Chapter 7. The Singleton Session Bean

So far, we’ve enjoyed the isolated invocation context provided by stateless and stateful session beans. These bean types service requests independently of one another in separate bean instances, relieving the EJB developer of the burden introduced by explicit concurrent programming. Sometimes, however, it’s useful to employ a scheme in which a single shared instance is used for all clients, and new to the EJB 3.1 Specification is the singleton session bean to fit this requirement.

Contrary to most late-generation feature additions, the singleton is actually a much simpler conceptual model than we’ve seen in SLSB and SFSB, as shown in Figure 7-1.