Value对象缓存用Hash防穿透

1@Override
2public Long lastMomentId(Long lessonId, Long userId) {
3	Long challengeMomentId = 0L;
4	String key = RedisKeyUtil.build(RedisConstants.ChallengeMoment.LAST_MOMENT_ID, lessonId, userId);
5
6	if(hashRedisTemplate.exists(key)) {
7		String json = hashRedisTemplate.hget(key, RedisConstants.HashEntity.VALUE);
8		if(StringUtils.isNotBlank(json)) {
9		challengeMomentId = Long.parseLong(json);
10	}
11	}else {
12		ChallengeMoment challengeMoment = challengeMomentRepository.findFirstByMap(Mapper.sql("lesson.last.moment"), new MapBuilder()
13		.append("createBy", userId)
14		.append("lessonId", lessonId)
15		.build());
16		if(null != challengeMoment) {
17			challengeMomentId = challengeMoment.getId();
18			hashRedisTemplate.hset(key, RedisConstants.HashEntity.VALUE, String.valueOf(challengeMomentId));
19			hashRedisTemplate.hset(key, RedisConstants.HashEntity.FLAG, RedisConstants.HashEntity.FLAG_EXIST); //防穿透
20		}else {
21			hashRedisTemplate.hset(key, RedisConstants.HashEntity.FLAG, RedisConstants.HashEntity.FLAG_NOT_EXIST);
22		}
23		hashRedisTemplate.expire(key, CommonConstants.Time.THREE_DAY);
24	}
25	return challengeMomentId;
26}
27
28@Override
29public void addLastMomentId(Long lessonId, Long userId, Long momentId) {
30	String key = RedisKeyUtil.build(RedisConstants.ChallengeMoment.LAST_MOMENT_ID, lessonId, userId);
31	hashRedisTemplate.hset(key, RedisConstants.HashEntity.FLAG, RedisConstants.HashEntity.FLAG_EXIST);
32	hashRedisTemplate.hset(key, RedisConstants.HashEntity.VALUE, String.valueOf(momentId));
33	hashRedisTemplate.expire(key, CommonConstants.Time.THREE_DAY);
34}

备注: hash中的flag字段来保持key一直存在..使用exist key判断是否需要查库.. 然后用flag的值来判断value是否存在..或者直接判断value是否存在