@Override
    protected Event doPreExecute(final RequestContext context) throws Exception {
        val credential = constructCredentialsFromRequest(context);
        if (credential == null) {
            LOGGER.info("No credentials could be extracted/detected from the current request");
            return error();
        }
        WebUtils.putCredential(context, credential);
        return super.doPreExecute(context);
    }
Abstract class to handle the retrieval and authentication of non-interactive
credential such as client certificates, NTLM, etc.

@author Scott Battaglia
@since 3.0.0
core/cas-server-core-webflow-api/src/main/java/org/apereo/cas/web/flow/actions/AbstractNonInteractiveCredentialsAction.java