code: public String signRoomToken(String roomAccess) throws Exception {
          String encodedRoomAcc = UrlSafeBase64.encodeToString(roomAccess);
          byte[] sign = HMac.HmacSHA1Encrypt(encodedRoomAcc, this.secretKey);
          String encodedSign = UrlSafeBase64.encodeToString(sign);
          return this.accessKey + ":" + encodedSign+":"+encodedRoomAcc;
      }
docs: 连麦 RoomToken