Merge pull request #3 from pitsios-s/master

Model-View-Presenter pattern

README.md

@@ -189,6 +189,15 @@
 * a snapshot of an object's state must be saved so that it can be restored to that state later, and
 * a direct interface to obtaining the state would expose implementation details and break the object's encapsulation
 
+##Model-View-Presenter
+**Intent:** Apply a "Separation of Concerns" principle in a way that allows developers to build and test user interfaces.
+
+![alt text](https://github.com/pitsios-s/java-design-patterns/blob/master/model-view-presenter/etc/model-view-presenter.jpg "Model-View-Presenter")
+
+**Applicability:** Use the Model-View-Presenter in any of the following situations
+* when you want to improve the "Separation of Concerns" principle in presentation logic
+* when a user interface development and testing is necessary.
+
 ##Observer
 **Intent:** Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
 

model-view-presenter/etc/data/test.txt

@@ -0,0 +1,2 @@
+Test line 1
+Test line 2

model-view-presenter/pom.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.0-SNAPSHOT</version>
+  </parent>
+  <groupId>com.iluwatar</groupId>
+  <artifactId>model-view-presenter</artifactId>
+  <version>1.0-SNAPSHOT</version>
+  <name>model-view-presenter</name>
+  <url>http://maven.apache.org</url>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+	   <groupId>net.java.dev.swing-layout</groupId>
+	   <artifactId>swing-layout</artifactId>
+	   <version>1.0.2</version>
+    </dependency>
+  </dependencies>
+</project>

model-view-presenter/src/main/java/com/iluwatar/FileLoader.java

@@ -0,0 +1,80 @@
+package com.iluwatar;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+
+/**
+ * Every instance of this class represents the Model component
+ * in the Model-View-Presenter architectural pattern.
+ * 
+ * It is responsible for reading and loading the contents of a given file.
+ */
+public class FileLoader {
+	
+	/**
+	 * Indicates if the file is loaded or not.
+	 */
+	private boolean loaded = false;
+	
+	/**
+	 * The name of the file that we want to load.
+	 */
+	private String fileName;
+	
+	/**
+	 * Loads the data of the file specified.
+	 */
+	public String loadData() {
+		try {
+			BufferedReader br = new BufferedReader(new FileReader(new File(this.fileName)));
+			String text = "";
+			String line = "";
+			
+			while( (line = br.readLine()) != null ) {
+				text += line + "\n";
+			}
+			
+			this.loaded = true;
+			br.close();
+			
+			return text;
+		}
+		
+		catch(Exception e) {
+			e.printStackTrace();
+		}
+		
+		return null;
+	}
+	
+	/**
+	 * Sets the path of the file to be loaded, to the given value.
+	 * 
+	 * @param fileName The path of the file to be loaded.
+	 */
+	public void setFileName(String fileName) {
+		this.fileName = fileName;
+	}
+	
+	/**
+	 * @return fileName The path of the file to be loaded.
+	 */
+	public String getFileName() {
+		return this.fileName;
+	}
+	
+	/**
+	 * @return True, if the file given exists, false otherwise.
+	 */
+	public boolean fileExists() {
+		return new File(this.fileName).exists();
+	}
+	
+	/**
+	 * @return True, if the file is loaded, false otherwise.
+	 */
+	public boolean isLoaded() {
+		return this.loaded;
+	}
+}

model-view-presenter/src/main/java/com/iluwatar/FileSelectorJFrame.java

@@ -0,0 +1,200 @@
+package com.iluwatar;
+
+import java.awt.Color;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JOptionPane;
+import javax.swing.JPanel;
+import javax.swing.JScrollPane;
+import javax.swing.JTextArea;
+import javax.swing.JTextField;
+
+/**
+ * This class is the GUI implementation of the View component
+ * In the Model-View-Presenter pattern.
+ */
+public class FileSelectorJFrame extends JFrame implements FileSelectorView, ActionListener {
+
+	/**
+	 * Default serial version ID.
+	 */
+	private static final long serialVersionUID = 1L;
+	
+	/**
+	 * The "OK" button for loading the file.
+	 */
+	private JButton OK;
+	
+	/**
+	 * The cancel button.
+	 */
+	private JButton cancel;
+	
+	/**
+	 * The information label.
+	 */
+	private JLabel info;
+	
+	/**
+	 * The contents label.
+	 */
+	private JLabel contents;
+	
+	/**
+	 * The text field for giving the name of the file
+	 * that we want to open.
+	 */
+	private JTextField input;
+	
+	/**
+	 * A text area that will keep the contents of the file opened.
+	 */
+	private JTextArea area;
+	
+	/**
+	 * The panel that will hold our widgets.
+	 */
+	private JPanel panel;
+	
+	/**
+	 * The Presenter component that the frame will interact with
+	 */
+	private FileSelectorPresenter presenter;
+	
+	/**
+	 * The name of the file that we want to read it's contents.
+	 */
+	private String fileName;
+	
+	/**
+	 * Constructor.
+	 */
+	public FileSelectorJFrame() {
+		super("File Loader");
+		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+		this.setLayout(null);
+		this.setBounds(100, 100, 500, 200);
+		
+		/*
+		 * Add the panel.
+		 */
+		this.panel = new JPanel();
+		panel.setLayout(null);
+		this.add(panel);
+		panel.setBounds(0, 0, 500, 200);
+		panel.setBackground(Color.LIGHT_GRAY);
+		
+		/*
+		 * Add the info label.
+		 */
+		this.info = new JLabel("File Name :");
+		this.panel.add(info);
+		info.setBounds(30, 10, 100, 30);
+		
+		/*
+		 * Add the contents label. 
+		 */
+		this.contents = new JLabel("File contents :");
+		this.panel.add(contents);
+		this.contents.setBounds(30, 100, 120, 30);
+		
+		/*
+		 * Add the text field.
+		 */
+		this.input = new JTextField(100);
+		this.panel.add(input);
+		this.input.setBounds(150, 15, 200, 20);
+		
+		/*
+		 * Add the text area.
+		 */
+		this.area = new JTextArea(100, 100);
+		JScrollPane pane = new JScrollPane(area);
+		pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
+		pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
+		this.panel.add(pane);
+		this.area.setEditable(false);
+		pane.setBounds(150, 100, 250, 80);
+		
+		/*
+		 * Add the OK button.
+		 */
+		this.OK = new JButton("OK");
+		this.panel.add(OK);
+		this.OK.setBounds(250, 50, 100, 25);
+		this.OK.addActionListener(this);
+		
+		/*
+		 * Add the cancel button. 
+		 */
+		this.cancel = new JButton("Cancel");
+		this.panel.add(this.cancel);
+		this.cancel.setBounds(380, 50, 100, 25);
+		this.cancel.addActionListener(this);
+		
+		this.presenter = null;
+		this.fileName = null;
+	}
+	
+	@Override
+	public void actionPerformed(ActionEvent e) {
+		if(e.getSource() == this.OK) {
+			this.fileName = this.input.getText();
+			presenter.fileNameChanged();
+			presenter.confirmed();
+		}
+		
+		else if(e.getSource() == this.cancel) {
+			presenter.cancelled();
+		}
+	}
+
+	@Override
+	public void open() {
+		this.setVisible(true);
+	}
+
+	@Override
+	public void close() {
+		this.dispose();
+	}
+
+	@Override
+	public boolean isOpened() {
+		return this.isVisible();
+	}
+
+	@Override
+	public void setPresenter(FileSelectorPresenter presenter) {
+		this.presenter = presenter;
+	}
+
+	@Override
+	public FileSelectorPresenter getPresenter() {
+		return this.presenter;
+	}
+
+	@Override
+	public void setFileName(String name) {
+		this.fileName = name;
+	}
+
+	@Override
+	public String getFileName() {
+		return this.fileName;
+	}
+
+	@Override
+	public void showMessage(String message) {
+		JOptionPane.showMessageDialog(null, message);
+	}
+
+	@Override
+	public void displayData(String data) {
+		this.area.setText(data);
+	}
+}

model-view-presenter/src/main/java/com/iluwatar/FileSelectorPresenter.java

@@ -0,0 +1,76 @@
+package com.iluwatar;
+
+/**
+ * Every instance of this class represents the Presenter component
+ * in the Model-View-Presenter architectural pattern.
+ * 
+ * It is responsible for reacting to the user's actions and update the View component.
+ */
+public class FileSelectorPresenter {
+	
+	/**
+	 * The View component that the presenter interacts with.
+	 */
+	private FileSelectorView view;
+	
+	/**
+	 * The Model component that the presenter interacts with.
+	 */
+	private FileLoader loader;
+	
+	/**
+	 * Constructor
+	 * 
+	 * @param view The view component that the presenter will interact with.
+	 */
+	public FileSelectorPresenter(FileSelectorView view) {
+		this.view = view;
+	}
+	
+	/**
+	 * Sets the FileLoader object, to the value given as parameter.
+	 * 
+	 * @param loader The new FileLoader object(the Model component).
+	 */
+	public void setLoader(FileLoader loader) {
+		this.loader = loader;
+	}
+	
+	/**
+	 * Starts the presenter.
+	 */
+	public void start() {
+		view.setPresenter(this);
+		view.open();
+	}
+	
+	/**
+	 * An "event" that fires when the name of the file to be loaded changes.
+	 */
+	public void fileNameChanged() {
+		loader.setFileName(view.getFileName());
+	}
+	
+	public void confirmed() {
+		if(loader.getFileName() == null || loader.getFileName().equals("")) {
+			view.showMessage("Please give the name of the file first!");
+			return;
+		}
+		
+		if(loader.fileExists()) {
+			String data = loader.loadData();
+			view.displayData(data);
+		} 
+		
+		else {
+			view.showMessage("The file specified does not exist.");
+		}
+	}
+	
+	/**
+	 * Cancels the file loading process.
+	 */
+	public void cancelled() {
+		view.close();
+	}	
+}

