A Look at EJB 3.1

With the introduction of JEE6, EJB 3.1 brought several improvements over EJB 3.0. With EJB 3.1 there is now no need to define home/local interfaces. Now an EJB can be defined simply with an annotation. For example to define a stateless session bean:

@Stateless
public class SimpleSessionBean {…}

Singleton Beans are introduced with version 3.1. The application server guarantees that there is a single instance of Singleton EJB which can be used for shared data at the application level.

Asynchronous EJB calls are now supported with the @Asynchronous method-level annotation. It is enough to annotate the method with this annotation to make it asynchronous.

The use of timer services have also been simplified with version 3.1:

@Schedule(second = "*/10", minute = "*", hour = "*", persistent = false)
    public void doWork() {
        System.out.println("timer fired");
    }

This method will be called every 10 seconds by the container. The @Schedule annotation is used for setting a timer to be fired based on a cron-like time expression.

To deploy an EJB, the EJB is packaged into a jar (it may also be packaged into a war) and the jar should be copied to $GLASSFISH_HOME/domains/domain1/autodeploy and the application server will handle the rest.

To use an EJB in another server-side component we can use dependency injection capabilities of the container with the @EJB annotation:

@EJB
SimpleSessionBean beanRef;

It is also possible to call an EJB from a standalone java client (outside a container):

Context ctx = new InitialContext();
//glassfish v3 uses a no-arg constructor in contrast to
//old way of creating an initial context with jndi properties
SimpleSessionBeanRemote mySessionBean = (SimpleSessionBeanRemote)
          ctx.lookup("java:global/TestEjb/SimpleSessionBean");
// obtain a remote reference

The classpath of the client should include the EJB jar file and $GLASSFISH_HOME/modules/gf-client.jar file. For the global JNDI naming of the EJB modules please see here.
The stateless session bean with a timer method example together with a standalone java test client can be downloaded from here