public function registerApiRequestHandler($api_request, $handler_class_name)
    {
        if (empty($api_request)) {
            throw new \Exception("The API request is undefined (empty)!");
        }
        
        if (!empty($this->handler_table[$api_request])) {
            throw new \Exception("The API request '$api_request' has already the handler '" . $this->handler_table[$api_request] . "'!");
        }
        
        $this->handler_table[$api_request] = $handler_class_name;
        
        return true;
    }