Redis高效实现点赞、取消点赞只需这四步

来自：掘金，作者：solocoder
本文链接：https://mp.weixin.qq.com/s/v4R6PuMjDJxlqyakw1QgLg

本文基于 SpringCloud, 用户发起点赞、取消点赞后先存入 Redis 中，再每隔两小时从 Redis 读取点赞数据写入数据库中做持久化存储。

点赞功能在很多系统中都有，但别看功能小，想要做好需要考虑的东西还挺多的。

点赞、取消点赞是高频次的操作，若每次都读写数据库，大量的操作会影响数据库性能，所以需要做缓存。

至于多久从 Redis 取一次数据存到数据库中，根据项目的实际情况定吧，我是暂时设了两个小时。

项目需求需要查看都谁点赞了，所以要存储每个点赞的点赞人、被点赞人，不能简单的做计数。

文章分四部分介绍：

• Redis 缓存设计及实现
• 数据库设计
• 数据库操作
• 开启定时任务持久化存储到数据库

一、Redis 缓存设计及实现

1.1 Redis 安装及运行

Redis 安装请自行查阅相关教程。

说下Docker 安装运行 Redis

docker?run?-d?-p?6379:6379?redis:4.0.8

如果已经安装了 Redis，打开命令行，输入启动 Redis 的命令

redis-server

1.2 Redis 与 SpringBoot 项目的整合

1.在 pom.xml 中引入依赖

<dependency>
????<groupId>org.springframework.boot</groupId>
????<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

2.在启动类上添加注释 @EnableCaching

@SpringBootApplication
@EnableDiscoveryClient
@EnableSwagger2
@EnableFeignClients(basePackages?=?"com.solo.coderiver.project.client")
@EnableCaching
public?class?UserApplication?{

????public?static?void?main(String[]?args)?{
????????SpringApplication.run(UserApplication.class,?args);
????}
}

3.编写 Redis 配置类 RedisConfig

import?com.fasterxml.jackson.annotation.JsonAutoDetect;
import?com.fasterxml.jackson.annotation.PropertyAccessor;
import?com.fasterxml.jackson.databind.ObjectMapper;
import?org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import?org.springframework.context.annotation.Bean;
import?org.springframework.context.annotation.Configuration;
import?org.springframework.data.redis.connection.RedisConnectionFactory;
import?org.springframework.data.redis.core.RedisTemplate;
import?org.springframework.data.redis.core.StringRedisTemplate;
import?org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;

import?java.net.UnknownHostException;


@Configuration
public?class?RedisConfig?{

????@Bean
????@ConditionalOnMissingBean(name?=?"redisTemplate")
????public?RedisTemplate<String,?Object>?redisTemplate(
????????????RedisConnectionFactory?redisConnectionFactory)
????????????throws?UnknownHostException?{

????????Jackson2JsonRedisSerializer<Object>?jackson2JsonRedisSerializer?=?new?Jackson2JsonRedisSerializer<Object>(Object.class);
????????ObjectMapper?om?=?new?ObjectMapper();
????????om.setVisibility(PropertyAccessor.ALL,?JsonAutoDetect.Visibility.ANY);
????????om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
????????jackson2JsonRedisSerializer.setObjectMapper(om);

????????RedisTemplate<String,?Object>?template?=?new?RedisTemplate<String,?Object>();
????????template.setConnectionFactory(redisConnectionFactory);
????????template.setKeySerializer(jackson2JsonRedisSerializer);
????????template.setValueSerializer(jackson2JsonRedisSerializer);
????????template.setHashKeySerializer(jackson2JsonRedisSerializer);
????????template.setHashValueSerializer(jackson2JsonRedisSerializer);
????????template.afterPropertiesSet();
????????return?template;
????}


????@Bean
????@ConditionalOnMissingBean(StringRedisTemplate.class)
????public?StringRedisTemplate?stringRedisTemplate(
????????????RedisConnectionFactory?redisConnectionFactory)
????????????throws?UnknownHostException?{
????????StringRedisTemplate?template?=?new?StringRedisTemplate();
????????template.setConnectionFactory(redisConnectionFactory);
????????return?template;
????}
}

至此 Redis 在 SpringBoot 项目中的配置已经完成，可以愉快的使用了。

1.3 Redis 的数据结构类型

Redis 可以存储键与5种不同数据结构类型之间的映射，这5种数据结构类型分别为String（字符串）、List（列表）、Set（集合）、Hash（散列）和 Zset（有序集合）。

