Mryntu

Currently Magento2 is providing JSON and XML response in web REST API
I want to include a custom response format PDF.

So if any third-party will call our API then we can sen them PDF in response.

Just my idea: We shouldn't do this. We can add the download link or generated link to API response.
There are some additional points:

• How about your server resource if serving PDF each time calling. Your server can be stress. We should consider about this case.


• Should consider security in this case as well.

First define your route in etc/webapi.xml

<route url="/V1/invoices/:id/pdf/:template" method="GET">
 <service class="ThousandmonkeysRestpdfApiPDFInterface" method="pdf"/>
 <resources>
 <resource ref="Magento_Sales::sales" />
 </resources>
</route>

Then in your Model class, which you've defined in di.xml as implementing your interface (in my case ThousandmonkeysRestpdfModelPDFMaker) you can return the generated pdf easily. I've used eadesignro/module-pdfgenerator as my pdf engine (it's rather friendlier than than doing it manually).

public function pdf($invoiceId, $templateId)
 $templateModel = $this->pdfGeneratorRepository->getById($templateId);
 if (!$templateModel) 
 throw new MagentoSalesException(
 __('Could not find template.')
 );
 
 $invoice = $this->invoiceRepository
 ->get($invoiceId);
 if (!$invoice) 
 throw new MagentoSalesException(
 __('Could not find invoice.')
 );
 
 $helper = $this->helper;
 $helper->setInvoice($invoice);
 $helper->setTemplate($templateModel);
 $pdfFileData = $helper->template2Pdf();
 return new PDFResponse(base64_encode($pdfFileData['filestream']));

PDFResponse is just a class with one getter that magento uses to generate json or xml.

It is a bit heavy so consider load, but it's a trade off between that and using the file system, which is not always a great idea (problems with load balancers & clean up). A respectful client wont cause any more issues with this than anything else. A disrespectful client could just request the pdf over and over.

It would be a bit of a problem to open this up to customers however. You can't guarantee that they will be respectful.

Full implementation https://github.com/lingwooc/restpdf-magento2 or just install thousandmonkeys/m2-restpdf-module