12 Mar
2015
12 Mar
'15
10:48 a.m.
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).
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.
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 <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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