下面来对这5种数据结构类型作简单的介绍：

1.4 点赞数据在 Redis 中的存储格式

用 Redis 存储两种数据，一种是记录点赞人、被点赞人、点赞状态的数据，另一种是每个用户被点赞了多少次，做个简单的计数。

由于需要记录点赞人和被点赞人，还有点赞状态（点赞、取消点赞），还要固定时间间隔取出 Redis 中所有点赞数据，分析了下 Redis 数据格式中 Hash 最合适。

因为 Hash 里的数据都是存在一个键里，可以通过这个键很方便的把所有的点赞数据都取出。这个键里面的数据还可以存成键值对的形式，方便存入点赞人、被点赞人和点赞状态。

设点赞人的 id 为 likedPostId，被点赞人的 id 为 likedUserId ，点赞时状态为 1，取消点赞状态为 0。将点赞人 id 和被点赞人 id 作为键，两个 id 中间用 :: 隔开，点赞状态作为值。

所以如果用户点赞，存储的键为：likedUserId::likedPostId，对应的值为 1 。取消点赞，存储的键为：likedUserId::likedPostId，对应的值为 0 。取数据时把键用 :: 切开就得到了两个id，也很方便。

在可视化工具 RDM 中看到的是这样子

1.5 操作 Redis

将具体操作方法封装到了 RedisService 接口里

RedisService.java

import?com.solo.coderiver.user.dataobject.UserLike;
import?com.solo.coderiver.user.dto.LikedCountDTO;

import?java.util.List;

public?interface?RedisService?{

????/**
?????*?点赞。状态为1
?????*?@param?likedUserId
?????*?@param?likedPostId
?????*/
????void?saveLiked2Redis(String?likedUserId,?String?likedPostId);

????/**
?????*?取消点赞。将状态改变为0
?????*?@param?likedUserId
?????*?@param?likedPostId
?????*/
????void?unlikeFromRedis(String?likedUserId,?String?likedPostId);

????/**
?????*?从Redis中删除一条点赞数据
?????*?@param?likedUserId
?????*?@param?likedPostId
?????*/
????void?deleteLikedFromRedis(String?likedUserId,?String?likedPostId);

????/**
?????*?该用户的点赞数加1
?????*?@param?likedUserId
?????*/
????void?incrementLikedCount(String?likedUserId);

????/**
?????*?该用户的点赞数减1
?????*?@param?likedUserId
?????*/
????void?decrementLikedCount(String?likedUserId);

????/**
?????*?获取Redis中存储的所有点赞数据
?????*?@return
?????*/
????List<UserLike>?getLikedDataFromRedis();

????/**
?????*?获取Redis中存储的所有点赞数量
?????*?@return
?????*/
????List<LikedCountDTO>?getLikedCountFromRedis();

}

实现类 RedisServiceImpl.java

import?com.solo.coderiver.user.dataobject.UserLike;
import?com.solo.coderiver.user.dto.LikedCountDTO;
import?com.solo.coderiver.user.enums.LikedStatusEnum;
import?com.solo.coderiver.user.service.LikedService;
import?com.solo.coderiver.user.service.RedisService;
import?com.solo.coderiver.user.utils.RedisKeyUtils;
import?lombok.extern.slf4j.Slf4j;
import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.data.redis.core.Cursor;
import?org.springframework.data.redis.core.RedisTemplate;
import?org.springframework.data.redis.core.ScanOptions;
import?org.springframework.stereotype.Service;

import?java.util.ArrayList;
import?java.util.List;
import?java.util.Map;

@Service
@Slf4j
public?class?RedisServiceImpl?implements?RedisService?{

????@Autowired
????RedisTemplate?redisTemplate;

????@Autowired
????LikedService?likedService;

????@Override
????public?void?saveLiked2Redis(String?likedUserId,?String?likedPostId)?{
????????String?key?=?RedisKeyUtils.getLikedKey(likedUserId,?likedPostId);
????????redisTemplate.opsForHash().put(RedisKeyUtils.MAP_KEY_USER_LIKED,?key,?LikedStatusEnum.LIKE.getCode());
????}

????@Override
????public?void?unlikeFromRedis(String?likedUserId,?String?likedPostId)?{
????????String?key?=?RedisKeyUtils.getLikedKey(likedUserId,?likedPostId);
????????redisTemplate.opsForHash().put(RedisKeyUtils.MAP_KEY_USER_LIKED,?key,?LikedStatusEnum.UNLIKE.getCode());
????}

????@Override
????public?void?deleteLikedFromRedis(String?likedUserId,?String?likedPostId)?{
????????String?key?=?RedisKeyUtils.getLikedKey(likedUserId,?likedPostId);
????????redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED,?key);
????}

????@Override
????public?void?incrementLikedCount(String?likedUserId)?{
????????redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT,?likedUserId,?1);
????}

