将复合外键映射到复合主键

Question

我在jpa / hibernate中映射复合键时遇到了问题。父实体和子实体都具有复合主键。

当父实体有一个简单的键而子实体有一个复合键时，我可以使用@mapsId。

在hibernate文档中，他们在映射中使用@JoinCoumns来演示两个复合键的映射。但是在他们的例子中，还不清楚这些列引用是在哪里定义的。

我有以下几点：

@Embeddable
public class PriceRequestLegKey implements Serializable {
   @Column(name = "leg_request_id")
   private String requestId;
   @Column(name = "display_index")
   private int displayIndex;
   ...
}

@Embeddable
public class AllocationKey implements Serializable {

   @Column(name = "leg_request_id")
   private String requestId;
   @Column(name = "display_index")
   private int displayIndex;
   @Column(name = "allocation_index")
   private int allocationIndex;
   ...
}

@Entity(name = "PriceRequestLeg")
public class PriceRequestLegModel {

   @EmbeddedId
   private PriceRequestLegKey legKey;
   @OneToMany(cascade = CascadeType.ALL)
   @JoinColumns({
      @JoinColumn(name = "leg_request_id", referencedColumnName = "leg_request_id"),
      @JoinColumn(name = "display_index", referencedColumnName = "display_index")
   })
   private List<AllocationModel> allocations;
   ...
}

@Entity(name = "Allocation")
public class AllocationModel {

   @EmbeddedId
   private AllocationKey allocationKey;
   @ManyToOne
   @MapsId
   @JoinColumns({
      @JoinColumn(name = "leg_request_id", referencedColumnName = "leg_request_id"),
      @JoinColumn(name = "display_index", referencedColumnName = "display_index")
   })
   private PriceRequestLegModel leg;
   ...
}

在运行时，保存时会出现以下异常：

org.springframework.orm.jpa.JpaSystemException: could not get a field value by reflection getter of com.lbg.legato.rfq.data.entity.AllocationKey.displayIndex; nested exception is org.hibernate.PropertyAccessException: could not get a field value by reflection getter of com.lbg.legato.rfq.data.entity.AllocationKey.displayIndex

我认为这是假的，因为有getter和setter。如果在mappedBy=上使用priceRequestLegModel“腿”和AllocationModel上使用@MapsId，我也会得到相同的错误。有人能指出我在这里做错了什么吗？

Answer 1

您应该将mappedBy="leg"还原到PriceRequestLegModel @OneToMany注释：

@Entity(name = "PriceRequestLeg")
public class PriceRequestLegModel {

   @EmbeddedId
   private PriceRequestLegKey legKey;
   @OneToMany(mappedBy="leg", cascade = CascadeType.ALL)
   private List<AllocationModel> allocations;
   ...
}

然后，您应该将AllocationKey更改为引用PriceRequestLegKey

@Embeddable
public class AllocationKey implements Serializable {

   PriceRequestLegKey legKey; // corresponds to PK type of PriceRequestLegModel
   @Column(name = "allocation_index")
   private int allocationIndex;
   ...
}

然后适当地设置Allocation.leg @MapsId注释的值：

@Entity(name = "Allocation")
public class AllocationModel {

   @EmbeddedId
   private AllocationKey allocationKey;
   @ManyToOne
   @MapsId("legKey")
   @JoinColumns({
      @JoinColumn(name = "leg_request_id", referencedColumnName = "leg_request_id"),
      @JoinColumn(name = "display_index", referencedColumnName = "display_index")
   })
   private PriceRequestLegModel leg;
   ...
}

在JPA2.2规范 2.4.1节中有一些类似的例子。