orm - 自动增量 ID 未反射(reflect)在使用 JPA 的复合键中

Question

我有以下映射

@Entity
@Table(name = "auctions")
public class Auction{
.
.
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "auction")
    private List<AuctionParamValue> auctionParamValueList;
.
.
}


@Entity
@Table(name = "auction_param_values")
public class AuctionParamValue {

    @EmbeddedId
    protected AuctionParamValuePK auctionParamValuePK;

    @JoinColumn(name = "auction_param_id", referencedColumnName = "auction_param_id",updatable=false,insertable=false)
    @ManyToOne @MapsId("auctionParamId")
        private AuctionParam auctionParam;

    @JoinColumn(name = "auction_id", referencedColumnName  = "auction_id",updatable=false,insertable=false)
    @ManyToOne @MapsId("auctionId") 
        private Auction auction;
}

@Embeddable
public class AuctionParamValuePK {

@Id
@Basic(optional = false)
       @Column(name = "auction_id")
       @Nullable
       private Long auctionId = null;

@Id
       @Basic(optional = false)
       @Column(name = "auction_param_id")
       @Nullable
       private Long auctionParamId = null;    
}

@Entity
@Table(name = "auction_params")    
public class AuctionParam {
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "auctionParam")
    private List<AuctionTypeParam> auctionTypeParamList;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "auctionParam")
    private List<AuctionParamValue> auctionParamValueList;
 }

}

当我尝试坚持拍卖时(我手动设置了uctionParamId并期望自动设置auctionId(可能是最后插入的id))

但我遇到了以下错误，我不确定为什么查询中的拍卖 ID 是 0 而不是拍卖中的最新 ID。(我正在使用 eclipselink jpa 提供程序)

Internal Exception: com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`portaldemo`.`auction_param_values`, CONSTRAINT `auction_param_values_auction_id_fk` FOREIGN KEY (`auction_id`) REFERENCES `auctions` (`auction_id`))
Error Code: 1452
Call: INSERT INTO auction_param_values (auction_param_val, create_ts, last_updt_ts, auction_param_id, auction_id) VALUES (?, ?, ?, ?, ?)
    bind => [2011-02-12 04:00:00, 2011-01-27 12:02:00.28, 2011-01-27 12:17:43.25, 2, 0]
Query: InsertObjectQuery(com.eaportal.domain.AuctionParamValue[auctionParamValuePK=com.eaportal.domain.AuctionParamValuePK[auctionId=0, auctionParamId=2]])

这里 [auctionId=0 总是作为 0 而不是最后插入的 id :(

这个映射有什么问题？

Answer 1

@GeneratedValue 只会设置它所注释的属性的值，如果其他类中有其他属性引用了您负责设置这些 id 的 id。

即，您需要首先持久化并刷新 Auction，然后使用其生成 Id 创建 AuctionParamValue。

或者，如果您使用 TABLE 或 SEQUENCE id 生成，那么您只需要调用persist，而不是flush。一般来说，我永远不会推荐 IDENTITY 排序，因为它的值不能预先分配。

但实际上你不应该有重复的字段。完全删除@EmbeddedIductionParamValuePK，只需将@Id 添加到两个@ManyToOnes，并使用@IdClass 代替。这将使事情变得更简单，并且即使使用 IDENTITY id 生成也能正常工作。

您也可以删除两个 @ManyToOne 映射上的 insertable/updateable=false 并将它们放在 @EmbeddedId 属性上，这将从关系中写入外键，但您的对象仍会在内存中损坏。

看，
http://en.wikibooks.org/wiki/Java_Persistence/Identity_and_Sequencing#Primary_Keys_through_OneToOne_and_ManyToOne_Relationships