How to forward a text with special characters in REST responses, in Delphi?-CodePudding

Please help. I'm trying to learn REST concepts and make the first programs using Delphi and REST objects. I came across a problem that I don’t know how to solve. In the database I have a test with special characters from my mother tongue (Bosnian): č, ć, đ, š, ž. When I pass this text via the GET method, objects that parse and display this text in objects on the form display these characters as "?", "æ", "æè" etc. I researched and tried unsuccessfully to solve the problem. I tried to use the Utf8ToAnsi function and put iso-8859-2 instead of UTF-8 in the RESTClient, RESTRequest and RESTResponce object parameters. Please for help, instruction or advice on how to solve or investigate this problem.

Source code on server side:

procedure TWebModule1.UsersGet(Request: TWebRequest; Response: TWebResponse);
var
  a: TJSONArray;
  o: TJSONObject;
  i: Integer;
  Q1: TADOQuery;
begin
  Q1:=TADOQuery.Create(nil);
  Q1.Connection:= BasicDBConn.Konekcija;
  with Q1 do
  begin
    Active:=False;
    SQL.Clear;
    SQL.Add('Select USER_ID, USER_NAME, ROLE_NAME  from USERS, ROLES  '  
      ' where USERS.ROLE_ID=ROLES.ROLE_ID ');
    Active:= True;
  end;
  a := TJSONArray.Create;

  if Q1.RecordCount > 0 then
  begin
    for i:=1 to Q1.RecordCount do
    begin
      o := TJSONObject.Create;
      o.AddPair('USER_ID', Q1.Fields.Fields[0].Value);
      o.AddPair('USER_NAME', Q1.Fields.Fields[1].Value);
      o.AddPair('ROLE_NAME', Q1.Fields.Fields[2].Value);
      Q1.Next;
      a.AddElement(o);
    end;
  end;

  Response.ContentType := 'application/json';
  Response.Content := a.ToString;
  a.DisposeOf;
  Q1.Free;
end;

on client side:

procedure TGlavna.Button1Click(Sender: TObject);
begin
  RESTRequest.Resource := 'Users';
  RESTRequest.Method   := TRESTRequestMethod.rmGet;
  RESTRequest.Response := RESTResponse;

  RESTRequest.Execute;

  if assigned(fJSONArray) then fJSONArray.DisposeOf;
  fJSONArray := TJSONObject.ParseJSONValue(RESTResponse.Content) as TJSONArray;

  if RESTResponse.Content.IsEmpty then Application.MessageBox('Empty', 'Information', MB_OK)
    else Memo1.Lines.Add(RESTResponse.Content);
end;

This is what a data in DB looks like

USER_ID USER_NAME ROLE_ID u1 Test User 2
u2 T_č_ć_š_đ_ž 1
u3 t_Č_Ć_Ž_Đ_Š 1
u4 Bradić Kenan 1

In web browser, responce data is:

[{"USER_ID":"u1","USER_NAME":"Test User","ROLE_ID":"2"},{"USER_ID":"u3","USER_NAME":"t_È_Æ_Ž_Ð_Š","ROLE_ID":"1"},{"USER_ID":"u4","USER_NAME":"Bradiæ Kenan","ROLE_ID":"1"},{"USER_ID":"u2","USER_NAME":"T_è_æ_š_ð_ž","ROLE_ID":"1"}]

Headers in web browser:
General:
    Request URL: http://localhost:8080/Users
    Request Method: GET
    Status Code: 200 OK
    Remote Address: [::1]:8080
    Referrer Policy: strict-origin-when-cross-origin
Response Headers:
    Connection: close
    Content-Length: 228
    Content-Type: application/json; charset=ISO-8859-1
    Date: Mon, 27 Dec 2021 17:07:54 GMT
Request Headers:
    Accept: text/html,application/xhtml xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
    Accept-Encoding: gzip, deflate, br
    Accept-Language: en-US,en;q=0.9
    Cache-Control: max-age=0
    Connection: keep-alive
    Host: localhost:8080
    sec-ch-ua: " Not A;Brand";v="99", "Chromium";v="96", "Google Chrome";v="96"
    sec-ch-ua-mobile: ?0
    sec-ch-ua-platform: "Windows"
    Sec-Fetch-Dest: document
    Sec-Fetch-Mode: navigate
    Sec-Fetch-Site: none
    Sec-Fetch-User: ?1
    Upgrade-Insecure-Requests: 1
    User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36

Thank you...

CodePudding user response：

The HTTP response contains this line:

Content-Type: application/json; charset=ISO-8859-1

So the client handles interprets the Response content as ISO-85591 encoded instead of UTF-8. Your server side codes contains this line:

Response.ContentType := 'application/json';

Your server side code should clear the charset=ISO-85591 part.