Mapping inheritance : WrongClassException

Danzzz · **Joined:** Fri Nov 25, 2005 12:48 pm **Posts:** 6

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Hibernate version: 3.2.0-CR1

Hibernate annotations version: 3.1.0-beta10

Name and version of the database you are using : mysql Ver 12.22 Distrib 4.0.24

Hello, I'm trying to map One To many bidirectional associations, I explain :

I have the following class :

Code:

@Entity
public Class CV 
{

   private Long id;
   private List<IFunctionalSkill> functionalSkills = new ArrayList<IFunctionalSkill>();
   private List<ITechnicalSkill> technicalSkills = new ArrayList<ITechnicalSkill>();

    @Id @GeneratedValue(strategy=GenerationType.AUTO)
   public Long getId() {
      return id;
   }
   
   public void setId(Long id) {
      this.id = id;
   }

    /**
     * @return Returns the functionalSkills.
     */
    @OneToMany(mappedBy="cv", targetEntity=FunctionalSkill.class, fetch = FetchType.EAGER)
    @Cascade({ org.hibernate.annotations.CascadeType.ALL, org.hibernate.annotations.CascadeType.DELETE_ORPHAN })
    public List<IFunctionalSkill> getFunctionalSkills()
    {
        return functionalSkills;
    }


    /**
     * @return Returns the technicalSkills.
     */
    @OneToMany(mappedBy="cv", targetEntity=TechnicalSkill.class, fetch = FetchType.EAGER)
    @Cascade({ org.hibernate.annotations.CascadeType.ALL, org.hibernate.annotations.CascadeType.DELETE_ORPHAN })
    public List<ITechnicalSkill> getTechnicalSkills()
    {
        return technicalSkills;
    }


}

CV has two bidirectional One To Many associations with technicalSkill and FunctionalSkill.
TechnicalSkill and FunctionalSkill are inherited from the abstract class "Skill".

I use the SINGLE_TABLE strategy :

Code:

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="TypeSkill", discriminatorType=DiscriminatorType.STRING)
public abstract class Skill implements ISkill 
{
   
   private Long id;
   private ICV cv;
   
    private Map<String, ISkillDetail> details = new LinkedHashMap<String, ISkillDetail>();
    
    public Skill() {}


   @Id @GeneratedValue(strategy=GenerationType.AUTO)
   public Long getId() {
      return id;
   }

   public void setId(Long id) {
      this.id = id;
   }    

   @ManyToOne(targetEntity=CV.class)
    public ICV getCv() {
      return cv;
   }

   public void setCv(ICV cv) {
      this.cv = cv;
   }   

   // other methods ..etc
    
    /**
     * @return Returns the details.
     */
   @OneToMany(mappedBy="skill", targetEntity=SkillDetail.class, cascade = CascadeType.ALL)
   @MapKey(name="language")    
    public Map<String, ISkillDetail> getDetails()
    {
        return details;
    }

    /**
     * @param details The details to set.
     */
    public void setDetails(Map<String, ISkillDetail> details)
    {
        this.details = details;
    }

   ...

}

Code:

@Entity
@DiscriminatorValue("FunctionalSkill")
public class FunctionalSkill extends Skill implements IFunctionalSkill 
{
   
    private IFunctionalSkillType type = null;
    
    public FunctionalSkill() {}
    

    ..etc

}

Code:

@Entity
@DiscriminatorValue("TechnicalSkill")
public class TechnicalSkill extends Skill implements ITechnicalSkill 
{
    private ITechnicalSkillType type = null;
    
    public TechnicalSkill() {}
    
..etc


}

In my web application, when I create a CV (ID is 1 so) , eachtime I add a functionalSkill or a technicalSkill ,the SAVING opération is OK :

In my database I have the table CV and the table SKILL which has a FK "cv_id" . The discriminator column is either "functionalSkill" or "technicalSkill". the cv_id column is not null and has the value 1.

But each time I want to retrieved (fetchmode = eager for the needs of the application) my CV with the ID = 1, the getFunctionalSkill() or the getTechnicalSkill() methods are called.

And ... I have the following exception :

Quote:

org.springframework.orm.hibernate3.HibernateObjectRetrievalFailureException: Object with id: 1 was not of the specified subclass: fr.model.hibernate.FunctionalSkill (loaded object was of wrong class); nested exception is org.hibernate.WrongClassException: Object with id: 1 was not of the specified subclass: fr.model.hibernate.FunctionalSkill (loaded object was of wrong class)
org.hibernate.WrongClassException: Object with id: 1 was not of the specified subclass: fr.model.hibernate.FunctionalSkill (loaded object was of wrong class)
at org.hibernate.loader.Loader.instanceAlreadyLoaded(Loader.java:1235)
at org.hibernate.loader.Loader.getRow(Loader.java:1186)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:569)
at org.hibernate.loader.Loader.doQuery(Loader.java:689)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadCollection(Loader.java:1919)
at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:36)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:520)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1679)
at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:454)
at org.hibernate.engine.StatefulPersistenceContext.initializeNonLazyCollections(StatefulPersistenceContext.java:755)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:229)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1785)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:48)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:42)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:2821)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:365)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:346)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:123)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:177)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:87)

Error of mapping of inheritance somewhere??!

Please, I really don't know how to solve my problem since one week !!! :( :(

Any help will be appreciate ![/b]

alesj · **Posted:** Mon Jun 26, 2006 3:41 am

I think you are missing

Quote:

@ManyToOne(targetEntity=CV.class)
@JoinColumn(name = "cv_id")
public ICV getCv() {
return cv;
}

in Skill class.

tpischke · **Posted:** Fri Jul 21, 2006 11:53 am

I'm having the exact same problem.

Two OneToMany collections, each consisting of a different subclass of a mapped superclass.

Hibernate fetches them only by the join column, ignoring the discriminator column. haven't figured out how to fix this.

Have you found a solution?

tpischke · **Posted:** Fri Jul 21, 2006 12:17 pm

Solution: Use a hand coded @Where clause to filter by the correct discriminator.

@Where(clause="discriminator_column_name='discriminator_value'")

eyall · **Joined:** Wed Aug 24, 2005 5:32 am **Posts:** 23

Hi,

There is another solution - use can use a unidirectional one-to-many with join table relation. Look here for an example
http://jroller.com/page/eyallupu?entry=getting_a_wrongclassexception_when_mapping

Eyal Lupu

bluca · **Joined:** Fri Jul 15, 2005 6:35 am **Posts:** 12

I have the same problem (I'm using the xml mapping, not the annotations)
Is this a bug (or just a bad issue) ?
It will be solved in futere release ?

t_altamimi · **Joined:** Wed Apr 18, 2007 7:22 am **Posts:** 4

The problem with using a custom Where clause is that you have to update it every time you add more subclasses of the class you intend to retrieve.

A better approach is to use Hibernate's extension annotation @org.hibernate.annotations.ForceDiscriminator. The equivalent in Hibernate XML is <discriminator column="..." force="true" />. This causes Hibernate to include a condition on the discriminator column in the Where clause of the generated SQL. The condition will include all subclasses, so you don't have to manually maintain any Where clauses.

anshuiitk · **Joined:** Tue May 18, 2010 5:39 am **Posts:** 19

The solution of force discriminator (Thanks t_altamimi) works well. But now if this entity is cached in a second level cache, then hibernate does not discriminates uses a discriminator and we have the same problem again ?. Any pointers how to handle this scenario while using second level cache ?

anshuiitk · **Joined:** Tue May 18, 2010 5:39 am **Posts:** 19

A little more explanation of this problem explained http://anshuiitk.blogspot.com/2011/04/h ... ption.html