On 12 Mar 2015 at 12:24:59, Eduard Moraru
([email protected](mailto:[email protected])) wrote:
> Hi,
>
> On Thu, Mar 12, 2015 at 12:03 PM, [email protected]
> wrote:
>
> > Hi Edy,
> >
> > On 12 Mar 2015 at 10:49:29, Eduard Moraru ([email protected](mailto:
> > [email protected])) wrote:
> >
> > > Hi,
> > >
> > > As it's documentation [1] mentions, the usage of the @Priority annotation
> > > should be defined by the classes it is used on:
> > >
> > > "The effect of using the Priority annotation in any particular instance
> > is
> > > defined by other specifications that define the use of a specific class.
> > > For example, the Interceptors specification defines the use of priorities
> > > on interceptors to control the order in which interceptors are called."
> > >
> > > Therefore, I suggest we use the @Priority annotation on components that
> > > need it and that like to specify the order in which they are *used* (i.e.
> > > perform their main task).
> >
> > so what you’re suggesting is that:
> >
> > @Component
> > @Name(“content”)
> > @Priority(1000)
> > public class ContentMacro implement Macro
> >
> > has a different meaning than:
> >
> > @Component
> > @Named(“XWiki.WatchListJobClass")
> > @Priority(1000)
> > public class WatchListJobClassDocumentInitializer ...
> >
> > because one if a Macro and the other one is a Document Initializer
> >
> > right?
> >
>
> ...and because they clearly express it, in their documentations, that they
> accept some annotations and they define how those annotations will be
> interpreted. Basically, the purpose of the javax.annotations package.
>
>
> > (BTW note that this wouldn’t work if in the future we start supporting
> > several roles per component impl.)
> >
> > So it means that people reading the code need to understand that even
> > though it’s the same annotation, it’ll have a different meaning.
> >
> > Compare this to:
> >
> > @Component
> > @Name(“content”)
> > @MacroPriority(1000)
> >
>
> I don`t find this better since it does not tell me what the macro does with
> that priority. @MacroExcutionPriority would have been clear, if that is
> what we pursue.
Yes I’m fine with MacroExecutionPriority, not a problem, we can discuss the
details of the names ;)
> public class ContentMacro implement Macro
> >
> > and
> >
> > @Component
> > @Named(“XWiki.WatchListJobClass")
> > @DocumentInitializerPriority(1000)
> > public class WatchListJobClassDocumentInitializer ...
> >
> > IMO the second one is more clear in its intent. WDYT?
> >
>
> Honestly, I am not a big fan of annotations, specially in Java, and I try
> to keep them to a minimal as much as possible. It feels like a shortcut
> that leads to a dead end. They are not code, but configuration and, as
> such, modifying configuration should not require recompiling the code.
I do not agree with this (and I know a lot of devs don’t agree either since
this is one topic we’ve discussed in a Java podcast interview not long ago on
the LesCastCodeurs.com).
Annotations are part of the language (contrary to Aspects!) and they are close
to the code so they are perfect to express cross-cutting concerns.
We’re already using annotations for component metadata (@Component, @Inject,
@Named, etc). Using annotations for component priority makes a lot of sense.
And again, what is wrong IMO is actually what we’ve done (me being the first to
have done it in Macros…), which is the addition of get/setPriority() methods in
our component interfaces. The priority concept is not a business concept and it
fits better the concept of annotations.
> Back to our particular discussion, AFAIK, we are not doing multiple roles
> per implementation. That, indeed, would probably not work with the javax
> Priority annotation due to lack of specificity.
>
> I do see the advantages of typed annotations, but also the need to be aware
> of more and more annotations, as they come, when our usecase is pretty
> simple and would be well satisfied by the javax Priority one. That is the
> main reason why I looked for a more generic solution instead of just making
> a new annotation for the document initializer use case. I find it uselessly
> polluting.
Yes, the intention was great: it’s always better to use something that already
exists rather than reinvent yours but in this case, as the javadoc for Priority
clearly states, the meaning of it is left to the code… If you have only 1
concept of priority it’s not a problem. In our case it’s more complex because
we use components for lots of things and we have various concepts of Priorities.
TBH when I first started this thread it was a [Proposal] to use @Priority
everywhere we need a priority and then while writing the mail I discovered the
namespace issue and I rewrote the mail as a brainstorming, and as a discussion
as to whether we should (or not) use the @Priority annotation only for the
Mandatory Document Initializers (Once we release XWiki 7.0 it’s going to be
harder to change).
> I`d love to hear more opinions on this :)
Yup
Thanks
-Vincent
> Thanks,
> Eduard
>
> >
> > > Priorities on other behaviors that are added to a component (for example
> > > through interfaces like Initializable or Disposable, interfaces which are
> > > not components themselves) should provide their own specialized
> > > (behavior-driven) priority annotations (e.g. @DisposePriority,
> > > @InitializationPriority, etc.).
> > >
> > > Note: If we want to explore the possibility of using our own generic
> > > Priority annotation, we need to consider the fact that multiple
> > annotations
> > > on the same java class is only supported [1] starting with java 1.8.
> > Until
> > > then, the commonly used workaround [3] seems cumbersome to use.
> >
> > Yep, I’d really not like to use a generic annotation with the namespace
> > being specified. I much much prefer typed annotations.
> >
> > Thanks
> > -Vincent
> >
> > > Thanks,
> > > Eduard
> > >
> > > ----------
> > > [1] http://docs.oracle.com/javaee/7/api/javax/annotation/Priority.html
> > > [2] http://bugs.java.com/bugdatabase/view_bug.do?bug_id=7151010
> > > [3]
> > >
> > http://stackoverflow.com/questions/1554112/multiple-annotations-of-the-same-type-on-one-element
> > >
> > > On Thu, Mar 12, 2015 at 10:41 AM, [email protected]
> > > wrote:
> > >
> > > > Hi devs,
> > > >
> > > > As part of http://jira.xwiki.org/browse/XWIKI-11905, Edy has started
> > > > using the Java @Priority annotation.
> > > >
> > > > This seems very good and I personally didn’t know about this annotation
> > > > before (maybe it’s been introduced not that long ago?). So for me it
> > raises
> > > > the question of: do we want to use this annotation more and how does it
> > > > compare with what we’ve done so far.
> > > >
> > > > I can think of a few places that could have used it:
> > > >
> > > > * Macros.get/setPriority(). It should be possible to add support for
> > > > @Priority and modify MacroTransformation to use that annotation.
> > > > * Transformations. We have a jira issue opened for adding support for
> > > > Priority in Transformation’s executions (in TransformationManager).
> > > > * @DisposePriority (used by ECM).
> > > > * TranslationBundle.get/setPriority()
> > > > * … and probably some other places…
> > > >
> > > > However, I think there’s a namespacing problem. For example imagine
> > that
> > > > we code a Macro and set @Priority on that Macro component. The ECM
> > could
> > > > interpret it as a dispose priority while the MacroTransformation could
> > > > interpret it as an execution priority…
> > > >
> > > > Globally I think that use an annotation for expressing priority is
> > great
> > > > and much better than what we’ve done in the past with get/setPriority()
> > > > methods. It’s better because priority is not a business concept and
> > we’re
> > > > polluting the business interface with it.
> > > >
> > > > Now, in order to fix the namespacing issue, I think that the best
> > solution
> > > > is that each module requiring some priority should introduce its own
> > > > annotation and should NOT depend on the @Priority one from the JDK
> > (i.e. we
> > > > ban the usage of it).
> > > >
> > > > WDYT?
> > > >
> > > > Thanks
> > > > -Vincent
> > > >
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