private function validate()
    {
        if (empty($this->modelName) && empty($this->model)) {
            throw new Exception\ModelNotSetException();
        }

        if (empty($this->model)) {
            $this->model = new $this->modelName();
        }

        if (empty($this->modelName)) {
            $this->modelName = get_class($this->model);
        }

        if (empty($this->db)) {
            $this->db = $this->model->getConnection();
        }
    }