21.备忘录模式

核心
-就是保存某个对象内部状态的拷贝，这样以后就可以将该对象回复到原先的状态。



结构：

源发器类Originator

备忘录类Memento

负责人类CareTaker

开发中常见的应用场景

-棋类游戏中的，悔棋

-普通软件中的，撤销操作

-数据库软件中的，事务管理中的，回滚操作
-Photoshop软件中的，历史记录

/**
* 源发器类(员工)
*
* @author Administrator
*
*/
public class Emp {
private String ename;
private int age;
private double salary;

//进行备忘录操作，并返回备忘录对象
public EmpMemento memento() {
return new EmpMemento(this);
}

//进行数据的回复，回复成指定备忘录对象的值
public void recovery(EmpMemento mmt) {
this.ename = mmt.getEname();
this.age = mmt.getAge();
this.salary = mmt.getSalary();
}

public Emp(String ename, int age, double salary) {
super();
this.ename = ename;
this.age = age;
this.salary = salary;
}

public String getEname() {
return ename;
}

public void setEname(String ename) {
this.ename = ename;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public double getSalary() {
return salary;
}

public void setSalary(double salary) {
this.salary = salary;
}

}

/**
* 备忘录类
* @author Administrator
*
*/
public class EmpMemento {
private String ename;
private int age;
private double salary;

public EmpMemento(Emp e) {
this.ename = e.getEname();
this.age = e.getAge();
this.salary = e.getSalary();
}

public String getEname() {
return ename;
}

public void setEname(String ename) {
this.ename = ename;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public double getSalary() {
return salary;
}

public void setSalary(double salary) {
this.salary = salary;
}

}

/**
* 负责人类
* 负责管理备忘录对象
* @author Administrator
*
*/
public class CareTaker {

private EmpMemento memento;

public EmpMemento getMemento() {
return memento;
}

public void setMemento(EmpMemento memento) {
this.memento = memento;
}

}

public class Client {
public static void main(String[] args) {
CareTaker taker = new CareTaker();

Emp emp = new Emp("melon",23,7000);
System.out.println("第一次创建对象:" + emp.getEname() + ",工资:" + emp.getSalary()+",年龄:" + emp.getAge());

taker.setMemento(emp.memento());

emp.setAge(25);
emp.setEname("melon2");
emp.setSalary(12000);
System.out.println("改变的对象:" + emp.getEname() + ",工资:" + emp.getSalary()+",年龄:" + emp.getAge());

emp.recovery(taker.getMemento());
System.out.println("恢复后的对象:" + emp.getEname() + ",工资:" + emp.getSalary()+",年龄:" + emp.getAge());
}
}