Hi, I'm migrating an application from EJB to Hibernate and I'm trying to keep the original architecture: the backend is decoupled from the frontend (servlet) and I'm using stateless EJB as façade. Also, the EJB are divided in different jar to keep the backend modular.

My question is: how should I configure Hibernate to access the mapping files contained in the different jars ? Is it possible to have multiple hibernate.cfg.xml files to keep the configuration modular ? Or should this be done programmatically ?

Any idea is welcome.

See Configuration.addResource(String) to specify individual mapping files (hbm.xml files) or Configuration.addClass(Class) to specify a class to map. (latter assumes that a mapping file named <ClassName>.hbm.xml exists in the same package directory as the specified class.) These methods look for the specified resources in your classpath, so multiple jars are fine.

You can also specify all mapping resources in your cfg.xml file. If you want to create multiple SessionFactory instances, use one cfg.xml per instance.

I suppose you could call Configuration.configure() multiple times, loading multiple cfg.xml files for one SessionFactory, but I'm not sure what that would do. However, there's nothing in the hibernate-configuration-3.0.dtd that says you couldn't create a mapping file with no properties and just references to mapping resources, effectively specifying a mapped "module" of hbm.xml files. Dunno. Check the source of Configuration.configure() before you try this. :)

From TFM: [url]file:///C:/hibernate/guide3.htm#session-configuration[/url]

What I currently have is a hibernate.property file for hibernate general configuration, and a hibernate.cfg.xml for object mapping.
I'm trying to use <mapping jar="" /> option to configure the ejb modules, but I've some problem with classloader (Hibernate can't find the configuration file).
Besides this, I'd like a pluggable configuration such that every module has it's own mapping configuration file.

I assume that you're trying to load a cfg.xml file using <mapping jar="">, right?

As far as I can tell, the "jar" option on the mapping tag calls Configuration.addJar(), which reads all hbm.xml files from a jar. This will NOT read any cfg.xml files from the jar. (Check the source to confirm this...)

I'd figure the best way to do this is to continue what you're doing, as far as specifying all mapping resources for one "module" in a single cfg.xml file. Group related classes in jars (along with their mapping files) and load them using jar="". Make sure all jars are in the classpath. (This is the only potential non-modular part of the design.) When you want to load a "module" load the cfg.xml file programmatically using Configuration.configure().