code: public boolean hexists(Object key, Object field) {
  		Jedis jedis = getJedis();
  		try {
  			return jedis.hexists(keyToBytes(key), fieldToBytes(field));
  		}
  		finally {close(jedis);}
  	}
docs: 查看哈希表 key 中，给定域 field 是否存在。