Google Contacts API - failing to refresh access token

Question

We use Google Contacts API with OAuth2:

credential = new GoogleCredential.Builder().setTransport(new NetHttpTransport())
        .setJsonFactory(new JacksonFactory())
        .setClientSecrets(OAuth2ClientId(), OAuth2ClientSecret())
        .addRefreshListener(new CredentialRefreshListener() {...});

myService = new ContactsService("My-App");
myService.setOAuth2Credentials(credential);

and quite regularly we receive '401 Unauthorized' response that the GData library can't handle. AuthenticationException throws NPE when WWW-Authenticate header is missing.

Caused by: java.lang.NullPointerException: No authentication header information
        at com.google.gdata.util.AuthenticationException.initFromAuthHeader(AuthenticationException.java:96) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.util.AuthenticationException.<init>(AuthenticationException.java:67) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.client.http.HttpGDataRequest.handleErrorResponse(HttpGDataRequest.java:608) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.client.http.GoogleGDataRequest.handleErrorResponse(GoogleGDataRequest.java:564) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.client.http.HttpGDataRequest.checkResponse(HttpGDataRequest.java:560) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.client.http.HttpGDataRequest.execute(HttpGDataRequest.java:538) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.client.http.GoogleGDataRequest.execute(GoogleGDataRequest.java:536) ~[gdata-core-1.0-1.47.1.jar:na]
        at com.google.gdata.client.Service.getFeed(Service.java:1135) ~[gdata-core-1.0-1.47.1.jar:1.47.1]
        at com.google.gdata.client.Service.getFeed(Service.java:1077) ~[gdata-core-1.0-1.47.1.jar:1.47.1]
        at com.google.gdata.client.GoogleService.getFeed(GoogleService.java:676) ~[gdata-core-1.0-1.47.1.jar:1.47.1]
        at com.google.gdata.client.Service.query(Service.java:1237) ~[gdata-core-1.0-1.47.1.jar:1.47.1]
        at com.google.gdata.client.Service.query(Service.java:1178) ~[gdata-core-1.0-1.47.1.jar:1.47.1]

We managed to add a wrapper that would try token refreshing on this NPE. It helps but then there are still many cases when refreshing fails:

credential.refreshToken() == false

When we run refreshToken() in the debugger we see that executeRefreshToken() is executed without an exception but tokenResponse==null is returned. As a result refreshToken() returns false and no reason is passed to the listeners

try {
    TokenResponse tokenResponse = executeRefreshToken();
    if (tokenResponse != null) {
      setFromTokenResponse(tokenResponse);
      for (CredentialRefreshListener refreshListener : refreshListeners) {
        refreshListener.onTokenResponse(this, tokenResponse);
      }
      return true;
    }
  } catch (TokenResponseException e) {
    boolean statusCode4xx = 400 <= e.getStatusCode() && e.getStatusCode() < 500;
    // check if it is a normal error response
    if (e.getDetails() != null && statusCode4xx) {
      // We were unable to get a new access token (e.g. it may have been revoked), we must now
      // indicate that our current token is invalid.
      setAccessToken(null);
      setExpiresInSeconds(null);
    }
    for (CredentialRefreshListener refreshListener : refreshListeners) {
      refreshListener.onTokenErrorResponse(this, e.getDetails());
    }
    if (statusCode4xx) {
      throw e;
    }
  }
  return false;

Our tokens are always for multiple scopes: https://www.googleapis.com/auth/userinfo.email https://www.google.com/m8/feeds https://www.googleapis.com/auth/calendar https://mail.google.com/ https://www.googleapis.com/auth/tasks

Update: We've successfully moved to People API and the new API is also used by our Unified API Contacts API https://docs.aurinko.io/article/25-contacts-api

Answer 1

There is currently a bug in the Contacts API where certain HTTP User-Agent strings, cause the 401 response to return as an HTML page instead of an XML response, and missing the WWW-Authenticate header that the AuthenticationException class is relying on. GContacts-Java is one of these special user agent strings. A workaround is to change the user agent of your client after you create it:

ContactsService service = new ContactsService(applicationName);
service.getRequestFactory().setHeader("User-Agent", applicationName);

This should eliminate the NPE, and allow the client library to automatically detect expired tokens and refresh them automatically.