在Hibernate中删除@OneToMany中的父记录时，将子记录外键设置为null

@Entity
public class Parent {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Child> children;

    // 其他属性和方法
}

@Entity
public class Child {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    private Parent parent;

    // 其他属性和方法
}

Parent parent = entityManager.find(Parent.class, parentId);
for (Child child : parent.getChildren()) {
    child.setParent(null);
}
parent.getChildren().clear();
entityManager.remove(parent);