Dart

Automatically Refresh Token for 401 Unauthorized

See more Google Calendar Examples

Demonstrates how to automatically refresh an access token (without user interaction) when the token expires and a 401 Unauthorized response is received. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final tokenFilePath = 'qa_data/tokens/googleCalendar.json';

  // Get our current access token.
  final jsonToken = CkJsonObject();
  jsonToken.loadFile(tokenFilePath);
  if (!jsonToken.hasMember('access_token')) {
    print('No access token found.');
    return;
  }

  final http = CkHttp();
  http.authToken = jsonToken.stringOf('access_token');

  var jsonResponse = '';
  try {
    jsonResponse = http.quickGetStr('https://www.googleapis.com/calendar/v3/users/me/calendarList');
  } on ChilkatException catch (e) {

    if (http.lastStatus != 401) {
      print(e.lastErrorText);
      print('----');
      print(http.lastResponseBody);
      return;
    }

    // The access token must've expired. 
    // Refresh the access token and then retry the request.
    final oauth2 = CkOAuth2();

    oauth2.tokenEndpoint = 'https://www.googleapis.com/oauth2/v4/token';

    // Replace these with actual values.
    oauth2.clientId = 'GOOGLE-CLIENT-ID';
    oauth2.clientSecret = 'GOOGLE-CLIENT-SECRET';

    // Get the "refresh_token"
    oauth2.refreshToken = jsonToken.stringOf('refresh_token');

    // Send the HTTP POST to refresh the access token..
    try {
      oauth2.refreshAccessToken();
    } on ChilkatException catch (e) {
      print(e.lastErrorText);
      return;
    }

    // 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.
    jsonToken.updateString('access_token', oauth2.accessToken);

    // Save the new JSON access token response to a file.
    final sbJson = CkStringBuilder();
    jsonToken.emitCompact = false;
    jsonToken.emitSb(sbJson);
    sbJson.writeFile(tokenFilePath, 'utf-8', false);

    print('OAuth2 authorization granted!');
    print('New Access Token = ${oauth2.accessToken}');

    // re-try the original request.
    http.authToken = oauth2.accessToken;
    try {
      jsonResponse = http.quickGetStr('https://www.googleapis.com/calendar/v3/users/me/calendarList');
    } on ChilkatException catch (e) {
      print(e.lastErrorText);
      return;
    }
  }

  print(jsonResponse);
  print('-----------------------------');
}