Fetching applicationDefault from GoogleCredentials

Question

I am working on a java spring project which requires me to publish a message to Google Pub/Sub. I need to send the access token as an Authorization header in the post request. I tried using GoogleCredentials.getApplicationDefault() but it requires GOOGLE_APPLICATION_CREDENTIALS to be set in the environmental variables.

Here is what I tried

Map<String, String> env = System.getenv();
Field field = env.getClass().getDeclaredField("m");
field.setAccessible(true);

((Map<String, String>) field.get(env)).put("GOOGLE_APPLICATION_CREDENTIALS", "/etc/gcp/sa_credentials.json");

GoogleCredentials credentials = GoogleCredentials.getApplicationDefault();
credentials.refreshIfExpired();

String accessToken = credentials.getAccessToken().toString();

When I try to run this, I get this error - java.io.IOException: Scopes not configured for service account. Scoped should be specified by calling createScoped or passing scopes to constructor

I am not sure how to add scope for the service account. Is there anything I am missing?

Answer 1

Simply create a scoped credential like this

GoogleCredentials credentials = GoogleCredentials.getApplicationDefault().createScoped(Arrays.asList("https://www.googleapis.com/auth/cloud-platform"));