code: private static SslProvider defaultSslProvider() {
      if (OpenSsl.isAvailable()) {
        logger.log(Level.FINE, "Selecting OPENSSL");
        return SslProvider.OPENSSL;
      }
      Provider provider = findJdkProvider();
      if (provider != null) {
        logger.log(Level.FINE, "Selecting JDK with provider {0}", provider);
        return SslProvider.JDK;
      }
      logger.log(Level.INFO, "netty-tcnative unavailable (this may be normal)",
          OpenSsl.unavailabilityCause());
      logger.log(Level.INFO, "Conscrypt not found (this may be normal)");
      logger.log(Level.INFO, "Jetty ALPN unavailable (this may be normal)",
          JettyTlsUtil.getJettyAlpnUnavailabilityCause());
      throw new IllegalStateException(
          "Could not find TLS ALPN provider; "
          + "no working netty-tcnative, Conscrypt, or Jetty NPN/ALPN available");
    }
docs: Returns OpenSSL if available, otherwise returns the JDK provider.