UserRepository, RoleRepository

UserRepository

public interface UserRepository extends JpaRepository<User, Long>{
	Optional<User> findByEmail(String email);
	Optional<User> findByUsernameOrEmail(String username, String email);
	Optional<User> findByUsername(String username);
	Boolean existsByUsername(String username);
	Boolean existsByEmail(String email);
}

RoleRepository

public interface RoleRepository extends JpaRepository<Role, Long> {
	Optional<Role> findByName(String name);
}