if (handler != null) {
            mergedConfiguration = mergedConfiguration.useCallbackHandler(handler, DEFAULT_CALLBACK_KINDS);
        }

            case SET_USER_CB_KINDS:
                // SANITAZE on above content
                if (this.principal != null) {
                    sanitazeOnMutation(SET_PRINCIPAL);
                }

                if (this.credentialSource != null) {
                    sanitazeOnMutation(SET_CRED_SOURCE);
                }

                if (this.setRealm != null) {
                    sanitazeOnMutation(SET_REALM);
                }

                if (this.parameterSpecs != null) {
                    sanitazeOnMutation(SET_PARAM_SPECS);
                }

                if (this.keyManagerFactory != null) {
                    sanitazeOnMutation(SET_KEY_MGR_FAC);
                }
                break;