How do I authenticate certificate for Processing's HTTP Request class - processing

Question

I'm using the HTTP-Request-for-Processing class by Rune Madson and Daniel Shiffman to process GetRequest and PostRequest for use with a sites OAuth.
I type in the right URL and parameters to be processed:
GetRequest req = new GetRequest("https://www.afakesite.com/oauth2/token");
req.addHeader("grant_type","authorization_code");
req.addHeader("client_id",ID);
req.addHeader("client_secret",fancyClientSecret);
req.addHeader("code",authorizationCode);
req.send();
but I am greeted with these errors:
javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated
I also tried to use the Processing method:
loadJSONObject("https://www.afakesite.com/oauth2/token?grant_type=authorization_code&client_id=...")
Which works successfully without the above error so I know the site is returning data, but I also want to use the PostRequest class to submit files to the site. This command also doesn't report back a 400 error with the attached JSON file the site gives but instead discards it and gives me an exception.
So how should I go about Authenticating this request in Processing and if it's not possible or too complicated, how should I go about sending files to this site.
The site I'm trying authenticating is DeviantArt if that information is useful in any way.

Answer 1

I'd recommend trying to get something working without the library. You can just use the HttpsUrlConnection from the standard Java API.
Here's a little example that posts some data to a URL:
import javax.net.ssl.HttpsURLConnection;
import java.io.OutputStreamWriter;
import java.net.URL;
HttpsURLConnection connection = (HttpsURLConnection) new URL("https://example.com").openConnection();
connection.setRequestMethod("POST");
connection.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
writer.write("param1=Data for param1");
writer.write("&param2=Data for param2"); //Ampersand is necessary for more than one parameter
writer.write("&param3=Data for param3");
writer.flush();
int responseCode = connection.getResponseCode();
if(responseCode == 200){
System.out.println("POST was successful!");
}
else{
System.out.println("Error: " + responseCode);
}
Shameless self-promotion: There are a few more examples (including specifying authentication) available here.
If you can get this working, then you know it's something wonky with the library itself. And honestly just doing the post yourself doesn't take very many lines of code, so you can probably just get rid of the library altogether.
EDIT Processing will not compile the code because of a MalformedURLException which can be avoided by encasing in a "try" block
i.e.
try {
HttpsURLConnection connection = (HttpsURLConnection) new URL("https://example.com").openConnection();
//so on and so forth...
} catch(Exception e) {}