使用外键的JPQL查询

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    // getters and setters
}

@Entity
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @ManyToOne
    @JoinColumn(name = "user_id")
    private User user;
    
    private String orderNumber;
    // getters and setters
}

String jpql = "SELECT o FROM Order o WHERE o.user.id = :userId";
TypedQuery<Order> query = entityManager.createQuery(jpql, Order.class);
query.setParameter("userId", 1L); // 假设要查询用户ID为1的所有订单
List<Order> orders = query.getResultList();

String jpql = "SELECT o FROM Order o WHERE o.user.id = :userId";
TypedQuery<Order> query = entityManager.createQuery(jpql, Order.class);
query.setParameter("userId", 1L);
query.setFirstResult(0); // 设置起始记录
query.setMaxResults(10); // 设置每页记录数
List<Order> orders = query.getResultList();

try {
    entityManager.getTransaction().begin();
    User user = entityManager.find(User.class, 1L);
    Order order = new Order();
    order.setUser(user);
    order.setOrderNumber("ORD123");
    entityManager.persist(order);
    entityManager.getTransaction().commit();
} catch (Exception e) {
    entityManager.getTransaction().rollback();
    throw e;
}