public void initialize() {
        val attributes = new HashSet<String>();
        LOGGER.debug("Initializing LDAP attribute configuration...");
        if (StringUtils.isNotBlank(this.principalIdAttribute)) {
            LOGGER.debug("Configured to retrieve principal id attribute [{}]", this.principalIdAttribute);
            attributes.add(this.principalIdAttribute);
        }
        if (this.principalAttributeMap != null && !this.principalAttributeMap.isEmpty()) {
            val attrs = this.principalAttributeMap.keySet();
            attributes.addAll(attrs);
            LOGGER.debug("Configured to retrieve principal attribute collection of [{}]", attrs);
        }
        this.authenticatedEntryAttributes = attributes.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
        LOGGER.debug("LDAP authentication entry attributes for the authentication request are [{}]", (Object[]) this.authenticatedEntryAttributes);
    }
Initialize the handler, setup the authentication entry attributes.
support/cas-server-support-ldap-core/src/main/java/org/apereo/cas/authentication/LdapAuthenticationHandler.java