Hibernate合并不会删除OneToMany旧实体

问题描述

研讨会课程：

  @Entity 
 @Table（name =seminars）
公开课讨论会{
 
 @Id 
 @GeneratedValue 
 private int id; 
 
 @OneToMany（cascade = CascadeType.ALL，mappedBy =seminar）
 private List< SeminarParticipation>参股; 
 ... 
} 
  

SeminarParticipation code> class：

  @Entity 
 @Table（name =seminar_participations）
 public class SeminarParticipation {
 
 @Id 
 @GeneratedValue 
 private int id; 
 
 @ManyToOne 
 @JoinColumn（name =seminar_id，nullable = false）
 private研讨会研讨会; 
 ... 
} 
  

在DAO中，我使用EntityManager来处理研讨会如下：

  em.persist（研讨会）
 em.merge（研讨会）
 em。删除（研讨会）
  

保存或删除研讨会实体， seminar_participations 中的记录也被创建/删除。 但是，当我尝试更新研讨会在使用 merge 方法设置新的 List< SeminarParticipation> 参与之后），根据列表创建新记录，但旧的不会被删除。

持久代码：

控制器代码（我也尝试更新现有列表，也没有工作）：

  seminar.setParticipations（newParticipations）; 
 seminarService.updateSeminar（研讨会）; 
  

服务等级

  @Service 
 public class SeminarServiceImpl implements SeminarService {
 $ b $ @Autowired 
 private SeminarDAO seminarDAO; 
 
 @Override 
 public void updateSeminar（研讨会研讨会）{
 seminarDAO.update（研讨会）; 
} 
 ... 
} 
  

3）DAO类

  @Repository 
 public class SeminarDAOImpl implements SeminarDAO {
 
 @PersistenceContext 
私人EntityManager em; 
 
 @Override 
 @Transactional 
 public void update（研讨会研讨会）{
 em.merge（研讨会）; 
} 
 ... 
} 
  

如何解决这个问题？有没有办法在DAO中手动删除它们？

.objectdb.com / api / java / jpa / OneToMany / orphanRemovalrel =nofollow> orphanRemoval = true @OneToMany参数。

I have the following entities:

Seminar class:

@Entity
@Table(name = "seminars")
public class Seminar {

    @Id
    @GeneratedValue
    private int id;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "seminar")
    private List<SeminarParticipation> participations;
...
}

SeminarParticipation class:

@Entity
@Table(name = "seminar_participations")
public class SeminarParticipation {

    @Id
    @GeneratedValue
    private int id;

    @ManyToOne
    @JoinColumn(name="seminar_id", nullable=false)
    private Seminar seminar;
...
}

In DAO, I use EntityManager to work with seminars like this:

em.persist(seminar)
em.merge(seminar)
em.remove(seminar)

When saving or deleting Seminar entities, records in seminar_participations are created/deleted as well.

But when I try to update a seminar (after setting new List<SeminarParticipation> of participations) using merge method, new records there are created in according to the list, but old ones are not deleted.

Persisting code:

1) Controller code (I've also tried to update the existing list, it does not work as well):

seminar.setParticipations(newParticipations);
seminarService.updateSeminar(seminar);

2) Service class

@Service
public class SeminarServiceImpl implements SeminarService {

@Autowired
private SeminarDAO seminarDAO;

@Override
    public void updateSeminar(Seminar seminar) {
        seminarDAO.update(seminar);
    }
...
}

3) DAO class

@Repository
public class SeminarDAOImpl implements SeminarDAO {

    @PersistenceContext
    private EntityManager em;

    @Override
    @Transactional
    public void update(Seminar seminar) {
        em.merge(seminar);
    }
...
}

How I can solve this problem? Is there a way without deleting them manually in DAO?

解决方案

You should try using orphanRemoval = true parameter for @OneToMany.

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