protected function getDomainMapper()
    {
        if ($this->domainMapper !== null) {
            return $this->domainMapper;
        }

        $this->domainMapper = new Helper\DomainMapper(
            $this->persistenceHandler->contentHandler(),
            $this->persistenceHandler->locationHandler(),
            $this->persistenceHandler->contentTypeHandler(),
            $this->getContentTypeDomainMapper(),
            $this->persistenceHandler->contentLanguageHandler(),
            $this->getFieldTypeRegistry()
        );

        return $this->domainMapper;
    }