Keycloak to save newly registered user into application database - spring

Question

In my app I have some entity relations such as User and Organization. I thought that I would use Keycloak so that I don't have to implement custom registration, login, password reset, authorization and authentication. Problem is, that when user registers to Keycloak I don't have new User entity in my internal database for the application. Is there any way to automatically create new User entity in my internal database upon his registration throughout Keycloak?
I thought of custom Security filter on in my app that would look something like that:
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.keycloak.KeycloakSecurityContext;
import org.springframework.web.filter.GenericFilterBean;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;
import java.util.Optional;
import java.util.UUID;
public class UserRegistrationFilter extends GenericFilterBean {
private static final Logger console = LogManager.getLogger(UserRegistrationFilter.class);
private final UserRepository userRepo;
public UserRegistrationFilter(UserRepository userRepository) {
this.userRepo = userRepository;
}
#Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
KeycloakSecurityContext ctx = (KeycloakSecurityContext) servletRequest.getAttribute(KeycloakSecurityContext.class.getName());
console.warn("executed");
if (ctx != null) {
console.warn(ctx.getToken().getSubject());
Optional<User> existing = userRepo.findById(UUID.fromString(ctx.getToken().getSubject()));
if (existing.isEmpty()) {
User user = new User();
user.setUuid(UUID.fromString(ctx.getToken().getSubject()));
userRepo.save(user);
}
}
}
}
but it seems like a bad idea.
Thank you for any advice.

Answer 1

I don't see a problem with your approach, I would probably do something similar.
Well, probably what I would do throughout the entire app is to retrieve the user not directly from UserRepository but from a UserService that uses UserRepository.
In UserService I would have a findById method that would internally ask the repo to find the user, and if it doesn't exists, then create it and return it.
This way, I wouldn't need the filter, which anyways I don't think it's that bad.
An alternative I can think of, is to listen to keycloak events via webhooks:
https://github.com/zonaut/keycloak-extensions/blob/master/spi-event-listener/README.md
https://github.com/jessylenne/keycloak-event-listener-http
So keycloak informs you about any changes, such as user creation.
This way you can create users directly in keycloak in a way that even if they never log in your app, you would still be able to register them in your app.
PS: I never tried keycloak events, so can't help with the details