A couple of notes about the business interface strategy.
1) The methods declared in the business interface need to throw RemoteException
in order for this to work. This is stated clearly in the book but I noticed you
didn't include the throw clauses in your example. The bean does not need to
declare these throw clauses when it implements the business interface.
2) This strategy does not work in the J2EE RI or (according to my readers) in
the Weblogic EJB server. The deployers and runtime engines of these servers do
not recognize interface inheritance.
EJB servers are supposed to support remote and home interface inheritance (EJB
1.1 specification section B.2). Its unclear if the business interface
inheritance strategy outline in the O'Reilly's EJB book is technically the same
kind of inheritance since the business interface is not a remote interface.
At any rate the business interface was not intended to, nor should it, be
specified as a parameter or return type in remote invocations. Only value types
and interface that inherit from java.rmi.Remote qualify as parameters and return
types in Java RMI. The business interface is simply intended to provide a
common interface between the remote and bean class to in force consistency
between these types. Its not required.
Thanks,
Richard
--
Richard Monson-Haefel
Author of Enterprise JavaBeans, 2nd Edition
Published by O'Reilly & Associates
http://www.EjbNow.com
Jeff Oh wrote:
> Phil Lewis wrote:
>
> <snip>
>
> The problem is that the MyClassEJBFactory creates an instance of the remote
> interface using MyClassHome. When I try to fave the MyClassEJBFactory return
> the remote interface, I get a compile time error saying that the factory
> method
> needs to return MyClassBusiness.
>
> </snip>
>
> This seems a bit strange to me, as I'm doing something very similar in some
> benchmark code that I've written, where I have a number of beans that
> implement the same interface with different implementations for
> benchmarking.
>
> Basically, I've implemented it as follows
>
> // Business interface holds all business methods (a la Monson-Haefel, et
> al)
> public interface MyClassBusiness {
> public method1()
> ...
> }
>
> // Remote Interface
> public interface MyClass extends MyClassBusiness, javax.ejb.EJBObject {}
>
> // Local version of same - could be an interface or a class
> public interface MyClassLocal extends MyClassBusiness {}
>
> public abstract class MyClassFactory {
> public MyClassFactory() {};
> public abstract MyClassBusiness create();
> }
>
> public MyClassEJBFactory extends MyClassFactory {
> ...
>
> public MyClassBusiness create() {
> return (myClassHome.create());
> }
> }
>
> While I haven't tested this construction, I see no reason why the compiler
> would complain about this since myClassHome.create() returns a MyClass
> interface which IS a MyClassBusiness. Note that to make this work, you need
> to put all your business methods in a separate interface which is inherited
> by both MyClass and MyClassLocal a la Monson-Haefel. If your MyClass
> interface extends MyClassBusiness, then your MyClassEJBFactory should be
> able to cast MyClass interfaces to MyClassBusiness interfaces with impunity.
>
> Note that this *does* mean that you lose the stuff in javax.ejb.EJBObject.
> If this is a problem, then your local object needs to implement
> javax.ejb.EJBObject as well, in which case MyClassFactory can return MyClass
> interfaces instead of MyClassBusiness interfaces. Alternatively, you could
> use run-time casting (yuck!), or implement a third interface which extends
> MyClassBusiness with the methods from javax.ejb.EJBObject() that you
> require...
>
> Jeff 8-)
>
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