Re: [Springframework-developer] Reworked transaction infrastructure

[<jue...@we...>]

Yep. I think it's the most intuitive thing do to: The first =
("upper-most") transaction manager will drive synchronization. After =
all, there's hardly any need to use multiple transaction managers (that =
are active at the same time) now anyway, as transaction suspension =
should cover most of those scenarios.
=20
Juergen
=20

________________________________

Von: spr...@li... im Auftrag =
von Colin Sampaleanu
Gesendet: Sa 31.01.2004 06:26
An: spr...@li...
Betreff: Re: [Springframework-developer] Reworked transaction =
infrastructure



Juergen,

I was looking a bit through the new code (although not enough), and was
wondering a bit about the transaction synchronization. The bug in
DataSourceTransactionManager/DataSourceUtils not allowing even one TM to
have synchronization on if there is more than one TM is of course no
longer there, and if there are multiple TMs and all except one have
synchronization turned off, all will be ok.

However,  I am not 100% clear on what happens if more than one has it
turned on (which will be the default when people use multiple TMs and
don't play with the flags). I am not talking about the
RequiresNew/Suspend situation, when it gets taken care of, but rather
with a simple PROPOGATION_REQUIRED. As I read the new code there will
not really be any ill effects, but rather the first TM to be involved
will handle all synchronization, e.g.
    private TransactionStatus newTransactionStatus(Object transaction,
boolean newTransaction,
                                                   boolean
newSynchronization, boolean debug,
                                                   Object
suspendedResources) {
        boolean actualNewSynchronization =3D newSynchronization &&
              =20
!TransactionSynchronizationManager.isSynchronizationActive();
        if (actualNewSynchronization) {
            TransactionSynchronizationManager.initSynchronization();
        }
        return new DefaultTransactionStatus(transaction, newTransaction,
actualNewSynchronization,
                                            debug, suspendedResources);
    }

Is this a correct assessment?

Regards,
Colin


j=FCrgen h=F6ller [werk3AT] wrote:

>Everybody,
>
>I've significantly reworked our transaction infrastructure last week, =
to effectively provide the same support for transaction suspension as =
EJB CMT does.  Accordingly, I've introduced propagation behaviors =
"REQUIRES_NEW", "NOT_SUPPORTED", and "NEVER" for all our =
PlatformTransactionManagers. I've committed this yesterday evening, now =
that CVS seems to work again.
>
>JtaTransactionManager needs to access the =
javax.transaction.TransactionManager for transaction suspension; =
unfortunately, the TransactionManager location is not defined by J2EE =
(O/R mappers have a similar problem for cache callbacks in a JTA =
environment). Thus, I've introduced a JtaDialect interface (analogous to =
our JdoDialect), containing "getInternalTransactionManager" and =
"applyIsolationLevel" methods (the latter factored out from =
JtaTransactionManager's template method into this strategy).
>
>The default dialect implementations is JndiLookupJtaDialect, with a =
configurable "templateManagerName" JNDI location (not doing anything =
about the isolation level); its Javadoc states a couple of well-known =
JTA TransactionManager locations in popular application servers. =
Additionally, I've added JotmJtaDialect and WebSphereJtaDialect, which =
both require specific static accessor methods to obtain the JTA =
TransactionManager. I've simply taken the corresponding code from =
Hibernate's TransactionManagerLookups.
>
>There's also a new "jtaDialect" property in LocalSessionFactoryBean, =
allowing to use a Spring-configured JtaDialect for Hibernate's =
TransactionManagerLookup. This avoids double configuration of the =
server-specific lookup strategy. As when providing a DataSource, the =
corresponding Hibernate property will be set implictly when a JtaDialect =
is provided.
>
>I've tested transaction suspension with HibernateTransactionManager and =
DataSourceTransactionManager in Tomcat, Resin, and JBoss; with =
JtaTransactionManager and a corresponding JndiLookupJtaDialect, in Resin =
and JBoss. Works nicely in all cases: I'd be happy if someone else tried =
WebLogic, WebSphere, JOTM, etc (there's nothing to worry about there, =
just validating the TransactionManager lookup strategies).
>
>I've also added a ClobStringType for Hibernate, using a =
LocalSessionFactoryBean-specified LobHandler for mapping Strings to =
CLOBs. You can specify ClobStringType for such fields in your Hibernate =
mappings even if just using CLOBs in certain environments: =
DefaultLobHandler will simply delegate to =
PreparedStatement.setString/ResultSet.getString anyway. On Oracle, =
simply configure OracleLobHandler in your application context - the =
Hibernate mapping file does not have to change.
>
>ClobStringType is particularly useful if you need Strings with more =
than 4000 characters in Oracle mapped to persistent objects via =
Hibernate. You need to use CLOBs for such long texts in Oracle; and due =
to Oracle's peculiar handling of LOBs, you need a special strategy like =
OracleLobHandler. On other databases like MySQL, type "longtext" is =
fine, to be used like normal String values. Our LobHandler abstraction =
allows to turn this into a configuration issue.
>
>If you get the chance, please check this out promptly, as we intend to =
release 1.0 RC1 this weekend!
>
>Juergen
>
>




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