JPA Example 默認 join

起因：

由於同事增加了一個對象關聯。並且採用了Example查詢，導致了一個Null的問題。

 

主表：BoBookingorder

關聯表：BoJobcontainerinfo

 

一 關聯如下：

@Entity
@Table(name = "bo_bookingorder",catalog = "kintech_bo")
public class BoBookingorder  {
    private String bookingOrderUUID;
    
    private BoJobcontainerinfo boJobcontainerinfo=new BoJobcontainerinfo();
     
    @Id
    public String getBookingOrderUUID() {
        return bookingOrderUUID;
    }
 
    
    @OneToOne
    @JoinColumn(name = "bookingOrderUUID", referencedColumnName = "orderUUID")
    public BoJobcontainerinfo getBoJobcontainerinfo() {
        return boJobcontainerinfo;
    }
 
    public void setBoJobcontainerinfo(BoJobcontainerinfo boJobcontainerinfo) {
        this.boJobcontainerinfo = boJobcontainerinfo;
    }
 
    
}

 

二 使用三種查詢方式，看sql生成

1 根據bookingOrderNo(非主鍵)查詢

生成的sql

// 生成了2段SQL
 
select
        * 
    from
        bo_bookingorder  
    where
        BookingOrderNo=? 
        and IsValid=1  
    order by
        CreateTime desc  limit 1 
 
======================================================
 
select
        *
    from
        kintech_bo.bo_jobcontainer bobookingo0_ 
    where
        bobookingo0_.orderUUID=?

PS：

很明顯，自己寫@Query註解sql (select * from xxx where .....)，分成了2次查詢，

這意味着，先查詢了主表：BoBookingorder，然後填充了關聯表：BoJobcontainerinfo

 

2 Example查詢

查詢代碼：還是根據bookingOrderNo 查詢

        BoBookingorder entity = new BoBookingorder();
        entity.setBookingOrderNo(bookingOrderNo);
        Example<BoBookingorder> ex = Example.of(entity);
        BoBookingorder bo1 = bookingorderJpaService.findOne(ex);

生成的sql

    select
        bo.*
    from
        kintech_bo.bo_bookingorder bo 
    inner join
        kintech_bo.bo_jobcontainerinfo boc 
            on bo .bookingOrderUUID=boc .OrderUUID 
    where
        bo.BookingOrderNo=? 

PS:

注意  inner join ，這個就是罪魁禍首。由於是inner join ，導致如果 jobcontainerinfo表沒有數據，則bookingorder也返回null

 

3 常規findOne 

調用Jpa自帶的findOne，通過主鍵查詢，看看是否會inner join 關聯

代碼：

BoBookingorder bo2=bookingorderJpaService.findOne("xxx");

生成的sql

select
        bo.* 
    from
        kintech_bo.bo_bookingorder bo 
    left outer join
        kintech_bo.bo_jobcontainerinfo boc 
            on bo.bookingOrderUUID=boc.OrderUUID 
    where
        bo.BookingOrderUUID=?

PS:

可以看到，JPA自帶的findOne是left join，所以沒有引發不適。

 

三  結論：慎用Example來做查詢條件。