Type safe collections (java 1.5)

de_tom · **Joined:** Wed Nov 30, 2005 11:13 am **Posts:** 10

Hi,

I'd like to know if there is a way, to use type safe collections for queries. Before posting my question, I've searched the forum for answers, but the best I could find is "yes, hibernate 3 has it, but we do not have a user friendly api for it yet...".

I'd be glad for any answers/pointers on how to do something like:

Code:

   Query query = session.createQuery("select p from Person as p where p.name=:name);
   query.setString("name", "Tom");
   List<Person> persons = query.list();

... without(!) getting warnings about type safety.

Regards,
Tom

max · **Posted:** Mon Feb 06, 2006 6:49 am

no, unfortunately not.

Maybe ejb3 entitymanger gives you that possibility...i actually dont remember.

I would love it for hibernate3 too, but pretty hard (impossible) to do without loosing compability....

de_tom · **Joined:** Wed Nov 30, 2005 11:13 am **Posts:** 10

Well thanks anyway - at least now I know that I don't have to keep wondering & googling.

So this basically means that we're stuck with non-type safe collections, until Hibernate moves to JDK 1.5, right?

Regards,
Tom

max · **Posted:** Mon Feb 06, 2006 7:47 am

yes, or someone comes up with an ingenius way of making a backward compatible solution ;)

You could actually make your own wrapper of Query that made this possible if it bothers you too much ;)

jkolb · **Joined:** Wed Nov 05, 2003 4:38 pm **Posts:** 29

Code:

Query query = session.createQuery("select p from Person as p where p.name=:name);
query.setString("name", "Tom");
List<? extends Person> persons = (List<? extends Amount>)query.list();
List<Person> results = new LinkedList<Person>();
results.addAll(persons)

return results;

This is how I do it, while it may be a slight performance hit, it does provide type safety without warnings and also when no records are found it returns an empty list instead of null which helps keep you from writing special checks for null.

max · **Posted:** Tue Feb 07, 2006 3:32 am

hibernate never returns null from a .list() operation, so i would say it is a pretty high price to have a addAll operation instead of a weak warning.

my idea of encapsulation would be:

Code:

Query5 query = new Query5(Person.class, session.createQuery("select p from Person as p where p.name=:name)); 
   query.setString("name", "Tom"); 
   List<Person> persons = query.list();

where Query5 then could encapsulate the warnings....i haven't done it, but should be able to work.

the-gtm · **Joined:** Wed Feb 08, 2006 3:59 pm **Posts:** 75

I think this is a little bit overenginered and @SuppressWarnings("unchecked") is just fine :)

Anyway you can still get unsafe collections (and therefore runtime errors) by messing with HQL ("from Business ..." in a wrapper expecting "from Person ...")

max · **Posted:** Thu Feb 09, 2006 4:13 am

sure - i didn't say it were perfect; only that the previous one would definitly be inefficient with no added value.