Issue posting JSON Data with REST AddBody method - rest

Question

I'm having trouble with a POST request to an API which I am not the owner of.
The request must simply post JSON data. Please have a look:
var
RESTRequest : TRESTRequest;
RESTClient : TRESTClient;
Response : TRESTResponse;
contract : TJSONObject;
begin
RESTClient := TRESTClient.Create('URL');
try
RESTRequest := TRESTRequest.Create(nil);
try
contract := TJSONObject.Create;
contract.AddPair(TJSONPair.Create('name','my_first_contract.pdf'));
RESTRequest.Client := RESTClient;
RESTRequest.Method := rmPOST;
RESTRequest.Accept := 'application/json';
RESTRequest.AddParameter('j_token','mytoken',pkHTTPHEADER,poDoNotEncode);
RESTRequest.AddBody(contract);
RESTRequest.Execute;
Response := RESTRequest.Response;
ShowMessage(Response.StatusText + ' : ' + Response.Content);
finally
RESTRequest.Free;
end;
finally
RESTClient.Free;
end;
end;
I obtained this error :
Not Found : {"errors":"Fatal error in JsonConvert. Passed parameter json object in JsonConvert.deserializeObject() is not of type object.\n"}
I've read online that the AddBody() method first serializes its content if it's an object. In this case, the content of the body is my TJSONObject, but when I try to replace that with a String, like this:
var
contract : String;
...
begin
contract := '{"name":"my_first_contract.pdf"}';
...
RESTRequest.AddBody(contract, ctAPPLICATION_JSON);
...
end;
I'm getting the exact same error.
So, does that mean that a TJSONObject is not viewed as an Object for the JsonConvert.deserializeObject() method ? Or, is the serialization of the AddBody() messed up?

Answer 1

The problem was on the 'j_token' header : as I was trying to solve it, some friends wanted to help me but I didn't want to give them the access token because it's exclusive to my company. They still tried to access the api with a false token wich resulted with the same error as I was getting :
Not Found : {"errors":"Fatal error in JsonConvert. Passed parameter json object in JsonConvert.deserializeObject() is not of type object.\n"}
Thanks to that I could deduce that the issue was on the j_token. After setting up my own api I could watch what was I posting and then I saw that my 'j_token' header was still getting encoded even though I added the poDoNotEncode options to my AddParameter method.
I created a new post on this forum to look for that poDoNotEncode error if you ever stumble upon this same problem : Trouble with poDoNotEncode option in TRESTRequest.AddParameter() method