通过join fetch来获取具有@OneToOne的实体时,会急切地获取@OneToOne

时间:2018-08-24 10:42:57

标签: hibernate jpa

我有以下3个课程:

public class Object {
    ...whatever
}

public class CustomerObject {

    @OneToOne(optional = false, fetch = FetchType.LAZY)
    @JoinColumn(name = "OBJECT_ID", referencedColumnName = "OBJECT_ID", insertable = false, updatable = false)  
    private Object object;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "CUSTOMER_TYPE_ID", referencedColumnName = "OBJECT_ID", insertable = false, updatable = false)
    private CustomerTypeObject customerTypeObject;

}

public class CustomerTypeObject {

    @JoinColumn(name = "OBJECT_ID", referencedColumnName = "OBJECT_ID", insertable = false, updatable = false)
    @OneToOne(optional = false, fetch = FetchType.LAZY)
    private Object object;

}

当我这样做时:

entityManager.createQuery(
"select cust from CustomerObject cust "
+ "left join fetch cust.customerTypeObject customerType "
+ "where cust.id = :customer_id 
, CustomerObject.class)
.setParameter("customer_id", BigDecimal.valueOf(1))
.getSingleResult();

Hibernate发出1条查询以获取带有其customerType的客户,但随后也发出查询以获取CustomerTypeObject实体中的Object关联。通过加入获取该关联即可解决问题(即仅发出一个查询):

entityManager.createQuery(
"select cust from CustomerObject cust "
+ "left join fetch cust.customerTypeObject customerType "
+ "left join fetch customerType.object customerTypeObject "
+ "where cust.id = :customer_id 
, CustomerObject.class)
.setParameter("customer_id", BigDecimal.valueOf(1))
.getSingleResult();

但是我不想这样做。有没有办法做到这一点? (即,不要急于在已经通过查询获取的实体中获取OneToOne关联。)

0 个答案:

没有答案