設(shè)計(jì)模式之備忘錄模式

備忘錄模式（Memento Pattern）官方的定義是這樣的：
在不破壞封閉的前提下，捕獲一個(gè)對(duì)象的內(nèi)部狀態(tài)，并在該對(duì)象之外保存這個(gè)狀態(tài)。這樣以后就可將該對(duì)象恢復(fù)到原先保存的狀態(tài)。它是面向?qū)ο蟮?3種設(shè)計(jì)模式中的一種，屬于行為模式的范圍。
直白點(diǎn)說(shuō)就是：
我們可以在不暴露更多字段的前提下，直接將某個(gè)對(duì)象保存到其他地方，可以是磁盤(pán)，也可以是內(nèi)存。
有些地方也將之稱(chēng)為快照模式，就是給當(dāng)前對(duì)象做一個(gè)快照。

一般我們將備忘錄模式定義為3個(gè)組成角色：
1、Originator 發(fā)起人，有些人將他翻譯為原發(fā)器，我是非常不認(rèn)同的。
什么叫原發(fā)器？本人查了辭海等在線(xiàn)網(wǎng)站，壓根就沒(méi)有這個(gè)詞，我非常不人認(rèn)同最初的譯者，憑感覺(jué)隨意造詞。
Originator 查詢(xún)了谷歌翻譯(防盜連接：本文首發(fā)自http://www.rzrgm.cn/jilodream/ )
a person who creates or initiates something.
大概可以理解為創(chuàng)始人或者是最初發(fā)起某個(gè)事情的人，所以這里可以理解為驅(qū)動(dòng)、發(fā)起生成備忘錄的角色。
2、Memento 備忘錄，用來(lái)存儲(chǔ)要保存對(duì)象的內(nèi)部狀態(tài)，也就是快照。
3、Caretaker 負(fù)責(zé)人負(fù)責(zé)保存和管理備忘錄的。

下面我們寫(xiě)一個(gè)例子，
背景：模仿超級(jí)馬里奧，可以吃金幣，移動(dòng)

主類(lèi)：

 1 package com.example.demo.learn.pattern.behavior.memento;
 2 
 3 import com.alibaba.nacos.shaded.com.google.common.collect.Maps;
 4 
 5 import java.util.Map;
 6 
 7 /**
 8  * @discription
 9  */
10 public class RecordSystem {
11 
12     private static Map<String, String> recordMap = Maps.newHashMap();
13 
14     public static void saveRecord(MapInfo mapInfo, String index) {
15         recordMap.put(index, mapInfo.saveRecord());
16     }
17 
18     public static MapInfo getRecord(String time) {
19         if (recordMap.containsKey(time)) {
20             return MapInfo.loadRecord(recordMap.get(time));
21         }
22         return null;
23     }
24 }

游戲內(nèi)容類(lèi)：

 1 package com.example.demo.learn.pattern.behavior.memento;
 2 
 3 import com.alibaba.fastjson.JSON;
 4 import lombok.Data;
 5 
 6 /**
 7  * @discription
 8  */
 9 @Data
10 public class MapInfo {
11     private Location marioLocation = new Location(0, 100, 1);
12     private int golden = 0;
13 
14     public void touchGolden() {
15         golden++;
16     }
17 
18     public void marioMove(int xv, int yv) {
19         int newX = marioLocation.getX() + xv;
20         marioLocation.setX(newX);
21 
22         int newY = marioLocation.getY() + yv;
23         marioLocation.setY(newY);
24     }
25 
26     //馬里奧調(diào)頭
27     public void marioTuneBack() {
28         int forward = marioLocation.getForward() * -1;
29         marioLocation.setX(forward);
30     }
31 
32     public String saveRecord() {
33         return JSON.toJSONString(marioLocation) + ";" + golden;
34     }
35 
36     public static MapInfo loadRecord(String recordContent) {
37         String[] contents = recordContent.split(";");
38         MapInfo mapInfo = new MapInfo();
39         Location marioLocation = JSON.parseObject(contents[0], Location.class);
40         mapInfo.setMarioLocation(marioLocation);
41         mapInfo.setGolden(Integer.valueOf(contents[1]));
42         return mapInfo;
43     }
44 
45     public static MapInfo initMap() {
46         MapInfo mapInfo = new MapInfo();
47         return mapInfo;
48     }
49 }

package com.example.demo.learn.pattern.behavior.memento;

import lombok.AllArgsConstructor;
import lombok.Data;

/**
 * @discription
 */

@AllArgsConstructor
@Data
public class Location {
    //坐標(biāo)
    private int x;
    //坐標(biāo)
    private int y;

    //方向 -1向左，1向右
    private int forward;
}

游戲記錄存儲(chǔ)

