Question

我在JPA中的@Id有问题，如下所述？有一个通用类如下？

    @MappedSuperclass
    public abstract class BaseEntity<T> implements Serializable {

        private static final long serialVersionUID = 4295229462159851306L;

        private T id;
        public T getId() {
          return id;
        }
        public void setId(T id) {
           this.id = id;
        }

    }

还有另一个课程如下所示？

@Entity
@Table(name = "DOC_CHANGE_CODE" )
 public class ChangeCode extends BaseEntity<Long> {

     @Id
     @GeneratedValue(generator = "sequence_db", strategy = GenerationType.SEQUENCE)
     @SequenceGenerator(name = "sequence_db", sequenceName = "SEQ_DOC_CHANGE_CODE", allocationSize = 1)     
     public Long getId () {
       return super.getId();
     }
}

因为任何子类都有自己的序列，所以我必须指定任何子类@Id，因为我覆盖了它的getter并在其中添加了一些注释。不幸的是它无法正常工作。我如何解决问题并实现目标？

Answer 1

试试这个：

@Entity
@Table(name = "DOC_CHANGE_CODE" )
@SequenceGenerator(name = "sequence_db", sequenceName = "SEQ_DOC_CHANGE_CODE", allocationSize = 1)     
@AttributeOverride(name = "id", column = @Column(name = "ID"))
public class ChangeCode extends BaseEntity<Long> {

    @Override
    @Id
    @GeneratedValue(generator = "sequence_db", strategy = GenerationType.SEQUENCE)
    public Long getId() {
        return id;
    }
}

Answer 2

无法从基类覆盖@Id。

唯一的方法是提供your own custom IentifierGenerator并根据子类提供不同的逻辑（例如，使用基于子类名称的序列名称）。

这就是为什么adding the @Id attribute in the @MappedSuperclass only makes sense for the assigned generator or for IDENTITY。

如何在jpa配置中覆盖id列的getter

2 个答案: