Question

is it possible to create something like static object using EJB3 in Jboss. in other words i need to create something like a static object using singleton pattern or something like that, that is because i need to preload a configuration from database and i want that every bean that jboss creates uses this class to read this configuration instead of that every bean load it from the database.

Cheers,

Answer 1

EJB 3.1 does have a standard @Singleton annotation but EJB 3.0 doesn’t. However, JBoss offers a JBoss extension to the EJB 3.0 spec to create a singleton with the @Service annotation.

From the JBoss EJB 3.0 Reference Documentation:

Chapter 6. JBoss EJB 3.0 extensions

JBoss provides a few extensions to the
EJB 3.0 spec. This chapter describes
those features here.

6.1. @Service EJBs

An extension offered by JBoss EJB 3.0
is the notion of a
@org.jboss.annotation.ejb.Service
annotated bean. They are singleton
beans and are not pooled, so only one
instance of the bean exists in the
server. They can have both @Remote and
@Local interfaces so they can be
accessed by java clients. When
different clients look up the
interfaces for @Service beans, all
clients will work on the same instance
of the bean on the server. When
installing the bean it gets given a
JMX ObjectName in the MBean server it
runs on. The default is

jboss.j2ee:service=EJB3,name=<Fully qualified name of @Service bean>,type=service

You can override this default
ObjectName by specifying the
objectName attribute of the
@Service annotation.

References

• JBoss EJB 3.0 Reference Documentation
  • 6.1. @Service EJBs
• JBoss EJB3 Tutorials
  • Chapter 28. Service POJOs (JBoss extension of EJB3)