Authentication Flow

Hello! Question about Blackbaud Sky Authentication.


I'm attempting to receive an authorization token so I can access the School API for a project that I'm working on. I have gone through the starter tutorials and can authenticate and use the school API through the developers console just fine. Previous projects worked on use Blackbaud-ON API which gives an authorization token through providing a login and password. I'm trying to replicate this flow as close as possible in a backend Java application. 


So my question is, is there a way I can achieve this without requiring a callback URL, and just simply get the token in a response after one request? Previous unrelated project that use OAuth usually had some work around where I could provide a secret and application ID and receive the token that way. If anyone could point me in the direction to documentation on how to achieve this functionality, I'd be grateful. Again, I'm trying to avoid having to use a callback url - ideally I would just need to make one request to authenticate, which the response would contain an access token (like the Blackbaud ON API).


Thanks!