Question

我在这里面临一个小问题。

我有两个实体：Parent和Child，Parent有一个注释@OneToMany。

问题是当我尝试插入一个新的Parent时，它会在持久化子代时崩溃，因为尚未生成父ID。

这是一个解决方法吗？

@Entity
@Table(name = "PRODUTO")
public class Parent extends BaseEntity
{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "ID_PRODUTO")
    private Integer produtoId;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "produtoId", orphanRemoval = true)
    // @JoinTable(name = "PRODUTO_TAMANHO", joinColumns = @JoinColumn(name = "ID_PRODUTO"))
    @OrderBy("preco ASC")
    private List<Child> children;
}


@Entity
@IdClass(Child.PrimaryKey.class)
@Table(name = "PRODUTO_TAMANHO")
public class Child extends BaseEntity
{
    public static class PrimaryKey extends BaseEntity
    {
        private static final long serialVersionUID = -2697749220510151526L;

        private Integer parentId;

        private String tamanho;

        //rest of implementation
    }

    @Id
    @Column(name = "ID_PRODUTO")
    private Integer parentId;

    @Id
    @Column(name = "TAMANHO")
    private String tamanho;

    @ManyToOne
    @JoinColumn(name = "ID_PRODUTO", insertable = false, updatable = false)
    private Parent parent;
}

我认为如果我先坚持父母，坚持孩子将是一个糟糕的方法。

这是一种在坚持父母的情况下坚持孩子的方法吗？

谢谢！

Guys，持久化Parent时发生的异常是： com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException：列'ID_PRODUTO'不能为空

我发现一个人面临同样的问题：@OneToMany and composite primary keys?（可能会更好地解释）

这是我的插入代码

Parent parent = new Parent();

Child child1 = new Child();
child1.setTamanho("Tamanho 1");
child1.setParent(parent);

Child child2 = new Child();
child2.setTamanho("Tamanho 1");
child2.setParent(parent);

List<Child> children = parent.getChildren();
children.add(child1);
children.add(child2);

save(parent);
//all of this instances, is coming from a view.jsp binded by spring, I can confirm it is exactly like this, with parentId as null
//when updating, it goes perfectly

Answer 1

您的实体类几乎没有问题。

父实体中的mappedBy属性应设置为parent：mappedBy =“parent”。
在子实体中，不需要以下字段。

@Id

@Column（name =“ID_PRODUTO”，nullable = true）

private Integer parentId;

更新的实体就是这样。

@Entity
@Table(name = "PRODUTO")
public class Parent extends BaseEntity
{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "ID_PRODUTO")
    private Integer produtoId;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "parent", orphanRemoval = true)
    // @JoinTable(name = "PRODUTO_TAMANHO", joinColumns = @JoinColumn(name = "ID_PRODUTO"))
    @OrderBy("preco ASC")
    private List<Child> children;
}


@Entity
@IdClass(Child.PrimaryKey.class)
@Table(name = "PRODUTO_TAMANHO")
public class Child extends BaseEntity
{
    public static class PrimaryKey extends BaseEntity
    {
        private static final long serialVersionUID = -2697749220510151526L;

        private Integer parentId;

        private String tamanho;

        //rest of implementation
    }

   /* @Id
    @Column(name = "ID_PRODUTO", nullable = true)
    private Integer parentId; */ // Not required.

    @Id
    @Column(name = "TAMANHO")
    private String tamanho;

    @ManyToOne
    @JoinColumn(name = "ID_PRODUTO", insertable = false, updatable = false)
    private Parent parent;
}

另外，我不了解主键的子内部类。使用正确的主要内容，因为您使用了父级。

插入时将父母和子女的父母都设置为父母。有关详细信息，请参阅我的博客。Here

Hibernate @ManyToOne级联子约束异常

1 个答案: