public function getControllerSubpackageKey()
    {
        $controllerObjectName = $this->getControllerObjectName();
        if ($this->controllerSubpackageKey !== null && $controllerObjectName !== '') {

            // Extract the subpackage key from the controller object name to assure that the case is correct.
            return substr($controllerObjectName, strlen($this->controllerPackageKey) + 1, strlen($this->controllerSubpackageKey));
        } else {
            return $this->controllerSubpackageKey;
        }
    }