This Talend job (J013_ReadGBQ_ExternalTable)  shows to read data from an external table in Google BigQuery and log the results. You will probably want to see how the access token is implemented and adapt it in your job.

JOB DESCRIPTION

• First step of the job is only to generate a dummy read to BigQuery to load all libraries needed for the authentication.
• the tJava compoenent will generate an access token to read the external tables using the following scopes:
  • https://www.googleapis.com/auth/spreadsheets
  • https://www.googleapis.com/auth/bigquery
  • https://www.googleapis.com/auth/drive
• The job uses the access token to read the external table