public void setCallbackLogicIfUndefined(final CallbackLogic callbackLogic) {
        if (this.callbackLogic == null) {
            setCallbackLogic(callbackLogic);
        }
    }
<p>setCallbackLogicIfUndefined.</p>

@param callbackLogic a {@link CallbackLogic} object
pac4j-core/src/main/java/org/pac4j/core/config/Config.java