private int convertStringToTransactionLevel(String transactionIsolationLevel) {
    switch (transactionIsolationLevel) {
      case "TRANSACTION_NONE":
        return Connection.TRANSACTION_NONE;
      case "TRANSACTION_READ_UNCOMMITTED":
        return Connection.TRANSACTION_READ_UNCOMMITTED;
      case "TRANSACTION_READ_COMMITTED":
        return Connection.TRANSACTION_READ_COMMITTED;
      case "TRANSACTION_REPEATABLE_READ":
        return Connection.TRANSACTION_REPEATABLE_READ;
      case "TRANSACTION_SERIALIZABLE":
        return Connection.TRANSACTION_SERIALIZABLE;
      default:
        throw new IllegalArgumentException("Invalid transaction level: " + transactionIsolationLevel);
    }
  }
Convert the String value to the Isolation level.
@param transactionIsolationLevel The string value of isolation level.
@return the Isolation level.
ambry-mysql/src/main/java/com/github/ambry/mysql/MySqlDataAccessor.java