????@Override
????public?void?decrementLikedCount(String?likedUserId)?{
????????redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT,?likedUserId,?-1);
????}

????@Override
????public?List<UserLike>?getLikedDataFromRedis()?{
????????Cursor<Map.Entry<Object,?Object>>?cursor?=?redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_KEY_USER_LIKED,?ScanOptions.NONE);
????????List<UserLike>?list?=?new?ArrayList<>();
????????while?(cursor.hasNext()){
????????????Map.Entry<Object,?Object>?entry?=?cursor.next();
????????????String?key?=?(String)?entry.getKey();
????????????//分离出?likedUserId，likedPostId
????????????String[]?split?=?key.split("::");
????????????String?likedUserId?=?split[0];
????????????String?likedPostId?=?split[1];
????????????Integer?value?=?(Integer)?entry.getValue();

????????????//组装成?UserLike?对象
????????????UserLike?userLike?=?new?UserLike(likedUserId,?likedPostId,?value);
????????????list.add(userLike);

????????????//存到?list?后从?Redis?中删除
????????????redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED,?key);
????????}

????????return?list;
????}

????@Override
????public?List<LikedCountDTO>?getLikedCountFromRedis()?{
????????Cursor<Map.Entry<Object,?Object>>?cursor?=?redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT,?ScanOptions.NONE);
????????List<LikedCountDTO>?list?=?new?ArrayList<>();
????????while?(cursor.hasNext()){
????????????Map.Entry<Object,?Object>?map?=?cursor.next();
????????????//将点赞数量存储在?LikedCountDT
????????????String?key?=?(String)map.getKey();
????????????LikedCountDTO?dto?=?new?LikedCountDTO(key,?(Integer)?map.getValue());
????????????list.add(dto);
????????????//从Redis中删除这条记录
????????????redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT,?key);
????????}
????????return?list;
????}
}

用到的工具类和枚举类

RedisKeyUtils, 用于根据一定规则生成 key

public?class?RedisKeyUtils?{

????//保存用户点赞数据的key
????public?static?final?String?MAP_KEY_USER_LIKED?=?"MAP_USER_LIKED";
????//保存用户被点赞数量的key
????public?static?final?String?MAP_KEY_USER_LIKED_COUNT?=?"MAP_USER_LIKED_COUNT";

????/**
?????*?拼接被点赞的用户id和点赞的人的id作为key。格式 222222::333333
?????*?@param?likedUserId?被点赞的人id
?????*?@param?likedPostId?点赞的人的id
?????*?@return
?????*/
????public?static?String?getLikedKey(String?likedUserId,?String?likedPostId){
????????StringBuilder?builder?=?new?StringBuilder();
????????builder.append(likedUserId);
????????builder.append("::");
????????builder.append(likedPostId);
????????return?builder.toString();
????}
}

LikedStatusEnum 用户点赞状态的枚举类

package?com.solo.coderiver.user.enums;

import?lombok.Getter;

/**
?*?用户点赞的状态
?*/
@Getter
public?enum?LikedStatusEnum?{
????LIKE(1,?"点赞"),
????UNLIKE(0,?"取消点赞/未点赞"),
????;

????private?Integer?code;

????private?String?msg;

????LikedStatusEnum(Integer?code,?String?msg)?{
????????this.code?=?code;
????????this.msg?=?msg;
????}
}

二、数据库设计

数据库表中至少要包含三个字段：被点赞用户id，点赞用户id，点赞状态。再加上主键id，创建时间，修改时间就行了。

建表语句

create?table?`user_like`(
????`id`?int?not?null?auto_increment,
????`liked_user_id`?varchar(32)?not?null?comment?'被点赞的用户id',
????`liked_post_id`?varchar(32)?not?null?comment?'点赞的用户id',
????`status`?tinyint(1)?default?'1'?comment?'点赞状态，0取消，1点赞',
????`create_time`?timestamp?not?null?default?current_timestamp?comment?'创建时间',
??`update_time`?timestamp?not?null?default?current_timestamp?on?update?current_timestamp?comment?'修改时间',
????primary?key(`id`),
????INDEX?`liked_user_id`(`liked_user_id`),
????INDEX?`liked_post_id`(`liked_post_id`)
)?comment?'用户点赞表';

对应的对象 UserLike

import?com.solo.coderiver.user.enums.LikedStatusEnum;
import?lombok.Data;

import?javax.persistence.Entity;
import?javax.persistence.GeneratedValue;
import?javax.persistence.GenerationType;
import?javax.persistence.Id;

/**
?*?用户点赞表
?*/
@Entity
@Data
public?class?UserLike?{

????//主键id
????@Id
????@GeneratedValue(strategy?=?GenerationType.IDENTITY)
????private?Integer?id;

????//被点赞的用户的id
????private?String?likedUserId;

????//点赞的用户的id
????private?String?likedPostId;

????//点赞的状态.默认未点赞
????private?Integer?status?=?LikedStatusEnum.UNLIKE.getCode();

????public?UserLike()?{
????}

????public?UserLike(String?likedUserId,?String?likedPostId,?Integer?status)?{
????????this.likedUserId?=?likedUserId;
????????this.likedPostId?=?likedPostId;
????????this.status?=?status;
????}
}

三、数据库操作

操作数据库同样封装在接口中

LikedService

import?com.solo.coderiver.user.dataobject.UserLike;
import?org.springframework.data.domain.Page;
import?org.springframework.data.domain.Pageable;

import?java.util.List;

public?interface?LikedService?{

????/**
?????*?保存点赞记录
?????*?@param?userLike
?????*?@return
?????*/
????UserLike?save(UserLike?userLike);

????/**
?????*?批量保存或修改
?????*?@param?list
?????*/
????List<UserLike>?saveAll(List<UserLike>?list);


????/**
?????*?根据被点赞人的id查询点赞列表（即查询都谁给这个人点赞过）
?????*?@param?likedUserId?被点赞人的id
?????*?@param?pageable
?????*?@return
?????*/
????Page<UserLike>?getLikedListByLikedUserId(String?likedUserId,?Pageable?pageable);

????/**
?????*?根据点赞人的id查询点赞列表（即查询这个人都给谁点赞过）
?????*?@param?likedPostId
?????*?@param?pageable
?????*?@return
?????*/
????Page<UserLike>?getLikedListByLikedPostId(String?likedPostId,?Pageable?pageable);

????/**
?????*?通过被点赞人和点赞人id查询是否存在点赞记录
?????*?@param?likedUserId
?????*?@param?likedPostId
?????*?@return
?????*/
????UserLike?getByLikedUserIdAndLikedPostId(String?likedUserId,?String?likedPostId);

????/**
?????*?将Redis里的点赞数据存入数据库中
?????*/
????void?transLikedFromRedis2DB();

????/**
?????*?将Redis中的点赞数量数据存入数据库
?????*/
????void?transLikedCountFromRedis2DB();

}

LikedServiceImpl 实现类

import?com.solo.coderiver.user.dataobject.UserInfo;
import?com.solo.coderiver.user.dataobject.UserLike;
import?com.solo.coderiver.user.dto.LikedCountDTO;
import?com.solo.coderiver.user.enums.LikedStatusEnum;
import?com.solo.coderiver.user.repository.UserLikeRepository;
import?com.solo.coderiver.user.service.LikedService;
import?com.solo.coderiver.user.service.RedisService;
import?com.solo.coderiver.user.service.UserService;
import?lombok.extern.slf4j.Slf4j;
import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.data.domain.Page;
import?org.springframework.data.domain.Pageable;
import?org.springframework.stereotype.Service;
import?org.springframework.transaction.annotation.Transactional;

import?java.util.List;

@Service
@Slf4j
public?class?LikedServiceImpl?implements?LikedService?{

????@Autowired
????UserLikeRepository?likeRepository;

????@Autowired
????RedisService?redisService;

????@Autowired
????UserService?userService;

????@Override
????@Transactional
????public?UserLike?save(UserLike?userLike)?{
????????return?likeRepository.save(userLike);
????}

????@Override
????@Transactional
????public?List<UserLike>?saveAll(List<UserLike>?list)?{
????????return?likeRepository.saveAll(list);
????}

????@Override
????public?Page<UserLike>?getLikedListByLikedUserId(String?likedUserId,?Pageable?pageable)?{
????????return?likeRepository.findByLikedUserIdAndStatus(likedUserId,?LikedStatusEnum.LIKE.getCode(),?pageable);
????}

????@Override
????public?Page<UserLike>?getLikedListByLikedPostId(String?likedPostId,?Pageable?pageable)?{
????????return?likeRepository.findByLikedPostIdAndStatus(likedPostId,?LikedStatusEnum.LIKE.getCode(),?pageable);
????}

????@Override
????public?UserLike?getByLikedUserIdAndLikedPostId(String?likedUserId,?String?likedPostId)?{
????????return?likeRepository.findByLikedUserIdAndLikedPostId(likedUserId,?likedPostId);
????}

