Dart

Refresh HMRC OAuth2 Access Token

See more OAuth2 Examples

Demonstrates how to refresh an HMRC access token. 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.

  // See Get HMRC Access Token 
  // for sample code showing how to obtain a HMRC access token for desktop apps.

  // It is assumed we previously obtained an OAuth2 access token for HMRC.

  final jsonToken = CkJsonObject();
  try {
    jsonToken.loadFile('qa_data/tokens/hmrc.json');
  } on ChilkatException {
    print('Failed to load hmrc.json');
    return;
  }

  // The access token JSON looks something like this:

  // {
  //   "token_type": "Bearer",
  //   "scope": "user_impersonation",
  //   "expires_in": "3599",
  //   "ext_expires_in": "0",
  //   "expires_on": "1524783438",
  //   "not_before": "1524779538",
  //   "resource": "https://mydomain.api.crm.dynamics.com",
  //   "access_token": "...",
  //   "refresh_token": "...",
  //   "id_token": "..."
  // }

  final oauth2 = CkOAuth2();

  oauth2.tokenEndpoint = 'https://test-api.service.hmrc.gov.uk/oauth/token';

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

  // Load the access token response into the json object 
  jsonToken.load(oauth2.accessTokenResponse);

  // If an "expires_on" member does not exist, then add the JSON member by
  // getting the current system date/time and adding the "expires_in" seconds.
  // This way we'll know when the token expires.
  if (!jsonToken.hasMember('expires_on')) {
    final dtExpire = CkDateTime();
    dtExpire.setFromCurrentSystemTime();
    dtExpire.addSeconds(jsonToken.intOf('expires_in'));
    jsonToken.appendString('expires_on', dtExpire.getAsUnixTimeStr(false));
  }

  // Save the new JSON access token response to a file.
  // The access + refresh tokens contained in this JSON will be needed for the next refresh.
  final sbJson = CkStringBuilder();
  jsonToken.emitCompact = false;
  jsonToken.emitSb(sbJson);
  sbJson.writeFile('qa_data/tokens/hmrc.json', 'utf-8', false);

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