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[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

  • From: Florent BENOIT <Florent.Benoit@...>
  • To: jsr342-experts@...
  • Subject: [javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces
  • Date: Fri, 5 Oct 2012 10:27:20 +0200
  • List-id: <jsr342-experts.javaee-spec.java.net>

What I like with annotation in the first example is when you don't want to override every methods
If you only want to apply one a single listener method it make sense

Like for Stateful Session Bean
In the past you had to implements javax.ejb.SessionSyncrhonization and for example have empty methods if you only want to apply for a single listener callback

With listener annotation you can only be notified for a set of event like @AfterBegin or @BeforeCompletion


Regards,

Florent

On Fri, Oct 5, 2012 at 1:52 AM, Jeff Genender <jgenender@...> wrote:
I agree with your view on the batch API and your proposal to the "rules".  They seem pretty straight forward to me.

Jeff

On Oct 4, 2012, at 3:36 PM, Bill Shannon <bill.shannon@...> wrote:

> Earlier this year I wrote up a bunch of our "rules" for how annotations
> should work: http://java.net/projects/javaee-spec/pages/AnnotationRules
>
> While reviewing the Batch spec:
> http://download.oracle.com/otndocs/jcp/batch-1_0-edr-spec/index.html
> I noticed that they were using annotations in places that I expected
> to see interfaces.
>
> For example, they allow a class to be a "listener" for events, and they
> declare that the class is a listener by annotating the class.  To indicate
> which method of the class should be called when the event occurs, they
> annotate the method.  The different events are a finite and fixed set,
> and each type of listener handles only a few events associated with that
> type.  You might have:
>
> @JobListener
> public class MyJobListener {
>    @JobStarted
>    public void jobStarted() { ... }
>    @JobFinished
>    public void jobFinished() { ... }
> }
>
> To me, this just felt like an abuse of annotations in a place where a
> listener interface is a widely used and well understood approach.
> Why would you not simply do:
>
> public interface JobListener {
>    public void jobStarted();
>    public void jobFinished();
> }
>
> public class MyJobListener implements JobListener {
>    public void jobStarted() { ... }
>    public void jobFinished() { ... }
> }
>
> Of course, you'll want an annotation on MyJobListener to configure
> the listener and associate it with a specific job.  (You don't want
> a class to be used just because it's been declared.)
>
> It seemed like it would be worth writing down some general principles
> as an update to my annotation rules page above.  Here's what I have so
> far, but I'd love your feedback.  Of course, it's likely that we haven't
> followed a consistent set of rules for things we've already done, so there
> will always be exceptions.  Let me know if you agree with the following,
> and especially let me know of any additions.
>
>
> - When defining an API that an application is going to implement and
>  the container is going to call, use an interface.
>
> - To configure the container to use a particular implementation of such
>  an interface in a particular situation, use an annotation.
>
> - If an application class is providing an API that's exposed to other
>  applications, and that class also needs to provide methods that the
>  container will call for lifecycle functions, use an annotation to
>  mark those methods so that the application has flexibility in the
>  choice of names for those methods.
>
> - If an application is going to expose an interface that another
>  application (or user) is going to use *without* Java, use annotations
>  to mark the methods that correspond to this interface.  This avoids
>  the need to define a Java interface that's never going to be used by
>  anyone other than the one class implementing the interface.




[javaee-spec users] [jsr342-experts] annotations vs. interfaces

Bill Shannon 10/04/2012

[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

Jeff Genender 10/04/2012

[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

Florent BENOIT 10/08/2012

[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

Pete Muir 10/10/2012

[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

Pete Muir 10/08/2012

[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

Bill Shannon 10/09/2012

[javaee-spec users] [jsr342-experts] Re: annotations vs. interfaces

Pete Muir 10/10/2012
 
 
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