code: protected static void registerAlpnSupport(SSLConnectionLink connLink, SSLEngine engine) {
          ThirdPartyAlpnNegotiator negotiator = null;
          boolean useAlpn = isH2Active(connLink);
          // try to register with one of the alpn providers.  If useAlpn is false, tell the active ALPN handler to skip negotiation
          if (tc.isDebugEnabled()) {
              Tr.debug(tc, "registerAlpnSupportDuringHandshake, h2 protocol enabled: " + useAlpn);
          }
          negotiator = alpnNegotiator.tryToRegisterAlpnNegotiator(engine, connLink, useAlpn);
          connLink.setAlpnNegotiator(negotiator);
      }
docs: Try to register supported ALPN protocols for a connection. This checks that:
  1. HTTP/2 support is enabled
  2. an ALPN provider is available - either via IBM JDK8, JDK9+, grizzly-npn, or jetty-alpn
  
  If the conditions are met, "h2" will be registered as a supported protocol for negotiation
  
  @param SSLConnectionLink
  @param engSSLEngineine