code: public static OpenSslX509KeyManagerFactory newKeyless(File chain)
              throws CertificateException, IOException,
              KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException {
          return newKeyless(SslContext.toX509Certificates(chain));
      }
docs: See {@link OpenSslX509KeyManagerFactory#newEngineBased(X509Certificate[], String)}.