I have a parent/child association. Can I get parent with children collection, containing some part of all parent's children using some HQL/Criteria query?

for example:

class Parent {
    Long id;
    String name;
    Collection children;
...
}

class Child {
    Long id;
    String name;
    Parent parent;
...
}

PARENT_TABLE
ID | NAME
=============
 1 | parent1
 2 | parent2

CHILDREN_TABLE
ID | NAME | PARENT_ID
======================
 1 | a1 | 1
 2 | b1 | 1
 3 | a2 | 2

Can I get parent list, where children collections contains only children, whoose name starts with 'a', so that:

List parents = someQuery.list();
for (Iterator iter = parents.iterator(); iter.hasNext(); ) {
   Parent parent = (Parent) iter.next();
   for (Iterator ch = parent.getChildren().iterator();
        ch.hasNext(); ) {
       Child child = (Child) ch.next();
       assertTrue(child.getName().startsWith("a"));
   }
}

Please, help.

Try Criteria query

But I don't know, what query to use! I tried some Criteria queries and some HQL queries, but I still can't find the solution.

Please, if you know, how to do this, write it.

Many thanks.

Am having a similar problem and am yet to find a suitable solution. Any assistance would be much appreciated!

I used something like following in spring&hibernate&oracle environment and it worked properly.

.....
String queryText = "Select prnt FROM " + Parent.Class.getName() + " prnt " + " where prnt in (SELECT chl.parent from " + Child.class.getName() + " chl where chl.name like 'a%' ")
try
{
Query query = getHibernateTemplate().createQuery(getSession(), queryText);
List result = query.list();

...

}
catch( HibernateException he )
{
.....
}

I used something like following in spring&hibernate&oracle environment and it worked properly.

.....
String queryText = "Select prnt FROM " + Parent.Class.getName() + " prnt " + " where prnt in (SELECT chl.parent from " + Child.class.getName() + " chl where chl.name like 'a%' ");
try
{
Query query = getHibernateTemplate().createQuery(getSession(), queryText);
List result = query.list();

...

}
catch( HibernateException he )
{
.....
}

from Parent prnt where prnt in (SELECT chl.parent from Child chl where chl.name like 'a%')

Only one question here: if I'll take any parent from the resulting list, will it contain only children, that starts with 'a' (that's what I want), or it will contain all of it's children?

It will contain all of it's children because getChildren() of parent has its own fetching strategy based on hbm file definition . This strategy is not related to fetching method of parent .

Oh yes, just as I thought. But this code doesnt solve the problem so far. Why then post? And I find separate mapping for each special case of fetching too expensive.