RE: [Springframework-developer] Nested transactions

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Thanks Colin. It all makes sense now.

Thanks
Tyson

-----Original Message-----
From: Colin Sampaleanu [mailto:col...@ex...]=20
Sent: Saturday, June 19, 2004 12:27 PM
To: spr...@li...
Subject: Re: [Springframework-developer] Nested transactions

Tyson,

REQUIRES_NEW actually just suspends the current transaction, and then=20
starts a new, unrelated transaction transaction to run the contained=20
code in. If you commit the inner, new transaction, then rollback the=20
outer, the inner transaciton will still be committed, as they are=20
unrelated. This should work properly inside any JTA environment (as long =

as spring can get at the jta transaction manager) and the model is also=20
essentially the same as the requires new support in the EJB spec.

PROPOGATION_NESTED means that a new nested, or child transaction is=20
created inside the outer one. If you commit the child (nested)=20
transaction, but roll back the outer, parent transaction, the effects of =

the child are also rolled back. JTA (and EJB) doesn't actually support=20
nested transactions. You essentially need a DB and JDBC driver, such as=20
Oracle, that does, which you can use directly.

Hope this clears things up,
Colin

Norris, Tyson wrote:

>Hi Juergen -=20
>How does this differ from the REQUIRES_NEW propagation?
>Thanks
>Tyson
>
>-----Original Message-----
>From: j=FCrgen h=F6ller [werk3AT] [mailto:jue...@we...]=20
>Sent: Saturday, June 19, 2004 3:02 AM
>To: spr...@li...
>Subject: [Springframework-developer] Nested transactions
>
>Thomas, Alef, Colin, everybody,
>=20
>Motivated by Rod, I've added support for nested transactions to our =
transaction infrastructure, via the new propagation behavior =
PROPAGATION_NESTED. The transaction manager needs to open a true nested =
transaction which can be rolled back individually while still being able =
to continue with the surrounding transaction.
>=20
>Furthermore, application code can also use custom savepoints: The =
TransactionStatus interface now has a SavepointManager superinterface, =
which provides generic means to create savepoints and roll back to them. =
This is only intended for advanced needs where the declarative nested =
transaction model is not sufficient.
>=20
>DataSourceTransactionManager implements nested transaction support via =
JDBC 3.0 Savepoints: basically, create a Savepoint on nested transaction =
begin, release it on nested transaction commit, roll back to it on =
nested transaction rollback. Of course, DataSourceTransactionManager is =
still compatible with JDBC 2.0 if not using nested transactions.
>=20
>HibernateTransactionManager and JdoTransactionManager offer support for =
JDBC 3.0 Savepoints too, but it's deactivated by default there: =
Savepoints are just able to roll back the underlying JDBC Connection, =
not the Session respectively PersistenceManager with its object cache. =
Savepoints are still useful for JDBC access code that participates in a =
Hibernate/JDO transaction, though, when used with care.
>=20
>All of this is already fully covered by unit tests. Unfortunately, I =
don't have a database with savepoint support available here, i.e. no =
Oracle; so I've just been able to test that it fails nicely against =
MySQL (on JDK 1.4 and 1.3). Thomas, do you have a chance to test this =
against a live database?
>=20
>An example for how PROPAGATION_NESTED is supposed to work. Note that =
the nested transaction sets the rollback-only flag: This should just =
cause a rollback of the second update statement but still allow the =
surrounding transaction to commit the first update statement.
>=20
>  DataSource ds =3D ...;
>  final PlatformTransactionManager tm =3D new =
DataSourceTransactionManager(ds);
>  final JdbcTemplate jt =3D new JdbcTemplate(ds);
>
>  TransactionTemplate tt1 =3D new TransactionTemplate(tm);
>  =
tt1.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRED);
>  tt1.execute(new TransactionCallbackWithoutResult() {
>    protected void doInTransactionWithoutResult(TransactionStatus =
status) {
>      jt.update("first update statement");
>
>      TransactionTemplate tt1 =3D new TransactionTemplate(tm);
>      =
tt1.setPropagationBehavior(TransactionDefinition.PROPAGATION_NESTED);
>      tt1.execute(new TransactionCallbackWithoutResult() {
>        protected void doInTransactionWithoutResult(TransactionStatus =
status) {
>          jt.update("second update statement");
>          status.setRollbackOnly();
>        }
>      });
>    }
>  });
>
>An example for the same effect via manual savepoint management:
>=20
>  TransactionTemplate tt1 =3D new TransactionTemplate(tm);
>  =
tt1.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRED);
>  tt1.execute(new TransactionCallbackWithoutResult() {
>    protected void doInTransactionWithoutResult(TransactionStatus =
status) {
>      jt.update("first update statement");
>
>      Object savepoint =3D status.createSavepoint();
>      jt.update("second update statement");
>      status.rollbackToSavepoint(savepoint);
>
>    }
>  });
>=20
>Juergen
>=20
>
>
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