structure « Cascade « JPA Q&A

1. Cascade saving Tree likes structure

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$Itr.checkForComodification( at java.util.AbstractList$ at net.sf.hibernate.collection.PersistentCollection$ at net.sf.hibernate.engine.Cascades.cascadeCollection( at net.sf.hibernate.engine.Cascades.cascade( at net.sf.hibernate.engine.Cascades.cascade( ...

2. Is this structure possible to cascade over?