Hibernate -包含父实体的持久化子实体

Question

尝试获取父实体(Msg)的实体，其中父PK (msg_id)是子实体中的FK时，尝试保持子实体(MsgRetry)时出错。

错误，如：org.hibernate.id.IdentifierGenerationException：试图从null一对一属性分配id

父实体，不需要知道子实体（至少我认为它不需要知道）。一旦子实体被持久化，我就会尝试也持久化父实体。我可以通过在子实体中没有父实体并调用关联的存储库来解决这个问题。但是，我不认为它像我尝试的那样干净，但显然更困难/复杂。

如果这是一个好的解决方案，感谢任何关于最佳实践或如何实现这一点的建议。

表：

型号：

@Entity
@Table(name="msg")
public class Msg {
    
    @Id
    @Column(name = "msg_id")
    @GeneratedValue(strategy = generationtype.sequence, generator = "msg_id_seq_gen")
    @SequenceGenerator(name = "msg_id_seq_gen", sequencename = "msg_id_seq", allocationsize = 1)
    private Long msgId;
    
    @Column(name = "msg_status", nullable = false)
    private String msgStatus;
    
    ...
    
    //getters setters
}

@Entity
@Table(name = "msg_retry")
public class MsgRetry implements Serializable{

    private static final long serialVersionUID = -7637385223556379976L;

    @Id
    @Column(name = "msg_id")
    private Long msgId;
    
    @OneToOne
    @JoinColumn(name="msg_id", referencedColumnName = "msg_id")
    private Msg msg;
    
    @Column(name = "count")
    private Long count;
    
    @Generated(value = GenerationTime.ALWAYS)
    @Column(name = "timestamp")
    private Date timestamp;
    
    
    
    public MsgRetry() {
    }

    public MsgRetry(Msg msg, Long count) {
        this.msg = msg;
        this.count = count;
    }
    
    public MsgRetry(Long msgId, Long count) {
        this.msgId = msgId;
        this.count = count;
    }
    
    public Msg getMsg() {
        return msg;
    }

    public void setMsg(Msg msg) {
        this.msg = msg;
    }

@Repository
public interface MsgRetryRepository extends JpaRepository<MsgRetry, Long>{

}

@Test
    public void testSaveMsgByMsgIdRetry() {
        
        msgRetryRepository.deleteAll();
        List<Msg> msgs = msgRepository.findAll();
        
        MsgRetry msgRetry = new MsgRetry(msgs.get(0).getMsgId(), 1L);
        
        msgRetry = msgRetryRepository.save(msgRetry);
        assertNotNull(msgRetry.getMsg());  // fails to load Msg entity
        LOG.info("msgRetry: {}", msgRetry);
    }

@Test
    public void testSaveMsgRetryByMsg() {
        
        msgRetryRepository.deleteAll();
        List<Msg> msgs = msgRepository.findAll();
        
        MsgRetry msgRetry = new MsgRetry(msgs.get(0), 1L);
        
        msgRetry = msgRetryRepository.save(msgRetry);
        assertNotNull(msgRetry.getMsg());
        LOG.info("msgRetry: {}", msgRetry);
    }

错误：org.springframework.orm.jpa.JpaSystemException：必须在调用保存（）：msgtest.MsgRetry之前手动分配此类的id；

Answer 1

首先，整理您的< code > MsgRetry id。FK应该够好了。

@Entity
@Table(name = "msg_retry")
public class MsgRetry {
    @Id
    @ManyToOne(optional = false)
    @JoinColumn(name = "msg_id")
    private Msg msg;
    
    @Column(name = "count")
    private Long count;
    
    @Generated(value = GenerationTime.ALWAYS)
    @Column(name = "timestamp")
    private Date timestamp;
    
    public Msg getMsg() { return msg; }
         
    public void setMsg(Msg msg) { this.msg = msg; }
}

接下来，确保 MsgRetryRepository 已正确子分类：

public interface MsgRetryRepository extends CrudRepository<MsgRetry, Msg>
{
  // Empty for now
}

最后，以正确的方式查询MsgRetry：

public class BizLogic {

    MsgRetryRepository retryRepo
    
    public MsgRetry retry(Msg msg, String msgStatus) {
    
        MsgRetry mr = retryRepo.findById(msg);        
        if (mr !=null) {
            // XXX I cannot tell from your logic what you are doing here.
            retryRepo.save(mr);
        }   
    }
}

您的持久性层是什么？也许您可以打开调试并访问日志以查看引擎盖下发生的情况。