code: private static Credential getSigningCredential(final Resource resource) {
          try (val inputStream = resource.getInputStream()) {
              val certificateFactory = CertificateFactory.getInstance("X.509");
              val certificate = (X509Certificate) certificateFactory.generateCertificate(inputStream);
              val publicCredential = new BasicX509Credential(certificate);
              LOGGER.debug("Signing credential key retrieved from [{}].", resource);
              return publicCredential;
          } catch (final Exception ex) {
              LOGGER.error(ex.getMessage(), ex);
          }
          return null;
      }
docs: getSigningCredential loads up an X509Credential from a file.
  
  @param resource the signing certificate file
  @return an X509 credential