Integrating BTM with Hibernate
Hibernate can be integrated straight with any JTA transaction manager.
The biggest added value (omitting the fact that you can use Hibernate and two databases) is Hibernate's Current Session context management. You do not have to take care about opening nor closing
Session as Hibernate will automatically bind them to the JTA transaction's lifecycle. You just have to make sure JTA transactions are properly started and ended.
Hibernate cannot directly create a BTM
PoolingDataSource. You will have to create them yourself (either via the API or the Resource Loader) then bind them to a JNDI server.
Creating the datasources
As you can expect, you will need to create one
PoolingDataSource per database. Say that you want to use two Embedded Derby databases, and configure them via the BTM API. Here is what your code would look like:
Binding the datasources to JNDI
You have to bind the datasources to some JNDI server. You can use any one you wish, including the one embedded in your application server.
In the case you want to run Hibernate in a standalone application, you can use Tomcat's JNDI server as it is very easy to use it in a standalone J2SE application.
Just create a
jndi.properties file at the root of your classpath. It should only contain this line:
Then add these two jar files to your classpath:
They are available in any Tomcat 5.5 distribution, just look into the
This will configure Tomcat's JNDI server as the default implementation. It is a simple intra-VM server that implements the most important JNDI features. You can now just create a InitialContext with the no-args constructor to have access to it.
Finally, here is the code to bind the datasources:
Hibernate Session factories
You need to configure exactly one
SessionFactory per datasource.
Datasource JNDI location
You have to tell Hibernate where to get the BTM datasource via JNDI. Add a connection.datasource property and set its value to the JNDI location of your datasource:
Current session context
You have to set current_session_context_class to
Transaction factory class
Transaction manager lookup class
Then add this property:
Here is what the
hibernate_testDS1.cfg.xml file will look like for the first datasource. Some other mandatory properties also have to be added, like the
cache.provider_class and of course the required object mappings.
And here is the
hibernate_testDS2.cfg.xml for the second datasource: