foreign key id

andersonbd27 · **Joined:** Wed Sep 14, 2005 9:11 am **Posts:** 22

Hi,
Suppose I've got a many-to-one (let's use PLAYER->TEAM) relationship in a class I'm retrieving. I want the query to be LAZY, so it only queries the PLAYER table at first. I then want to grab the id of the TEAM and do something with that. However, I still don't want the TEAM table to be queried, because I just need the teamId (which I should already have). For now, I've just added a separate property (teamId) to the Player class. Is there a better way to do this in hibernate? Here's my hbm.xml in case this helps:

<class name="us.benanderson.Player"
table="player">
...
<property name="teamId" type="string" column="team_id"/>
<many-to-one name="team"
column="team_id"
class="us.benanderson.Team"/>

Thanks,
Ben

vgiguere · **Posted:** Mon Oct 03, 2005 11:02 am

I believe that is the only way that you can do it. Or you can have a query on a DAO that retrieves them for you.

CollinL · **Joined:** Wed Feb 02, 2005 6:33 am **Posts:** 70

Could use HQL to retrieve more than one object in the select clause, e.g.

Queries may return multiple objects and/or properties as an array of type Object[],

Code:

select mother, offspr, mate.name 
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

or as a List,

Code:

select new list(mother, offspr, mate.name)
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

or as an actual typesafe Java object,

Code:

select new Family(mother, mate, offspr)
from DomesticCat as mother
    join mother.mate as mate
    left join mother.kittens as offspr

assuming that the class Family has an appropriate constructor.

CSwinney · **Joined:** Mon Aug 16, 2004 6:15 am **Posts:** 24

My experience is currently with Hibernate 2, so apologies if it has changed for version 3.

Have you tried accessing the id property of the Team object that is retrieved with the Player? Hibernate is smart enough to know that this data is already available, so won't actually query the database until you call the accessor for a non-key field.

Code:

/* Some query to get Player Objects here */
System.out.println(player.getTeam().getId());
System.out.println(player.getTeam().getNonKeyData());  <==  Query happens here

So you should be able to use your current model happily and just refer to your Team Id property, with no need to define a second property on the Player class.