keycloak has REST API for creating an access_token using refresh_token. It is a POST endpoint with application/x-www-form-urlencoded
Here is how it looks:
Method: POST
URL: https://keycloak.example.com/auth/realms/myrealm/protocol/openid-connect/token
Body type: x-www-form-urlencoded
Form fields:
client_id : <my-client-name>
grant_type : refresh_token
refresh_token: <my-refresh-token>
This will give you new access token using refresh token.
NOTE: if your refresh token is expired it will throw 400 exception in that you can make user login again.
Check out a sample in Postman, you can develop and corresponding API using this.
