Hibernate 中的继承。插入示例

Question

我想在产品类和笔记本电脑之间建立联系 产品类别

@Entity
@Table(name = "products")
@Inheritance(strategy = InheritanceType.JOINED)
public class Product {
    @Id
    @Column(unique = true, nullable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    @Column(nullable = false, unique = true)
    private String name;
    @Column(nullable = false)
    private BigDecimal cost;
    @Column(nullable = false)
    private int count;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "productStatus", nullable = false)
    private ProductStatus productStatus;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "productManufacture", nullable = false)
    private ProductManufacture productManufacture;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "productCategory", nullable = false)
    private ProductCategory productCategory;

和 笔记本电脑类

@Entity
@Table(name = "laptops")
public class Laptop extends Product {
    @Id
    @Column(unique = true, nullable = false)
    private int id;
    @Column(nullable = false)
    private String processor;
    private int videoMemory;
    @Column(nullable = false)
    private int ram;

但是我的变种不起作用...（我怎样才能正确 我怎样才能在数据库中插入一些数据？（请举例）

Answer 1

Laptop 正在扩展 Product 类并继承父类的所有字段，包括 ID。您正在笔记本电脑类上再次定义 ID。继承策略也已加入，这意味着它为父类和子类处理 Id 生成。删除 Id 字段及其注释。