Delphi REST API Post Sample

You would just use Indy's TIdHTTP component and call the Post method. Pass the URL as the first argument and your JSON string as the second argument. Something like this:

procedure TForm1.Button1Click(Sender: TObject);
var
  jsonToSend: TStringList;
  http: TIdHTTP;
begin
  http := TIdHTTP.Create(nil);
  try
    http.HandleRedirects := True;
    http.ReadTimeout := 5000;
    jsonToSend := TStringList.create;
    try
      jsonToSend.Add('{ Your JSON-encoded request goes here }');
      http.Post('http://your.restapi.url', jsonToSend);
    finally
      jsonToSend.Destroy;
    end;
  finally
    http.Destroy;
  end;
end;

I'm assuming you are already able to encode and decode the JSON and that you were just asking how to perform an HTTP post using Delphi.

One option, using some part of our mORMot Open Source framework:

uses SynCrtSock, SynCommons;
var t: variant;
begin
  TDocVariant.New(t);
  t.name := 'john';
  t.year := 1982;
  TWinHTTP.Post('http://servername/resourcename',t,'Content-Type: application/json');
end;

Note that here you can construct your JSON content using a custom variant storage, which will be converted as JSON text when sent to the server.