Editing EJB (section)

====Stateless Session Beans====
In a stateless session bean (SLSB), the client-side stub object can route your method call to any bean instance that happens to be available in the container-managed object pool. Hence, you should not have any field variables to store the bean state in the bean class.
To define a session bean, you first need to define the local and remote service interface containing all its business methods. The session bean interface is just plain old Java interface without any annotation e.g.

 public interface Calculator {
   public double calculate (int start, int end, double growthrate, double saving);
 }
 public interface RemoteCalculator {
   public double calculate (int start, int end, double growthrate, double saving);
   public String getServerInfo ();
 }

and the implementation class:
 import javax.ejb.*  // for annotations
 
 @javax.ejb.Stateless                                                     
 @javax.ejb.Local ({Calculator.class})                                    // specification of the local interface or direct at the interface
 @LocalBinding (jndiBinding="EJB3Trail/LocalCalculator")                  // optional
 @javax.ejb.Remote ({RemoteCalculator.class})                             // specification of the remote interface or direct at the interface
 @RemoteBinding (jndiBinding="EJB3Trail/RemoteCalculator")                // optional
 public class StatelessCalculator 
   implements Calculator, RemoteCalculator {
   public double calculate (int start, int end, double growthrate, double saving) {
     double tmp = Math.pow(1. + growthrate / 12., 12. * (end - start) + 1);
     return saving * 12. * (tmp - 1) / growthrate;
   }
 }

The default naming binding is <EAR-FILE-BASE-NAME>'''/'''<EJB-CLASS-NAME>'''/'''('''local'''|'''remote''').

=====Features=====
* not bound to a client, can be pooled
* multi-method transactions by client or within one method
* methods can be published as web service