Lazarus Pascal

Refresh GMail SMTP OAuth2 Access Token

See more OAuth2 Examples

Demonstrates how to refresh an access token for sending email via GMail (SMTP). Lazarus Pascal

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;

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

procedure RunDemo;
var
  success: Boolean;
  jsonToken: TJsonObject;
  oauth2: TOAuth2;
  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 GMail SMTP Access Token 
  //  for sample code showing how to obtain a GMail SMTP access token for desktop apps.

  //  It is assumed we previously obtained an OAuth2 access token for GMail (one with a scope for sending email).

  jsonToken := TJsonObject.Create;
  success := jsonToken.LoadFile('qa_data/tokens/_gmailSmtp.json');
  if (success <> True) then
    begin
      WriteLn('Failed to load _gmailSmtp.json');
      Exit;
    end;

  //  The access token JSON looks something like this:

  //  	{ 
  //  	 "access_token": "abac.Ci-ZabcdF37-NUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5ofCzRabcdTDMGaa2Q",
  //  	 "token_type": "Bearer",
  //  	 "expires_in": 3600,
  //  	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
  //  	}
  //  

  oauth2 := TOAuth2.Create;

  oauth2.TokenEndpoint := 'https://www.googleapis.com/oauth2/v4/token';

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

  //  The response contains a new access token, but we must keep
  //  our existing refresh token for when we need to refresh again in the future.
  jsonToken.UpdateString('access_token',oauth2.AccessToken);

  //  Save the new JSON access token response to a file.
  sbJson := TStringBuilder.Create;
  jsonToken.EmitCompact := False;
  jsonToken.EmitSb(sbJson);
  sbJson.WriteFile('qa_data/tokens/_gmailSmtp.json','utf-8',False);

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


  jsonToken.Free;
  oauth2.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.