Hibernate JPA值删除OneToMany关系

Question

I have two tables where there is a OneToMany, MnatToOne relation.

When I have added instance of AlarmnotifyEmailEntity into alarmnotifyEmailEntityList object and update instance of AlarmnotifyEmailConfEntity, value is save properly into Database.

Bu I could not do the same thing when deleting one of the item of alarmnotifyEmailEntityList. I am sure that value is removed from alarmnotifyEmailEntityList but it does not reflect this changes into Database

    @Entity(name ="alarmnotify_email_conf")
    @Table(name = "alarmnotify_email_conf")
    public class AlarmnotifyEmailConfEntity implements Serializable {

    @OneToMany(mappedBy = "alarmnotifyEmailConfRef",cascade=CascadeType.ALL)
        private List<AlarmnotifyEmailEntity> alarmnotifyEmailEntityList;

    }//end of Class

    @Entity (name ="alarmnotify_email")
    @Table(name = "alarmnotify_email")
    public class AlarmnotifyEmailEntity implements Serializable {
     @JoinColumn(name = "alarmnotify_email_conf_ref", referencedColumnName = "id")
        @ManyToOne
        private AlarmnotifyEmailConfEntity alarmnotifyEmailConfRef;
    }end of Class

I am only invoking following statement to update.

JPAManager.getJPAManagerInstance().update(alarmnotifyemailconf);

 public Object update(Object o) {

  try {
     tx.begin();
     EntityManager em = getEntityManager();          
     System.out.println("updating object:" + o);
     o = em.merge(o);
     em.close();
     tx.commit();
     System.out.println("closed and commited merge operation");
     return o;
  }
  catch (Exception e) {
     e.printStackTrace();
  }
  return o;

}

Answer 1

From my experience cascade only applied for same operation. If we save parent, then children also will saved same case with update. But I think when you want to remove one of children, we have to remove explicitly using entity manager, and cannot just merging parent and expect will cascade remove to children.

Answer 2

I have found out the answer in jpa removing child from collection . as a result adding orphanRemoval=true solved the problem.

@Entity(name ="alarmnotify_email_conf") @Table(name = "alarmnotify_email_conf") public class AlarmnotifyEmailConfEntity implements Serializable {

@OneToMany(mappedBy = "alarmnotifyEmailConfRef",cascade=CascadeType.ALL , orphanRemoval=true ) private List alarmnotifyEmailEntityList;

 }//end of Class