model-view-presenter/src/main/java/com/iluwatar/FileSelectorStub.java

@@ -0,0 +1,109 @@
+package com.iluwatar;
+
+/**
+ * Every instance of this class represents the Stub component in
+ * the Model-View-Presenter architectural pattern.
+ * 
+ * The stub implements the View interface and it is useful when
+ * we want the test the reaction to user events, such as mouse clicks.
+ * 
+ * Since we can not test the GUI directly, the MVP pattern provides
+ * this functionality through the View's dummy implementation, the Stub.
+ */
+public class FileSelectorStub implements FileSelectorView {
+
+	/**
+	 * Indicates whether or not the view is opened. 
+	 */
+	private boolean opened;
+	
+	/**
+	 * The presenter Component.
+	 */
+	private FileSelectorPresenter presenter;
+	
+	/**
+	 * The current name of the file.
+	 */
+	private String name;
+	
+	/**
+	 * Indicates the number of messages that were "displayed" to the user.
+	 */
+	private int numOfMessageSent;
+	
+	/**
+	 * Indicates if the data of the file where displayed or not.
+	 */
+	private boolean dataDisplayed;
+	
+	/**
+	 * Constructor
+	 */
+	public FileSelectorStub() {
+		this.opened = false;
+		this.presenter = null;
+		this.name = "";
+		this.numOfMessageSent = 0;
+		this.dataDisplayed = false;
+	}
+	
+	@Override
+	public void open() {
+		this.opened = true;
+	}
+
+	@Override
+	public void setPresenter(FileSelectorPresenter presenter) {
+		this.presenter = presenter;
+	}
+
+	@Override
+	public boolean isOpened() {
+		return this.opened;
+	}
+
+	@Override
+	public FileSelectorPresenter getPresenter() {
+		return this.presenter;
+	}
+
+	@Override
+	public String getFileName() {
+		return this.name;
+	}
+
+	@Override
+	public void setFileName(String name) {
+		this.name = name;
+	}
+
+	@Override
+	public void showMessage(String message) {
+		this.numOfMessageSent++;
+	}
+	
+	@Override
+	public void close() {
+		this.opened = false;
+	}
+
+	@Override
+	public void displayData(String data) {
+		this.dataDisplayed = true;
+	}
+	
+	/**
+	 * Returns the number of messages that were displayed to the user.
+	 */
+	public int getMessagesSent() {
+		return this.numOfMessageSent;
+	}
+	
+	/**
+	 * @return True if the data where displayed, false otherwise.
+	 */
+	public boolean dataDisplayed() {
+		return this.dataDisplayed;
+	}
+}

model-view-presenter/src/main/java/com/iluwatar/FileSelectorView.java

@@ -0,0 +1,62 @@
+package com.iluwatar;
+
+/**
+ * This interface represents the View component in the 
+ * Model-View-Presenter pattern. It can be implemented 
+ * by either the GUI components, or by the Stub.
+ */
+public interface FileSelectorView {
+	
+	/**
+	 * Opens the view.
+	 */
+	public void open();
+	
+	/**
+	 * Closes the view.
+	 */
+	public void close();
+	
+	/**
+	 * @return True, if the view is opened, false otherwise.
+	 */
+	public boolean isOpened();
+	
+	/**
+	 * Sets the presenter component, to the one given as parameter.
+	 * 
+	 * @param presenter The new presenter component.
+	 */
+	public void setPresenter(FileSelectorPresenter presenter);
+	
+	/**
+	 * @return The presenter Component.
+	 */
+	public FileSelectorPresenter getPresenter();
+	
+	/**
+	 * Sets the file's name, to the value given as parameter.
+	 * 
+	 * @param name The new name of the file.
+	 */
+	public void setFileName(String name);
+	
+	/**
+	 * @return The name of the file.
+	 */
+	public String getFileName();
+	
+	/**
+	 * Displays a message to the users.
+	 * 
+	 * @param message The message to be displayed.
+	 */
+	public void showMessage(String message);
+	
+	/**
+	 * Displays the data to the view.
+	 * 
+	 * @param data The data to be written.
+	 */
+	public void displayData(String data);
+}

