Post JSON data to RESTful datasnap server from delphi client

Question

I need to send a simple JSON object to a Restful datasnap server (Delphi) from a Delphi client. I am using Delphi XE. Can anybody help me out with the code? I am trying for hours but not getting it.. Please ask if details are not sufficient

Edit: Here is server side method declaration:

procedure updatemethodnme(str:string):string;

and here is client side code:

function PostData(request: string): boolean;
var
param: TStringList;
url, Text,str: string;
code: Integer;
http: TIDHttp;
begin
Result:= false;
http:= TIDHttp.Create(nil);
http.HandleRedirects:= true;
http.ReadTimeout:= 50000;
http.request.Connection:= 'keep-alive';
str:= '{"lamp":"'+lamp+'","floor":"'+floor+'","op":"'+request+'"}';
param:= TStringList.Create;
param.Clear;
param.Add(str);
url:= 'h***p://xx2.168.xx.xx:xxxx/Datasnap/rest/TserverMethods1/methdname/';
try
Text:= http.Post(url, param);
Result:= true;
except on E: Exception do
begin
Result := false;
end;
end;
end;

Please take a moment to explain a little more detail about what problems you've been facing. Do you have some trial code you can post so we can see what you've tried? — Jerry Dodge, Jul 28 '13 at 01:01
So where do you get an error? Can you verify on the server that you actually receive something? Looking at the code I would say that it looks as if it should work. — Birger, Jul 29 '13 at 06:43
Server is not receiving anything. on client side, sometimes its showing internal server error exception, n some time no error but nothing happens. — Prince Agrawal, Jul 29 '13 at 07:17
You are posting the data using a `TStringList` but you need to post it using a `TStream` instead. Posting a `TStringList` creates a very different kind of HTTP request than posting a `TStream`, which affects how the server interprets and parses the request. — Remy Lebeau, Jul 29 '13 at 07:35

score 6 · Accepted Answer · edited Jul 29 '13 at 07:30

Here's some simple XE2 test code sending JSON data through HTTP Post using SuperObject (using Indy's TIdHTTP):

procedure TFrmTTWebserviceTester.Button1Click(Sender: TObject);
var
  lJSO : ISuperObject;
  lRequest: TStringStream;
  lResponse: String;
begin
  // Next 2 lines for Fiddler HTTP intercept:
  IdHTTP.ProxyParams.ProxyServer := '127.0.0.1';
  IdHTTP.ProxyParams.ProxyPort := 8888;
  lJSO := SO('{"name": "Henri Gourvest", "vip": true, "telephones": ["000000000", "111111111111"], "age": 33, "size": 1.83, "adresses": [ { "adress": "blabla", "city": "Metz", "pc": 57000 }, { "adress": "blabla", "city": "Nantes", "pc": 44000 } ]}');
  lRequest := TStringStream.Create(lJSO.AsString, TEncoding.UTF8);
  try
    IdHTTP.Request.ContentType := 'application/json';
    IdHTTP.Request.Charset := 'utf-8';
    try
      lResponse := IdHTTP.Post('http://127.0.0.1:8085/ttposttest', lRequest);
      ShowMessage(lResponse);
    except
      on E: Exception do
        ShowMessage('Error on request:'#13#10 + E.Message);
    end;
  finally
    lRequest.Free;
  end;
  lJSO := nil;
end;

This is the data that goes out:

POST http://127.0.0.1:8085/ttposttest HTTP/1.0
Content-Type: application/json; charset=utf-8
Content-Length: 204
Connection: keep-alive
Host: 127.0.0.1:8085
Accept: text/html, */*
Accept-Encoding: identity
User-Agent: Mozilla/3.0 (compatible; Indy Library)

{"vip":true,"age":33,"telephones":["000000000","111111111111"],"adresses":[{"adress":"blabla","pc":57000,"city":"Metz"},{"adress":"blabla","pc":44000,"city":"Nantes"}],"size":1.83,"name":"Henri Gourvest"}

