@Override
    public String[] getId() {
        val ids = new ArrayList<String>();
        ids.add(getClass().getSimpleName());
        personAttributeDaos.forEach(dao -> ids.addAll(List.of(dao.getId())));
        return ids.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }
Force all provided person attribute DAOs to
produce results, and otherwise, halt execution
if any of them cannot resolve the principal and return null.
core/cas-server-core-authentication-api/src/main/java/org/apereo/cas/authentication/attribute/AbstractAggregatingDefaultQueryPersonAttributeDao.java