public class ItemSummary {
    public ItemSummary(Long itemId, String name, Date auctionEnd) {
    }
}

@SqlResultSetMapping(
    name = "ItemSummaryResult",
    classes = {
        @ConstructorResult(
            targetClass = ItemSummary.class,
            columns = {
                @ColumnResult(name = "ITEM_ID"),
                @ColumnResult(name = "ITEM_NAME"),
                @ColumnResult(name = "ITEM_AUCTIONEND")
            }
        )
    }
)

Query q = em.createNativeQuery(
    "select " +
        "i.ID as ITEM_ID, i.NAME as ITEM_NAME, i.AUCTIONEND as ITEM_AUCTIONEND " +
        "from ITEM i ",
    "ItemSummaryResult"
);
List<ItemSummary> result = q.getResultList();
assertTrue(result.get(0) instanceof ItemSummary); // Fails, Object[]