How to add custom logic for authorizing and authentication in OAuth2.0 with Spring boot?

Question

While authorizing and generating access token using OAuth 2.0 implemented with Spring boot.. we implement UserEntity with UserDetails in which we return respective fields from methods getUsername() and getPassword() which is gets called while authorizing and authenticating. I tried to find APIs that will help me achieve this.. but i got no breakthrough yet. How can we enable OAuth 2.0 for single username and multiple passwords?. Thanks!