I've added an attachment. It contains a simple project with a rest service. Deploy it in WildFly. It is set to use a MongoDB instance on localhost. You can invoke the service just to trigger the insert of an entity into MongoDB. In the persistence.xml, I've commented the "<class>" tag, and doing so I obtain the following exception:

org.jboss.resteasy.spi.UnhandledException: javax.ejb.EJBException: java.lang.IllegalArgumentException: Unknown entity: com.gregoriopalama.example.Person

Uncommenting the "<class>" tag, it works perfectly.

Let me know if you need more informations.