How do I send a request to a Java server in such a way it can use polymorphism (enum.valueof string)?

The Java server in question is SignServer. When I send a get request to /signserver/process with processType = signDocument, it works. However, when I send with processType = validateDocument, the server responds with:

Received request wasn't an expected GenericSignRequest

If we look in PDFSigner.java on line 207 we see that exception is thrown if !(signRequest instanceof GenericSignRequest). A GenericSignRequest is made via parsing, as seen in GenericSignRequest.java. If we look in GenericProcessServlet.java we see that at some point the processType is turned in to an ISO-8859-1 string (processTypeAttribute = item.getString("ISO-8859-1")) and then in to an enum (ProcessType.valueOf(processTypeAttribute)).

That process relies on intricacies of the Java language, and I'm writing in JavaScript. I believe this is the reason for the error.

Here's how I send a request to SignServer:

var formdata = require('form-data');

var form = new formdata();

form.append('workerName', 'PDFSigner');
form.append('processType', 'validateDocument');
form.append('data', file_buffer, { filename: 'document.pdf });

var request = form.submit('http://localhost:8080/signserver/process', function(err, res) {});

I tried setting forms headers charset to 'utf-8', I also tried 'ISO-8859-1'. It did not work.

I tried sending processType as a buffer instead of a string, and it didn't work either.

(The same code works perfectly if processType is 'signDocument' - it successfuly sends a pdf and receives a signed pdf)

via Ivan Rubinson