(Delphi ActiveX) OAuth2 for a GMail using a JSON Service Account Key

Demonstrates how get an OAuth2 access token for GMail (Google Service Account) using a JSON private key.

After the access token is obtained, it may be used to send email. When the access token expires, a new access token needs to be obtained (using this same procedure).

Note: This is for OAuth2 using Google Service account keys.

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
fac: TCkFileAccess;
jsonKey: WideString;
gAuth: TChilkatAuthGoogle;
tlsSock: TChilkatSocket;
success: Integer;
mailman: TChilkatMailMan;
email: TChilkatEmail;

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

// First load the JSON key into a string.
fac := TCkFileAccess.Create(Self);
jsonKey := fac.ReadEntireTextFile('qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json','utf-8');
if (fac.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(fac.LastErrorText);
    Exit;
  end;

// A JSON private key should look like this:

// 	{
// 	  "type": "service_account",
// 	  "project_id": "chilkattest-1350",
// 	  "private_key_id": "fa2e36ee26986eab628b59868af8bec1d1c64c38",
// 	  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIjFa...28N64N2n1E4FYzBZjSdy\n-----END PRIVATE KEY-----\n",
// 	  "client_email": "598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a@developer.gserviceaccount.com",
// 	  "client_id": "598922945226-00rb0ppfg0snd9jo7bhvd4v17jtj2d3a.apps.googleusercontent.com",
// 	  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
// 	  "token_uri": "https://accounts.google.com/o/oauth2/token",
// 	  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
// 	  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a%40developer.gserviceaccount.com"
// 	}

gAuth := TChilkatAuthGoogle.Create(Self);
gAuth.JsonKey := jsonKey;

// Choose a scope.
gAuth.Scope := 'https://mail.google.com/';

// Request an access token that is valid for this many seconds.
gAuth.ExpireNumSeconds := 3600;

// If the application is requesting delegated access:
// The email address of the user for which the application is requesting delegated access,
// then set the email address here. (Otherwise leave it empty.)
gAuth.SubEmailAddress := '';

// Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
// The Chilkat socket object is used so that the connection can be established
// through proxies or an SSH tunnel if desired.
tlsSock := TChilkatSocket.Create(Self);
success := tlsSock.Connect('www.googleapis.com',443,1,5000);
if (success <> 1) then
  begin
    Memo1.Lines.Add(tlsSock.LastErrorText);
    Exit;
  end;

// Send the request to obtain the access token.
success := gAuth.ObtainAccessToken(tlsSock.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(gAuth.LastErrorText);
    Exit;
  end;

// Examine the access token:
Memo1.Lines.Add('Access Token: ' + gAuth.AccessToken);

// Now that we have the access token, it may be used to send email
// while it remains valid.  Once the access token expires, a new access token 
// should be obtained using the same code as above.

// -----------------------------------------------------------------------
mailman := TChilkatMailMan.Create(Self);

// Set the properties for the GMail SMTP server:
mailman.SmtpHost := 'smtp.gmail.com';
mailman.SmtpPort := 587;
mailman.StartTLS := 1;

mailman.SmtpUsername := 'YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS';
mailman.OAuth2AccessToken := gAuth.AccessToken;

// Create a new email object
email := TChilkatEmail.Create(Self);

email.Subject := 'This is a test';
email.Body := 'This is a test';
email.From := 'YOUR NAME <YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS>';
success := email.AddTo('Chilkat Admin','admin@chilkatsoft.com');
// To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

// Call SendEmail to connect to the SMTP server and send.
// The connection (i.e. session) to the SMTP server remains
// open so that subsequent SendEmail calls may use the
// same connection.  
success := mailman.SendEmail(email.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(mailman.LastErrorText);
    Exit;
  end;

// You may close the connection here.  If the connection is kept open, 
// the next call to mailman.SendEmail will continue using the already-established connection
// (and automatically re-connect if needed).
success := mailman.CloseSmtpConnection();
if (success <> 1) then
  begin
    Memo1.Lines.Add('Connection to SMTP server not closed cleanly.');
  end;

Memo1.Lines.Add('Email Sent via GMail using an OAuth2 Service Account Key.');
end;