I have 3 Entities that I am dealing with:
Employee, Dependent and Beneficiary. All of them extend the abstract type person,
I am using a table per hierarchy format, hence all the of the entities are in the same table.
Employee has one-to-many relation with Beneficiary and Dependent.
everything works fine when I add or get dependents from or to the employee. However when I do employee.getBeneficiaries,
where beneficiaries is a lazily loaded Set which gets objects of type Beneficiary from the database, I get the exception below..

Please refer to the mapping files ..

Mapping file for Person


<hibernate-mapping
>
<class
name="com.tps.gen.bo.Person"
table="xperson"
>
<cache usage="transactional" />

<id
name="guid"
column="guid"
type="java.lang.String"
length="36"
>
<generator class="com.tps.framework.core.GuidGenerator">
<!--
To add non XDoclet generator parameters, create a file named
hibernate-generator-params-Person.xml
containing the additional parameters and place it in your merge dir.
-->
</generator>
</id>

<discriminator
column="classtype"
force="true"
/>

<version
name="version"
column="version"
type="java.lang.Integer"
unsaved-value="negative"
/>


......

<subclass
name="com.tps.gen.bo.Beneficiary"
>

<component
name="allotment"
class="com.tps.type.Percent"
>

<property
name="value"
type="java.lang.Double"
update="true"
insert="true"
column="allotment_value"
/>

</component>

<many-to-one
name="employee"
class="com.tps.gen.bo.Employee"
cascade="save-update"
outer-join="auto"
update="true"
insert="true"
column="employee_guid"
not-null="false"
/>

.....

</subclass>
<subclass
name="com.tps.gen.bo.Dependent"
>

</component>

<many-to-one
name="employee"
class="com.tps.gen.bo.Employee"
cascade="save-update"
outer-join="auto"
update="true"
insert="true"
column="employee_guid"
not-null="false"
/>

.....


<subclass
name="com.tps.gen.bo.Employee"
>


<set
name="dependents"
lazy="true"
cascade="all"
sort="unsorted"
>

<key
column="employee_guid"
>
</key>

<one-to-many
class="com.tps.gen.bo.Dependent"
/>

</set>


<set
name="beneficiaries"
lazy="true"
cascade="all"
sort="unsorted"
>

<key
column="employee_guid"
>
</key>

<one-to-many
class="com.tps.gen.bo.Beneficiary"
/>

</set>


Hibernate Version: 2.1
Database: MySQL 4.1


I am facing a WrongClassException:

11:00:13,718 ERROR [net.sf.hibernate.collection.PersistentCollection] - Failed to lazily initialize a collection
net.sf.hibernate.WrongClassException: Object with id: cff4e90f-5599-4f87-8e7f-84adab68856f was not of the specified subclass: com.tps.gen.bo.Beneficiary (loaded object was of wrong class)
at net.sf.hibernate.loader.Loader.instanceAlreadyLoaded(Loader.java:535)
at net.sf.hibernate.loader.Loader.getRow(Loader.java:502)
at net.sf.hibernate.loader.Loader.getRowFromResultSet(Loader.java:218)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:285)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:138)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:1020)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:995)
at net.sf.hibernate.loader.OneToManyLoader.initialize(OneToManyLoader.java:93)
at net.sf.hibernate.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:288)
at net.sf.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:3315)
at net.sf.hibernate.collection.PersistentCollection.initialize(PersistentCollection.java:195)
at net.sf.hibernate.collection.PersistentCollection.write(PersistentCollection.java:84)
at net.sf.hibernate.collection.Set.clear(Set.java:212)
at net.sf.hibernate.type.PersistentCollectionType.copy(PersistentCollectionType.java:235)
at net.sf.hibernate.type.TypeFactory.copy(TypeFactory.java:284)
at net.sf.hibernate.impl.SessionImpl.doCopy(SessionImpl.java:4113)
at net.sf.hibernate.impl.SessionImpl.copy(SessionImpl.java:4045)
at net.sf.hibernate.engine.Cascades$5.cascade(Cascades.java:132)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:436)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:503)
at net.sf.hibernate.impl.SessionImpl.doCopy(SessionImpl.java:4107)
at net.sf.hibernate.impl.SessionImpl.copy(SessionImpl.java:4045)
at net.sf.hibernate.engine.Cascades$5.cascade(Cascades.java:132)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:436)
at net.sf.hibernate.engine.Cascades.cascadeCollection(Cascades.java:526)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:452)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:503)
at net.sf.hibernate.impl.SessionImpl.doCopy(SessionImpl.java:4107)
at net.sf.hibernate.impl.SessionImpl.saveOrUpdateCopy(SessionImpl.java:4041)

I am sure that there are no objects of type beneficiary in the database. I traced the error, and it seems like it is loading an object of type dependent in the set of beneficiaries, which is causing the error.

Does anyone have an idea of how to rectify this?

I've had the same problem. I solved it by adding a where attribute to the set that checks the discriminator column is equal to the discrimnitor-value for the subtype you want. I don't see discrimintor-value in your mapping so you probably need to add that.

Perman,

Any idea why this "where" attribute is needed? Hibernate should already know what the discriminator value is by looking up the specified "class" and then using "discriminator". Any idea why it doesn't do this?