Receiver is a TWebAction on a TWebModule, with handler:

procedure TWebModuleWebServices.WebModuleWebServicesTTPostTestAction(
  Sender: TObject; Request: TWebRequest; Response: TWebResponse;
  var Handled: Boolean);
var
  S   : String;
  lJSO: ISuperObject;
begin
  S := Request.Content;
  if S <> '' then
    lJSO := SO('{"result": "OK", "encodingtestcharacters": "Typed € with Alt-0128 Will be escaped to \u20ac"}')
  else
    lJSO := SO('{"result": "Error", "message": "No data received"}');
  Response.ContentType := 'application/json';  // Designating the encoding is somewhat redundant for JSON (http://stackoverflow.com/questions/9254891/what-does-content-type-application-json-charset-utf-8-really-mean)
  Response.Charset := 'utf-8';
  Response.Content := lJSO.AsJSON;
  Handled := true;
end; { WebModuleWebServicesTTPostTestAction }

It uses TIdHTTPWebBrokerBridge:

FWebBrokerBridge := TIdHTTPWebBrokerBridge.Create(Self);
// Register web module class.
FWebBrokerBridge.RegisterWebModuleClass(TWebModuleWebServices);
// Settings:
FWebBrokerBridge.DefaultPort := 8085;

This is the actual response:

HTTP/1.1 200 OK
Connection: close
Content-Type: application/json; charset=utf-8
Content-Length: 92

{"encodingtestcharacters":"Typed\u20acwithAlt0128FollowedBy8364escaped\u8364","result":"OK"}

Hey.. thanx for the reply... Client side m able to send data using super object. but coming to server side, I want to use datasnap servermethods only. is there any way to do that? — Prince Agrawal, Jul 30 '13 at 03:58
What do you mean by using ISuperObject? When you are using lJSO.AsString then that super object is useless. — saeed khalafinejad, Aug 03 '20 at 15:02

score 0 · Answer 2 · answered Jul 27 '13 at 19:19

0

You can use Indy's TIdHTTP component to Post() JSON-encoded data to a REST server. You would simply have to encode and decode the JSON data in your own code.

answered Jul 27 '13 at 19:19

Remy Lebeau

454,445
28
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620

I was going to mention exactly this, except that I'm unsure if the OP needs help with the Client, Server, or Both. – Jerry Dodge Jul 27 '13 at 20:16
I thought it was very clear in his first sentence: "I need to send a simple JSON object **to a Restful datasnap server** (Delphi) **from a Delphi client**". – Remy Lebeau Jul 28 '13 at 00:56
I understand that's the server-side which is being used, and there's also a client-side as well, both written in Delphi. I'm just not sure if the difficulties are related to the Client, Server, or Both. – Jerry Dodge Jul 28 '13 at 00:58
Are you joking? It's clear that he is trying to write a client that needs to post to a server. – Remy Lebeau Jul 28 '13 at 01:28
I've tried with indy idhttp component already.. actually m not getting hw to encode json data in client side. earlier I sent a string & an integer by idhttp n it worked... but no idea how to deal with json – Prince Agrawal Jul 28 '13 at 01:59
@achievelimitless The the issue is with serializing JSON data? – Jerry Dodge Jul 28 '13 at 02:20
@achievelimitless: put the JSON data into a `TStringStream` or `TMemoryStream` and then `Post()` that. You will likely need to set the `TIdHTTP.Request.ContentType` to `'application/json'`, and maybe the `TIdHTTP.Request.Charset` as well. – Remy Lebeau Jul 28 '13 at 20:54
1

@achievelimitless: you are posting the JSON data using a `TStringList`, which is wrong. You have to use a `TStream` instead, like I mentioned earlier. Posting a `TStringList` creates a very different kind of HTTP request body than posting a `TStream`. – Remy Lebeau Jul 29 '13 at 07:34

score 0 · Answer 3 · answered Sep 28 '18 at 11:53

From Delphi6 posting to a datasnap server built in XE5 the above works for me, but I had found out the server method needed the parameter to be defined as a TJSONObject instead of TStream. Something odd in addition to this, the Datansap server changes the lookup method when you do a post instead of a get. For example I had a method named ImportData. But when you debug the server it was looking for an UpdateImportData method. So when I added the new method and changed the parameter type to Data.DBXJSON.TJSONObject it worked.

Post JSON data to RESTful datasnap server from delphi client

3 Answers3

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