private static void runDemo( EntityManager em ) throws Exception
    {
        em.getTransaction().begin();
       
        TestEntity e;
       
        long start = System.currentTimeMillis();
       
        //let us create 10 dummy data, every one will have a TestEntityMultiExtensionA instance
        //5 of them will have a TestEntityMultiExtensionB instance
        for( int i=0; i<10; i++ )
        {
            e = new TestEntity();

            e.customValues = new ArrayList<TestKeyValueEntity>();
           
            TestEntityExtensionA meA = new TestEntityExtensionA();
            meA.setParent( e );
            meA.customValueA = "extA_"+i;
            e.setExtension( meA );
           
            if( i % 2 == 0 )
            {
                TestEntityExtensionB meB = new TestEntityExtensionB();
                meB.customValueB = "extB_"+i;
                meB.setParent( e );
                e.setExtension( meB );
            }

            em.persist( e );
        }
        em.getTransaction().commit();
       
        System.out.println( "\n\nCreation Time: " + ( System.currentTimeMillis() - start ) + "ms" );
       
        //for testing without use of cache
        em.clear();
        em.getEntityManagerFactory().getCache().evictAll();
       
        start = System.currentTimeMillis();
       
        List<Tuple> result;
       
        final CriteriaBuilder cb = em.getCriteriaBuilder();
       

        //creating a Tuple query from TestEntity
        final CriteriaQuery<Tuple> cq = cb.createTupleQuery();
        final Root<TestEntity> root = cq.from( TestEntity.class );

        final List<Selection<?>> selections = new LinkedList<Selection<?>>();

        selections.add( root.get( "id" ) );
       
        //now let us join to TestEntityMultiExtensionA and TestEntityMultiExtensionB:
       
        final ListJoin< TestEntity, TestEntityExtension > baseJoinExtA = root.<TestEntity, TestEntityExtension>joinList( "extensions", JoinType.LEFT );
        //additional on restriction to fetch only instances of TestEntityMultiExtensionA
        baseJoinExtA.on( cb.equal( baseJoinExtA.get( "extensionType" ), TestEntityExtensionA.class.getName() ) );
        //treat joined TestEntityExtension as TestEntityExtensionA to provide access of TestEntityExtensionA properties
        final ListJoin<TestEntity, TestEntityExtensionA> joinExtA = cb.treat(
                baseJoinExtA,
                TestEntityExtensionA.class
        );
        selections.add( joinExtA.get( "id" ) );
        selections.add( joinExtA.get( "customValueA" ) );
       
       
        final ListJoin< TestEntity, TestEntityExtension > baseJoinExtB = root.<TestEntity, TestEntityExtension>joinList( "extensions", JoinType.LEFT );
        //additional on restriction to fetch only instances of TestEntityMultiExtensionB
        baseJoinExtB.on( cb.equal( baseJoinExtB.get( "extensionType" ), TestEntityExtensionB.class.getName() ) );
        //treat joined TestEntityExtension as TestEntityExtensionB to provide access of TestEntityExtensionB properties
        final ListJoin<TestEntity, TestEntityExtensionB> joinExtB = cb.treat(
                baseJoinExtB,
                TestEntityExtensionB.class
        );
        selections.add( joinExtB.get( "id" ) );
        selections.add( joinExtB.get( "customValueB" ) );

        cq.multiselect( selections );
       
        result = em.createQuery( cq ).getResultList();
       
        System.out.println( "\n\nFetch Time: " + ( System.currentTimeMillis() - start ) + "ms" );
       
        for( Tuple r : result )
            System.out.println( Arrays.toString( r.toArray() ) );
       
        em.close();
    }

@MappedSuperclass
//EclipseLink Annotation
@PrimaryKey(validation=IdValidation.ZERO)
public abstract class Entity {
   
    //JPA Annotations
    @Id
    @Column(name="id")
    @GeneratedValue( generator = EntityConstants.HILO_GENERATOR )
    //Hibernate Annotations, IdGenerator is a custom extension of MultipleHiLoPerTableGenerator which uses the SimpleClass name as valueName
    @GenericGenerator( name = EntityConstants.HILO_GENERATOR, strategy = IdGenerator.NAME )   
    private long id;
   
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
}

@javax.persistence.Entity(name="tests")
public class TestEntity extends Entity{

    @OneToMany( cascade={CascadeType.ALL}, mappedBy="parent" )
    @BatchFetch( size=EntityConstants.DEFAULT_BATCH_FETCH_SIZE, value=BatchFetchType.IN )
    @CascadeOnDelete
    private List<TestEntityExtension> extensions;
       
