(Delphi DLL) Google Sheets Refresh an Expired Access Token

Demonstrates how to refresh an expired access token. If a Google Sheets REST API call results in a 401 "unauthorized" response, then it is likely the access token expired. An application should be able to automatically refresh the access token with no user interaction and then re-try the request with the newly obtained access token.

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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, OAuth2, StringBuilder, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
jsonToken: HCkJsonObject;
success: Boolean;
oauth2: HCkOAuth2;
sbJson: HCkStringBuilder;

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

//  It is assumed we previously obtained an OAuth2 access token.
//  This example loads the JSON access token file
//  saved by this example: Get Google Sheets OAuth2 Access Token

jsonToken := CkJsonObject_Create();
success := CkJsonObject_LoadFile(jsonToken,'qa_data/tokens/googleSheets.json');
if (success <> True) then
  begin
    Memo1.Lines.Add('Failed to load googleSheets.json');
    Exit;
  end;

//  The access token JSON looks like this:

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

oauth2 := CkOAuth2_Create();

CkOAuth2_putTokenEndpoint(oauth2,'https://www.googleapis.com/oauth2/v4/token');

//  Replace these with actual values.
CkOAuth2_putClientId(oauth2,'GOOGLE-CLIENT-ID');
CkOAuth2_putClientSecret(oauth2,'GOOGLE-CLIENT-SECRET');

//  Get the "refresh_token"
CkOAuth2_putRefreshToken(oauth2,CkJsonObject__stringOf(jsonToken,'refresh_token'));

//  Send the HTTP POST to refresh the access token..
success := CkOAuth2_RefreshAccessToken(oauth2);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkOAuth2__lastErrorText(oauth2));
    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.
CkJsonObject_UpdateString(jsonToken,'access_token',CkOAuth2__accessToken(oauth2));

//  Save the new JSON access token response to a file.
sbJson := CkStringBuilder_Create();
CkJsonObject_putEmitCompact(jsonToken,False);
CkJsonObject_EmitSb(jsonToken,sbJson);
CkStringBuilder_WriteFile(sbJson,'qa_data/tokens/googleSheets.json','utf-8',False);

Memo1.Lines.Add('OAuth2 authorization granted!');
Memo1.Lines.Add('New Access Token = ' + CkOAuth2__accessToken(oauth2));

CkJsonObject_Dispose(jsonToken);
CkOAuth2_Dispose(oauth2);
CkStringBuilder_Dispose(sbJson);

end;