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设计模式之备忘录模式

通用代码实现

class Originator {   //需要保存的属性，可以是多个  private String state = "";  public String getState() {   return state;  }  public void setState(String state) {   this.state = state;  }   //创建备忘录，将当前需要保存的信息导入并实例化出一个Memento对象  public Memento createMemento(){   return new Memento(this.state);  }     //回复备忘录，将Memento导入并将相关数据恢复  public void restoreMemento(Memento memento){         this.setState(memento.getState());  } }

class Memento {   private String state = "";  public Memento(String state){   this.state = state;  }  public String getState() {   return state;  }  public void setState(String state) {               this.state = state;  } }

class Caretaker {  private Memento memento;  public Memento getMemento(){   return memento;  }   public void setMemento(Memento memento){           this.memento = memento;  } }

public class Client {  public static void main(String[] args){   Originator originator = new Originator();   originator.setState("状态1");   System.out.println("初始状态:"+originator.getState());   Caretaker caretaker = new Caretaker();   caretaker.setMemento(originator.createMemento());   originator.setState("状态2");   System.out.println("改变后状态:"+originator.getState());   originator.restoreMemento(caretaker.getMemento());   System.out.println("恢复后状态:"+originator.getState());      } }

代码演示了一个单状态单备份的例子，逻辑非常简单：Originator类中的state变量需要备份，以便在需要的时候恢复；Memento类中，也有一个state变量，用来存储Originator类中state变量的临时状态；而Caretaker类就是用来管理备忘录类的，用来向备忘录对象中写入状态或者取回状态。

举例说明：

以保存游戏进度为例，在游戏角色大战Boss前将该角色的状态存储，与Boss作战后角色的各项能力会下降，如果没有通关，则可利用备忘录进行恢复到战前状态。

游戏角色类：

package com.zyh.designpattern.memento; public class PlayRole { private int vitality; private int aggressivity; private int defencivity; public PlayRole(int vitality, int aggressivity, int defencivity) { super(); this.vitality = vitality; this.aggressivity = aggressivity; this.defencivity = defencivity; } public PlayRole() {} public int getVitality() { return vitality; } public void setVitality(int vitality) { this.vitality = vitality; } public int getAggressivity() { return aggressivity; } public void setAggressivity(int aggressivity) { this.aggressivity = aggressivity; } public int getDefencivity() { return defencivity; } public void setDefencivity(int defencivity) { this.defencivity = defencivity; } //增加“保存角色状态的方法”，将游戏角色的三个状态值通过实例化“角色状态存储箱”返回 public RoleMemento createMemento() { RoleMemento memento = new RoleMemento(); memento.setAggressivity(aggressivity); memento.setDefencivity(defencivity); memento.setVitality(vitality); return memento; }  //新增“恢复角色状态”方法，可将外部的“角色状态存储箱”中状态值恢复给游戏角色 public void setMemento(RoleMemento memento) { this.aggressivity = memento.getAggressivity(); this.defencivity = memento.getDefencivity(); this.vitality = memento.getVitality(); } public void showState() { System.out.println("攻击力：" + this.aggressivity + "|防御力：" + this.defencivity + "|生命力：" + this.vitality); } }

备忘录类：

package com.zyh.designpattern.memento;                                                                            public class RoleMemento { private int vitality; private int aggressivity; private int defencivity; public int getVitality() { return vitality; } public void setVitality(int vitality) { this.vitality = vitality; } public int getAggressivity() { return aggressivity; } public void setAggressivity(int aggressivity) { this.aggressivity = aggressivity; } public int getDefencivity() { return defencivity; } public void setDefencivity(int defencivity) { this.defencivity = defencivity; } }

管理者类

package com.zyh.designpattern.memento;                                                                            public class Caretaker { RoleMemento memento; public RoleMemento getMemento() { return memento; } public void setMemento(RoleMemento memento) { this.memento = memento; } }

客户端：

package com.zyh.designpattern.memento;                                                                            public class Client { public static void main(String[] args) { // 测试程序 // 新建角色 PlayRole role = new PlayRole(100, 100, 100); // 新建管理者 Caretaker taker = new Caretaker(); // 角色初始状态 System.out.println("游戏刚开始，角色各属性:"); role.showState(); // 利用备忘录模式保存当前状态 System.out.println("/n【保存游戏状态！】/n"); taker.setMemento(role.createMemento()); role.setAggressivity(20); role.setDefencivity(30); role.setVitality(0); // 大战过后，角色能力值下降 System.out.println("与Boss对战后，角色各项能力已大大下降:"); role.showState(); // 恢复保存的角色状态 role.setMemento(taker.getMemento()); System.out.println("/n【恢复保存的角色状态！】"); System.out.println("/n恢复后角色的当前状态："); role.showState(); } }