 1 package com.example.demo.learn.pattern.behavior.memento;
 2 
 3 import com.alibaba.nacos.shaded.com.google.common.collect.Maps;
 4 
 5 import java.util.Map;
 6 
 7 /**
 8  * @discription
 9  */
10 public class RecordSystem {
11 
12     private static Map<String, String> recordMap = Maps.newHashMap();
13 
14     public static void saveRecord(MapInfo mapInfo, String index) {
15         recordMap.put(index, mapInfo.saveRecord());
16     }
17 
18     public static MapInfo getRecord(String time) {
19         if (recordMap.containsKey(time)) {
20             return MapInfo.loadRecord(recordMap.get(time));
21         }
22         return null;
23     }
24 }

輸出大概是這樣：

"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:E:\Program Files\JetBrains\IntelliJ IDEA 2023.2\lib\idea_rt.jar=65256:E:\Program Files\JetBrains\IntelliJ IDEA 2023.2\bin" -Dfile.encoding=UTF-8 -classpath E:\code\common\learn-design-pattern\target\classes;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter\2.6.15\spring-boot-starter-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot\2.6.15\spring-boot-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-autoconfigure\2.6.15\spring-boot-autoconfigure-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter-logging\2.6.15\spring-boot-starter-logging-2.6.15.jar;E:\Maven\learnDesignPattenRepo\ch\qos\logback\logback-classic\1.2.12\logback-classic-1.2.12.jar;E:\Maven\learnDesignPattenRepo\ch\qos\logback\logback-core\1.2.12\logback-core-1.2.12.jar;E:\Maven\learnDesignPattenRepo\org\slf4j\slf4j-api\1.7.36\slf4j-api-1.7.36.jar;E:\Maven\learnDesignPattenRepo\org\apache\logging\log4j\log4j-to-slf4j\2.17.2\log4j-to-slf4j-2.17.2.jar;E:\Maven\learnDesignPattenRepo\org\apache\logging\log4j\log4j-api\2.17.2\log4j-api-2.17.2.jar;E:\Maven\learnDesignPattenRepo\org\slf4j\jul-to-slf4j\1.7.36\jul-to-slf4j-1.7.36.jar;E:\Maven\learnDesignPattenRepo\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-core\5.3.27\spring-core-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-jcl\5.3.27\spring-jcl-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\yaml\snakeyaml\1.29\snakeyaml-1.29.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter-web\2.6.15\spring-boot-starter-web-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter-json\2.6.15\spring-boot-starter-json-2.6.15.jar;E:\Maven\learnDesignPattenRepo\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.13.5\jackson-datatype-jdk8-2.13.5.jar;E:\Maven\learnDesignPattenRepo\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.13.5\jackson-datatype-jsr310-2.13.5.jar;E:\Maven\learnDesignPattenRepo\com\fasterxml\jackson\module\jackson-module-parameter-names\2.13.5\jackson-module-parameter-names-2.13.5.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter-tomcat\2.6.15\spring-boot-starter-tomcat-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\apache\tomcat\embed\tomcat-embed-core\9.0.75\tomcat-embed-core-9.0.75.jar;E:\Maven\learnDesignPattenRepo\org\apache\tomcat\embed\tomcat-embed-el\9.0.75\tomcat-embed-el-9.0.75.jar;E:\Maven\learnDesignPattenRepo\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.75\tomcat-embed-websocket-9.0.75.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-web\5.3.27\spring-web-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-beans\5.3.27\spring-beans-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-webmvc\5.3.27\spring-webmvc-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-expression\5.3.27\spring-expression-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-test\2.6.15\spring-boot-test-2.6.15.jar;E:\Maven\learnDesignPattenRepo\junit\junit\4.13.2\junit-4.13.2.jar;E:\Maven\learnDesignPattenRepo\org\hamcrest\hamcrest-core\2.2\hamcrest-core-2.2.jar;E:\Maven\learnDesignPattenRepo\org\hamcrest\hamcrest\2.2\hamcrest-2.2.jar;E:\Maven\learnDesignPattenRepo\org\apache\commons\commons-lang3\3.13.0\commons-lang3-3.13.0.jar;E:\Maven\learnDesignPattenRepo\com\alibaba\nacos\nacos-spring-context\1.1.1\nacos-spring-context-1.1.1.jar;E:\Maven\learnDesignPattenRepo\javax\annotation\javax.annotation-api\1.3.2\javax.annotation-api-1.3.2.