    @Override
    public List<TestEntityExtension> getExtensions() {
        return extensions;
    }

    @Override
    public void setExtensions(List<TestEntityExtension> extensions) {
        this.extensions = extensions;
    }

    @Override
    public <EE extends TestEntityExtension> EE getExtension( Class<EE> extension) {
        if( extensions == null || extension == null )
            return null;
       
        for( E ext : extensions )
        {
            if( ext.getClass() == extension )
                return (EE) ext;
        }
       
        return null;
    }

    @Override
    public void setExtension( TestEntityExtension extension ) {
        if( extensions == null )
            extensions = new ArrayList<TestEntityExtension>();
       
        if( extension != null )
        {
            @SuppressWarnings("unchecked")
            final TestEntityExtension existingExtension = getExtension( extensions, (Class<? extends TestEntityExtension>)extension.getClass() );
           
            if( existingExtension == null )
                extensions.add( extension );
            else if( existingExtension != extension )
            {
                extensions.remove( existingExtension );
                extensions.add( extension );
            }
        }
    }
}

@javax.persistence.Entity(name="tests_extensions")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn( name=IExtension.EXTENSION_TYPE_COLUMN_NAME, discriminatorType=DiscriminatorType.STRING )
@DiscriminatorOptions( force=true, insert=true)
public abstract class TestEntityExtension extends Entity
{
    @Column(name=IExtension.EXTENSION_TYPE_COLUMN_NAME)
    private String extensionType = getClass().getName();
   
    public String getExtensionType() {
        return extensionType;
    }
   
    @ManyToOne
    @JoinColumn(name="test_id", nullable=false)
    private TestEntity parent;

    @Override
    public TestEntity getParent() {
        return parent;
    }

    @Override
    public void setParent(TestEntity parent) {
        this.parent = parent;
    }
}

@Entity(name="tests_extensions_a")
public class TestEntityExtensionA extends TestEntityExtension {
    @Column(name = "custom_value_a")
    public String customValueA;
}

@Entity(name="tests_extensions_b")
public class TestEntityExtensionB extends TestEntityExtension {
    @Column(name = "custom_value_b")
    public String customValueB;
}

Creation Time: 22ms


Fetch Time: 9ms
[1, 1, extA_0, 2, extB_0]
[2, 3, extA_1, 0, null]
[3, 4, extA_2, 5, extB_2]
[4, 6, extA_3, 0, null]
[5, 7, extA_4, 8, extB_4]
[6, 9, extA_5, 0, null]
[7, 10, extA_6, 11, extB_6]
[8, 12, extA_7, 0, null]
[9, 13, extA_8, 14, extB_8]
[10, 15, extA_9, 0, null]

Creation Time: 22ms
java.lang.IllegalArgumentException: Unable to resolve attribute [customValueA] against path [null]
   at org.hibernate.jpa.criteria.path.AbstractPathImpl.unknownAttribute(AbstractPathImpl.java:112)
   at org.hibernate.jpa.criteria.path.AbstractPathImpl.locateAttribute(AbstractPathImpl.java:209)
   at org.hibernate.jpa.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:180)
   at JpaTest.runDemo(Tester2.java:119)
   at JpaTest.main(Tester2.java:41)

    //treat patch member
    private ManagedType<?> treatedManagedType = null;
   
    @Override
    public <T extends E> ListAttributeJoin<O,T> treatAs(Class<T> treatAsType) {
        //original implementation:
        //return new TreatedListAttributeJoin<O,T>( this, treatAsType );
       
        this.resetJavaType( treatAsType );
        this.treatedManagedType = criteriaBuilder().getEntityManagerFactory().getMetamodel().managedType( treatAsType );
        return (ListAttributeJoin<O, T>) this;
    }
   
    @Override
    protected ManagedType<E> locateManagedType() {
        if( treatedManagedType == null )
            return super.locateManagedType();
        else
            return (ManagedType<E>) treatedManagedType;
    }

Creation Time: 20ms


Fetch Time: 20ms
[1, 1, extA_0, 2, extB_0]
[2, 3, extA_1, null, null]
[3, 4, extA_2, 5, extB_2]
[4, 6, extA_3, null, null]
[5, 7, extA_4, 8, extB_4]
[6, 9, extA_5, null, null]
[7, 10, extA_6, 11, extB_6]
[8, 12, extA_7, null, null]
[9, 13, extA_8, 14, extB_8]
[10, 15, extA_9, null, null]