Getting Started with WebSphere Application Server

1. Define local and remote interfaces for the EJB
2. Implement the EJB class
5.2.1.1 Defining local and remote interfaces
Chapter 5 – Enterprise Java Beans 91
To avoid code duplication, define a common interface which can then be inherited by both,
local and remote interfaces. In an EJB, a local interface is used by an invoker using the
same Java Virtual Machine (JVM) while a remote interface is used by an invoker in
a different JVM. Following the EJB 3.0 specification, the local interface is annotated with
@Local while the remote interface is annotated with @Remote. Listing 5.1 below provides
an example of how you can define the business interface of an EJB. In the example, you
define a business interface named HelloInterface.
package hello;
public interface HelloInterface {
public void sayHello();
}
Listing 5.1 - Defining the business interface of the EJB
Listing 5.2 provides an example of how you can define the local interface of the EJB. It
inherits the business interface.
package hello;
import javax.ejb.Local;
@Local
public interface HelloInterfaceLocal extends HelloInterface {}
Listing 5.2 - Defining local interface of the EJB
Listing 5.3 provides an example of how you can define the remote interface of the EJB.
package hello;
import javax.ejb.Remote;
@Remote
public interface HelloInterfaceRemote extends HelloInterface{}
Listing 5.3 - Defining the remote interface of the EJB
5.2.1.2 Implementing the EJB class
Now that the interfaces have been defined, you can implement them. In this step, all the
methods of the EJB class will be implemented. As defined in the EJB 3.0 specification,
@Stateless is used for a stateless EJB, an EJB that is normally short lived and does not
maintain the state on behalf of the client. @Stateful is used for a stateful EJB. Listing 5.4
provides an example.
package hello;
import javax.ejb.Stateless;
@Stateless
public class HelloEJB implements HelloInterfaceLocal,
HelloInterfaceRemote {