Posting you mapping would be useful.
Anyway, here's and example:
Let Solicitante be an interface
Let ProductoImpl be a class wich implements Solicitante
Code:
<hibernate-mapping>
<class name="Solicitante" table="SOLICITANTES">
<id name="codigo" type="string" unsaved-value="null">
<column name="CODIGO" sql-type="char(16)" not-null="true" />
<generator class="uuid.hex"/>
</id>
<discriminator column="tipo" type="string" force="true" />
...
...
<subclass name="SolicitanteImpl" />
</class>
</hibernate-mapping>
IMHO, you should separate the user interface componentes (struts ActionForms) from your bussines objects.