Java design patterns learning - memo mode

Disclaimer: This article is a blogger original article, shall not be reproduced without the bloggers allowed. https://blog.csdn.net/qq_40646143/article/details/85532310

Memo mode core is:

• Save a copy of the internal state of an object, so that later you can return the object to its original state.

Next, using the code to implement

1) create a primary class

/**
 * 原发器类
 */
public class Emp {

    private String name;
    private int age;
    private int salary;

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

    /**
     * 回滚到上一个保存节点
     * @param empMemento
     */
    public void recovery(EmpMemento empMemento){
    this.name=empMemento.getName();
    this.age=empMemento.getAge();
    this.salary=empMemento.getSalary();
    }



    public Emp(String name, int age, int salary) {
        this.name = name;
        this.age = age;
        this.salary = salary;
    }




    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

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

    public int getSalary() {
        return salary;
    }

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

 

2) Create a memo class

/**备忘录类
 * @author 晓电脑
 */
public class EmpMemento {

    private String name;
    private int age;
    private int salary;

    /**
     * 进行备份
     * @param emp
     */
    public EmpMemento(Emp emp) {
        this.name=emp.getName();
        this.age=emp.getAge();
        this.salary=emp.getSalary();
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

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

    public int getSalary() {
        return salary;
    }

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

3) Create responsible for human

import java.util.ArrayList;
import java.util.List;

/**负责人类 负责管理备忘录对象
 * @author 晓电脑
 */
public class CareTasker {


    private EmpMemento empMemento;
    //如果保存很多次
    //private List<EmpMemento> lists = new ArrayList<>();

    public EmpMemento getEmpMemento() {
        return empMemento;
    }

    public void setEmpMemento(EmpMemento empMemento) {
        this.empMemento = empMemento;
    }
}

 

4) Create a client for testing

public class Client {
    public static void main (String[] args) {

        CareTasker tasker = new CareTasker();


        //创建一个对象
        Emp emp = new Emp("zs", 18, 2800);
        System.out.println("第一次打印:" + emp.getName() + emp.getAge() + emp.getSalary());

        //进行备份
        tasker.setEmpMemento(emp.memento());

         emp.setName("www");
         emp.setAge(19);
         emp.setSalary(5000);
        System.out.println("第二次打印:" + emp.getName() + emp.getAge() + emp.getSalary());

        System.out.println("################");
        emp.recovery(tasker.getEmpMemento());

        System.out.println("第三次打印:" + emp.getName() + emp.getAge() + emp.getSalary());

    }
}

 

operation result

FIG class uml

                 

 

When the memo point relatively long time:

The memorandum push

public class CareTaker{

    private Memento memento;

    private Stack<Memento> stacks = new Stack<Memento>();

}

• A plurality of memo object sequence and persistence

 

Development of common scenarios:

• Common software, undo
• Database software, management of things, rollback
• PS software, history