[keycloak-user] Authorize with local Login Form

Hello, my application is Spring Security based. I've added and configured the Keycloak Spring Security Adapter. Now I would like to have my own Login page without redirect and customizing or adding any Keycloak Themes. Is it possible to use a local Login Form to authorize on the external Keycloak Server? If so, how to realize it? I've read something about Bearer Tokens. Is it the right way? Can someone point me into the right direction please?