code: public Long getCounter(Object key) {
  		Jedis jedis = getJedis();
  		try {
  			String ret = (String)jedis.get(keyNamingPolicy.getKeyName(key));
  			return ret != null ? Long.parseLong(ret) : null;
  		}
  		finally {close(jedis);}
  	}
docs: 获取记数器的值