I have an folloving problem:
I have two classes Father and Son, that extends Father. I also have an interface Interface, that is implemented by the Son. Some getters and setters in the Father and Son manipulate with the Interface (they are typed to the Interface, but the object are instances of Son of course).
I have created an xml description of the mapping with tha <class>element for the Father and an <subclass> element for the Son, both with the right configured discriminator. When I try to run the program I get an exception, that says, that Interface isn't configured. When i add an <class> element for the Interface I get an exception, that says The Interface is an interface or abstract class, that can not be instantionised.
What should the maping look like for the situation, where I want to map a subclass of an already mapped class that implements an interface?

How about you show the actual mapping that you currently have, and we can help you fix it.

OK, it is a bit more complicated, that the first description, that has been designed to be as minimalist as possible:

There is part of acces-right system. There are objects, subjects and groups of subejcts and groups of objects. Each Subject is also an object and each Group of soemthing is also something. I would like to use this tree of infaritance:
Object

-Group of objects
-Subject

-Group of subjects

it seems also usefull to have an interface Group, that is implemented bt Group of objects and group of subjects. Some getters and setters in the system use the type Group.

The connection classes are to provide many-to many relationship. I can't to use built-in one, for some reasons.

It sems to bee everything usefull, i remember. Ok, the last notice: of course I don't use the classname Object, names are in Czech and use here translation for your better orientation :)


<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>
<class name="Object" table="object" discriminator-value="1">

<id name="id" type="long" column="id">
<generator class="sequence">
<param name="sequence">idsequence</param>
</generator>
</id>

<discriminator column="discriminator" type="int" />

<property name="domain" />
<property name="idVRamciDomeny" column = "id_v_domene" />

<subclass name="Subject" discriminator-value="4" >
<subclass name="GroupSubjects" discriminator-value="6" />
</subclass>

<subclass name="GroupObjects" discriminator-value="2" >
</subclass>

</class>

<class name="ConnectionSubjGroup" table="skupiny_subjektu" >
<id name="id" type="long" column="id">
<generator class="sequence">
<param name="sequence">idsequence</param>
</generator>
</id>
<many-to-one name="subject" />
<many-to-one name="group" />
</class>

<class name="ConnectionObjGroup" table="skupiny_predmetu" >
<id name="id" type="long" column="id">
<generator class="sequence">
<param name="sequence">idsequence</param>
</generator>
</id>
<many-to-one name="object" />
<many-to-one name="group" />
</class>

<class name="Group" table="object" discriminator-value="0">
<id name="id" type="long" column="id">
<generator class="sequence">
<param name="sequence">idsequence</param>
</generator>
</id>
<discriminator column="discriminator" type="int" />

</class>

</hibernate-mapping>

net.sf.hibernate.HibernateException: Cannot instantiate abstract class or interface: Group

Change <many-to-one name="group" /> to <many-to-one name="group" class="Object" />
This will cause, that the system will not try to guess the type of property by reflection (the result would be Group), but will search in the class hierarchy with the root in Object.