@Entity
@Table(name = "MY_TABLE")
@DiscriminatorColumn(name = "DISC_COL", discriminatorType = DiscriminatorType.INTEGER)
@DiscriminatorValue("0")
public class ConcreteParentClass {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name = "ID")
    private Integer id;
}

@Entity
@DiscriminatorValue("1")
public class ChildA extends ConcreteParentClass {
	
	@JoinColumn(name = "REF_COL", foreignKey = @ForeignKey(name = "FK_REF_00"))
    @ManyToOne
    @Fetch(FetchMode.SELECT)
	ConcreteParentClass reference;
}

@Entity
@DiscriminatorValue("2")
public class ChildB extends ConcreteParentClass {

    @JoinColumn(name = "REF_COL", foreignKey = @ForeignKey(name = "FK_REF_00"))
    @ManyToOne
    @Fetch(FetchMode.SELECT)
    ConcreteParentClass reference;
}


public class ORMUnitTestCase extends BaseCoreFunctionalTestCase {
	
	// Add your entities here.
	@Override
	protected Class<?>[] getAnnotatedClasses() {
		return new Class<?>[] {
				ConcreteParentClass.class,
				ChildA.class,
				ChildB.class,
		};
	}

	// Add in any settings that are specific to your test.  See resources/hibernate.properties for the defaults.
	@Override
	protected void configure(Configuration configuration) {
		super.configure( configuration );

		configuration.setProperty( AvailableSettings.SHOW_SQL, Boolean.TRUE.toString() );
		configuration.setProperty( AvailableSettings.FORMAT_SQL, Boolean.TRUE.toString() );
		configuration.setProperty(AvailableSettings.DEFAULT_BATCH_FETCH_SIZE, "10");
	}

	// Add your tests, using standard JUnit.
	@Test
	public void hhh123Test() throws Exception {
		// BaseCoreFunctionalTestCase automatically creates the SessionFactory and provides the Session.
		Session s = openSession();
		Transaction tx = s.beginTransaction();
		ChildA child1 = new ChildA();
		ChildB child2 = new ChildB();
		ChildA child3 = new ChildA();
		ChildB child4 = new ChildB();
		
		child1.reference = child2;
		child4.reference = child3;
		
		s.persist(child1);
		s.persist(child2);
		s.persist(child3);
		s.persist(child4);
		
		tx.commit();
		s.close();
		
		s = openSession();
		tx = s.beginTransaction();
		Query<ConcreteParentClass> query = s.createQuery("from ConcreteParentClass", ConcreteParentClass.class);
		
		query.list();
		tx.commit();
		s.close();
	}
}
	
jakarta.persistence.PersistenceException: Converting `org.hibernate.PropertyAccessException` to JPA `PersistenceException` : Could not set value of type [org.hibernate.bugs.ChildA] : `org.hibernate.bugs.ChildA.reference` (setter)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:165)
	at org.hibernate.query.spi.AbstractSelectionQuery.list(AbstractSelectionQuery.java:374)
	at org.hibernate.query.sqm.internal.QuerySqmImpl.list(QuerySqmImpl.java:1073)
	at org.hibernate.bugs.ORMUnitTestCase.hhh123Test(ORMUnitTestCase.java:83)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.hibernate.testing.junit4.ExtendedFrameworkMethod.invokeExplosively(ExtendedFrameworkMethod.java:45)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:299)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:293)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: org.hibernate.PropertyAccessException: Could not set value of type [org.hibernate.bugs.ChildA] : `org.hibernate.bugs.ChildA.reference` (setter)
	at org.hibernate.property.access.spi.SetterFieldImpl.set(SetterFieldImpl.java:81)
	at org.hibernate.sql.results.graph.entity.internal.BatchEntitySelectFetchInitializer.setInstance(BatchEntitySelectFetchInitializer.java:105)
	at org.hibernate.sql.results.graph.entity.internal.BatchEntitySelectFetchInitializer.lambda$endLoading$1(BatchEntitySelectFetchInitializer.java:79)
	at java.base/java.util.HashMap.forEach(HashMap.java:1421)
	at org.hibernate.sql.results.graph.entity.internal.BatchEntitySelectFetchInitializer.endLoading(BatchEntitySelectFetchInitializer.java:73)
	at org.hibernate.sql.results.internal.StandardRowReader.finishUp(StandardRowReader.java:160)
	at org.hibernate.sql.results.spi.ListResultsConsumer.consume(ListResultsConsumer.java:223)
	at org.hibernate.sql.results.spi.ListResultsConsumer.consume(ListResultsConsumer.java:33)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.doExecuteQuery(JdbcSelectExecutorStandardImpl.java:443)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.executeQuery(JdbcSelectExecutorStandardImpl.java:166)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.list(JdbcSelectExecutorStandardImpl.java:91)
	at org.hibernate.sql.exec.spi.JdbcSelectExecutor.list(JdbcSelectExecutor.java:31)
	at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.lambda$new$0(ConcreteSqmSelectQueryPlan.java:113)
	at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.withCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:335)
	at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.performList(ConcreteSqmSelectQueryPlan.java:276)
	at org.hibernate.query.sqm.internal.QuerySqmImpl.doList(QuerySqmImpl.java:571)
	at org.hibernate.query.spi.AbstractSelectionQuery.list(AbstractSelectionQuery.java:363)
	... 17 more
Caused by: java.lang.IllegalArgumentException: Can not set org.hibernate.bugs.ConcreteParentClass field org.hibernate.bugs.ChildA.reference to org.hibernate.bugs.ChildB
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
	at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:75)
	at java.base/java.lang.reflect.Field.set(Field.java:799)
	at org.hibernate.property.access.spi.SetterFieldImpl.set(SetterFieldImpl.java:53)
	... 33 more