code: static synchronized boolean isJettyAlpnConfigured() {
      try {
        Class.forName("org.eclipse.jetty.alpn.ALPN", true, null);
        return true;
      } catch (ClassNotFoundException e) {
        jettyAlpnUnavailabilityCause = e;
        return false;
      }
    }
docs: Indicates whether or not the Jetty ALPN jar is installed in the boot classloader.