public function getConnection()
    {
        if (null === $this->conn) {
            $this->checkConfiguration();

            try {
                $this->conn = new SQL(
                    $this->buildDsn(),
                    $this->config['username'],
                    $this->config['password']
                );
            } catch (Exception $e) {
                throw new RuntimeException(static::E_CONNECT);
            }
        }

        return $this->conn;
    }