Head First EJB

But enough about the home... let’s talk about the EJB object. The component interface. The thing you REALLY want.

Remember, all that InitialContext-JNDI-lookup-cast-narrow-create business was just to get what you really wanted all along—something with the business methods. Something you can use to get the bean to do whatever it is that bean was created for. Number crunching, online shopping, advice.

package headfirst;

import javax.ejb.*;
import java.rmi.RemoteException;


public interface Advice extends EJBObject {

   public String getAdvice() throws RemoteException;

}

Rules for the component interface

1. Import javax.ejb.* and java.rmi.RemoteException.

2. Extend EJBObject.

3. Declare one or more business methods, that throw a RemoteException.

   • Arguments and return types must be RMI-IIOP compatible (Serializable, primitive, Remote, or arrays or collections of any of those).

   • You can have overloaded methods.

   • Each method must declare a RemoteException.

   • You can declare your own application exceptions, but they must NOT be runtime exceptions (in other words, they must be compiler-checked exceptions—subclasses of Exception but not subclasses of RuntimeException).