For some reason registration process is very dificult and I have to wait some time to use my account and I couldn't finish one. So I'm asking about my problem from this login.

I want to save Tree like structire with Hibernate 2.1.4 and see next exception:
[code]
java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:448)
at java.util.AbstractList$Itr.next(AbstractList.java:419)
at net.sf.hibernate.collection.PersistentCollection$IteratorProxy.next(PersistentCollection.java:437)
at net.sf.hibernate.engine.Cascades.cascadeCollection(Cascades.java:526)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:452)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:503)
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:951)
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:857)
at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier(SessionImpl.java:779)
at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:738)
[/code]

I have next class that I want to save:
[code]
package hibertest;

import java.util.List;
import java.util.ArrayList;

public class TestObj {
private String id;
private String name;
private List children = new ArrayList(0);

public TestObj() {

}

public TestObj(String name) {
this.name = name;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

private TestObj parent;

public TestObj getParent() {
return parent;
}

public void setParent(TestObj parent) {
this.parent = parent;
if (parent != null)
parent.children.add(this);
}

public List getChildren() {
return children;
}

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

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}
}
[/code]

and next Hibernate mapping file:
[code]
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping package="hibertest">
<class name="TestObj" table="test">
<id name="id" column="pk" type="string" >
<generator class="uuid.hex"/>
</id>
<property name="name" column="name" type="string" not-null="true"/>


<many-to-one name="parent" cascade="all">
<column name="parent" index="pind"/>
</many-to-one>

<bag name="children" inverse="true" cascade="all">
<key column="parent"/>
<one-to-many class="TestObj"/>
</bag>
</class>

</hibernate-mapping>
[/code]

If I remove [i]cascading[/i] attribute from [i]bag[/i] XML tag. It's work but I have to save each element that not possible for my.

Can somebody help me with my problem?