Hibernate序列停留在值41

Question

在我的课堂上，我有以下的顺序-

@Entity
public class CustomerOrder {

   @Id
   @SequenceGenerator( name = "CUSTOMER_ORDER_INVOICE_NO_SEQ_NAME", sequenceName = "CUSTOMER_ORDER_INVOICE_NO_SEQ", allocationSize = 20 )
   @GeneratedValue( strategy = GenerationType.SEQUENCE, generator = "CUSTOMER_ORDER_INVOICE_NO_SEQ_NAME" )
   private int id;

   private long orderInvoiceNo;

   //.. getters and setters

}

这是spring data jpa repository类，具有获取下一个值的方法

  @Repository
  public interface CustomerOrderRepository
    extends CrudRepository<CustomerOrder, Long>, JpaSpecificationExecutor<CustomerOrder> {

     @Query( value = "SELECT next_val FROM CUSTOMER_ORDER_INVOICE_NO_SEQ", nativeQuery = true )
     Long getNextOrderInvoiceNoSeq();
 }

我需要从序列中获取next_val，并将该值传递到两个不同的位置。所以我调用我的存储库的getNextOrderInvoiceNoSeq（）方法，并将该值存储为orderInvoiceNo-

@Autowired
private CustomerOrderRepository customerOrderRepository;

public void placeCustomerOrder( CustomerOrder customerOrder )
{

 long orderInvoiceNo = customerOrderRepository.getNextOrderInvoiceNoSeq();
 customerOrder.setOrderInvoiceNo(orderInvoiceNo);

 // using the same orderInvoiceNo to my other pojo
 // CustomerPurchase customerPurchase = new CustomerPurchase
 // customerPurchase.setOrderInvoiceNo(orderInvoiceNo);

 //....
 customerOrderRepository.save(customerOrder);
}


 @Entity
 public class CustomerPurchase {

   private String itemId;
   private long orderInvoiceNo;
   //.....     
 }

所以现在发生了什么，对于放置客户订单的前两次迭代，我得到的订单发票号为1和41，但在那之后，每次我得到41作为序列的next_val，因此使每个订单都有相同的发票号为41。

Answer 1

MySQL没有序列，所以在本例中Hibernate将创建一个表生成器。

Hibernate将执行选择更新以获取最新的下一个值，并执行更新以增加值：

SELECT next_val as id_val 
FROM CUSTOMER_ORDER_INVOICE_NO_SEQ FOR UPDATE

UPDATE CUSTOMER_ORDER_INVOICE_NO_SEQ 
SET next_val= 2 where next_val=1

getNextOrderInvoiceNoSeq（）只为最新值选择，但不增加它。

尽管如此，我不建议实施这一点。最好切换到本机序列，并使用外键CustomerOrder和CustomerPurchase。