Hello!

I have to access many MySQL databases that share the same schema via Hibernate. I can't add a connection parameter set for all of them to a configuration file, since they are very many and their number increases. Nevertheless, they all reside on the same MySQL server and the only difference in the connection parameters is their database name.

Is there a way to get different Sessions or SessionFactorys depending on a parameter (i.e. the database name)? Or do I have to create the connections by myself and hand them to the Session? In addition, I'd like to use the Spring Framework, which hides very much of the session stuff, which makes it more complicated, I suppose...

Does anybody have some experience with this scenario?

Thanks in advance!
Christian Gruber

Use Configuration.configure(DOM) api and build the appropriate DOM based on a template.

You can change the hibernate.connection.url property just before you build the session factory by calling Configuration.addProperties().

You could also leave the database name off the hibernate.connection.url property and set the hibernate.default_schema property to the name of the database. If you do this though, you need to subclass MySQLDialect and override getSchemaSeperator() and return a dot instead of an underscore.

I'm not entirely sure how you would do this with spring. I guess it depends on how/when you create the spring context. But it looks like there are a couple of ways to set those properties using the LocalSessionFactoryBean. First is by setting either of the above properties in the LocalSessionFactoryBean definition's hibernateProperties property. The other is by subclassing LocalSessionFactoryBean and override postProcessConfiguration() to add the properties manually.

Hope this helps...

Joe

Hi!

Thanks for your help! Here's what I have found out and tried:

In Hibernate, It was rather easy:



In Spring Framework, it was more complicated, but I have now the following solution, which might be a bit strange and perhaps not according to the intention of Spring:

In the beans XML file, I use a PropertyPlaceholderConfigurer to replace bean values like "${db}" by the real database. The database name which is determined at runtime is stored in a singleton class. The "db" property is fetched out of this singleton class in an own class that is derived from a PropertiesFactoryBean. For each session to a specific database, I create a new ApplicationContext after setting the database name in my singleton class. Sounds complicated, but it works... Or does somebody have a better idea?

Greetings,
Christian

First of all, I assume you mean "for each SessionFactory to a specific database, I create a new ApplicationContext...".

If you're just doing this to create a LocalSessionFactoryBean for a specific database URL, then there is an easier way: Simply instantiate LocalSessionFactoryBean yourself, invoke its setters, invoke afterPropertiesSet, and fetch the SessionFactory via getObject():



Instead of setting the database URL via "hibernateProperties", you could also pass a corresponding pre-determined DataSource into setDataSource.

Note that you can use Spring's transaction management and HibernateTemplate with any SessionFactory, even if manually created. HibernateTransactionManager and HibernateTemplate just take a SessionFactory reference in their respective setters, not caring where it came from - LocalSessionFactoryBean is just a convenient way to create one.

Even if our documentation and our examples focus on using Spring as framework, many parts of it can also be used in a library style. After all, that's the point of an IoC framework: The components do not unnecessarily depend on the framework but typically lend themselves nicely to standalone usage as plain objects.

Juergen