Testing in Java Applications Testing and optimizing Java code without test automation for
handling concurrent activities is rather difficult. Even with test
automation, being able to correlate the test activity from the client side
to observations of thread, memory, object and database connection use on the
server side is difficult at best.
A new feature of Singleton Beans is added in EJB 3.1 that is used to store
application-wide shared data. The JEE container maintains a single shared
instance of an EJB 3.1 Singleton that can cache state across the application
tier. Like all other EJBs, Singletons are simply annotated POJOs.