Question

我有以下JPA实体关系：

@Entity
public class Hardware {
  @Id
  @Column(name="id")
  @GeneratedValue(strategy=GenerationType.AUTO)
  protected Long id;

 @OneToOne( fetch = FetchType.LAZY, mappedBy = "parent", cascade = { CascadeType.MERGE } )
  protected HardwareStatus status;
}

@Entity
public class HardwareStatus {
  @Id
  @Column(name="id")
  @GeneratedValue(strategy=GenerationType.AUTO)
  protected Long id;

  @OneToOne(fetch=FetchType.LAZY)
  @JoinColumn(name="parent_id", nullable=false)
  protected Hardware parent;

  @Column(name="product_status", nullable=false)
  @Enumerated(EnumType.STRING)
  protected ProductStatus productStatus;

  // .. lots of other fields
}

HardwareStatus记录每天在午夜左右计算一次，并包含有关该硬件的统计信息。大多数人懒得好。但是，我希望在硬件实体中可以使用其中一个字段（productStatus）而不加载整个HardwareStatus对象。有可能有类似的东西：

@Entity
public class Hardware {
  @Id
  @Column(name="id")
  @GeneratedValue(strategy=GenerationType.AUTO)
  protected Long id;

 @OneToOne( fetch = FetchType.LAZY, mappedBy = "parent", cascade = { CascadeType.MERGE } )
  protected HardwareStatus status;

  @Column(name="product_status", nullable=false)
  // Some sort of JPA @Attribute to map to the HardwareStatus table to load just this field eagerly?
  @Enumerated(EnumType.STRING)
  protected ProductStatus productStatus;
}

提前致谢

JPA @OneToOne映射与单独的@Column定义

0 个答案: