JPA2.0& Hibernate：使用父实体合并删除子表行（在从父子实体集中删除条目时） [英] JPA2.0 & Hibernate: Removing Child table rows with Parent entity merge (On removing entries from parent's child entity set)

问题描述

我在Hibernate中使用JPA2.O。我有用户和地址之间的一对多关系，我有以下关系配置：

  cascade = CascadeType.ALL，fetch = FetchType.LAZY，
  

例如，我在数据库表中有以下条目：

用户表

 栏：UserID |用户名
 row1：User1 |用户名
  

地址表

 列：AddressId |用户ID |地址
 
 row1：Address1 | User1 |实际地址
 
 row2：地址2 | User1 |实际地址
  

我可以使用userId的find来获取User实体：

  User user = entityManager.find（User.class，userId）; 
  

还可以使用user.getAddresses（）获取答案。 getAddressess（）的代码如下所示：

  public class User {
 @OneToMany（cascade = CascadeType.ALL， fetch = FetchType.LAZY，mappedBy =user）
 public Set< Address> getAddresses（）{
 return this.addresses; 
 
 
 $ / code $ / pre 
 
现在我正在尝试做什么，一组地址并删除一个条目。假设我在第一次获取地址1和2时获取了地址集。我从地址集中删除了地址2实体。现在，用户实体指向的Set仅有1个用于Address1的条目。
 
 
 
现在，如果我使用下面的方法合并用户实体，我认为，row for address 2应从地址表中删除。但它没有发生。我是否缺少任何东西，或者它不是一种方法。请建议。  
 
 
  entityManager.merge（user）; 
  
 
 
解决方案
只是想添加更多的细节， 。  
 
 
我用 @OneToMany 关系添加了 orphanRemoval = true ： 
 
 
  public class User {
 @OneToMany（cascade = CascadeType.ALL，fetch = FetchType.LAZY，orphanRemoval = true，mappedBy =user）
 public Set< Address> getAddresses（）{
 return this.addresses; 
 
 
 $ / code> 
更改我的代码后，我重新测试它并得到错误： 
 
 
 引起：org.hibernate.HibernateException：cascade =all-delete-orphan的集合是否为更长的被拥有实体实例引用：
  
 此链接帮助我解决了上述问题：
 
 
现在我可以从数据库中删除子实体，如果这些子实体与父实体中已定义的集合断开连接（已删除）。 / p> 
I am using JPA2.O with Hibernate. I have one to many relationship between User and Address and I have below configuration with this relationship:
cascade = CascadeType.ALL, fetch = FetchType.LAZY,
For example I have below entries in database tables:


User Table 
Column: UserID | UserName
row1:    User1 | UserName
Address Table 
Column: AddressId| UserID | Address    

row1:   Address1 | User1  | Actual Address

row2:   Address2 | User1  | Actual Address
I can fetch User entity using find by userId: 
User user = entityManager.find(User.class, userId);
And also can fetch Answers using user.getAddresses(). Code for getAddressess() is like below:
public class User{
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "user")
    public Set<Address> getAddresses() {
       return this.addresses;
    }
}
Now what I am trying to do, I am fetching the set of addresses and removing one entry. Let say I fetched addressess set first time I have address 1 and 2. I removed address 2 entity from set of addresses. Now User entity is pointing to the Set which is having only 1 entry that is for Address1.

Now If I merge user entity using below method, I think, row for address 2 should be deleted from address table. But it is not happening. Am I missing any thing or it is not a way to do it. Please suggest. 
entityManager.merge(user); 

解决方案
Just want to add more detail as I got this working. 

I added orphanRemoval = true with @OneToMany relationship:
public class User{
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, orphanRemoval = true, mappedBy = "user")
    public Set<Address> getAddresses() {
       return this.addresses;
    }
}
After changing my code I re-tested it and got below error:
Caused by: org.hibernate.HibernateException: A collection with cascade="all-delete-orphan" was no longer referenced by the owning entity instance:
This link helped me to solve above problem:

Now I can delete the child entities from database, if those are disconnected(removed) from defined collection in parent entity.

                        
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