API request refused with "Request had insufficient authentication scopes"

The service account generated according to the Java API GA4 quickstart guide lacks the necessary authentication scopes to grant access to the associated GA4 Account and Property, as indicated in the Service Account .json file.

As a result, utilizing the API to fetch analytics metrics in Java becomes unfeasible.

I encountered persistent issues when attempting to use the Java client library, consistently encountering the same error. However, I found success when I utilized the Python library with the same Service Account JSON credentials.

This was solved by using a different GA4 Data API Java method to obtain the required credential from the client_secrets.json file. See

stackoverflow.com/questions/76882694/google-analytics-4-api-service-account-has-full-admin-privileges-still-permi/77106015#77106015

In essence, in my code as at the above location I needed to replace

GoogleCredentials gc = ServiceAccountCredentials.fromStream(this.getClass().getResourceAsStream("/client_secrets.json")).createScoped(Collections.singletonList(StorageScopes.DEVSTORAGE_FULL_CONTROL));

with

GoogleCredentials gc = GoogleCredentials.fromStream(this.getClass().getResourceAsStream("/client_secrets.json"));

to solve the "insufficient authentication scopes" error.