Question

我想删除与另一个实体有@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，我想只删除未售出的汽车。无论我尝试什么，Hibernate都会通过级联删除与经销商联系的所有汽车。这是我一直在尝试的。在这个例子中，我试图将售出的汽车转移到另一个经销商，然后我删除经销商。这应该删除经销商，其员工，以及只有未售出的汽车：

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用新的经销商更新汽车。它会更新它们，然后删除它们。非常感谢帮助。感谢。

Answer 1

你可能会尝试这样的事情：

首先将外键设置为可空：

public class Car implements Serializable {

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

}

然后你得到经销商的IdToRemove：

int id = dealershipToRemove.getId();

然后您删除所有具有给定ID

经销商的汽车

query = session.createNativeQuery("delete from cars where co_id = :id and date is null");
query.setParameter(1,id);
query.executeUpdate();

然后你打破了dealerhipToRemove和它的汽车之间的关系：

dealershipToRemove .setCars(null);
session.remove(dealershipToRemove);

Answer 2

只需刷新（）经销商对象，然后再将其删除，以反映与Car类关系所做的更改。稍微修改一下代码，试试这个：

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();

如何在删除实体之前刷新关系

2 个答案: