@Override
    protected String resolvePrincipalInternal(final X509Certificate certificate) {
        return subjectDnFormat == null
            ? certificate.getSubjectDN().getName()
            : certificate.getSubjectX500Principal().getName(subjectDnFormat);
    }
Returns a principal based on the Subject DNs name.

@author Scott Battaglia
@since 3.0.0
support/cas-server-support-x509-core/src/main/java/org/apereo/cas/adaptors/x509/authentication/principal/X509SubjectDNPrincipalResolver.java