updating serialized / unserialized object

squeebie · **Joined:** Thu Oct 23, 2003 1:17 pm **Posts:** 44

I have an object that was loaded, serialized and unserialized. When I try to update it (using the same session that loaded it), I get this error:

Quote:

net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 1, of class: com.agentscape.associate.to.ServerInfoTO
at net.sf.hibernate.impl.SessionImpl.checkUniqueness(SessionImpl.java:1673)
at net.sf.hibernate.impl.SessionImpl.doUpdateMutable(SessionImpl.java:1442)
at net.sf.hibernate.impl.SessionImpl.doUpdate(SessionImpl.java:1469)
at net.sf.hibernate.impl.SessionImpl.update(SessionImpl.java:1354)
at com.agentscape.associate.bo.BaseBO.update(BaseBO.java:45)
at com.agentscape.associate.test.SerializableTest.doLoad(SerializableTest.java:61)
at com.agentscape.associate.test.SerializableTest.<init>(SerializableTest.java:21)
at com.agentscape.associate.test.SerializableTest.main(SerializableTest.java:69)

Is it a "bad thing" to update an object that was serialized / unserialized? If I comment out the serialize / unserialize part, the update works great.

I can post an example if needed.

I'm using Hibernate 2.1.4 with MySQL 4.0.20a.

Thanks in advance,
Jesse

VampBoy · **Posted:** Fri Aug 06, 2004 2:42 pm

The 'problem' is that the SessionImpl uses instance equality to check if the object is already in the session. Since you've serialized/deserialized your objects then you have new instances of them.

You are then turning around (using the same Session) and attempting to update the object. It doesn't find it in the session (due to different instances) but it DOES find another object (your original) with the same identifier. The proverbial all hell breaks loose at that point.

Do you need to have the same session? Do you need to serialize?

I feel your pain.

christian · **Posted:** Fri Aug 06, 2004 2:44 pm

Uhm, guys, this is easier than you make it. Also check "saveOrUpdateCopy()", which is the counterpart to "saveOrUpdate()". In real applications with long running transactions you need both. And to understand long running transactions and how they are implemented, you need Hibernate in Action :)

squeebie · **Joined:** Thu Oct 23, 2003 1:17 pm **Posts:** 44

christian wrote:

Uhm, guys, this is easier than you make it. Also check "saveOrUpdateCopy()", which is the counterpart to "saveOrUpdate()". In real applications with long running transactions you need both. And to understand long running transactions and how they are implemented, you need Hibernate in Action :)

That's exactly what I was looking for.

You're right, I think it is time that I picked myself up a copy.

Thanks for the help.

Jesse

VampBoy · **Posted:** Fri Aug 06, 2004 2:52 pm

You know Christian, you're right. I need to go and read that right now while it's in my head. I'm trying to get my head wrapped around some of the finer points of all of this. (including Lazy loading objects that have dirty components ;)

I'll be formulating my code hack a bit later :)

spyromus · **Posted:** Tue Aug 10, 2004 7:24 am

Hi guys,

I have slightly different, but yet similar problem. Maybe you could help me.

The problem is that I have the following exception each time I try to load or delete item using Hibernate from database:

de.nava.informa.core.ChannelBuilderException: Unable to reload item: a different object with the same identifier value was already associated with the session: 3, of class: de.nava.informa.impl.hibernate.Item
at de.nava.informa.impl.hibernate.ChannelBuilder.reload(Unknown Source)
at de.nava.informa.utils.PersistChanGrpMgr.deleteItemFromChannel(Unknown Source)
at com.salas.bb.informa.InformaBackEnd.deleteArticleFromCGE(InformaBackEnd.java:388)

---

ChannelBuilder.reload() by now simply uses Hibernate Session load(...) method to load contents of item back from database before operations. Even iif comment line with reload() method call in PersisteChanGrpMgr.deleteItemFromChannel() the next operation will fail as well (which is Session.delete()) with the same error.

Any tips?