利用Redis实现点赞功能的示例代码

/**
* 将用户被其他用户点赞的数据存到redis
*/
@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());
}

//取消点赞
@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());
}

/**
* 将被点赞用户的数量+1
*/
@Override
public void incrementLikedCount(String likedUserId) {
    redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT,likedUserId,1);
}

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

/**
* 获取Redis中的用户点赞详情记录
*/
@Override
public List<UserLikeDetail> getLikedDataFromRedis() {
    Cursor<Map.Entry<Object,Object>> scan = redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_KEY_USER_LIKED, ScanOptions.NONE);
    List<UserLikeDetail> list = new ArrayList<>();
    while (scan.hasNext()){
        Map.Entry<Object, Object> entry = scan.next();
        String key = (String) entry.getKey();
        String[] split = key.split("::");
        String likedUserId = split[0];
        String likedPostId = split[1];
        Integer value = (Integer) entry.getValue();
        //组装成 UserLike 对象
        UserLikeDetail userLikeDetail = new UserLikeDetail(likedUserId, likedPostId, value);
        list.add(userLikeDetail);
        //存到 list 后从 Redis 中删除
        redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED, key);
    }
    return list;
}

/**
* 获取Redis中的用户被点赞数量
*/
@Override
public List<UserLikCountDTO> getLikedCountFromRedis() {
    Cursor<Map.Entry<Object,Object>> cursor = redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT, ScanOptions.NONE);
    List<UserLikCountDTO> list = new ArrayList<>();
    while(cursor.hasNext()){
        Map.Entry<Object, Object> map = cursor.next();
        String key = (String) map.getKey();
        Integer value = (Integer) map.getValue();
        UserLikCountDTO userLikCountDTO = new UserLikCountDTO(key,value);
        list.add(userLikCountDTO);
        //存到 list 后从 Redis 中删除
        redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT,key);
    }
    return list;
}

DROP TABLE IF EXISTS `user_like_detail`;
CREATE TABLE `user_like_detail`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `liked_user_id` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '被点赞的用户id',
  `liked_post_id` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '点赞的用户id',
  `status` tinyint(1) NULL DEFAULT 1 COMMENT '点赞状态，0取消，1点赞',
  `create_time` timestamp(0) NOT NULL DEFAULT CURRENT_TIMESTAMP(0) COMMENT '创建时间',
  `update_time` timestamp(0) NOT NULL DEFAULT CURRENT_TIMESTAMP(0) ON UPDATE CURRENT_TIMESTAMP(0) COMMENT '修改时间',
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `liked_user_id`(`liked_user_id`) USING BTREE,
  INDEX `liked_post_id`(`liked_post_id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '用户点赞表' ROW_FORMAT = Dynamic;

SET FOREIGN_KEY_CHECKS = 1;

DROP TABLE IF EXISTS `user_like_count`;
CREATE TABLE `user_like_count`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `like_num` int(11) NULL DEFAULT 0,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

SET FOREIGN_KEY_CHECKS = 1;

//同步redis的用户点赞数据到数据库
@Override
@Transactional
public void transLikedFromRedis2DB() {
    List<UserLikeDetail> list = redisService.getLikedDataFromRedis();
    list.stream().forEach(item->{
        //查重
        UserLikeDetail userLikeDetail = userLikeDetailMapper.selectOne(new LambdaQueryWrapper<UserLikeDetail>()
           .eq(UserLikeDetail::getLikedUserId, item.getLikedUserId())
           .eq(UserLikeDetail::getLikedPostId, item.getLikedPostId()));
        if (userLikeDetail == null){
            userLikeDetail = new UserLikeDetail();
            BeanUtils.copyProperties(item, userLikeDetail);
            //没有记录，直接存入
            userLikeDetail.setCreateTime(LocalDateTime.now());
            userLikeDetailMapper.insert(userLikeDetail);
        }else{
            //有记录，需要更新
            userLikeDetail.setStatus(item.getStatus());
            userLikeDetail.setUpdateTime(LocalDateTime.now());
            userLikeDetailMapper.updateById(item);
        }
    });
}

@Override
@Transactional
public void transLikedCountFromRedis2DB() {
    List<UserLikCountDTO> list = redisService.getLikedCountFromRedis();
    list.stream().forEach(item->{
        UserLikeCount user = userLikeCountMapper.selectById(item.getKey());
        //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() + item.getValue();
            user.setLikeNum(likeNum);
            //更新点赞数量
            userLikeCountMapper.updateById(user);
        }
    });
}