Lazarus Pascal Requires Chilkat v10.1.2+

Dropbox: OAuth2 Authorization to Obtain an Access Token

See more Dropbox Examples

Demonstrates how to get a Dropbox OAuth2 access token from a desktop application or script.

This example runs the OAuth 2.0 authorization flow that lets the user sign in to Dropbox and authorize your app.

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.JsonObject;

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

procedure RunDemo;
var
  success: Boolean;
  oauth2: TOAuth2;
  url: string;
  numMsWaited: Integer;
  json: TJsonObject;

begin
  success := False;

  //  For more information about the OAuth2, see OAuth 2.0 Authorization Flow

  oauth2 := TOAuth2.Create;

  //  The port should match the Authorized Redirect URL in your Dropbox app, 
  //  which would look like "http://localhost:3017/"
  oauth2.ListenPort := 3017;

  //  IMPORTANT: One of the OAuth2 redirect URIs for your Dropbox app must be
  //  exactly this string:  http://localhost:3017/

  oauth2.AuthorizationEndpoint := 'https://www.dropbox.com/oauth2/authorize';
  oauth2.TokenEndpoint := 'https://api.dropboxapi.com/oauth2/token';

  //  Replace this with your actual Dropbox App Key
  oauth2.ClientId := 'DROPBOX_APP_KEY';

  //  This is for Require Proof Key for Code Exchange (PKCE)
  //  See OAuth2 PKCE Explained
  oauth2.CodeChallenge := True;
  oauth2.CodeChallengeMethod := 'S256';

  //  Add token_access_type=offline to also get a refresh token in the response
  oauth2.AddAuthQueryParam('token_access_type','offline');

  //  Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
  url := oauth2.StartAuth();
  if (oauth2.LastMethodSuccess = False) then
    begin
      WriteLn(oauth2.LastErrorText);
      Exit;
    end;

  WriteLn('url = ' + url);

  //  Launch the default browser on the system and navigate to the url.
  //  The LaunchBrowser method was added in Chilkat v10.1.2.
  success := oauth2.LaunchBrowser(url);
  if (success = False) then
    begin
      WriteLn(oauth2.LastErrorText);
      Exit;
    end;

  //  Wait for the user to approve or deny authorization in the browser.
  numMsWaited := 0;
  while (numMsWaited < 90000) and (oauth2.AuthFlowState < 3) do
    begin
      oauth2.SleepMs(100);
      numMsWaited := numMsWaited + 100;
    end;

  //  If the browser does not respond within the specified time, AuthFlowState will be:
  //  
  //  1: Waiting for Redirect - The OAuth2 background thread is waiting for the browser's redirect request.
  //  2: Waiting for Final Response - The thread is awaiting the final access token response.
  //  In either case, cancel the background task initiated by StartAuth.

  if (oauth2.AuthFlowState < 3) then
    begin
      oauth2.Cancel();
      WriteLn('No response from the browser!');
      Exit;
    end;

  //  Check AuthFlowState to determine if authorization was granted, denied, or failed:
  //  
  //  3: Success - OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
  //  4: Access Denied - OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
  //  5: Failure - OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

  if (oauth2.AuthFlowState = 5) then
    begin
      WriteLn('OAuth2 failed to complete.');
      WriteLn(oauth2.FailureInfo);
      Exit;
    end;

  if (oauth2.AuthFlowState = 4) then
    begin
      WriteLn('OAuth2 authorization was denied.');
      WriteLn(oauth2.AccessTokenResponse);
      Exit;
    end;

  if (oauth2.AuthFlowState <> 3) then
    begin
      WriteLn('Unexpected AuthFlowState:' + oauth2.AuthFlowState);
      Exit;
    end;

  WriteLn('OAuth2 authorization granted!');

  json := TJsonObject.Create;
  json.Load(oauth2.AccessTokenResponse);
  json.EmitCompact := False;

  WriteLn('Access Token Response = ' + json.Emit());

  //  A sample access token response:

  //  {
  //    "access_token": "...",
  //    "token_type": "bearer",
  //    "expires_in": 14399,
  //    "refresh_token": "...",
  //    "scope": "account_info.read",
  //    "uid": "562542581",
  //    "account_id": "dbid:AACQhDS0E3_Vb72Ynd0F-GxGWdTI2qcTHzA"
  //  }

  WriteLn('Access Token = ' + oauth2.AccessToken);

  //  Save the JSON access token response to a file for subsequent use..
  json.WriteFile('qa_data/tokens/dropbox.json');


  oauth2.Free;
  json.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.