You have an error in your Sql syntax;check the manual that corresponds to your MySql server version fro the right syntax to  use near'( ORDER order0_where exists(select orderitems1_

public class OrderTest {

	Session session = null;
	@Test
	public void testWhere1() {
		String hql = "from Order o where o.orderItems is not empty";
		Query query = session.createQuery(hql);
		List<Order> list = query.list();
		for (Order order : list) {
			System.out.println(order.getCustomer().getName());
			System.out.println(order.getAmount());
			System.out.println(order.getTradeDate());
			
		}
	}
	@Before
	public void setUp() throws Exception {
		session = HibernateSessionFactory.getCurrentSession();
	}
	@After
	public void tearDown() throws Exception {
		session.close();
	}
}

.ID from ORDERITEM orderitems1_ w' at line 1