Implement Access Token generation logic in App Engine for Oauth2

Hello,

We have setup an Oauth2 Service Application to connect to external vendor by using client ID and client secret. We are able to retrieve the access token when we click on the Access Token Link under below path.

PeopleTools >>Security>>Oauth2Administration>>AuthorizedUsers

Any guidance on how can I automate the action of clicking the link manually inside an App Engine to schedule the process. I tried using the same App Package Class method - UserLogin under PT_SECURITY.OAuth2.SEC_AUTHTOKEN but am not able to generate access token into the PSPTSECUSERTOKN table.