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-context\5.3.27\spring-context-5.3.27.jar;E:\Maven\learnDesignPattenRepo\com\alibaba\spring\spring-context-support\1.0.11\spring-context-support-1.0.11.jar;E:\Maven\learnDesignPattenRepo\org\projectlombok\lombok\1.18.30\lombok-1.18.30.jar;E:\Maven\learnDesignPattenRepo\com\alibaba\fastjson\1.2.83\fastjson-1.2.83.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter-aop\2.6.15\spring-boot-starter-aop-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-aop\5.3.27\spring-aop-5.3.27.jar;E:\Maven\learnDesignPattenRepo\cglib\cglib\3.1\cglib-3.1.jar;E:\Maven\learnDesignPattenRepo\org\ow2\asm\asm\4.2\asm-4.2.jar;E:\Maven\learnDesignPattenRepo\org\springframework\boot\spring-boot-starter-amqp\2.6.15\spring-boot-starter-amqp-2.6.15.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-messaging\5.3.27\spring-messaging-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\springframework\amqp\spring-rabbit\2.4.12\spring-rabbit-2.4.12.jar;E:\Maven\learnDesignPattenRepo\org\springframework\amqp\spring-amqp\2.4.12\spring-amqp-2.4.12.jar;E:\Maven\learnDesignPattenRepo\org\springframework\retry\spring-retry\1.3.4\spring-retry-1.3.4.jar;E:\Maven\learnDesignPattenRepo\com\rabbitmq\amqp-client\5.13.1\amqp-client-5.13.1.jar;E:\Maven\learnDesignPattenRepo\org\springframework\spring-tx\5.3.27\spring-tx-5.3.27.jar;E:\Maven\learnDesignPattenRepo\org\aspectj\aspectjweaver\1.9.7\aspectjweaver-1.9.7.jar;E:\Maven\learnDesignPattenRepo\com\alibaba\nacos\nacos-client\2.2.0\nacos-client-2.2.0.jar;E:\Maven\learnDesignPattenRepo\com\alibaba\nacos\nacos-auth-plugin\2.2.0\nacos-auth-plugin-2.2.0.jar;E:\Maven\learnDesignPattenRepo\com\alibaba\nacos\nacos-encryption-plugin\2.2.0\nacos-encryption-plugin-2.2.0.jar;E:\Maven\learnDesignPattenRepo\commons-codec\commons-codec\1.15\commons-codec-1.15.jar;E:\Maven\learnDesignPattenRepo\com\fasterxml\jackson\core\jackson-core\2.13.5\jackson-core-2.13.5.jar;E:\Maven\learnDesignPattenRepo\com\fasterxml\jackson\core\jackson-databind\2.13.5\jackson-databind-2.13.5.jar;E:\Maven\learnDesignPattenRepo\com\fasterxml\jackson\core\jackson-annotations\2.13.5\jackson-annotations-2.13.5.jar;E:\Maven\learnDesignPattenRepo\org\apache\httpcomponents\httpasyncclient\4.1.5\httpasyncclient-4.1.5.jar;E:\Maven\learnDesignPattenRepo\org\apache\httpcomponents\httpcore\4.4.16\httpcore-4.4.16.jar;E:\Maven\learnDesignPattenRepo\org\apache\httpcomponents\httpcore-nio\4.4.16\httpcore-nio-4.4.16.jar;E:\Maven\learnDesignPattenRepo\org\apache\httpcomponents\httpclient\4.5.14\httpclient-4.5.14.jar;E:\Maven\learnDesignPattenRepo\io\prometheus\simpleclient\0.12.0\simpleclient-0.12.0.jar;E:\Maven\learnDesignPattenRepo\io\prometheus\simpleclient_tracer_otel\0.12.0\simpleclient_tracer_otel-0.12.0.jar;E:\Maven\learnDesignPattenRepo\io\prometheus\simpleclient_tracer_common\0.12.0\simpleclient_tracer_common-0.12.0.jar;E:\Maven\learnDesignPattenRepo\io\prometheus\simpleclient_tracer_otel_agent\0.12.0\simpleclient_tracer_otel_agent-0.12.0.jar com.example.demo.learn.pattern.behavior.memento.PatternMain
16:10:40.045 [main] WARN com.example.demo.learn.pattern.behavior.memento.PatternMain - 存檔中。。。
16:10:40.173 [main] WARN com.example.demo.learn.pattern.behavior.memento.PatternMain - 1號(hào)存檔已完成。。。
16:10:40.173 [main] WARN com.example.demo.learn.pattern.behavior.memento.PatternMain (防盜連接：本文首發(fā)自http://www.rzrgm.cn/jilodream/ )- 存檔中。。。
16:10:40.173 [main] WARN com.example.demo.learn.pattern.behavior.memento.PatternMain - 2號(hào)存檔已完成。。。
16:10:40.173 [main] WARN com.example.demo.learn.pattern.behavior.memento.PatternMain - 讀檔中。。。
16:10:40.192 [main] WARN com.example.demo.learn.pattern.behavior.memento.PatternMain - 1號(hào)讀檔已完成。。。

Process finished with exit code 0

在這個(gè)例子中 MapInfo 擁有了所有內(nèi)部狀態(tài)屬性，但是并不直接暴露出來(lái)，我們通過(guò)它的save接口，來(lái)獲取對(duì)象的所有狀態(tài)。

這個(gè)例子中它負(fù)責(zé)發(fā)起數(shù)據(jù)的保存，充當(dāng)了Originator的角色；
而RecordSystem類(lèi)，負(fù)責(zé)管理和保存?zhèn)渫泴儆赾aretaker角色。
RecordSystem類(lèi)中的 recordMap，負(fù)責(zé)充當(dāng)備忘錄的角色，也就是保存快照的對(duì)象；

posted @ 2024-09-02 18:50 王若伊_恩賜解脫閱讀(96) 評(píng)論(0) 收藏舉報(bào)

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設(shè)計(jì)模式之備忘錄模式

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