Question

我有以下课程

具体类项目

@Entity
@Table(name = "ITEM")
@Inheritance(strategy= InheritanceType.JOINED)
Class Item implements Serializable {        
  private static final long serialVersionUID = 1L;
  @Id
  @Column(name = "NAME")
  private final String name;
  @Column(name = "PRICE")
  private BigDecimal price;
}

扩展Item

的具体类AddedItem

@Entity
@Table(name = "ADDED_ITEM")
@PrimaryKeyJoinColumn(name = "NAME")
public class AddedItem extends Item {
   @Column(name = "TOTAL_PRICE")
   private BigDecimal totalPrice;
   @Column(name = "QUANTITY")
   private Integer quantity;
   @ManyToOne
   @JoinColumn(name = "INVOICE_ID")
   private Invoice invoice;
 }

与AddedItem

具有一对多映射的Invoice类

@Entity
@Table(name = "INVOICE"
public class Invoice implements Serializable {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "INVOICE_ID")
  private Long billNo;
  @Column(name = "BILLDATE")
  @Temporal(TemporalType.TIMESTAMP)
  private Date billDate;
  @Column(name = "CUSTOMERNAME")
  private String customerName;
  @OneToMany(fetch = FetchType.LAZY, mappedBy = "invoice", cascade = CascadeType.ALL)
  private final List<AddedItem> itemsAdded;
}

当我尝试保存Invoice实例时，我收到以下异常：

org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: ORA-00001: unique constraint (ITEM_PK) violated

org.hibernate.event.def.AbstractFlushingEventListener performExecutions
SEVERE: Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch      update
...

当我预取Item相关信息时，如何告诉Hibernate只存储子类信息？

Answer 1

在@Inheritance(strategy= InheritanceType.JOINED)中，您必须定义@DiscriminatorColumn 确定行的类。添加它可以解决问题。如果您正在使用Hibernate 3.1或更低版本（希望您不是），@DiscriminatorFormula应该完成这项工作，但我从未亲自尝试过。

接下来在AddedItem实体上，@PrimaryKeyJoinColumn(name = "NAME")（javadoc，stackoverflow几乎只是为了展示，但它不会造成任何伤害。

如果AddedItem是公开的，那么Item实体应该是公开的。

编辑：由于您的ID字段是字符串，您确定要使用正确的唯一值吗？

如何在Hibernate中只保存子类相关数据

1 个答案: