Redis DAO for spring

RedisDAO.java

@Repository
@Transactional
public class TopicRedisDAO {


    @Autowired
    RedisTemplate < String, Object > redisTemplate;


    ValueOperations < String, Object > valueOperations = null;

    TimeUnit TOPIC_EXPIRED_TIME_UNIT = TimeUnit.HOURS;
    int TOPIC_TIME_OUT = 3; // 3 hours


    public TopicRedisDAO() {}

    public TopicRedisDAO(RedisTemplate < String, Object > redisTemplate) {
        this.redisTemplate = redisTemplate;
    }


    public boolean setTopic(String topic_key, String topic_value) {

        valueOperations = redisTemplate.opsForValue();


        /** if topic_key doesn't exist in redis, add to redis. */
        boolean hasKey = redisTemplate.hasKey(topic_key);
        if (!hasKey)
            valueOperations.set(topic_key, topic_value, TOPIC_TIME_OUT, TOPIC_EXPIRED_TIME_UNIT);

        return true;

    }
    public String getTopic(String topic_key) {
        String topic_info = null;
        valueOperations = redisTemplate.opsForValue();
        boolean hasKey = redisTemplate.hasKey(topic_key);
        if (hasKey) {

            topic_info = (String) valueOperations.get(topic_key);

        }

        return topic_info;

    }
    
    public RedisTemplate < String, Object > getRedisTemplate() {
        return redisTemplate;
    }

    public void setRedisTemplate(RedisTemplate < String, Object > redisTemplate) {
        this.redisTemplate = redisTemplate;
    }
}