There are a number of implementation features that you should be aware of when developing applications for JBoss Application Server 5.0.0.
The Release Notes for JBoss Application Server contain information on EJB3 features that are not yet implemented, or partially implemented. The Release Notes include links to issues in JIRA for information on workarounds and further details.
JBoss Application Server 5 fully supports the entire Java 5 Enterprise Edition specification. JBoss Application Server 4.2.2 implemented EJB3 functionality by way of an EJB MBean container running as a plugin in the JBoss Application Server. This had certain implications for application development.
The EJB3 plugin injects references to an EntityManager and @EJB references from one EJB object to another. However this support is limited to the EJB3 MBean and the JAR files it manages. Any JAR files which are loaded from a WAR (such as Servlets, JSF backing beans, and so forth) do not undergo this processing. The Java 5 Enterprise Edition standard specifies that a Servlet can reference a Session Bean through an @EJB annotated reference, this was not implemented in JBoss Application Server 4.2.2.