Hibernate 3.3.1.GA

Problem: In joined inheritance type hibernate proxy have incorrect supertype !

Billing billing = customer.getBilling();

boolean result = billing instanceof PersonBilling || billing instanceof CorporateBilling;

If billing object is not proxy(lazy=false) result is true (all ok);
But if billing object is proxy - result is false, and proxy supertype is Billing.

Why proxy has never supertype PersonBilling or CorporateBilling??

Customer.hbm.xml:
...
<class name="Customer" table="customers">
...
<many-to-one name="billing" column="billing_id" class="Billing" cascade="all" not-null="false" unique="true" />
...

Billing.hbm.xml:

<class name="Billing" table="billings">
...
<joined-subclass name="PersonBilling" table="person_billings">
...
<joined-subclass name="CorporateBilling" table="corporate_billings">
...

Hibernate is designed that way and it is due to Java's single inheritance model.
See http://www.hibernate.org/hib_docs/v3/reference/en-US/html_single/#performance-fetching-proxies
for a solution.
You should create interfaces for each subclass and use these as proxy.
Or disable proxies for these associations.

Thanks!