I'm having a simple question regarding collection initialize for the following code:

Session session = HibernateUtil.getSession();
Query q = session.createQuery("FROM Parent WHERE status = :p");

List result q = q.list();

Assuming that Parent class has 1 collection property :
- childrens List that would be lazy loaded.

I need to eagerly fetch the "children" collections only for some "parents" that satisfy a criteria. So I did:

for( Parent p : result )
{
if ( p.name = "John" ) {
Hibernate.initialize(p.getChildrens());
}
}

To my surprise after the loop all the parents have the childrens initialized and I was hoping to see that only for John I initialized the childrens.


Am I doing anything wrong? Thanks,
Sivec

Try this:



instead of:




Your if condition is wrong in the first place. But I guess its a typing mistake.... otherwise it will throw a compilation error. Also try removing the Hiberate.initialize. As long as you are in the current session scope, a simple call to the getChildren method should populate the children for the particular parent object. Ofcourse, Hibernate.initialize() performs the same operation and should work. Just check your if condition again. Thats the only problem I can see.

Forgot to tell that the code was just pseudo code not the real one. It seems that Hibernate.initialize(parent.getChildrens() ) won't initialize only the childrens for a particular parent but all the childrens for all the parents from the initial response set.

So, having a result set

Query q = session.createQuery("Select Parent p");

List result = q.list();

Now I want to initialize only the childrens for parents with name John; and leave the others alone; so I was doing

for(Parent p : result )
{
if ("John".equals(p.getName() ) {
Hibernate.initialize(p.getChildrens() );
}
}


After the loop I see all the childrens initialized even for parents with name different than John.


I suspect that this is a BUG in the way Hibernate.initialize works.


Sivec

have you define lazy=true in your hbm.xml? I tried it with Hibernate 3.2.5, it runs well, only "John" children's loaded.

Here is the code:


PARENT - mapping

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.app">
<class name="Parent"
table="Parent"
dynamic-update="true"
dynamic-insert="true"
lazy="true">

<id name="id" type="long" column="id">
<generator class="sequence">
<param name="sequence">SQ_ID</param>
</generator>
</id>


<list name="children" table="CHILDREN" cascade="all" batch-size="100" lazy="true">
<key column="PARENT_ID" />
<index column="INDEX_COL"/>
<one-to-many class="com.ssgm.Children" />
</list>

</class>
</hibernate-mapping>


CHILDREN mapping ======================

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.app">
<class name="Children"
table="Children"
dynamic-update="true"
dynamic-insert="true"
lazy="true">

<id name="id" type="long" column="id">
<generator class="sequence">
<param name="sequence">SQ_ID</param>
</generator>
</id>

<property name="indexCol" column="index_col" update="false" insert="false"/>
</class>
</hibernate-mapping>


JAVA CODE ==================================

public class Parent {

private Long id;
private List children = new ArrayList();

public Parent(){

}

public Long getId(){
return this.id;
}

public void setId(Long id){
this.id = id;
}



public List getChildren() {
return children;
}

public void setChildren(List children) {
this.children = children;
}

}

=========================================

public class Children {

private Long id;
private Long indexCol;

public Long getIndexCol() {
return indexCol;
}

public void setIndexCol(Long indexCol) {
this.indexCol = indexCol;
}

public Children(){

}

public Long getId(){
return this.id;
}

public void setId(Long id){
this.id = id;
}

}
==============================================



Session session= HibernateUtil.getSessionFactory().openSession();

Transaction tx = session.beginTransaction();


Query qry = session.createQuery("FROM Parent t WHERE t.id in (1,2) ");


List<Parent> result2 =qry.list();


for(Parent ts: result2){
Hibernate.initialize(ts.getChildren());
break;
}

tx.commit();

session.close();

for(Parent ts: result2){
System.out.println( ts.getChildren().size() );
}


I would expect that the second parent not to have the childrens initialized and the lazy exception to be thrown.

Try this instead

for(Parent ts: result2){
ts.getChildren();
break;
}

Just to check if the problem is only with Hibernate.initialize()

ts.getChildren() won't init the collection, but isEmpty and size() shoud do it. Unfortunatelly, for some reasons all parents childrens gets initialized; same happens with Hibernate.initialize.

I suspect I have something wrong in the mapping files. Any help?

try to remove batch-size="100" in tag list

Thanks!

Removing batch attribute fixed the problem; Not sure why Hibernate.initialize would be messed up by "batch" attribute.

Sivec