Bitcoind returning "Invalid JSON-RPC 2.0 response"?

Question

I am starting to use a basic implementation of Bitcoin JSON RPC (dzhuvinov library), and I am getting a strange result. Here is my code:

public static void main(String[] args)
{
    URL serverURL = null;

    final String rpcuser ="user";
      final String rpcpassword ="pass";

      Authenticator.setDefault(new Authenticator() {
          protected PasswordAuthentication getPasswordAuthentication() {
              return new PasswordAuthentication (rpcuser, rpcpassword.toCharArray());
          }
      });
    try {
        serverURL = new URL("http://127.0.0.1:18332/");

    } catch (MalformedURLException e) {
        System.err.println(e.getMessage());
        return;
    }
     JSONRPC2Session mySession = new JSONRPC2Session(serverURL);
     String method = "getinfo";
     int requestID = 0;
     JSONRPC2Request request = new JSONRPC2Request(method, requestID);
     JSONRPC2Response response = null;
     try {
             response = mySession.send(request);

     } catch (JSONRPC2SessionException e) {
             System.err.println(e.getMessage());
             return;
     }
     if (response.indicatesSuccess())
        System.out.println(response.getResult());
    else
        System.out.println(response.getError().getMessage());
}

And the response I am getting is:

Invalid JSON-RPC 2.0 response

Just to note - when executing this Python script:

access = jsonrpc.ServiceProxy("http://user:pass@127.0.0.1:18332/")
print access.getinfo()

I get a proper results.

What might be causing this problem and how should I go about fixing it?

Answer 1

As it turns out, the library I am using does not like JSON responses that contain both the field "error" and "response", even if the "error" field is set to null. I have already notified the creator of the library to possibly fix that issue and I have patched it myself as well:

In the private Map<String,Object> parseJSONObject(final String jsonString) function, one needs to add this at the end:

    Map<String,Object> answer = (Map<String,Object>)json;

    if (answer.containsKey("error")){
        if (answer.get("error")==null){
            answer.remove("error");
        }
    }
    if (answer.containsKey("result")){
        if (answer.get("result")==null){
            answer.remove("result");
        }
    }

    return answer;