Q:

Java EE without Application Server

Since EJB 3 we have embeddable EJB containers, JPA implementations can be used without an application server, there is Weld for contexts and dependency injection and so on.  Since on many systems is only Tomcat available, I wonder, if Java EE could be used without an application server but with a Servlet container like Tomcat.  
What would I have to do to set up an Java environment?  What drawbacks do you see? 

A:

Note that Tomcat is an Application Server.   That said, in October we released Apache TomEE which is Tomcat with the missing JavaEE parts added, then Java EE 6 certified using the official TCK from Oracle. 
The stack evolved from what used to be simply called "OpenEJB/Tomcat", which was a useful stack with a bad name :)  Commonly overlooked because of the "EJB" part, meanwhile it also delivered Transactions, JMS, WebServices and more to Tomcat.   The new name is far better and now it's officially certified like JBoss or GlassFish.   We're pretty excited about its future.