备忘录模式
备忘录模式（Memento Pattern）保存一个对象的某个状态，以便在适当的时候恢复对象。
备忘录模式属于行为型模式。
实际案例
类信息概览：
| 类名 | 说明 |
|---|---|
| Main.java | 方法的总入口 |
| Memento.java | 记忆者 |
| MementoManager.java | 记忆管理者 |
| Original.java | 原始内容 |
定义
- Memento.java
package com.ryo.design.pattern.note.memento;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/17
* @since 1.7
*/
public 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;
}
}
- MementoManager.java
package com.ryo.design.pattern.note.memento;
import java.util.LinkedList;
import java.util.List;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/17
* @since 1.7
*/
public class MementoManager {
private List<Memento> mementoList = new LinkedList<>();
public void add(Memento memento) {
this.mementoList.add(memento);
}
public Memento get(int index) {
return mementoList.get(index);
}
}
- Original.java
package com.ryo.design.pattern.note.memento;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/17
* @since 1.7
*/
public class Original {
private String state;
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
//-------------------public method;
/**
* 保存到 记忆体中
* @return
*/
public Memento saveToMemento() {
return new Memento(this.getState());
}
/**
* 从记忆体中获取对应的状态
* @param memento
*/
public void getStateFromMemento(Memento memento) {
String state = memento.getState();
this.state = state;;
}
}
测试
- Main.java
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
* Copyright (c) 2012-2018. houbinbini Inc.
* design-pattern All rights reserved.
*/
package com.ryo.design.pattern.note.memento;
/**
* <p> </p>
*
* <pre> Created: 2018/5/23 下午8:46 </pre>
* <pre> Project: design-pattern </pre>
*
* @author houbinbin
* @version 1.0
* @since JDK 1.7
*/
public class Main {
public static void main(String[] args) {
Original original = new Original();
MementoManager manager = new MementoManager();
original.setState("State #1");
original.setState("State #2");
manager.add(original.saveToMemento());
original.setState("State #3");
manager.add(original.saveToMemento());
original.setState("State #4");
System.out.println("Current State: " + original.getState());
original.getStateFromMemento(manager.get(0));
System.out.println("First saved State: " + original.getState());
original.getStateFromMemento(manager.get(1));
System.out.println("Second saved State: " + original.getState());
}
}
- 测试结果
Current State: State #4
First saved State: State #2
Second saved State: State #3
实现方式
UML & Code
UML
UML 图示如下
Code
代码地址
