Projection recursive open

UserRepository.java

public interface UserRepository extends CrudRepository<User, Long> {
    
    @RestResource(path = "username", rel = "getUsername")
    UserUsernameAndGroupName findUsernameAndGroupNameById(@Param("id") Long id);
    
    interface UserUsernameAndGroupName {
        
        String getUsername();
        
        default String getGroupName() {
            
            return getGroup().getName();
        }
        
        @JsonIgnore
        GroupName getGroup();
        
        interface GroupName {
            
            String getName();
        }
    }
}