刪除實體

Question

之前如何刷新關係我想刪除與另一個的@OneToMany關係的實體，成立這樣的：

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; 

} 

的事情是，當我刪除了經銷店，我只想刪除未售出的汽車。無論我嘗試什麼，Hibernate都會通過級聯刪除與經銷商並列的所有汽車。這是我一直在嘗試的。在這個例子中，我試圖將售出的汽車轉移到另一個經銷商，然後我刪除經銷商。這應該刪除經銷商，其僱員，並且只有未售出的汽車：

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(); 

但它總是刪除所有汽車。即使我設法讓Hibernate用新的經銷商來更新汽車。它更新它們，然後刪除它們。幫助將不勝感激。謝謝。

Answer 1

刪除它，以反映其與汽車class.Have關係所做的更改稍加修改你的代碼之前就刷新（）經銷店的對象，試試這個：

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(); 

Answer 2

，你可以嘗試這樣的事：

首先將外鍵可空：

public class Car implements Serializable { 

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

} 

那麼你得到dealershipToRemove的Id：

int id = dealershipToRemove.getId(); 

然後刪除所有汽車與代理商一樣具有經銷商

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

然後你打破dealershipToRemove和汽車之間的關係：

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