????@Override
????@Transactional
????public?void?transLikedFromRedis2DB()?{
????????List<UserLike>?list?=?redisService.getLikedDataFromRedis();
????????for?(UserLike?like?:?list)?{
????????????UserLike?ul?=?getByLikedUserIdAndLikedPostId(like.getLikedUserId(),?like.getLikedPostId());
????????????if?(ul?==?null){
????????????????//没有记录，直接存入
????????????????save(like);
????????????}else{
????????????????//有记录，需要更新
????????????????ul.setStatus(like.getStatus());
????????????????save(ul);
????????????}
????????}
????}

????@Override
????@Transactional
????public?void?transLikedCountFromRedis2DB()?{
????????List<LikedCountDTO>?list?=?redisService.getLikedCountFromRedis();
????????for?(LikedCountDTO?dto?:?list)?{
????????????UserInfo?user?=?userService.findById(dto.getId());
????????????//点赞数量属于无关紧要的操作，出错无需抛异常
????????????if?(user?!=?null){
????????????????Integer?likeNum?=?user.getLikeNum()?+?dto.getCount();
????????????????user.setLikeNum(likeNum);
????????????????//更新点赞数量
????????????????userService.updateInfo(user);
????????????}
????????}
????}
}

数据库的操作就这些，主要还是增删改查。

四、开启定时任务持久化存储到数据库

定时任务 Quartz 很强大，就用它了。

Quartz 使用步骤：

1.添加依赖

<dependency>
????<groupId>org.springframework.boot</groupId>
????<artifactId>spring-boot-starter-quartz</artifactId>
</dependency>

2.编写配置文件

package?com.solo.coderiver.user.config;

import?com.solo.coderiver.user.task.LikeTask;
import?org.quartz.*;
import?org.springframework.context.annotation.Bean;
import?org.springframework.context.annotation.Configuration;

@Configuration
public?class?QuartzConfig?{

????private?static?final?String?LIKE_TASK_IDENTITY?=?"LikeTaskQuartz";

????@Bean
????public?JobDetail?quartzDetail(){
????????return?JobBuilder.newJob(LikeTask.class).withIdentity(LIKE_TASK_IDENTITY).storeDurably().build();
????}

????@Bean
????public?Trigger?quartzTrigger(){
????????SimpleScheduleBuilder?scheduleBuilder?=?SimpleScheduleBuilder.simpleSchedule()
//????????????????.withIntervalInSeconds(10)??//设置时间周期单位秒
????????????????.withIntervalInHours(2)??//两个小时执行一次
????????????????.repeatForever();
????????return?TriggerBuilder.newTrigger().forJob(quartzDetail())
????????????????.withIdentity(LIKE_TASK_IDENTITY)
????????????????.withSchedule(scheduleBuilder)
????????????????.build();
????}
}

3.编写执行任务的类继承自 QuartzJobBean

package?com.solo.coderiver.user.task;

import?com.solo.coderiver.user.service.LikedService;
import?lombok.extern.slf4j.Slf4j;
import?org.apache.commons.lang.time.DateUtils;
import?org.quartz.JobExecutionContext;
import?org.quartz.JobExecutionException;
import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.scheduling.quartz.QuartzJobBean;

import?java.text.SimpleDateFormat;
import?java.util.Date;

/**
?*?点赞的定时任务
?*/
@Slf4j
public?class?LikeTask?extends?QuartzJobBean?{

????@Autowired
????LikedService?likedService;

????private?SimpleDateFormat?sdf?=?new?SimpleDateFormat("yyyy-MM-dd?HH:mm:ss");

????@Override
????protected?void?executeInternal(JobExecutionContext?jobExecutionContext)?throws?JobExecutionException?{

????????log.info("LikeTask--------?{}",?sdf.format(new?Date()));

????????//将?Redis?里的点赞信息同步到数据库里
????????likedService.transLikedFromRedis2DB();
????????likedService.transLikedCountFromRedis2DB();
????}
}

在定时任务中直接调用 LikedService 封装的方法完成数据同步。

以上就是点赞功能的设计与实现，不足之处还请各位大佬多多指教。

另外，点赞/取消点赞 跟 点赞数 +1/ -1 应该保证是原子操作 , 不然出现并发问题就会有两条重复的点赞记录 , 所以要给整个原子操作加锁 . 同时需要在Spring Boot 的系统关闭钩子函数中补充同步redis中点赞数据到mysql中的过程 . 不然有可能出现距离上一次同步1小时59分的时候服务器更新 , 把整整两小时的点赞数据都给清空了 . 如果点赞设计到比较重要活动业务的话这就很尴尬了 .

如有更好的实现方案欢迎在评论区交流…

链接：https://juejin.im/post/5bdc257e6fb9a049ba410098

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