String hql = "select r from MyUser r where 1=1 and r.firstname = :firstname";
		Query query = entityManager.createQuery(hql);
		query.setParameter("firstname", null);
		Object result = query.getSingleResult();

  select
        m1_0.MY_USER_ID,
        m1_0.FIRSTNAME,
        m1_0.LASTNAME 
    from
        MY_USER m1_0 
    where
        1=1 
        and 1 is not null 
        and 1 is not null 
        and m1_0.FIRSTNAME=? 
        and m1_0.FIRSTNAME is not null