Default project id in BigQuery Java API - google-bigquery

Question

I am performing a query using the BigQuery Java API with the following code:
try (FileInputStream input = new FileInputStream(serviceAccountKeyFile)) {
GoogleCredentials credentials = GoogleCredentials.fromStream(input);
BigQuery bigQuery = BigQueryOptions.newBuilder()
.setCredentials(credentials)
.build()
.getService();
QueryRequest request = QueryRequest.of("SELECT * FROM foo.Bar");
QueryResponse response = bigQuery.query(request);
// Handle the response ...
}
Notice that I am using a specific service account whose key file is given by serviceAccountKeyFile.
I was expecting that the API would pick up the project_id from the key file. But it is actually picking up the project_id from the default key file referenced by the GOOGLE_APPLICATION_CREDENTIALS environment variable.
This seems like a bug to me. Is there a way to workaround the bug by setting the default project explicitly?

Answer 1

Yeah, that doesn't sound right at all. It does sound like a bug. I always just use the export the GOOGLE_APPLICATION_CREDENTIALS environment variable in our applications.
Anyway, you try explicitly setting the project id to see if it works:
BigQuery bigQuery = BigQueryOptions.newBuilder()
.setCredentials(credentials)
.setProjectId("project-id") //<--try setting it here
.build()
.getService();

Answer 2

I don't believe the project is coming from GOOGLE_APPLICATION_CREDENTIALS. I suspect that the project being picked up is the gcloud default project set by gcloud init or gcloud config set project.
From my testing, BigQuery doesn't use a project where the service account is created. I think the key is used only for authorization, and you always have to set a target project. There are a number of ways:
.setProjectId(<target-project>) in the builder
Define GOOGLE_CLOUD_PROJECT
gcloud config set project <target-project>
The query job will then be created in target-project. Of course, your service key should have access to target-project, which may or may not be the same project where your key is created. That is, you can run a query on projects other than the project where your key is created, as long as your key has permission to do so.