public function export()
    {
        if (!$this->isXmlHttpRequest()) {
            throw new \Exception('Only ajax call allowed.');
        }

        if (!$this->hasRequestParameter(self::PARAMETER_DELIVERY_CLASS_URI) && !$this->hasRequestParameter(self::PARAMETER_DELIVERY_URI)) {
            throw new \common_Exception('Parameter "'. self::PARAMETER_DELIVERY_CLASS_URI .'" or "'. self::PARAMETER_DELIVERY_URI .'" missing');
        }

        $resourceUri = $this->hasRequestParameter(self::PARAMETER_DELIVERY_URI)
            ? \tao_helpers_Uri::decode($this->getRequestParameter(self::PARAMETER_DELIVERY_URI))
            : \tao_helpers_Uri::decode($this->getRequestParameter(self::PARAMETER_DELIVERY_CLASS_URI));

        /** @var ResultsExporter $exporter */
        $exporter = $this->propagate(new ResultsExporter($resourceUri, ResultsService::singleton()));

        return $this->returnTaskJson($exporter->createExportTask());
    }