Inheritance problem duplicate objects from List

epllcr · **Joined:** Sat Mar 04, 2006 10:07 am **Posts:** 9

Hi, have a question about inheritance i hope somebody can help me with. Dont know if it is my mapping or and error. Check question after mapping part.

Using Hibernate version 3.1.2, Hibernate annotations version 3.1beta7
PostgreSql 8.1.3

Mapping is:

Code:

@Entity(access=AccessType.PROPERTY)
@org.hibernate.annotations.Entity(optimisticLock=OptimisticLockType.VERSION)
@Inheritance(strategy=InheritanceType.JOINED)
public abstract class Event extends AbstractEntity implements IEvent {
   private Match match;
   
   @ManyToOne(fetch=FetchType.LAZY, cascade=CascadeType.ALL)
   @JoinColumn(name="matchid")
   public Match getMatch() {
      return match;
   }

   public void setMatch(Match match) {
      this.match = match;
   }

Code:

@Entity(access=AccessType.PROPERTY)
@Table(name="startedevents")
public class StartedEvent extends Event {
      private static final long serialVersionUID = -1974642009202477133L;
      private Date timeOfStart;

}

Code:

@Entity(access=AccessType.PROPERTY)
@org.hibernate.annotations.Entity(optimisticLock=OptimisticLockType.VERSION)
@Table(name="matches")
public class Match extends AbstractEntity {
     private List<Event> events = new ArrayList<Event>();

     @OneToMany(mappedBy="match", fetch=FetchType.LAZY, cascade=CascadeType.ALL)
   public List<Event> getEvents() {
      return events;
   }

   public void setEvents(List<Event> events) {
      this.events = events;
   }
}

AbstractEntity is not mapped, tables are created as expected event, startedevent and match. Data is inserted correct, the problem i have is when i create one StartedEvent and add it to the Match events list and persists it. When I load a Match and call its getEvents method it returns 2 equal StartedEvent instances with the same PK.
Is this an error or wrong mapping. Hope somebody can help.

Have implemented equals and hashcode methods in the classes.

epllcr · **Joined:** Sat Mar 04, 2006 10:07 am **Posts:** 9

Disregard this post the problem was caused by a query that eager fetched more than one collection. With inheritance you can apprantly only be sure that the correct number of objects are returned, when only eager fetching one collection according to Hibernate In Action.

zhirenshao · **Posted:** Fri Mar 31, 2006 2:49 am

So how do you avoid multiple eager fetch? I got the same problem as yours.

ruben_inoto · **Joined:** Fri Apr 07, 2006 3:50 am **Posts:** 3

I have the same problem and the only workaround I've found is to fetch the first collection eagerly, and the second lazy, to iterate through all the elements afterwards (because I need them anyway).
Has anybody found a solution for this?

emmanuel · **Posted:** Sun Apr 16, 2006 12:06 pm

Loading more than one collection per query is incredibly evil. So your solution is the right one.

http://opensource.atlassian.com/projects/hibernate/browse/HHH-1413