Spring Data JPA - 刪除子實體而不是在更新時設置為 null？

Question

我有以下域模型

users
----
id (PK)
name

orders
------
id (PK)
userid (PK)
name

Orders.userid 引用 User 中的 id 並且是復合主鍵的一部分。 （我需要在主鍵中使用 userid，因為它是一個分區鍵，而在 MySQL 中我們不能在沒有分區鍵的情況下創建主鍵）

在使用 JPA 更新用戶時，如果我嘗試使用清除關聯的訂單集合

User user = userRepository.getOne(id);
user.getOrders().clear();
userRepository.save(user);

JPA 首先嘗試將關聯訂單上的 userid 設置為 null，然后刪除該行。 這將失敗，因為 userid 不可為空並且是主鍵的一部分。 有沒有辦法告訴 JPA 它只需要刪除 Order 行而不先將 userid 列設置為 null？

更新

映射：我擁有的映射是這樣的：

@Entity
@Table(name = "users")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="id")
    public Long id;

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

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    @JoinColumn(name="userid", referencedColumnName = "id", insertable = true, updatable = true)
    @Fetch(FetchMode.JOIN)
    private Set<Order> orders;

}

@Entity
@Table(name = "orders")
@IdClass(Order.OrderPk.class)
public class Order implements Serializable {

    @Id
    @Column(name="id")
    private Long id;

    @Id
    @Column(name="userid")
    private Long userId;

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

    public static class OrderPk implements Serializable  {

        private Long id;

        private Long userId;
    }
}

你能告訴我映射會有什么變化嗎？

更新：

也嘗試了以下映射：

@Entity
@Table(name = "users")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="id", nullable = false)
    public Long id;

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

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.EAGER, mappedBy = "orderPk.user")
    @Fetch(FetchMode.JOIN)
    private Set<Order> orders;
}

@Entity
@Table(name = "orders")
public class Order implements Serializable {

    @EmbeddedId
    private OrderPk orderPk;

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

    @Embeddable
    public static class OrderPk implements Serializable {

        @GeneratedValue
        @Column(name="id", insertable = false, updatable = false, nullable = false)
        private Long id;

        @ManyToOne(fetch = FetchType.LAZY)
        @JoinColumn(name="userid", referencedColumnName = "id", insertable = false, updatable = false, nullable = false)
        private User user;
    }
}

在插入時，它抱怨說“為：class Order 生成了 null id”（也嘗試過使用 insertable=true 和 updatable=true）

Answer 1

您可以使用標識符保持連接，並確保刪除不會嘗試使用集合上的可更新和可插入注釋將 null 寫入集合 FK。

@Entity
@Table(name = "users")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="id", nullable = false)
    public Long id;

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

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch =     FetchType.EAGER)
    @JoinColumn(name = "userId", updatable = false, insertable = false)
    private Set<Order> orders;
}

@Entity
@Table(name = "orders")
public class Order implements Serializable {

    @Id
    @Column(name="id")
    private Long id;

    @Column(name="userid")
    private Long userId;

    @Column(name="name")
    private String name;
}

這

@JoinColumn(name = "userId", updatable = false, insertable = false)

part 表示子表不會更新，但可以刪除

Answer 2

這里的原因是關聯是單向的，所以User是擁有方（因為它是唯一的一方）。

使關聯雙向並使Order成為關聯所有者。 這樣您就可以避免冗余更新（而not null違反not null約束）。

Answer 3

以下實體映射對我有用。 為簡潔起見，刪除了所有 getter 和 setter。

用戶類

@Entity
public class User {

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    @OneToMany(mappedBy = "userId", cascade = { CascadeType.ALL }, orphanRemoval = true)
    private List<Orders> orders;

    public void removeOrder(Orders orders) {
        orders.setUserId(null);
        this.orders.remove(orders);
    }

    public void removeAllOrders() {
        orders.forEach(order -> order.setUserId(null));
        this.orders.clear();
    }
}

訂單類

@Entity
@IdClass(Orders.OrderPk.class)
public class Orders {

    @Id
    private Integer id;

    @Id
    @ManyToOne
    @JoinColumn(name = "userid")
    private User userId;

    private String name;

    public static class OrderPk implements Serializable {
        private Integer id;
        private Integer userId;
    }
}

要刪除的代碼

@Override
@Transactional
public void run(String... args) throws Exception {
    User user = userRepository.findOne(1);
    user.removeAllOrders();
    userRepository.save(user);
    System.out.println("Done");
}

生成的sql

Hibernate: select user0_.id as id1_1_0_, user0_.name as name2_1_0_ from user user0_ where user0_.id=?
Hibernate: select orders0_.userid as userid2_1_0_, orders0_.id as id1_0_0_, orders0_.userid as userid2_0_0_, orders0_.id as id1_0_1_, orders0_.userid as userid2_0_1_, orders0_.name as name3_0_1_ from orders orders0_ where orders0_.userid=?
Done
Hibernate: delete from orders where id=? and userid=?
Hibernate: delete from orders where id=? and userid=?