Hi, I have this mapping:

<hibernate-mapping package="model">
<class name="Partner" table="partners" abstract="true">
<id name="id" type="long" column="id">
<generator class="hilo"/>
</id>

<discriminator column="partnerType" type="string" force="true"/>

<property name="nameDisplay"/>
</class>

<subclass name="Contact" extends="Partner" discriminator-value="contact">
<join table="contacts">
<key column="partners_id"/>

<property name="nameFirst"/>
<property name="nameMiddle"/>
<property name="nameLast"/>
<many-to-one name="company" column="company_id"/>
</join>
</subclass>

<subclass name="Company" extends="Partner" discriminator-value="company">
<join table="company">
<key column="partners_id"/>

<property name="nameOfficial"/>
</join>
</subclass>

<class name="Invoice" table="invoices">
<id name="id" type="int" column="id">
<generator class="native"/>
</id>

<many-to-one name="partner" column="partners_id" fetch="join"/>
<property name="summary"/>
</class>

The class Partner is really abstract:

public abstract class Partner {
private Long id;
private String nameDisplay;

public Long getId() {
return id;
}

public String getNameDisplay() {
return nameDisplay;
}

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

public void setNameDisplay(String nameDisplay) {
this.nameDisplay = nameDisplay;
}
}

But in this code I have ClassCastException:

try {
tx = session.beginTransaction();
Query q = session.createQuery(
"from Invoice"
);
result = q.list();
tx.commit();
} catch (HibernateException he) {
if (tx != null) {
tx.rollback();
}
throw he;
}

Invoice invoice = (Invoice) result.get(0);
Partner partner;
partner = invoice.getPartner();
System.out.println(((Contact) partner).getNameFirst()); // !!!!!!! Exception

I need to get the objects of subclasses such as Contact or Company. Please, say me where is my error... =(

Before you cast the object, what is the object's type?

You can just print it before trying the cast

Class Invoice has method:


This method return all Partner objects associated with this Invoice. But the Partner class is abstract! Then I try to cast real type program throw exception.

Hibernate load the Partner classes from multiple tables, but I cant resolve the real type of class. The method:

everything return "Partner". And i lost the real type of objects.

[/code]

have you tried using interfaces? I have a similar set up (but using joined-sublclasses with their own tables). I can cast with no problems...

I specify this kind of thing:

<class name="org.thorne.lettings.referencedata.api.Contact" table="contact">
<id name="id" column="id" unsaved-value="-1">
<generator class="identity"/>
</id>
<component name="personName" class="org.thorne.lettings.referencedata.api.PersonNameImpl">
<property name="firstName" column="first_name"/>
<property name="secondName" column="second_name"/>
<property name="middleName1" column="middle_name_1"/>
<property name="middleName2" column="middle_name_2"/>
<many-to-one name="title" class="org.thorne.lettings.referencedata.api.TitleImpl" column="title_id_fk" unique="true" cascade="none" />
</component>
<one-to-one name="address" class="org.thorne.lettings.referencedata.api.AddressImpl" property-ref="contact" cascade="all"/>
<one-to-one name="homeNumber" class="org.thorne.lettings.referencedata.api.TelephoneNumberImpl" cascade="all" />
<one-to-one name="workNumber" class="org.thorne.lettings.referencedata.api.TelephoneNumberImpl" cascade="all"/>
<one-to-one name="mobileNumber" class="org.thorne.lettings.referencedata.api.TelephoneNumberImpl" cascade="all"/>
<joined-subclass name="org.thorne.lettings.referencedata.api.TenantImpl" table="tenant">
<key column="id"/>
<many-to-one name="maritalStatus" class="org.thorne.lettings.referencedata.api.MaritalStatusImpl" column="marital_status_id_fk" unique="true" cascade="none" />
<property name="pets" column="has_pets"/>
<property name="petDescription" column="pet_description"/>
<property name="smoker" column="is_smoker"/>
<property name="children" column="has_children"/>
<component name="employmentDetails" class="org.thorne.lettings.referencedata.api.EmploymentDetailsImpl" >
<many-to-one name="employmentType" class="org.thorne.lettings.referencedata.api.EmploymentTypeImpl" column="employment_type_id_fk" unique="true" cascade="none" />
<property name="occupation"/>
<many-to-one name="employer" class="org.thorne.lettings.referencedata.api.EmployerImpl" column="employer_id_fk" unique="true" cascade="none" />
</component>
</joined-subclass>
<joined-subclass name="org.thorne.lettings.referencedata.api.EmployerImpl" table="employer">
<key column="id"/>
<set name="employees" cascade="none" inverse="true" >
<key column="employer_id_fk"/>
<one-to-many class="org.thorne.lettings.referencedata.api.TenantImpl"/>
</set>
</joined-subclass>
</class>

That is I have an interface called Contact, (which is implemented by ContactImpl) and two concrete subclasses EmployerImpl and TenantImpl.

Notice that I never use ContactImpl in my mapping - just the interface Contact.

Try introducing an interface and use that in your mapping class.