Hi Pinaki,
As I pointed out, it would only be a "fake" JDBC driver, I know, that the
TM does not care, what type of resource is behind the XAResource,
it's just that we need to enlist our XAResource with the current
transactions.
Either the app server picks it up itself (pull-approach, via a fake JDBC
driver, or -in theory- a JCA adapter) or we enlist it directly
(push-approach)
> In effect, I do not see why a non-JDBC based JPA provider has to appear
as a JDBC connection to a application server to participate in a JTA
transaction.
Two simple reasons:
-app servers do support JDBC connection pools and JCA is not a viable
approach
-there is no standard way to get access to the TransactionManager (however
there is a standard way to get the TransactionSynchronizationRegistry,
which is sufficient
for other JPA implementations)
However we will probably still use the alternative, to enlist our
XAResource directly with the TransactionManager.
So we will do some probing in the code, to find out which app server we are
in and/or try out a list of well-known JNDI-names
to look-up the TransactionManager.
Regards,
Christian
On Mon, May 14, 2012 at 7:11 PM, Pinaki Poddar <ppoddar_at_us.ibm.com> wrote:
> Christian,
> In a JPA environment, a JPA Persistence Unit registers as a transactional
> resource to the application server's global transaction management
> coordination system via JTA standard i.e. by caling
> javax.transation.registerSynchronization(x) where x is something that a
> provider provides which implements javax.transaction.Synchronization. In a
> non-JDBC JPA provider like yours, you will possibly pass an instance of
> persistence context i.e EntityManager as x.
> For an application server transaction management sevices, all it knows is
> x whether x is using an underlying JDBC or non-JDBC database is not
> relevant. So essentially the provider will receive a beforeCompletion()
> call from application server when time comes to commit the global
> transaction via x because x is a registered Synchronization object. At
> beforeCompletion(), the provider is responsible to commit on the underlying
> database be it JDBC or somethiing else.
>
> If a provider's persistence unit is also XA-enabled that capability is
> communicated by a) implementing javax.transaction.xa.XAResource and b)
> enlisting that resource to the application server. A resource, in this
> case, is the persistence unit, not the jta-data-source as declared in
> persistence.xml.
>
> In effect, I do not see why a non-JDBC based JPA provider has to appear as
> a JDBC connection to a application server to participate in a JTA
> transaction.
>
>
> > I think I forgot to emphasize, that we are not an ORM and are not using
> JDBC connections.
> I did notice that :)
>
>
> Regards --
>
> Pinaki Poddar
> Chair, Apache OpenJPA Project http://openjpa.apache.org/
> JPA Expert Group Member
> Application & Integration Middleware
>
>
>
>
>
>
> [image: Inactive hide details for Christian Romberg ---05/14/2012 01:17:26
> AM---Hi Michael and Pinaki, Yes, I understood how this is su]Christian
> Romberg ---05/14/2012 01:17:26 AM---Hi Michael and Pinaki, Yes, I
> understood how this is supposed to work, however this does not and
>
> From: Christian Romberg <cromberg_at_versant.com>
>
> To: michael keith <michael.keith_at_oracle.com>
> Cc: jsr338-experts_at_jpa-spec.java.net
> Date: 05/14/2012 01:17 AM
> Subject: [jsr338-experts] Re: question regarding jta-data-source
> ------------------------------
>
>
>
> Hi Michael and Pinaki,
>
> Yes, I understood how this is supposed to work, however this does not and
> can not work for us this way out-of-the box.
>
> I think I forgot to emphasize, that we are not an ORM and are not using
> JDBC connections.
>
> Of course we can (and would) register a Synchronization object with the
> global transaction.
>
> But where should the container get the XAResource from? Because we are not
> using JDBC connections, which implies, we
> are not using any DataSource. So there is simply no way for the app server
> to drive the XA protocol.
>
> Unless of course, we would provide a "fake" XADataSource in a "fake" JDBC
> driver, and given the pseudo-code assumption
> from my previous mail, we would then just call "getConnection()" on the
> jta-data-source (which points to an app server pool
> configured with our "fake" JDBC driver, configured to return enlisted
> connections) and don't actually use the result
> of the "getConnection()" invocation (which is a dummy implementation
> anyways)
>
> I'm pretty sure, that my pseudo-code assumption is correct, mostly because
> I can not think of any other straight-forward
> (or even weird) way how to implement that in the app server.
