protected function onInit()
    {
        $username = Util::get($this->params, "username", "");
        $password = Util::get($this->params, "password", "");
        $connString = Util::get($this->params, "connectionString", "");

        $key = md5($username.$password.$connString);

        if (isset(OracleDataSource::$connections[$key])) {
            $this->connection = OracleDataSource::$connections[$key];
        } else {
            $conn = oci_connect($username, $password, $connString);
            if ($conn) {
                $this->connection = $conn;
            } else {
                throw new \Exception("Connection failed: " . print_r(oci_error(), true));
            }
            OracleDataSource::$connections[$key] = $this->connection;
        }
    }