Google App Engine Cloud Endpoints userId为null

Question

I am using a (little modified) workaround from this course , to fetch the userId, which is null if the request was sent from an Android client.

/**
 * This is an ugly workaround for null userId for Android clients.
 *
 * @param user A User object injected by the cloud endpoints.
 * @return the App Engine userId for the user.
 */
private static String getUserId(User user) {
    String userId = user.getUserId();
    if (userId == null) {
        LOG.info("userId is null, so trying to obtain it from the datastore.");
        AppEngineUser appEngineUser = new AppEngineUser(user);
        ofy().save().entity(appEngineUser).now();

        AppEngineUser savedUser = ofy().load().key(appEngineUser.getKey()).now();
        userId = savedUser.getUser().getUserId();
        LOG.info("Obtained the userId: " + userId);
    }
    return userId;
}

Although I am not able to get the userId.

INFO: Obtained the userId: null

This workaround has already worked perfectly in other projects, so the problem must be elsewhere. My endpoints api is annotated with the following scopes, clientIds and audiences:

scopes = {
            Constants.EMAIL_SCOPE
    },
    clientIds = {
            Constants.API_EXPLORER_CLIENT_ID,
            Constants.WEB_CLIENT_ID,
            Constants.ANDROID_CLIENT_ID
    },
    audiences = {
            Constants.ANDROID_AUDIENCE
    }

Constants.ANDROID_AUDIENCE and Constants.WEB_CLIENT_ID are the same. I am not using a web client, but Google told me to add a web client id. Does this client id need to have redirect uris and javascript origins specified?

In my Android client I am using the following to specify the audience.

mCredential = GoogleAccountCredential.usingAudience(
        EndpointService.this,
        "server:client_id:IDIDIDID.apps.googleusercontent.com"
);

Please help me to figure this one out.

Answer 1

I just understood why this workaround works. I need to begin a new objectify session so the cache is not used and the userId can be populated.

Objectify objectify = ofy().factory().begin();
AppEngineUser savedUser = objectify.load();