model-view-presenter/src/main/java/com/iluwatar/MainApp.java

@@ -0,0 +1,12 @@
+package com.iluwatar;
+
+public class MainApp {
+	
+	public static void main(String[] args) {
+		FileLoader loader = new FileLoader();
+		FileSelectorJFrame jFrame = new FileSelectorJFrame();
+		FileSelectorPresenter presenter = new FileSelectorPresenter(jFrame);
+		presenter.setLoader(loader);
+		presenter.start();
+	}
+}

model-view-presenter/src/test/java/com/iluwatar/FileSelectorPresenterTest.java

@@ -0,0 +1,122 @@
+package com.iluwatar;
+
+import static org.junit.Assert.*;
+
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * This test case is responsible for testing our application
+ * by taking advantage of the Model-View-Controller architectural pattern.
+ */
+public class FileSelectorPresenterTest {
+	
+	/**
+	 * The Presenter component.
+	 */
+	private FileSelectorPresenter presenter;
+	
+	/**
+	 * The View component, implemented this time as a Stub!!!
+	 */
+	private FileSelectorStub stub;
+	
+	/**
+	 * The Model component.
+	 */
+	private FileLoader loader;
+	
+	
+	/**
+	 * Initializes the components of the test case.
+	 */
+	@Before
+	public void setUp() {
+		this.stub = new FileSelectorStub();
+		this.loader = new FileLoader();
+		presenter = new FileSelectorPresenter(this.stub);
+		presenter.setLoader(loader);
+	}
+	
+	/**
+	 * Tests if the Presenter was successfully connected with the View.
+	 */
+	@Test
+	public void wiring() {
+		presenter.start();
+		
+		assertNotNull(stub.getPresenter());
+		assertTrue(stub.isOpened());
+	}
+	
+	/**
+	 * Tests if the name of the file changes.
+	 */
+	@Test
+	public void updateFileNameToLoader() {
+		String EXPECTED_FILE = "Stamatis";
+		stub.setFileName(EXPECTED_FILE);
+		
+		presenter.start();
+		presenter.fileNameChanged();
+		
+		assertEquals(EXPECTED_FILE, loader.getFileName());
+	}
+	
+	/**
+	 * Tests if we receive a confirmation when we attempt to open a file
+	 * that it's name is null or an empty string.
+	 */
+	@Test
+	public void fileConfirmationWhenNameIsNull() {
+		stub.setFileName(null);
+		
+		presenter.start();
+		presenter.fileNameChanged();
+		presenter.confirmed();
+		
+		assertFalse(loader.isLoaded());
+		assertEquals(1, stub.getMessagesSent());
+	}
+	
+	/**
+	 * Tests if we receive a confirmation when we attempt to open a file
+	 * that it doesn't exist.
+	 */
+	@Test
+	public void fileConfirmationWhenFileDoesNotExist() {
+		stub.setFileName("RandomName.txt");
+		
+		presenter.start();
+		presenter.fileNameChanged();
+		presenter.confirmed();
+		
+		assertFalse(loader.isLoaded());
+		assertEquals(1, stub.getMessagesSent());
+	}
+	
+	/**
+	 * Tests if we can open the file, when it exists.
+	 */
+	@Test
+	public void fileConfirmationWhenFileExists() {
+		stub.setFileName("etc/data/test.txt");
+		presenter.start();
+		presenter.fileNameChanged();
+		presenter.confirmed();
+		
+		assertTrue(loader.isLoaded());
+		assertTrue(stub.dataDisplayed());
+	}
+	
+	/**
+	 * Tests if the view closes after cancellation.
+	 */
+	@Test
+	public void cancellation() {
+		presenter.start();
+		presenter.cancelled();
+		
+		assertFalse(stub.isOpened());
+	}
+}

pom.xml

@@ -36,6 +36,7 @@
     <module>iterator</module>
     <module>mediator</module>
     <module>memento</module>
+    <module>model-view-presenter</module>
     <module>observer</module>
     <module>state</module>
     <module>strategy</module>
@@ -59,4 +60,4 @@
 	</plugins>
 </build>
   
-</project>
+</project>