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Hibernate version:
3.0.5

Name and version of the database you are using:
Oracle 9i

I want to do a simple select of children from a parent using the createCriteria.

This is how I do it in createQuery:
session.createQuery("select p.children from Parent p").list(); // get a list of Child objects

How would you do this with createCriteria? I cant get the returnMaps to work :(

Mapping docs please?

Mapping:

<class name="Parent" table="tbl_parent">
<id name="parentID" type="java.lang.Long" column="parent_id">
<generator class="sequence">
<param name="sequence">seq_parent_id</param>
</generator>
</id>

<property name="name" type="string">
<column name="name" />
</property>

<set name="children" inverse="true" cascade="none">
<key column="parent_id"/>
<one-to-many class="Child" />
</set>

</class>

<class name="Child" table="tbl_child">
<id name="childID" type="java.lang.Long" column="child_id">
<generator class="sequence">
<param name="sequence">seq_child_id</param>
</generator>
</id>

<property name="name" type="string">
<column name="name" />
</property>

<many-to-one name="parent" column="parent_id" cascade="none"/>

</class>

I may be mistaken, but i believe you can do this (may be a simpler way):



HTH,
Jason

See this post. http://forum.hibernate.org/viewtopic.ph ... highlight=

So does that mean we cant get a collection from an object using createCriteria? Thats all I want to do.
From the looks of the link, seems like this is a feature request, and currently cant be done. Maybe i am misinterpretting something here?

Thanks!

I do think it is can't be done now (atleast as of 3.0.5) and I don't see it in the road map either (this exact feature). So I am waiting for someone from Hibernate team to confirm this so that I can file for a feature request or as an issue.

Hopefull some one will respond.

Thanks,
Prasad

But that is from child to parent and not the other way round which is what the original poster wanted.

Thanks,
Prasad

Yes thats fine. But the direction is reversed. I want to do add other restrictions on the parent later on, which if done in the direction from child to parent, will not only become complicated, but also result into performance degradation in the long term.

If this feature is not in the current version, then howcome in the manual there is a returnMaps() example? I dont mind using the depricated method as i just want my code to work right now. I can change it once the Hibernate team adds another way of doing this.
Has anyone got the returnMaps example to work? I cant.

I am unable to find any reference to returnMaps() in the code base that I have. May be returnMaps() doesn't work any more so it got removed?
I looked into the code for Criteria queries and Projections and I can't find any code that does similar things that an HQL query with elements() does.

A work around which is not entirely unsatisfactory (performance would be same but you need to do more work) is to do the following.

step1:
select child.id from parent where parent.id = ...

step2:
process each id from the previous result and load them.

This is what HQL query with elements() tag does and Criteria Query is not yet set up to do this. I might end up coding it this way if I think it will not be done in Hibernate in the near future.

The performance is may be bad relatively because you can load all the children properties in the first query itself and build the objects that way like below

step1:
select child.id, child.prop1, child.prop2, ... from parent join child where where child.parent_id = parent.id and ...
step2:
for each result row, construct the child object.

This would reduce the number of queries but the code could be cumbersome and it is better if hibernate can do this.

setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP)

It works for me too then.