>
> So this would be the way to go for us.
>
> Regards,
>
> Christian
>
> On Fri, May 11, 2012 at 10:45 PM, michael keith <*michael.keith_at_oracle.com
> * <michael.keith_at_oracle.com>> wrote:
>
> Hi Christian,
>
> Yes, that's pretty much how it works.
>
> -Mike
>
>
> On 11/05/2012 9:45 AM, Christian Romberg wrote:
> Hi Mike,
>
> Unlike ORMs, we need to provide the XAResource instances to the app
> server
> (which in turn are associated with our internal connections to the
> database server)
>
> But I guess, if the user just sees a DataSource, then that will be
> an app server proxy which eventually delegates to the XADataSource of
> our "JDBC" driver (provided I configure a DataSource that returns
> enlisted connection in the app server using our JDBC driver)
>
> So my pseudo-code assumption of the app servers DataSource proxy is
> like this:
>
> public class ContainerDataSourceProxy implements DataSource {
>
> XADataSource xaDs = ...; //XADataSource of the installed JDBC
> driver for this pool
>
> public Connection getConnection() throws SQLException {
> XAConnection xaCon = xaDs.getXAConnection();
> enlist(xaCon.getXAResource());
> return xaCon.getConnection();
> }
> ...
> }
>
> So we could simply call getConnection() (and not using the returned
> value at all) to trigger the app servers
> enlisting our XAResource.
>
> Regards,
>
> Christian
>
> On Fri, May 11, 2012 at 3:14 PM, michael keith <*
> michael.keith_at_oracle.com* <michael.keith_at_oracle.com>> wrote:
> Hi Christian,
>
> The data source referenced by the jta-data-source name is a
> DataSource provided by the container in JNDI. It is the same one that any
> application could look up and use, hence it is a javax.sql.DataSource.
>
> XADataSource is an internal type used by the driver and
> container to coordinate XA, but users of the data source are not expected
> to participate at that level. The JPA provider acts like a client of the
> data source, using its connections to read and write, so it does not need
> to be aware of the XA protocol being implemented underneath.
>
> Hope this makes things clearer.
>
> Regards,
> -Mike
>
>
> On 10/05/2012 7:50 AM, Christian Romberg wrote:
> Hello,
>
> It is not explicitly mentioned in the spec, but I guess I can
> safely assume, that the data source denoted by
> jta-data-source is of type "javax.sql.XADataSource"?
>
> After the JPA implementation has obtained an XAConnection
> from this XADataSource, is it expected to
> to do any calls (and if so, in any specific order) on this
> XAConnection?
>
> E.g. is it necessary, to call XAConnection.getConnection() to
> trigger that the app server calls XAConnection.getXAResource()
> on the very same XAConnection? Or is it sufficient to just
> call "XADataSource.getXAConnection()" to trigger this?
>
> (Some background: we don't use JDBC connections (being not an
> ORM) and probably we would need to provide our own
> XADataSource implementation, so that the app server picks up
> our own XAResource implementation)
>
> Thank you!
>
> Christian
>
> -- *
> Christian Romberg
> Chief Engineer* | Versant GmbH
> (T) *+49 40 60990-0* <%2B49%2040%2060990-0>
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> GmbH is incorporated in Germany. Company registration number:
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> 54723, Amtsgericht Hamburg. Registered Office: Halenreie 42,
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> -- *
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> (T) *+49 40 60990-0* <%2B49%2040%2060990-0>
> (F) *+49 40 60990-113* <%2B49%2040%2060990-113>
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> Versant
> GmbH is incorporated in Germany. Company registration number: HRB
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>
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> -- *
> Christian Romberg
> Chief Engineer* | Versant GmbH
> (T) +49 40 60990-0
> (F) +49 40 60990-113
> (E) *cromberg_at_versant.com* <cromberg_at_versant.com>*
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> --
> Versant
> GmbH is incorporated in Germany. Company registration number: HRB
> 54723, Amtsgericht Hamburg. Registered Office: Halenreie 42, 22359
> Hamburg, Germany. Geschäftsführer: Bernhard Wöbker, Volker John
>
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--
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(F) +49 40 60990-113
(E) cromberg_at_versant.com
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--
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GmbH is incorporated in Germany. Company registration number: HRB
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