This blog post is on study material for Sun certification for J2EE:
Architecture considers the functions of components, their interfaces, their interactions and components. The architecture specification helps with the basis of for application design and implementation steps. This book mentions that flexible systems minimize the need to adapt by maximizing their range of normal situations. In J2EE environment, there could be a JNDI agent - Java Naming and Directory interface agent who knows what systems elements are present, where they are and what services they offer.
Classes and Interfaces for an Enterprise JavaBeans Component include the following: Home(EJBHome) Interface, Remote(EJBObject) Interface, XML deployment descriptor, Bean class, and the Context objects. The Home interface provides the lifecycle operations (Create, remove, find) for an EJB. The JNDI agent is used by the client to locate an EJBHome object.
The remote object interface provides access to the business methods within the EJB. An EJBObject represents a client view of the EJB. The EJBObject is a proxy for the EJB. It exposes the application related interfaces for the object but not the interfaces that allows the container to manage and control the object. The container implements the state management, transaction control, security and persistence services transparently. For each EJB instance, there is a SessionContext object and an EntityContext Object. The context object is used to co-ordinate transactions, security persistence and other system services.
package examples
public interface Service {
   public void sayBeanExample();
 }
@Stateless
@TransactionAttribute(NEVER)
@Remote({examples.Service.class})
@ExcludeDefaultInterceptors
public class ServiceBean
  implements Service
{
   public void sayBeanExample() {
    System.out.println("Hello From Service Bean!");
  }
 }
The import statements are used to import say the metadata annotations, the InvocationContext that maintains state between interceptors etc. The @Stateful specifies that the EJB is of type stateful, the @Remote interface specifies the name of the remote interface, the @EJB annotation is used for dependency injection and specifies the dependent "ServiceBean" stateless session bean context. The @Interceptors and @ExcludeClassInterceptors specifies that the bean is associated with an Interceptor class and that the interceptors methods should not fire  for the annotated method respectively. The @PreDestroy method is used for cleanup