is there any difference between Criteria and HQL for query..

william1975 · **Joined:** Wed Jul 27, 2005 11:13 pm **Posts:** 10

is there any difference between Criteria and HQL for query an object?

Hibernate version:3.0

Mapping documents:

Code:

<class deviceInfo>
...
      <many-to-one name="deviceType"  column="device_type" class="DeviceType" fetch="join" not-null="true"/>
...

Code between sessionFactory.openSession() and session.close():
Criteria:

Code:

            resultList = session.createCriteria((DeviceInfo.class))
                                .list();

HQL:

Code:

            Query query = session.createQuery("from DeviceInfo");
            resultList = query.list();

Doubt is:
after close the session, I can get infomation of DeviceType(class, may to one in DeviceInfo) when I use Creteria, but I can't get the information of DeviceType when I use HQL.
How can I get the same result, thanks....

ramnath · **Posted:** Sun Aug 21, 2005 11:53 pm

Hi

Look closely in to the Query generated because of Criteria?
You could see a select for the child table too.

Since you have set the LAZY="true" in mapping you get all the values in Child Table when you use Criteria.

If you want to use HQL then you have explicitly call the child too.

I will give +1 to Criteria than HQL.

william1975 · **Joined:** Wed Jul 27, 2005 11:13 pm **Posts:** 10

ramnath,
I mean the conditions is same to Criteria and HQL query,
including lazy setting.

I can get all object values via HQL except to call the child?

thanks a lot.

William

pearl8 · **Joined:** Tue Aug 16, 2005 8:28 am **Posts:** 15

Ramnath,

In HQL your associations have to be specified in your HQL, otherwise they will not get loaded.

Read up "Hibernate ignores my outer-join="true" setting and fetches an association lazily, using n+1 selects!"

at

http://www.hibernate.org/117.html#A18

william1975 · **Joined:** Wed Jul 27, 2005 11:13 pm **Posts:** 10

hi,
Except using left join fetch, how can we get child table object?
call the child property? it not seem good method...

regards,
William

william1975 · **Joined:** Wed Jul 27, 2005 11:13 pm **Posts:** 10

I got it,

AS pearl8 said, ref: http://www.hibernate.org/117.html#A18

HQL

Code:

            Query query = session.createQuery("from DeviceInfo dev [b]left join fetch dev.deviceType[/b]"); 
            resultList = query.list();

but the HQL can't run in Hibernate3.0, have to update it to 3.1 later....