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Version number in optimistic locking scenario not updated

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alistair

Post subject: Version number in optimistic locking scenario not updated

Posted: Wed Jul 28, 2004 5:19 am

Beginner

Joined: Wed Mar 03, 2004 6:02 am
Posts: 46
Location: Kuala Lumpur, Malaysia

Context: Hibernate 2.1.4, JBoss 3.2.3 environment

In my code below, I can successfully update an existing object and also create new
objects.

However my version column is not being updated and stays at zero.

My mapping for the version column:

Code:

The code:

Code:

Session session = HibernateSessionUtility.currentSession();
List list = session.find("from Foo as foo where foo.id = ?",
                                     key,
                                     Hibernate.STRING);
if (list.size() > 0) {
    logger.info("Replacing existing foo: " + key);                
    Foo persistentFoo = (Foo)list.get(0);                
    persistentFoo.setValue("updated Value");
                
}else if(list.size() == 0) {
    logger.info("Creating new foo: " + key);
    Foo transientFoo = new Foo();
    transientFoo.setValue("new Value");
    session.save(transientFoo);
}
session.flush();

Thanks.

Alistair

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shl

Post subject:

Posted: Wed Jul 28, 2004 8:15 am

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

your version mapping is not correct, use <version column=.../>
instead of <property name="version" column=.../>
http://www.hibernate.org/hib_docs/reference/en/html/mapping.html#mapping-declaration-version

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alistair

Post subject:

Posted: Wed Jul 28, 2004 10:12 pm

Beginner

Joined: Wed Mar 03, 2004 6:02 am
Posts: 46
Location: Kuala Lumpur, Malaysia

Thank you. It's working now.

Regards,

Alistair

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alistair

Post subject:

Posted: Wed Jul 28, 2004 10:29 pm

Beginner

Joined: Wed Mar 03, 2004 6:02 am
Posts: 46
Location: Kuala Lumpur, Malaysia

Could someone also confirm these thought of mine:

1) One should not add the version column to the equals/hashCode method because equals is used only for logical equality during code execution.

2) Whereas the version column is used by Hibernate or application developer to do a "dirty check" between the in-memory instance and its persisted instance.

Another quesiton: in the event of the version number difference, what will Hibernate do when I update a persistent object ?

Thanks

Alistair

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shl

Post subject:

Posted: Thu Jul 29, 2004 3:12 am

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

alistair wrote:

1) One should not add the version column to the equals/hashCode method because equals is used only for logical equality during code execution.

http://www.hibernate.org/109.html
You are right, don't add version to the equals/hashCode. Authours of HIA (chapter 4.1.6) , argue to use "business key equality", that is implement equals/hashCode using only business fields that form business key/natural key (unique combination of business fields), and don't use any synthetic identifiers.

alistair wrote:

2) Whereas the version column is used by Hibernate or application developer to do a "dirty check" between the in-memory instance and its persisted instance.

Version is checked in the SQL UPDATE:

Code:

update User set name='new name' version=3 where userId=123 and version=2

if JDBC execute statement returned zero, you will get StaleObjectStateException. As you see performance do not suffer when you use versioned classes.
Delete should be handled similar. (where userId=123 and version=2)

[quote="alistair"]Another quesiton: in the event of the version number difference, what will Hibernate do when I update a persistent object ?[/code]
you will get StaleObjectStateException

--
Leonid

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