备忘录模式

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定义：在不破坏封装性的前提下，捕获一个对象的内部状态，并咋该对象之外保存这个状态

类图：

代码：

public class Originator {

	private String state = "";
	
	public String getState(){
		return state;
	}
	
	public void setState(String state){
		this.state  =state;
	}
	
	public Memento createMemento(){
		return new Memento(this.state);
	}
	
	public void restoreMemento(Memento memento){
		setState(memento.getState());
	}
}

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;
	}
	
}

public 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();
		Caretaker caretaker = new Caretaker();
		caretaker.setMemento(originator.createMemento());
		originator.restoreMemento(caretaker.getMemento());
	}
}

clone方式的备忘录

类图：

代码：

public class Originator implements Cloneable{

	private String state = "";
	
	private Originator backup;
	
	public String getState(){
		return state;
	}
	
	public void setState(String state){
		this.state  =state;
	}
	
	public void createMemento(){
		backup =  this.clone();
	}
	
	public void restoreMemento(){
		this.setState(backup.state);
	}
	
	@Override
	protected Originator clone(){
		try{
			return (Originator) super.clone();
		}catch(Exception e){
			e.printStackTrace();
		}
		return null;
	}
}

多种状态备忘录模式

实现思路：通过反射方式，将各个状态的getter和setter方法以及各个状态保存在map中，而Memento中存储这个map

更好的封装：

目的：防止备份被修改

类图：

public class Originator {

	private String state = "";
	
	public String getState(){
		return state;
	}
	
	public void setState(String state){
		this.state  =state;
	}
	
	public Memento createMemento(){
		return new Memento(state);
	}
	
	public void restoreMemento(IMemento imemento){
		setState(((Memento) imemento).getState());
	}
	
	private class Memento implements IMemento{
		private String state = "";
		
		private Memento(String state){
			this.state = state;
		}
		
		private String getState(){
			return state;
		}
		
		private void setState(String state){
			this.state = state;
		}
	}
	
	
}

备忘录模式

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原文地址：http://blog.csdn.net/renpengddxx/article/details/52143030