Perform Callout, get byte[] and view pdf

Question

I have a requirement to perform a callout, get response (byte array) that is a PDF base 64 encoded. Then, i need to show the pdf, without saving any data in Salesforce. I just need to view the response in PDF. So, is there a way to achieve this? What i have done is: I have created an LWC to perform the callout on rowaction of a Lightning data table. So onRowAction a JS function is called which calls Apex. Apex performs the callout, gets response and then i need to render the result in PDF. I have tried opening a Visualforce page (calling it either from JS Controller of LWC or from Apex, but i could not find solution... I could not pass my parameter to the page so the PDF was always blank. Please find below a high level diagram of the problem that i am facing and what i want to do..

Answer 1

You could do something like this in VF.

<apex:page>
<script>

    function getBase64FromCallout(){
        //Make a callout to fetch base64, you may use VF Remoting or VF action function to get the base64 string  
    }

    window.addEventListener("load",function (){
        let base64 = this.getBase64FromCallout();
        let pdfurl = "data:application/pdf;base64, " + base64;
        document.getElementById("pdfFrame").setAttribute("src",pdfurl);
    })

</script>

<iframe id="pdfFrame"></iframe>

</apex:page>

Unfortunately, LWC does not allow rendering data: and blob: urls in an iframe as it violates CSP. Alternatively, for LWC, you can try implementing PDF.js or PDFTron but it could be costlier both time and effort wise.