From: Pinaki Poddar <ppoddar_at_us.ibm.com>
Date: Fri, 11 May 2012 11:29:53 -0700

Hi Christian,
  A persistence unit in JPA does not expose whether it is using a XAResouce
for underlying database. In a managed container enviroment, a persistence
context synchronizes its transaction with the containers transaction via
JTA transaction synchrization interface i.e. before/afterCompletion().
.
Regards --

Pinaki Poddar
Chair, Apache OpenJPA Project http://openjpa.apache.org/
JPA Expert Group Member
Application & Integration Middleware








From: Christian Romberg <cromberg_at_versant.com>
To: michael keith <michael.keith_at_oracle.com>
Cc: jsr338-experts_at_jpa-spec.java.net
Date: 05/11/2012 06:46 AM
Subject: [jsr338-experts] Re: question regarding jta-data-source



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>
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
        (F) +49 40 60990-113
        (E) cromberg_at_versant.com
        www.versant.com | www.db4o.com

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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
www.versant.com | www.db4o.com
--
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
CONFIDENTIALITY
NOTICE: This e-mail message, including any attachments, is for the sole
use of the intended recipient(s) and may contain confidential or
proprietary information. Any unauthorized review, use, disclosure or
distribution is prohibited. If you are not the intended recipient,
immediately contact the sender by reply e-mail and destroy all copies of
the original message.