It's certainly possible to deploy n EJBs that have the same ejb-class. It's one of those things that deployment descriptors can do but annotations can't.
But be aware of this issue:
https://glassfish.dev.java.net/issues/show_bug.cgi?id=3547
Environment resource injection fails in MDB.
Actually this issue affects MDB and session beans as well. To work around it, lookup your resources in lieu of injection.
Use <resource-ref> for ConnectionFactory, DataSource, etc.
Use <message-destination-ref> for jms dest
-cheng
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