@Override
    public Collection<X509CRL> fetch(final Collection<Resource> crls) {
        return crls.stream()
            .map(crl -> {
                try {
                    LOGGER.debug("Fetching CRL data from [{}]", crl);
                    try (val ins = crl.getInputStream()) {
                        return (X509CRL) CertUtils.getCertificateFactory().generateCRL(ins);
                    }
                } catch (final Exception e) {
                    LoggingUtils.warn(LOGGER, e);
                }
                return null;
            })
            .filter(Objects::nonNull)
            .collect(Collectors.toSet());
    }
Handles the fetching of CRL objects based on resources.
Supports http/ldap resources.

@author Misagh Moayyed
@since 4.1
support/cas-server-support-x509-core/src/main/java/org/apereo/cas/adaptors/x509/authentication/ResourceCRLFetcher.java