how to save only child object

seenuarvela · **Joined:** Fri Jul 17, 2009 1:00 am **Posts:** 5

Hi All,
I have two tables one is "Author" and "Book".

Here only one-to-many unidirectional mapping is there.
Author--------------->Book

Author id is there in Book table as a foreign key with not null field. and book have his own id.

First time i saved successfully with Author as well as Book.
From second time onwards i need to save only Book object( not Author object) by using reference id.

How to save only child Object?.

If u have any example please send it to me.

Thanks & Regards,
Srinivas,
seenuindia555@gmail.com

Cameron McKenzie · **Posted:** Wed Sep 02, 2009 6:38 am

The easy way is to simply load the child object, not the parent or containing object. Make sure it's loaded in a lazy fashion, and there will be no update to the containing object.

But if the containing object changes, why wouldn't you want to update it? In fact, it almost sounds like a flaw in the design?

seenuarvela · **Joined:** Fri Jul 17, 2009 1:00 am **Posts:** 5

When i'm trying to save the child object i got this error.

org.hibernate.PropertyValueException: not-null property references a null or transient value: Book._booksBackref
at org.hibernate.engine.Nullability.checkNullability(Nullability.java:72)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:290)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:181)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:107)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:187)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:172)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:535)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:523)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:519)
at AuthorManager.main(AuthorManager.java:32)

What i need to do for this error.

tarun walia · **Joined:** Sat Aug 01, 2009 5:28 am **Posts:** 42

i think u r having bi-directional association.In ur Child Object u have a not-nullable Instance variable of Parent
then how u will save a Object without value for not-nullable column.
i think u should load the parent then update u r child.

Cameron McKenzie · **Posted:** Wed Sep 02, 2009 6:15 pm

Looks like you're going to have to make that back reference nullable in the database.

seenuarvela · **Joined:** Fri Jul 17, 2009 1:00 am **Posts:** 5

Can u tell me how to resolve "bakref" problem.

Thanks & Regards,
Srinivas