12 Mar
2015
12 Mar
'15
12:24 p.m.
Hi,
On Thu, Mar 12, 2015 at 12:03 PM, vincent(a)massol.net <vincent(a)massol.net>
wrote:
Hi Edy,
On 12 Mar 2015 at 10:49:29, Eduard Moraru (enygma2002(a)gmail.com(mailto:
enygma2002(a)gmail.com)) wrote:
...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.
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?
(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.
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.
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.
I`d love to hear more opinions on this :)
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…
On Thu, Mar 12, 2015 at 10:41 AM, vincent(a)massol.net
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
>
>
> W
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