Hello.

Please take a look at my mapping. I've always get a WrongClassException:

10:34:14,760 WARN [ProjektHelperImpl] Projekt 2 nicht gefunden net.sf.hibernate.WrongClassException: Object with id: 2 was not of the specified subclass: PlanKostenImpl (loaded object was of wrong class)

<hibernate-mapping>
<class name="MarketingkostenImpl" table="mkz_marketingkosten" polymorphism="explicit" discriminator-value="B">

<discriminator column="type" type="java.lang.String" length="2"/>

<property ... />

<subclass name="IstKostenImpl" discriminator-value="I">
<property .../>
</subclass>

<subclass name="PlanKostenImpl" discriminator-value="P">
<property .../>
</subclass>

</hibernate-mapping>


<hibernate-mapping>
<class name="ProjektImpl" table="mkz_projekt">

<property .../>

<set name="istKosten" lazy="false" inverse="false" cascade="all" sort="unsorted">
<key column="projekt_id"/>

<one-to-many class="IstKostenImpl"/>
</set>

<set
name="planKosten" lazy="false" inverse="false" cascade="all" sort="unsorted">

<key column="projekt_id"/>

<one-to-many class="PlanKostenImpl"/>
</set>

<one-to-one name="vertriebsBudget" class="MarketingkostenImpl" cascade="all" outer-join="auto" constrained="false"

</hibernate-mapping>

Use:

Another approach is to use force="true" in the discriminator element: <discriminator column="..." force="true" />. This causes Hibernate to include a condition on the discriminator column in the Where clause of the generated SQL. Moreover, the condition will include all subclasses further down the inheritance hierarchy, so you don't have to manually update the Where clause every time you add a new subclass of the class you intend to retrieve.

This feature is also available through the Hibernate annotation @org.hibernate.annotations.ForceDiscriminator but it is not part of the JPA standard.

I also use a table per class hierarchy.
I've added the annotation and that solves the problem for me. However, now I see where this_.DTYPE in (x,y,z) in all my queries relating to that entity when leaving the entire clause out would have the exact same query result without the performance loss involved in performing this superfluous selection.

Is there some way to get around this issue without this? Apparently, Hibernate needs this to get all the subclasses, but from a query standpoint it doesn't make any sense and it's certainly not without significant cost.

Kind regards,

Marc