设计模式读书笔记之备忘录模式(Memento)

备忘录模式：在不破坏封装性的前提下，捕获对象的内部状态并保存，这样以后就可以恢复该对象恢复到保存的状态。



备忘录模式比较简单,　不要因为名字比较陌生而不敢学它.　它没有复杂的结构,　上图已经能足够说明问题.

Originator: 备忘录发起人,　通常是需要备忘的对象自己.

Memento: 备忘录对象, 保存了Originator的内部状态.

CareTaker: 备忘录管理者.

基本代码：

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//备忘录发起人，即需要备忘的对象

package designpattern.memento;

public class Originator {

private String state;

public String getState() {

return state;

}

public void setState(String state) {

this.state = state;

}

public Memento createMemo(){

return new Memento(state);

}

public void recover(Memento m){

this.state = m.getState();

}

public void show(){

System.out.println("state = " + state);

}

}

//备忘录

package designpattern.memento;

public class Memento {

private String state;

public String getState() {

return state;

}

public Memento(String state){

this.state = state;

}

}

//备忘录管理者

package designpattern.memento;

public class CareTaker {

private Memento memento;

public Memento getMemento() {

return memento;

}

public void setMemento(Memento memento) {

this.memento = memento;

}

}

//test case

package designpattern.memento;

public class Test {

public static void main(String[] args) {

Originator o = new Originator();

o.setState("On");

o.show();

CareTaker c = new CareTaker();

c.setMemento(o.createMemo());

o.setState("Off");

o.show();

o.recover(c.getMemento());

o.show();

}

}

举例：

打rpg游戏的时候经常在打大boss之前把游戏保存一下，如果死了，就重新来。其实这就是备忘录模式。看代码：

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package designpattern.memento.game;

public class GameRole {

private int vitality;

private int attack;

private int defense;

public GameRole(){

this.vitality = 100;

this.attack = 100;

this.defense = 100;

}

public void showState(){

System.out.println("vitality = " + vitality + "/nattack = " + attack + "/ndefence = " + defense);

}

public RoleStateMemo save(){

return new RoleStateMemo(vitality, attack, defense);

}

public void recover(RoleStateMemo m){

System.out.println("太菜了我，还好我存盘了，哈哈。");

System.out.println("复活中......");

this.vitality = m.getVitality();

this.attack = m.getAttack();

this.defense = m.getDefense();

System.out.println("又复活了.");

}

public void fight(){

System.out.println("与大Boss决战./n......");

System.out.println("你输了, 你的生命，防御, 战斗力都将减为0.");

this.vitality = 0;

this.defense = 0;

this.attack = 0;

}

}

//

package designpattern.memento.game;

public class RoleStateMemo {

private int vitality;

private int attack;

private int defense;

public RoleStateMemo(int v, int a, int d){

this.vitality = v;

this.attack = a;

this.defense = d;

}

public int getVitality() {

return vitality;

}

public void setVitality(int vitality) {

this.vitality = vitality;

}

public int getAttack() {

return attack;

}

public void setAttack(int attack) {

this.attack = attack;

}

public int getDefense() {

return defense;

}

public void setDefense(int defense) {

this.defense = defense;

}

}

//

package designpattern.memento.game;

public class RoleMemoManager {

private RoleStateMemo m;

public RoleStateMemo getM() {

return m;

}

public void setM(RoleStateMemo m) {

this.m = m;

}

}

//test case

package designpattern.memento.game;

public class Test {

public static void main(String[] args) {

GameRole role = new GameRole();

role.showState();

RoleMemoManager manager = new RoleMemoManager();

manager.setM(role.save());

role.fight();

role.showState();

role.recover(manager.getM());

role.showState();

}

}

适用情景：

需要维护或记录历史的类。