备忘录模式

1.定义：保存一个对象的某个状态，以便在适当的时候恢复对象，即“后悔药”。

2.类型：行为型

3.适用场景：保存及恢复数据相关业务场景；后悔的时候，即想恢复到之前的状态。

4.优点：为用户提供一种可恢复机制；存档信息的封装。

5.缺点：资源占用

6.相关设计模式：状态模式

7.实例目录package

8.实例UML类图

9.代码

package com.geely.design.pattern.behavioral.memento;

public class Article {
    private String title;
    private String content;
    private String imgs;

    public Article(String title, String content, String imgs) {
        this.title = title;
        this.content = content;
        this.imgs = imgs;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getImgs() {
        return imgs;
    }

    public void setImgs(String imgs) {
        this.imgs = imgs;
    }

    public ArticleMemento saveToMemento(){
        ArticleMemento articleMemento = new ArticleMemento(this.title,this.content,this.imgs);
        return articleMemento;
    }

    public void undoFromMemento(ArticleMemento articleMemento){
        this.title = articleMemento.getTitle();
        this.content = articleMemento.getContent();
        this.imgs = articleMemento.getImgs();
    }

    @Override
    public String toString() {
        return "Article{" +
                "title='" + title + "'" +
                ", content='" + content +"'" +
                ", imgs='" + imgs + "'" +
                "}";
    }
}

package com.geely.design.pattern.behavioral.memento;

public class ArticleMemento {
    private String title;
    private String content;
    private String imgs;

    public ArticleMemento(String title, String content, String imgs) {
        this.title = title;
        this.content = content;
        this.imgs = imgs;
    }

    public String getTitle() {
        return title;
    }

    public String getContent() {
        return content;
    }

    public String getImgs() {
        return imgs;
    }
    @Override
    public String toString() {
        return "ArticleMemento{" +
                "title='" + title + "'" +
                ", content='" + content +"'" +
                ", imgs='" + imgs + "'" +
                "}";
    }
}

package com.geely.design.pattern.behavioral.memento;

import java.util.Stack;

public class ArticleMementoManager {

    private final Stack<ArticleMemento> ARTICLE_MEMENTO = new Stack<>();
    public ArticleMemento getMemento(){
        ArticleMemento articleMemento = ARTICLE_MEMENTO.pop();
        return articleMemento;
    }

    public void addMemento(ArticleMemento articleMemento){
        ARTICLE_MEMENTO.push(articleMemento);
    }
}

package com.geely.design.pattern.behavioral.memento;

public class Test {
    public static void main(String[] args) {
        ArticleMementoManager articleMementoManager = new ArticleMementoManager();
        Article article = new Article("如影随行的设计模式A","手记内容A","手记图片A");
        ArticleMemento articleMemento = article.saveToMemento();
        articleMementoManager.addMemento(articleMemento);
        System.out.println("标题："+article.getTitle()+"内容："+article.getContent()+"图片：" + article.getImgs());
        System.out.println("手记完整信息：" + article);

        System.out.println("修改手记start");
        article.setTitle("如影随行的设计模式B");
        article.setContent("手记内容B");
        article.setImgs("手记图片B");
        System.out.println("修改手记end");
        System.out.println("手记完整信息：" + article);

        articleMemento = article.saveToMemento();
        articleMementoManager.addMemento(articleMemento);

        System.out.println("暂存回退start");
        System.out.println("回退出栈1次");
        articleMemento = articleMementoManager.getMemento();
        article.undoFromMemento(articleMemento);
        System.out.println("手记完整信息：" + article);

        System.out.println("回退出栈2次");
        articleMemento = articleMementoManager.getMemento();
        article.undoFromMemento(articleMemento);

        System.out.println("暂存回退end");
        System.out.println("手记完整信息：" + article);
    }
}