Pascal (Lazarus/Delphi)

Refresh HMRC OAuth2 Access Token

See more OAuth2 Examples

Demonstrates how to refresh an HMRC access token. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.OAuth2,
  Chilkat.StringBuilder,
  Chilkat.JsonObject,
  Chilkat.CkDateTime;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  jsonToken: TJsonObject;
  oauth2: TOAuth2;
  dtExpire: TCkDateTime;
  sbJson: TStringBuilder;

begin
  success := False;

  //  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 := TJsonObject.Create;
  success := jsonToken.LoadFile('qa_data/tokens/hmrc.json');
  if (success <> True) then
    begin
      WriteLn('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 := TOAuth2.Create;

  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 <> True) then
    begin
      WriteLn(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') = False) then
    begin
      dtExpire := TCkDateTime.Create;
      dtExpire.SetFromCurrentSystemTime();
      dtExpire.AddSeconds(jsonToken.IntOf('expires_in'));
      jsonToken.AppendString('expires_on',dtExpire.GetAsUnixTimeStr(False));
    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 := TStringBuilder.Create;
  jsonToken.EmitCompact := False;
  jsonToken.EmitSb(sbJson);
  sbJson.WriteFile('qa_data/tokens/hmrc.json','utf-8',False);

  WriteLn('OAuth2 authorization granted!');
  WriteLn('New Access Token = ' + oauth2.AccessToken);


  jsonToken.Free;
  oauth2.Free;
      dtExpire.Free;
  sbJson.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.