java - 如何在删除实体之前刷新关系

Question

我想删除一个与另一个实体具有 @OneToMany 关系的实体，设置如下:

public class Dealership implements Serializable {

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "dealership", orphanRemoval = true)
    private Set<Car> cars;
}

public class Car implements Serializable {

    @ManyToOne
    @JoinColumn(name="co_id") 
    private Dealership dealership;

}

问题是，当我删除经销商时，我只想删除未售出的汽车。无论我尝试什么，Hibernate 都会通过级联删除与经销商相关的所有汽车。这就是我一直在尝试的。在此示例中，我尝试将已售出的汽车转移到另一个经销店，然后删除该经销店。这应该删除经销商、其员工以及仅未售出的汽车:

Session session = SessionManager.getSession();
Transaction tx = session.beginTransaction();

Dealership dealershipToDelete = (Dealership) session.load(Dealership.class, idDealership);

for(Car c: dealershipToDelete.getCars().stream().filter(c -> c.isSold()).toArray(Car[]::new)){
    Dealership newDealership = (Dealership) session.load(Dealership.class, idNewDealership);
    c.setDealership(newDealership);
    dealershipToDelete.getCars().remove(c);
}

session.update(dealershipToDelete);

session.flush();

session.delete(dealershipToDelete);

tx.commit();

session.close();

但它总是删除所有汽车。即使我设法让 Hibernate 更新新经销商的汽车。它更新它们，然后删除它们。帮助将不胜感激。谢谢。

Answer 1

只需在删除 Dealership 对象之前刷新()它即可反射(reflect)对其与 Car 类的关系所做的更改。稍微修改了您的代码，请尝试以下操作:

Dealership dealershipToDelete = (Dealership) session.load(Dealership.class, idDealership);
Dealership newDealership = (Dealership) session.load(Dealership.class, idNewDealership);
for(Car c: dealershipToDelete.getCars().stream().filter(c -> c.isSold()).toArray(Car[]::new)){   
    c.setDealership(newDealership);
    newDealership.getCars().add(c);
}
session.flush(); //this will flush the updates to sold Car, with the new Dealership details 
session.refresh(dealershipToDelete); //this will load the updated "dealershipToDelete" without the 'Sold Car' object,the 'Unsold' ones will still be there
session.delete(dealershipToDelete); //this will delete the Dealership and its related unsold car objects.

tx.commit();

session.close();