我有两个实体：“user”和“request”：

@Entity
@Table(name = "user")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Integer id;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @Builder.Default
    @OneToMany(cascade = {CascadeType.ALL}, mappedBy = "user", orphanRemoval = true)
    private List<Request> requests = new ArrayList<>();

@Entity
@Table(name = "request")
public class Request {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Integer id;

    @Column(name = "start_date")
    private LocalDate startDate;

    @Column(name = "end_date")
    private LocalDate endDate;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id")
    private User user;

我想得到一个结果集，它能够根据这两个实体的字段进行排序。按姓氏（来自用户）和开始日期（来自请求）。
以下是我的标准api类：

@Override
    public Page<Request> getRequests(Integer userId, PageableRequest request) {

        Pageable pageable = request.getPageRequest();
        int pageSize = pageable.getPageSize();
        long offset = pageable.getOffset();
        CriteriaBuilder cb = entityManager.getCriteriaBuilder();
        CriteriaQuery<Request> criteriaQuery = cb.createQuery(Request.class);
        Root<Request> requestRoot = criteriaQuery.from(Request.class);

        Predicate userPredicate = criteriaBuilder.equal(root.get(Request_.USER).get(User_.ID), userId);

        CriteriaQuery<Request> select = criteriaQuery.select(requestRoot)
            .where(userPredicate)
            .orderBy(QueryUtils.toOrders(pageable.getSort(), requestRoot, cb));

        TypedQuery<Request> typedQuery = entityManager.createQuery(select);
        typedQuery.setFirstResult((int) offset);
        typedQuery.setMaxResults(pageSize);

        Long count = getTotalCount(cb);
        return new PageImpl<>(typedQuery.getResultList(), pageable, count);
    }

我希望能够排序方式：sort=lastname或sort=startdate
以下是不起作用的选项：

.orderBy(QueryUtils.toOrders(pageable.getSort(), requestRoot.join(User_.LAST_NAME), cb));

和

.orderBy(QueryUtils.toOrders(pageable.getSort(), requestRoot.join(Request.USER), cb));

如何能够同时按根实体（请求）和加入的（用户）进行排序？