How to get past the URL limit error of maximum 4096 characters?

Question

I've a need to generate a PDF with dynamic content intercepted by end user in an editable input form.

So, I tried reading everything on the form into a string and passed the string as a URL parameter that is ready by my PDF generation visualforce page and is getting an error like this now:

ERROR Message:

URL starting with 'https://java-ability-7401-dev-ed--c.visualforce.com/apex/generatepdf?customFormData=%7B%22saveRecor'... is longer than the maximum allowed length of 4,096

Here is a brief excerpt from my code:

PageReference thePage   = Page.generatePDF;
thePage.getParameters().put('Id', recordId);
thePage.getParameters().put('customFormData', customFormData);
thePage.getContent();

I'm getting error at this line thePage.getContent().

Anyway I can generate this PDF file. Please note that this data needs to be accepted from end user via an input form (i.e. this data is not saved in salesforce objects, so I can't fire SOQL and read it from there).

------ EDIT from provided comments & suggestions ------

PageReference thePage   = Page.generatePDF;
thePage.getParameters().put('Id', recordId);
thePage.getParameters().put('tempId', templateId);
thePage.getParameters().put('type', type);
//thePage.getParameters().put('customFormData', customFormData);

Http h              = new Http();
HttpRequest req     = new HttpRequest();
req.setEndpoint(URL.getOrgDomainUrl().toExternalForm() + thePage.getUrl());
req.setMethod('POST');
req.setHeader('Authorization', 'Bearer '+UserInfo.getSessionId());
req.setHeader('Content-Type', 'application/json');
req.setBody('customFormData='+customFormData);

HttpResponse httpRes = h.send(req);
system.debug('httpRes '+ httpRes.getBody());
system.debug('httpRes blob'+ httpRes.getBodyAsBlob());

And this is not throwing me exception like before but now my PDFs are generated as corrupt.

The Debug Output looks correct to me and no errors as such:

16:04:29:175 CALLOUT_REQUEST [99]|System.HttpRequest[Endpoint=https://java-ability-7401-dev-ed.cs41.my.salesforce.com/apex/generatepdf?Id=a0f55000002e7gaAAA&tempId=a0655000003P0HiAAK&type=pdf, Method=POST] 16:04:29:237 CALLOUT_RESPONSE [99]|System.HttpResponse[Status=OK, StatusCode=200]

---

--------- EDIT 2 ------------ After more debugging it turns out the Visualforce PDF output is executed based on the Endpoint URL of the HttpRequest.

Visualforce Output PDF correctly if 'm using following Endpoint:

req.setEndpoint(URL.getSalesforceBaseUrl().toExternalForm() + thePage.getUrl());

And Visualforce Output PDF is corrupt when endpoint is:

req.setEndpoint(URL.getOrgDomainUrl().toExternalForm() + thePage.getUrl());

But this endpoint change is troubling because if I use getSalesforceBaseUrl() then it has to be provided into Remote Site Settings, and if I use 'getOrgDomainUrl()` then I can use it without Remote Site Setting entry.

Now, this behaviour is coming out differently only for Visualforce URL. If I access basic REST API endpoint with my above code to read a ListView or records, then same Authentication header works fine with getOrgDomainUrl() endpoint.

Answer 1

There are a few options, but basically you need to get the bulk data out of the query string.

Typically you would do this by using a POST request rather than a GET request. Since a PageReference doesn't give you this option you could do the redirect from the client side directly to the target Visualforce page. That way all the form data can go in the request rather than the URL.

Alternatively, you could do an HttpRequest from the Apex directly to the Visualforce page. The response will still come back from the Http send. It does mean you will need to handle the headers required by Salesforce to authenticate the request.

One final option would be to store the form data in an intermediate sobject before redirecting to the Visualforce page. They target page could then read the data from the sObject rather than from the query string.

---

PageReference pdf = Page.generatePDF;
thePage.getParameters().put('Id', recordId);

Http http = new Http();
HttpRequest req = new HttpRequest();
req.setEndpoint(Url.getOrgDomainUrl().toExternalForm() + pdf.getUrl());
req.setMethod('POST');
req.setHeader('Authorization', 'Bearer '+getAccessToken());

// Rather than including the data in the GET header we put it into a POST request body.
req.setBody('customFormData=' + customFormData);

HTTPResponse res = http.send(req);
Blob pdfContent = res.getBodyAsBlob();