I am trying to read data from the database, using Hibernate.
I have following data model, which holds some user credentials data, split into several entities, with Entity C holding User authorization roles (user can have more than 1 role, hence ManyToMany):

A -> OneToOne -> B <- ManyToMany -> C

as written:

@Entity
public class A {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String s1;
    private String s2;
//getters, setters, etc.
}

@Entity
public class B {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String s1;
    private String s2;
    @OneToOne(cascade = CascadeType.REMOVE,
            fetch = FetchType.LAZY)
    private A aElement;
    @ManyToMany(targetEntity = C.class,
                fetch = FetchType.EAGER,
                cascade = CascadeType.ALL)
    @JoinTable(
            name = "b_x_c",
            joinColumns = @JoinColumn(table = "b", referencedColumnName = "id"),
            inverseJoinColumns = @JoinColumn(table = "c", referencedColumnName = "id")
    )
    private Set<C> cSet;
//getters, setters, etc.
}

@Entity
public class C {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String description;
    @ManyToMany(targetEntity = B.class,
            mappedBy = "cSet",
            cascade = CascadeType.ALL,
            fetch = FetchType.EAGER)
    private Set<B> bSet;
//getters, setters, etc.
}

I did write a CustomUserDetailService (using Spring Security for authorizaiton) for some user tweaking:

@Service
public class CustomUserDetailsService implements UserDetailsService {
    private final LoginService loginService ;

    public CustomUserDetailsService(LoginService loginService ) {
        this.loginService = loginService ;
    }

    @Override
    public UserDetails loadUserByUsername(String s) throws UsernameNotFoundException {
        return loginService.findCredentialsByS1(s)
                .map(this::createUserDetails)
                .orElseThrow(() -> new UsernameNotFoundException("no user found"));
    }

    private UserDetails createUserDetails(B credentials) {
        return User.builder()
                .username(credentials.getS1())
                .password(credentials.getS2())
                .roles(credentials.getCSet().toArray(String[]::new))
                .build();
    }
}

loginService is:

@Service
public class LoginService {
    public final BRepository bRepository;

    public ClientLoginService(BRepository bRepository) {
        this.bRepository = bRepository;
    }

    public Optional<B> findCredentialsByS1(String s) {
        return bRepository.findByS1IgnoreCase(s);
    }
}

and BRepository:

public interface BRepository extends JpaRepository<B, Long> {
        Optional<B> findByS1IgnoreCase(String s);
}

Now, when I login a User, CustomUserDetailsService is being invoked and loadUserByUsername() called, through which a Repository executes a call to the database, but somehow, the contents of C table are not loaded (they are properly connected in the intermediate (connector) database). Data of A table are being loaded, but C table not – and no error is given. What can be a reason here? I don’t quite understand why, especially that when I turn on Hibernate logging, and look into the queries that are being given, it should actually provide correct data, but debugging loadUserByUsername shows, that it’s empty.