(Delphi ActiveX) Get XOAUTH2 Access Token from Google OAuth 2.0 Authorization Server

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount

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
http: TChilkatHttp;
cert: TChilkatCert;
success: Integer;
iss: WideString;
scope: WideString;
oauth_sub: WideString;
numSec: Integer;
accessToken: WideString;

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

http := TChilkatHttp.Create(Self);

// --------------------------------------------------------------------------------
// For a step-by-step guide for setting up your Google Workspace service account,
// see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
// --------------------------------------------------------------------------------
// Begin by loading your Google service account key (.p12)
cert := TChilkatCert.Create(Self);
success := cert.LoadPfxFile('c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12','notasecret');
if (success <> 1) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

// The ISS is your service account email address ending in gserviceaccount.com.
iss := 'chilkatsvc@chilkat25.iam.gserviceaccount.com';

// The scope is always the following string:
scope := 'https://mail.google.com/';

// The sub is your company email address
oauth_sub := 'bob@yourcompany.com';

// The access token is valid for this number of seconds.
numSec := 3600;

accessToken := http.G_SvcOauthAccessToken(iss,scope,oauth_sub,numSec,cert.ControlInterface);
if (http.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end
else
  begin
    Memo1.Lines.Add('access token: ' + accessToken);
  end;

// The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.
end;