<!-- using an existing domain model where many classes are marked
  as final, and setters do not exist always -->
hibernate.cglib.use_reflection_optimizer=false
hibernate.max_fetch_depth=1

<hibernate-mapping default-access="field" default-lazy="false">
   <class name="de.acme.Outer" table="outerTable">
      <id name="id" column="id">
          <generator class="sequence">
                <param name="sequence">SEQ_acme</param>
           </generator>
      </id>
      <many-to-one name="nested" class="de.acme.Outer$Inner" column="innerTable" fetch="join"/>
   </class>
      
   <class name="de.acme.Outer$Inner" table="innerTable">
      <id name="id" column="id"/>
      <property name="customerScore" column="score"/>
   </class>
</hibernate>

public final class Outer extends Base
{
  private int id;
  private Outer outer;

  public static class Outer extends Base
  {
    private int id;
    // DB column is NUMBER
    private int customerScore;
  }
}

13:15:28.519 INFO [DefaultLoadEventListener]- <Error performing load command>
org.hibernate.PropertyAccessException: could not set a field value by reflection setter of de.acme.OuterClass$InnerClass.customerScore   at org.hibernate.property.DirectPropertyAccessor$DirectSetter.set(DirectPropertyAccessor.java:81)
   at org.hibernate.tuple.AbstractTuplizer.setPropertyValues(AbstractTuplizer.java:207)
   at org.hibernate.tuple.PojoTuplizer.setPropertyValues(PojoTuplizer.java:176)
   at org.hibernate.persister.entity.BasicEntityPersister.setPropertyValues(BasicEntityPersister.java:2919)
   at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:113)
   at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:530)
   at org.hibernate.loader.Loader.doQuery(Loader.java:436)
   at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:218)
   at org.hibernate.loader.Loader.loadEntity(Loader.java:1345)
   at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:116)
   at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:101)
   at org.hibernate.persister.entity.BasicEntityPersister.load(BasicEntityPersister.java:2471)
   at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:351)
   at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:332)
   at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:113)
   at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:151)
   at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:79)
   at org.hibernate.impl.SessionImpl.get(SessionImpl.java:621)
   at org.hibernate.impl.SessionImpl.get(SessionImpl.java:614)
   at
Caused by: java.lang.IllegalArgumentException
   at sun.reflect.UnsafeIntegerFieldAccessorImpl.set(Unknown Source)
   at java.lang.reflect.Field.set(Unknown Source)
   at org.hibernate.property.DirectPropertyAccessor$DirectSetter.set(DirectPropertyAccessor.java:78)
   ... 36 more