使用hibernate Criteria返回set而不是list

Question

criteria = createCriteria("employee");  
criteria.add(Restrictions.eq("name", "John"));  
criteria.addOrder(Order.asc("city"));
criteria.addOrder(Order.asc("state"));
List result = criteria.list();

This statement returns a list of Employee objects. How can I make it return a Set of Employee objects instead, in order to remove duplicate data?

I understand I can achieve this by creating a set out of the returned list like below, but then I would lose the sorting order of the list. And I don't want to have to write code to sort the set.

Set<Employee> empSet = new HashSet<Employee>(result); 

Answer 1

I don't think it's possible to return a Set using Criteria based on the javadoc. However, if you want to remove duplicate data, why don't add a Projections.distinct(...) to your existing Criteria to remove the duplicates?

http://docs.jboss.org/hibernate/envers/3.6/javadocs/org/hibernate/criterion/Projections.html

UPDATE

For example, if you want to apply a SELECT DISTINCT on the employee name (or some identifier(s)) to get a list of unique employees, you can do something like this:-

List result = session.createCriteria("employee")
            .setProjection(Projections.distinct(Projections.property("name")))
            .add(Restrictions.eq("name", "John"))
            .addOrder(Order.asc("city"))
            .addOrder(Order.asc("state"))
            .list();

This way, you don't really need to worry about using Set at all.

Answer 2

As the comments and javadoc suggest, you have to return a List from Criteria . Therefore, your only option is to remove uniques after the fact. As KepaniHaole said, you should use a LinkedHashSet if you want to preserve order.