carfield.com.hk

Main.java

2004-03-24T16:00:00Z

package examples.memento.java;

/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This file is part of the design patterns project at UBC
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ca.ubc.cs.spl.patterns.
 *
 * Contributor(s): 
 */

/**
 * Implements the driver for the memento design pattern example. 
 *
 * Intent: Without violating encapsulation, capture and externalize an 
 * object's internal state so that the object can be restored to this state
 * later
 *
 * Participatng objects are <code>Memento</code> and <code>Originator</code>
 * 
 *
 * This example changes the state of the Originator five times, but
 * creates a Memento of it after the third change. After the 5 changes
 * are done, the Memento is used to restore the Originator's
 * state.
 *
 * This is the Java version. 
 *
 * Memento and Originator are tightly coupled.
 *
 * @author Jan Hannemann
 * @author Gregor Kiczales
 * @version 1.0, 07/13/02
 * 
 * @see Memento
 * @see Originator
 */

public class Main {
	
 /**
 * This example changes the state of the Originator five times, but
 * creates a Memento of it after the third change. After the 5 changes
 * are done, the Memento is used to restore the Originator's
 * state. 
 */
	
	public static void main(String[] args) { 
		
		Memento storedState = null;
		Originator counter = new Originator(); 
		
		for (int i=1; i<=5; i++) {
			counter.increment();
			counter.show(); 
			if (i==3) { storedState = counter.createMemento(); }
		}
		
		System.out.println("\nTrying to reinstate state (3)...");
		counter.setMemento(storedState);
		counter.show(); 
	}
}

Memento.java

2004-03-24T16:00:00Z

package examples.memento.java;

/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This file is part of the design patterns project at UBC
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ca.ubc.cs.spl.patterns.
 *
 * Contributor(s): 
 */

/**
 * Implements a sample Memento class. This particular menento stores
 * the counter of its originator (an int value), and returns it upon request.
 *
 * @author Jan Hannemann
 * @author Gregor Kiczales
 * @version 1.0, 07/13/02
 * 
 * @see Originator
 */

public class Memento { 
	
 /**
 * stores the originator's state
 */

	private int state;
	
 /**
 * Captures the originator's state and stores it
 *
 * @param newState the state to store
 */

	public void setState(int newState) { 
	 state = newState; 
	}
	
 /**
 * Returns the stored originator state
 *
 * @returns the stored state
 */

	public int getState() { 
	 return state; 
	} 
	
 /**
 * Creates a memento object specifically designed for this example
 *
 * @param init the initial state to store
 */

	public Memento(int init) {
		state = init;
	}
}

MyOriginator.java

2004-03-24T16:00:00Z

Originator.java

2004-03-24T16:00:00Z

package examples.memento.java;


/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This file is part of the design patterns project at UBC
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ca.ubc.cs.spl.patterns.
 *
 * Contributor(s): 
 */

/**
 * Implements a sample Originator class. Objects of this particular 
 * originator have stat: an int representing the number of time the <code>
 * increment()</code> method was called.
 *
 * @author Jan Hannemann
 * @author Gregor Kiczales
 * @version 1.0, 07/13/02
 * 
 * @see Memento
 */

public class Originator {
 
 /**
 * the number of times <code>increment()</code> was called on this object
 */

	protected int currentValue = 0;
	
 /**
 * increments the counter (this originator's state) by one
 */

	public void increment() { 
	 currentValue++; 
	}
	
 /**
 * Displays a the state of this originator
 */

	public void show() { 
	 System.out.println("Originator value is " + currentValue); 
	} 
	
 /**
 * Creates a memento from this originator, storing the current state
 */

	public Memento createMemento() { 
	 return new Memento(currentValue); 
	}
	
 /**
 * Restores this originator to former state stored by the memento passed
 *
 * @param m the memento that stores the prior state
 */

	public void setMemento(Memento m) { 
	 currentValue = m.getState(); 
	}
}

StateMemento.java

2004-03-24T16:00:00Z

package examples.memento.aspectj; 

/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This file is part of the design patterns project at UBC
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ca.ubc.cs.spl.patterns.
 *
 * Contributor(s): 
 */

import ca.ubc.cs.spl.pattern.library.Memento;
import ca.ubc.cs.spl.pattern.library.MementoException;
import ca.ubc.cs.spl.pattern.library.MementoProtocol;

/**
 * Implements an instance of the memento design pattern. 
 *
 * @author Jan Hannemann
 * @author Gregor Kiczales
 * @version 1.0, 07/13/02
 *
 * @see MyOriginator 
 */


public aspect StateMemento extends MementoProtocol { 

 /**
 * Assigns the Originator role to <code>MyOriginator</code>
 */

	declare parents: MyOriginator implements Originator; 

 /**
 * Creates a Memento object for an Originator. An anonymous
 * class is used to realize the Memento
 *
 * @param o the originator to create a memento for
 * @returns the memento storing the originator's state
 */

	public Memento createMementoFor(Originator o) {
	 if (o instanceof MyOriginator) { 
 		Memento m = new Memento() {
 			private Integer state;
 			
 			public void setState(Object state) {
 				this.state = (Integer) state;
 			}
 			
 			public Object getState() {
 				return state;
 			}
 		};
 		m.setState(new Integer(((MyOriginator)o).currentValue));
 		return m;
 	} else {
 	 throw new MementoException("Invalid originator");
 	}
	}
	
 /**
 * Restores this originator to former state using the memento passed
 *
 * @param o the originator to restore
 * @param m the memento that stores the prior state
 */

	public void setMemento(Originator o, Memento m) {
	 if (o instanceof MyOriginator) {
 		Integer integer = (Integer) m.getState(); 
	 	((MyOriginator)o).currentValue = integer.intValue();
 	} else {
 	 throw new MementoException("Invalid originator");
 	}
	}
}

files.lst

2004-03-24T16:00:00Z