手把手教你用Redis实现点赞功能并且与数据库同步-编程学习网

一、Redis 缓存设计及实现

Linux下安装Redis或者Docker下安装Redis并且启动(redis-server)

SpringBoot整合Redis

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

3.编写 Redis 配置类 RedisConfig

@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;  
    }
}

二、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
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，所以 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 giveLikeId，被点赞人的 id 为 likeUserId ，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。

类似于这样：

在这里插入图片描述

在service层操作Redis

public interface RedisService {    
    
void saveLiked2Redis(String likedUserId, String giveLikeId);    
    
void unlikeFromRedis(String likedUserId, String giveLikeId);    
    
void deleteLikedFromRedis(String likedUserId, String giveLikeId);    
    
void incrementLikedCount(String likedUserId);    
    
void decrementLikedCount(String likedUserId);    
    
List<UserLike> getLikedDataFromRedis();    
    
List<LikedCountDTO> getLikedCountFromRedis();}

实现类 RedisServiceImpl ：

@Service
@Slf4j
public class RedisServiceImpl implements RedisService {    
    @Autowired    
    RedisTemplate redisTemplate;    
    @Autowired    
    LikedService likedService;    
  @Override    
  public void saveLiked2Redis(String likedUserId, String giveLikeId) {          
      String key = RedisKeyUtils.getLikedKey(likedUserId, giveLikeId);            
      redisTemplate.opsForHash().put(RedisKeyUtils.MAP_USER_LIKED, 
      key, LikedStatusEnum.LIKE.getCode());    
      }    
  @Override    
  public void unlikeFromRedis(String likedUserId, String giveLikeId) {          
      String key = RedisKeyUtils.getLikedKey(likedUserId, giveLikeId);            
      redisTemplate.opsForHash().put(RedisKeyUtils.MAP_USER_LIKED, 
      key, LikedStatusEnum.UNLIKE.getCode());    
      }    
  @Override    
  public void deleteLikedFromRedis(String likedUserId, String giveLikeId) {    
      String key = RedisKeyUtils.getLikedKey(likedUserId, giveLikeId);            
      redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_USER_LIKED, key);   
      }    
  @Override    
  public void incrementLikedCount(String likedUserId) {
      redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_USER_LIKED_COUNT,likedUserId,1);    
 }    
 @Override
 public void decrementLikedCount(String likedUserId) {        
     redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_USER_LIKED_COUNT,likedUserId,-1);    
 }    
 @Override
 public List<UserLike> getLikedDataFromRedis() {                
     Cursor<Map.Entry<Object, Object>> cursor =redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_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，giveLikeId
         String[] split = key.split("::");
         String likedUserId = split[0];
         String giveLikeId = split[1];
         Integer value = (Integer) entry.getValue();
         //组装成 UserLike 对象
         UserLike userLike = new UserLike(likedUserId, giveLikeId, value);
         list.add(userLike);
         //存到 list 后从 Redis 中删除
         redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_USER_LIKED, key);        
         }        return list;    
    }   
 @Override    
 public List<LikedCountDTO> getLikedCountFromRedis() {
     Cursor<Map.Entry<Object, Object>> cursor =    redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_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_USER_LIKED_COUNT, key);        
        }        
    return list;    
    }
}

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_USER_LIKED = "MAP_USER_LIKED";
    //保存用户被点赞数量的key
    public static final String MAP_USER_LIKED_COUNT = "MAP_USER_LIKED_COUNT";

    
    public static String getLikedKey(String likedUserId, String giveLikeId){
        StringBuilder builder = new StringBuilder();
        builder.append(likedUserId);
        builder.append("::");
        builder.append(giveLikeId);
        return builder.toString();
    }
}

LikedStatusEnum 用户点赞状态的枚举类


@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;
    }
}

三、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。

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',
    `give_liked_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 `give_liked_id`(`give_liked_id`)
) comment '用户点赞表';

对应的对象 UserLike


@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 giveLikedId;

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

    public UserLike() {
    }

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

在service层操作数据库

public interface LikedService {

    
    UserLike save(UserLike userLike);

    
    List<UserLike> saveAll(List<UserLike> list);


    
    Page<UserLike> getLikedListByLikedUserId(String likedUserId, Pageable pageable);

    
    Page<UserLike> getLikedListByGiveLikedId(String giveLikedId, Pageable pageable);

    
    UserLike getByLikedUserIdAndGiveLikedId(String likedUserId, String giveLikedId);

    
    void transLikedFromRedis2DB();

    
    void transLikedCountFromRedis2DB();

}

LikedServiceImpl 实现类

@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> getLikedListByGiveLikedId(String giveLikedId, Pageable pageable) {
        return likeRepository.findByGiveLikedIdAndStatus(giveLikedId, LikedStatusEnum.LIKE.getCode(), pageable);
    }

    @Override
    public UserLike getByLikedUserIdAndGiveLikedId(String likedUserId, String giveLikedId) {
        return likeRepository.findByLikedUserIdAndLikedPostId(likedUserId, giveLikedId);
    }

    @Override
    @Transactional
    public void transLikedFromRedis2DB() {
        List<UserLike> list = redisService.getLikedDataFromRedis();
        for (UserLike like : list) {
            UserLike ul = getByLikedUserIdAndGiveLikedId(like.getLikedUserId(), like.getGiveLikedId());
            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);
            }
        }
    }
}

四、开启定时任务持久化存储到数据库

这里使用的是定时任务 Quartz框架

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

@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


@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。

五、注意事项

1.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。

2.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。

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手把手教你用Redis实现点赞功能并且与数据库同步

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