (final IOException e) {
-					logger.error("ModuleTest::readFile()", e);
+					logger.error("ModuleTest::readFirstLine()", e);
 				}
 			}
 		}