Implement custom JTA XAResource for using with hibernate

Question

I have two level access to database: the first with Hibernate, the second with JDBC. The JDBC level work with nontransactional tables (I use MyISAM for speed). I want make both levels works within transaction. I read about JTA which can manage distributed transactions. But there is lack information in the internet about how to implement and use custom resource.

Does any one have experience with using custom XAResources?

Answer 1

I want make both levels works within transaction.

Then you'll have to change your storage engine for InnoDB, MyISAM tables do not support transactions (technically, you won't get an error but a rollback won't rollback anything).

Does any one have experience with using custom XAResources?

I'm not sure to understand what you're talking about. The only XA resource I see here is your database and you don't need to implement anything custom. What you need to do is to use XA connections very likely obtained from two XA DataSources (which are supported by MySQL Connector/J 5.0.0+), use the JTA API and let the Transaction Manager do its job .

But to be honest, you should really clarify your requirements. There might be other (and easier) options than using XA. And if all the above sounds like Chinese, then I have the feeling that don't use XA would be a good advice here.

Answer 2

Connection are obtained via a DataSource that can be configured to support distributed transaction or not. To use multiple connections in a distributed transaction, you must configure the multiple DataSource to support XA and return XA connections.

That said, you need several physical connections only if you connects to different database, which doesn't seem to be your case (that's not clear in the question).

A DataSource can be smart enough to make sure that the same physical connection is used as long as you are in the same thread; each time you ask for a connection, it actually returns a "handle" to the same physical connection, and the physical connection returns to the pool when all handles have been closed. (But that depends on the DataSource implementation).

Hibernate per se is not an XA resource: it uses underlying a connection obtained via a DataSource. But it hooks itself in the transaction manager via JTA, in particular to flush all pending changes before the distributed transaction commits.

You can most of the time obtain the underlying connection used by the EntityManager using implementation specific API (it's at least possible with Hibernate). This means that you can maybe fulfill your requirement without using JTA and XA at all: use the underlying connection of the EntityManager for your JDBC stuffs.

In summary:

1. No need to mess with XAResource
2. Switch to InnoDB
3. You can try to switch to a XA DataSource and obtain a connection with DataSource.getConnection()
4. You can try to switch to a XA DataSource and obtain the underlying EntityManager connection
5. You can try to stick with a non-XA DataSource and obtain the underlying EntityManager connection

Hope I understood your question right and that it helps.