(Delphi ActiveX) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
jsonToken: TChilkatJsonObject;
success: Integer;
oauth2: TChilkatOAuth2;
dtExpire: TCkDateTime;
sbJson: TChilkatStringBuilder;

begin
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// See Get HMRC Access Token 
// for sample code showing how to obtain a HMRC access token for desktop apps.

// It is assumed we previously obtained an OAuth2 access token for HMRC.

jsonToken := TChilkatJsonObject.Create(Self);
success := jsonToken.LoadFile('qa_data/tokens/hmrc.json');
if (success <> 1) then
  begin
    Memo1.Lines.Add('Failed to load hmrc.json');
    Exit;
  end;

// The access token JSON looks something like this:

// {
//   "token_type": "Bearer",
//   "scope": "user_impersonation",
//   "expires_in": "3599",
//   "ext_expires_in": "0",
//   "expires_on": "1524783438",
//   "not_before": "1524779538",
//   "resource": "https://mydomain.api.crm.dynamics.com",
//   "access_token": "...",
//   "refresh_token": "...",
//   "id_token": "..."
// }

oauth2 := TChilkatOAuth2.Create(Self);

oauth2.TokenEndpoint := 'https://test-api.service.hmrc.gov.uk/oauth/token';

// Replace these with actual values.
oauth2.ClientId := 'HMRC-CLIENT-ID';
oauth2.ClientSecret := 'HMRC-CLIENT-SECRET';

// Get the "refresh_token"
oauth2.RefreshToken := jsonToken.StringOf('refresh_token');

// Send the HTTP POST to refresh the access token..
success := oauth2.RefreshAccessToken();
if (success <> 1) then
  begin
    Memo1.Lines.Add(oauth2.LastErrorText);
    Exit;
  end;

// Load the access token response into the json object 
jsonToken.Load(oauth2.AccessTokenResponse);

// If an "expires_on" member does not exist, then add the JSON member by
// getting the current system date/time and adding the "expires_in" seconds.
// This way we'll know when the token expires.
if (jsonToken.HasMember('expires_on') = 0) then
  begin
    dtExpire := TCkDateTime.Create(Self);
    dtExpire.SetFromCurrentSystemTime();
    dtExpire.AddSeconds(jsonToken.IntOf('expires_in'));
    jsonToken.AppendString('expires_on',dtExpire.GetAsUnixTimeStr(0));
  end;

// Save the new JSON access token response to a file.
// The access + refresh tokens contained in this JSON will be needed for the next refresh.
sbJson := TChilkatStringBuilder.Create(Self);
jsonToken.EmitCompact := 0;
jsonToken.EmitSb(sbJson.ControlInterface);
sbJson.WriteFile('qa_data/tokens/hmrc.json','utf-8',0);

Memo1.Lines.Add('OAuth2 authorization granted!');
Memo1.Lines.Add('New Access Token = ' + oauth2.AccessToken);
end;