[Springframework-developer] Hibernate support and DataSource transactions

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

Hi everybody,

I've just checked the Hibernate stuff in, including the Hibernate =
libraries that are necessary for executing the test suite (not enough =
for full usage by applications). It's in com.interface21.orm.hibernate. =
Most of it should be pretty self-evident and extensively documented, for =
people who already know Hibernate's basics.

A special issue is handling a Hibernate SessionFactory: I've provided 2 =
classes named LocalSessionFactory and JndiSessionFactory. Being =
FactoryBeans, they behave like a Hibernate SessionFactory when used as =
bean reference. This allows for setting up a SessionFactory in an =
application context, and handing it to =
HibernateTemplate/HibernateTransactionManager's "sessionFactory" =
property as bean reference (or to any custom services having a =
SessionFactory-type property). This way, changing from a locally built =
SessionFactory to a JNDI one (when using the J2EE Connector) is just a =
matter of configuration. For convenience, =
HibernateTemplate/HibernateTransactionManager also provide a property =
"sessionFactoryName", for direct JDNI lookup.

I've also reworked our DataSourceUtils and our DataSource =
implementations (DriverManagerDataSource and =
SingleConnectionDataSource), reusing code as far as possible, and =
allowing for bean-style configuration. All the DataSource-related stuff =
is now in com.interface21.jdbc.datasource, taking some classes from =
jdbc.core and jdbc.mock (jdbc.mock doesn't exist anymore). On the =
occasion, I've introduced a JndiDataSource class that applies the =
FactoryBean setup approach to DataSource (as elaborated above regarding =
Hibernate). This allows for setting up a DataSource bean in an =
application context, either =
DriverManagerDataSource/SingleConnectionDataSource or the JndiDataSource =
factory, all of them representing a DataSource when given as bean =
reference, e.g. to JdbcTemplate, DataSourceTransactionManager, or =
HibernateTemplate. Changing from a JNDI DataSource to a local DataSource =
is just a matter of configuration, which is nice for test or standalone =
environments. Of course, we still support mock JNDI with our =
com.interface21.jndi.mock too.

Apropos: There's a DataSourceTransactionManager now, an implementation =
of PlatformTransactionManager capable of handling transactions for a =
single DataSource. It allows applications that just access a single =
database to use high-level transaction demarcation, either via =
TransactionTemplate or the AOP transaction interceptor - without =
requiring JTA support in the container! HibernateTransactionManager =
applies the same approach to a single Hibernate SessionFactory, for =
applications that access their single database just via Hibernate, =
allowing for Hibernate's transactional caching. If the latter isn't =
required, DataSourceTransactionManager can be used with Hibernate too, =
with the requirement that the Hibernate Sessions must be fed with a =
custom DataSourceUtils-looked-up JDBC connection. HibernateTemplate =
conveniently supports this with its dataSource/dataSourceName property. =
With this approach, direct JDBC access is supported too, while other =
code can leverage Hibernate on the same DataSource - within one =
transaction!

We're already using that stuff in a new product we're developing at =
werk3AT, and are pleased with it so far. Have a look at it, I'm looking =
forward to your feedback!

Regards,
Juergen

P.S.:
In contrast to standard JTA and thus our JtaTransactionManager, both =
DataSourceTransactionManager and HibernateTransactionManager do support =
isolation levels!

P.P.S.:
An obvious follow-up is similar support for JDO: a JdoTemplate, a =
JdoTransactionManager for JDO-only access to a single database, a =
LocalPersistenceManagerFactory and a JndiPersistenceManagerFactory. I =
_might_ look at this myself some time, but I've invested quite a lot of =
time on the stuff above, so it would definitely take a while. Any =
volunteers? :-)


DI J=FCrgen H=F6ller
Senior System Architect
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werk3ATS - division systementwicklung
part of werk3AT internetmedien oeg

europaplatz 4
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t.  +43 (0) 732 71 65 29 502
f.  +43 (0) 732 71 65 29 3
jue...@we...
www.werk3at.com
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