“Login Required” 401 Unauthorized message when calling the v3 Google Calendar API using a Service Account via OAuth 2.0

Question

First, let me explain what I am trying to do, as this is a two part question.

I am building a JAX-RS service that internally authenticates with a Google account via

Answer 1

OK, so I have been playing around with this and have got past the 401 error, but I am now hitting a 403. However, I will detail the code I have written that at least answers the 401 problem.

I did not change any of the service account settings or re-generate any of the keys etc, that is all the same.

What has change is some of the code, and I upgraded to v3r20lv1.12.0-beta of the Calendar API.

The code below, as detailed above in the OP, remains the same, i.e.:

private static final HttpTransport HTTP_TRANSPORT = new NetHttpTransport();
private static final JsonFactory JSON_FACTORY = new JacksonFactory();
.
.
.
GoogleCredential credential = new GoogleCredential.Builder().setTransport(HTTP_TRANSPORT)
        .setJsonFactory(JSON_FACTORY)
        .setServiceAccountId("284XXXXXXXX@developer.gserviceaccount.com")
        .setServiceAccountScopes(CalendarScopes.CALENDAR)
        .setServiceAccountPrivateKeyFromP12File(new File("D:/3cd8XXXXXXXXXXXXXXXXXXXXXXXXXXXXXd635e-privatekey.p12"))
        .build();

The code to get a handle for the Calendar has changed, but this was forced by an API change:

Calendar calendar = new Calendar(HTTP_TRANSPORT, JSON_FACTORY, credential);

At this point, I can iterate through my calendar and see the events, by running the following code (this prints an event summary):

Events events = calendar.events().list(CALENDAR_ID).execute();

for (Event event : events.getItems())
{
    System.out.println(event.getSummary());
}

But, if I try and update an event, I get a 403 Forbidden error. I will raise a separate thread for this, and will link the two threads together.

Thanks to all for your help!

EDIT: here is the new thread.