An EJB server uses JTA and JTS to communicate with other XA enabled servers. The Two Phased Commit Process . This mechanism enables proper coordination to take place amoung all transaction servers. Introduction to EJB . EJB divides the development process up into a number of separate containers that can be addressed separately by different development efforts.
Entity beans interact with external resources such as databases and other enterprise servers.
In the original spec, EJB 1.0 supported only session beans -not entity beans. But everything changed in June 1999. As Sun introduced the EJB 1.1 spec now requiring entity beans. Richard has a very useful site called EJB Now . The Enterprise JavaBean Model and the rest of the JOnAS whitepaper from Bullsoft.