java - hibernate 和 oracle 序列 GenericGenerator 造成差距

Question

我已经将我的类映射如下(省略了其他字段，因为只有 ID 很重要):

@Entity
@Table(name = "MODEL_GROUP")
@Cache(usage = CacheConcurrencyStrategy.TRANSACTIONAL)
public class SettlementModelGroup implements Serializable
{


@Id
@GeneratedValue(generator = "MODEL_GROUP_SEQ", strategy = GenerationType.SEQUENCE)
@GenericGenerator(name = "MODEL_GROUP_SEQ",
        strategy = "sequence",
        parameters = @Parameter(name = "sequence", value = "SEQ_MODEL_GROUP_MODEL_GROUP_ID"))
@Column(name = "MODEL_GROUP_ID", nullable = false)
private Integer modelId;
}

当我保存新对象时:

Integer modelGroupId = sessionFactory.getCurrentSession().save( modelGroup );
System.out.println( modelGroupId );

ID 设置为例如 23，但当我查看数据库时它实际上是 24。这会导致很多问题，因为我稍后会使用这个 ID。知道为什么会造成这种差距吗？

SQL 日志显示一切正常(我是这么认为的):

Hibernate: 
 select
     SEQ_MODEL_GROUP_MODEL_GROUP_ID.nextval 
 from
     dual
Hibernate: 
 insert 
 into
     MODEL_GROUP
     (DOMAIN_ID, DESCRIPTION, NAME, PERIOD_TYPE_ID, MODEL_GROUP_TYPE_ID, STATUS_ID, OWNER_ID, MODEL_GROUP_ID) 
 values
     (?, ?, ?, ?, ?, ?, ?, ?)

触发器和序列:

CREATE SEQUENCE "SEQ_MODEL_GROUP_MODEL_GROUP_ID" 
  INCREMENT BY 1 
  START WITH 1 
  NOMAXVALUE 
  MINVALUE 1 
 NOCYCLE 
 NOCACHE 
 NOORDER
;

CREATE OR REPLACE TRIGGER "TRG_MODEL_GROUP_MODEL_GROUP_ID" 
BEFORE INSERT 
ON "MODEL_GROUP" 
FOR EACH ROW 
WHEN (NEW."MODEL_GROUP_ID" is NULL)
BEGIN 
    SELECT "SEQ_MODEL_GROUP_MODEL_GROUP_ID".NEXTVAL 
    INTO :NEW."MODEL_GROUP_ID" 
    FROM DUAL; 
END;

Answer 1

显然，当 Hibernate 向您的数据库询问 ID 的 nextValue 时，它​​也会触发 Trigger。因此，当我请求 ID 时，我得到的是 23，但是当通过提交事务实际保存到数据库时，它又增加了，所以我得到了 24。此处描述了解决方案:

HIbernate issue with Oracle Trigger for generating id from a sequence

为了使其正常工作，我更改了 Trigger:

CREATE OR REPLACE TRIGGER "TRG_MODEL_GROUP_MODEL_GROUP_ID" 
BEFORE INSERT 
ON "MODEL_GROUP" 
FOR EACH ROW 
WHEN (NEW."MODEL_GROUP_ID" is NULL)
BEGIN 
    SELECT "SEQ_MODEL_GROUP_MODEL_GROUP_ID".NEXTVAL 
    INTO :NEW."MODEL_GROUP_ID" 
    FROM DUAL; 
END;