I have 2 classes, Product (for core product info) and DisplayProduct (has extra fields) which is a subclass of Product. Display product is read only & used as a data aggregation class, i *could* load the product instance & then copy to a DisplayProduct instance, but it means 2x overhead for something desired to be an optimisation, i.e. not a great solution.
What happens is the loader gets confused & after loading an instance of one class, i can not load an instance of the other, yes they are both mapped to one table, share the same key & one is a subclass, but they are not the same object in the context of the application. I get the following error:

<snip>
net.sf.hibernate.WrongClassException: Object with id: XXX was not of the specified subclass: com.woolly.store.product.DisplayProduct (loaded
object was of wrong class)
       at net.sf.hibernate.loader.Loader.instanceAlreadyLoaded(Loader.java:531)

</snip>


samplecode from classes:


class Product {
 private String code;
 private String description;
...
//getters/setters etc
...
}

and;

class DisplayProduct extends Product {
 private List images;
 private BigDecimal price;
...
//getters/setters etc
...
}

If i map both of these classes to the same table;

<class name="Product" table="str_products">

<id name="code" unsaved-value="null">
<generator class="assigned"/>
</id>

<version name="version" type="int"/>

<property name="name"/>
<property name="description"/>
<property name="taxCode"/>
...

</class>

and


<class name="DisplayProduct" table="str_products" mutable="false">

<id name="code" unsaved-value="null">
<generator class="assigned"/>
</id>

<property name="name"/>
<property name="description"/>
<property name="taxCode"/>
        ...

</class>



I have tried switching off the secondary level cache, but the problem seems to run deeper than this. (assuming that setting hibernate.cache.use_second_level_cache=false to do this.)

Ideas?