Trying to associate two objects not yet saved

Ot · **Posted:** Sat Dec 27, 2003 3:58 pm

I have a object called Setor, which is already saved. Now, I want to add an object Quadra to Setor, and many objects Lote to Quadra. Neither Quadra or Lote are saved. The following code shows the way I'm trying to do it (I get a null pointer exception). It may give you an idea of what i want to do.

Code:

Setor set =
            (Setor) session.load(Setor.class, new Long(paf.getId()));
         int k = Integer.parseInt(paf.getQuantLotes());
         Quadra quadra = new Quadra();
         quadra.setNome(paf.getNome());
         quadra.setComentario(paf.getComentario());
         quadra.setSetor(set);
         set.getQuadras().add(quadra);
         Long newId = (Long)session.save(quadra);
         Quadra quad =
                     (Quadra) session.load(Quadra.class, newId);

         for (int i = 0; i <= k; i++){
            Lote lote = new Lote();
            lote.setNome(new Integer(i+1).toString());
            lote.setQuadra(quad);
            lote.setSetor(set);
            lote.setComentario("");
            lote.setLivre(true);
            quad.getLotes().add(lote);
            session.save(lote);   
         }
         session.flush();
         session.close();

The problem is: I'm getting a NullPointerException at line "quad.getLotes().add(lote);" (I can say that beause I'm logging it - I cut the log4j code for readable reasons).
Would anyone tell me what I'm doing wrong?

Thanks a lot

max · **Posted:** Sat Dec 27, 2003 4:51 pm

eh - how about initializing the collection field that probably is null and returned by getLotes() ?

It's a good place to do in e.g. a constructor ;)

Ot · **Posted:** Sat Dec 27, 2003 4:57 pm

Is it a good idea doing it with an ArrayList() object?

Thanks for the reply.

max · **Posted:** Sat Dec 27, 2003 5:03 pm

eh - yes, it it is a List type...

This is normal java stuff, nothing to do with hibernate ;)
Just do whatever you would normally do with fields - initialize them with some good defaults (sometimes null is a good default, but not in this case) - and then use'em ;)

The only thing hibernate wants is that your property type matches whatever you have defined in the hibernate mapping - in this case (i guess) a <bag>, <list> or something.

Note, that when hibernate gets a hold of your object, the set will be "forcefully" initialized/set with a collection that is one of hibernate's own.

Ot · **Posted:** Sat Dec 27, 2003 10:18 pm

Well, now I'm getting this exception:

java.lang.ClassCastException
at net.sf.hibernate.type.SetType.wrap(SetType.java:27)
at net.sf.hibernate.impl.SessionImpl.wrap(SessionImpl.java:2519)
at net.sf.hibernate.impl.SessionImpl.wrap(SessionImpl.java:2459)
at net.sf.hibernate.impl.SessionImpl.flushEntities(SessionImpl.java:2170)
at net.sf.hibernate.impl.SessionImpl.flushEverything(SessionImpl.java:2017)
at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2004)
at struts.action.CadastraQuadraAction.execute(Unknown Source)

When trying to save data. I'm using java.util.Collection in my java classes, and using <set> statements in my hibernate mapping file.
What might be wrong ?

thanks

max · **Posted:** Sun Dec 28, 2003 7:00 am

Please go read the documenation about collections !

If the property is mapped as a set, the actual type should of course also be a instance of a set (like a HashSet()).

Ot · **Posted:** Sun Dec 28, 2003 8:38 am

That is correct. Actually, I got this working last night. I have some <set> mappings and some <map> mappings, for which I respectvely use Set and Map interfaces from Java Api.
I have another question. This is the mapping for the <map> collection I'm using:

<map name="lotes" inverse="true" cascase="all">
<key column="id_quadra"/>
<index column="nome" type="string" length="20" />
<one-to-many class="beans.Lote"/>
</map>

How to make this work in ways that it forbids a lotes collection with repeated (id_quadra, nome)? If I try to insert something inside lotes collection with same (id_quadra, nome) of another one already in this collection, it is normaly inserted. that is not what i want. I want something as if (id_quadra, nome) was a key.
Sorry for that, but the docs did not show me too much about this issue.

Thanks for the attention.

dimas · **Posted:** Sun Dec 28, 2003 1:00 pm

Looks like you need to use composite-index