RE: [Tm4j-developers] Transactions and concurrent modification

[Kal A. <ka...@te...>]

On Mon, 2004-05-17 at 17:27, Andy Peel wrote:
> > There is a way to make more coarse-grained transactions with the
> > Hibernate backend. The relevant methods are:
> > TopicMapProvider.isTransactional() which returns true if the backend
> > supports transactions (currently only the Hibernate backend does).
> > TopicMapProvider.openTransaction() which starts a new transaction and
> > returns a org.tm4j.topicmap.ProviderTransaction instance.
> > TopicMapProvider.getOpenTransaction() which returns a handle to the
> > current transaction.
> > and then the methods of org.tm4j.topicmap.ProviderTransaction which you
> > can use to commit or rollback the transaction.
> 
> Excellent. Sorry, I'd misread the code, and just assumed that the commit
> always happened, whereas it actually only commits if the method created the
> new transaction itself. Cool.
> 
> > Currently nested transactions are not supported at all, but the
> > hibernate implementation only starts a new transaction for an API call
> > if one is not already started, so you should be able to do something
> > like:
> >
> > txn = tm.getProvider().openTransaction();
> > // Do some stuff here
> > txn.commit(); // or txn.rollback()
> 
> I'd actually like to tell the TopicMapProvider to use a transaction that
> already exists, so that my existing Hibernate transaction manager can create
> a transaction for use in a service method that does some other stuff in my
> app and then does the topic map stuff and then maybe does some other stuff
> specific to my app. I can't see a way to do that at the moment, but I think
> it'd be easy to add.
> 
I think you would need to hack the code a bit to do that. But it should
all be localised in the HibernateProviderTransaction class I think.

> The other thing was concurrent modification preventation. I had a quick look
> through the hbf.xml files and couldn't see a version column so I guess it
> doesn't do optimistic locking.
> 

I didn't enable that, no. Without having a specific application in mind
its always a bit difficult to tell what should be turned on and what
should not. I guess that it should be possible for you to just hack the
configuration files and go with that - I don't think that any of the
code should need to change...

Cheers,

Kal

-- 
Kal Ahmed <ka...@te...>
techquila