"JGF1" wrote : BTW: Have just taken a look at the code download from Apress website for this book. | It has defined an extra exception class and iused it in StockList interface, and as a consequence StockListBean. | Because the design pattern in the class that was found by JBoss didn't match what it was expecting, could this be the root cause of the exception that got thrown? Nope...your exception is complaining about a lack of default persistence unit. Please take a look at http://trailblazer.demo.jboss.com/EJB3Trail/persistence S, ALR View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4134691#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...