(Delphi DLL) Get a Xero OAuth2 Access Token via PKCE

See more Xero Examples

Gets a Xero OAuth2 access token via PKCE.

For more information, see https://github.com/XeroAPI/Xero-Postman-Tutorial-PKCE-Edition

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;

...

procedure TForm1.Button1Click(Sender: TObject);
var
oauth2: HCkOAuth2;
success: Boolean;
url: PWideChar;
numMsWaited: Integer;
sbJson: HCkStringBuilder;

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

oauth2 := CkOAuth2_Create();

// For Xero OAuth2, set the listen port equal to the port used
// in the Authorized Redirect URL for the Client ID.
// For example, in this case the Authorized Redirect URL would be http://localhost:55568/
// (The final "/" char is important to include in your Authorized Redirect URL in the Xero application settings in the Xero developer portal.)
// Your app should choose a port not likely not used by any other application.
// See Xero OAuth2 for Desktop Apps for more information.
CkOAuth2_putListenPort(oauth2,55568);

CkOAuth2_putAuthorizationEndpoint(oauth2,'https://login.xero.com/identity/connect/authorize');
CkOAuth2_putTokenEndpoint(oauth2,'https://identity.xero.com/connect/token');

// Replace this with your actual Client ID.
CkOAuth2_putClientId(oauth2,'XERO_APP_OAUTH2_CLIENT_ID');

// To use PKCE, enable code challenge and set the code challenge method to "S256".
CkOAuth2_putCodeChallenge(oauth2,True);
CkOAuth2_putCodeChallengeMethod(oauth2,'S256');

// See https://developer.xero.com/documentation/oauth2/scopes for a complete list of scopes.
// You will need to change the scopes depending on what access is needed..
CkOAuth2_putScope(oauth2,'openid profile email accounting.transactions accounting.attachments accounting.settings payroll.employees offline_access');

// Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
url := CkOAuth2__startAuth(oauth2);
if (CkOAuth2_getLastMethodSuccess(oauth2) <> True) then
  begin
    Memo1.Lines.Add(CkOAuth2__lastErrorText(oauth2));
    Exit;
  end;

Memo1.Lines.Add('URL: ' + url);

// At this point, your application should load the URL in a browser.
// For example, 
// in C#: System.Diagnostics.Process.Start(url);
// in Java: Desktop.getDesktop().browse(new URI(url));
// in VBScript: Set wsh=WScript.CreateObject("WScript.Shell")
//              wsh.Run url
// in Xojo: ShowURL(url)  (see http://docs.xojo.com/index.php/ShowURL)
// in Dataflex: Runprogram Background "c:\Program Files\Internet Explorer\iexplore.exe" sUrl        
// in dBASE: run(false, 'rundll32 url.dll,FileProtocolHandler "' + lcUrl + '"')
// The Google account owner would interactively accept or deny the authorization request.

// Add the code to load the url in a web browser here...
// Add the code to load the url in a web browser here...
// Add the code to load the url in a web browser here...
// System.Diagnostics.Process.Start(url);

// Now wait for the authorization.
// We'll wait for a max of 60 seconds.
numMsWaited := 0;
while (numMsWaited < 60000) and (CkOAuth2_getAuthFlowState(oauth2) < 3) do
  begin
    CkOAuth2_SleepMs(oauth2,100);
    numMsWaited := numMsWaited + 100;
  end;

// If there was no response from the browser within 30 seconds, then 
// the AuthFlowState will be equal to 1 or 2.
// 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
// 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
// In that case, cancel the background task started in the call to StartAuth.
if (CkOAuth2_getAuthFlowState(oauth2) < 3) then
  begin
    CkOAuth2_Cancel(oauth2);
    Memo1.Lines.Add('No response from the browser!');
    Exit;
  end;

// Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
// The possible AuthFlowState values are:
// 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
// 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
// 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
if (CkOAuth2_getAuthFlowState(oauth2) = 5) then
  begin
    Memo1.Lines.Add('OAuth2 failed to complete.');
    Memo1.Lines.Add(CkOAuth2__failureInfo(oauth2));
    Exit;
  end;

if (CkOAuth2_getAuthFlowState(oauth2) = 4) then
  begin
    Memo1.Lines.Add('OAuth2 authorization was denied.');
    Memo1.Lines.Add(CkOAuth2__accessTokenResponse(oauth2));
    Exit;
  end;

if (CkOAuth2_getAuthFlowState(oauth2) <> 3) then
  begin
    Memo1.Lines.Add('Unexpected AuthFlowState:' + IntToStr(CkOAuth2_getAuthFlowState(oauth2)));
    Exit;
  end;

// Save the full JSON access token response to a file.
sbJson := CkStringBuilder_Create();
CkStringBuilder_Append(sbJson,CkOAuth2__accessTokenResponse(oauth2));
CkStringBuilder_WriteFile(sbJson,'qa_data/tokens/xero-access-token.json','utf-8',False);

// The saved JSON response looks like this:

// 	{
// 	 "access_token": "...",
// 	 "token_type": "Bearer",
// 	 "expires_in": 3600,
// 	 "refresh_token": "..."
// 	}
// 
Memo1.Lines.Add('OAuth2 authorization granted!');
Memo1.Lines.Add('Access Token = ' + CkOAuth2__accessToken(oauth2));

CkOAuth2_Dispose(oauth2);
CkStringBuilder_Dispose(sbJson);

end;