Guaranteed order of annotations?

[Gunnar Morling]

Hi Joe,

Thanks for your confirmation. Bean Validation may benefit from it, but
I understand that just a single request hardly justifies the change.

--Gunnar




2017-01-23 23:05 GMT+01:00 joe darcy <joe.darcy at oracle.com>:
> Hi Gunnar,
>
> Annotations went into the platform way back in Java SE 5.0, with a GA during
> 2004. When working on repeating annotations, I was surprised to find there
> weren't stronger ordering guarantees for annotations from core reflection.
> However, requests to tighten this aspect of the platform haven't come up
> very often in the interim and I don't like it is likely to happen at this
> point.
>
> HTH,
>
> -Joe
>
>
>
> On 1/17/2017 11:26 PM, Gunnar Morling wrote:
>>
>> Joseph, all,
>>
>> Thanks for the clarification.
>>
>> Are there chances to establish such guaranteed ordering in a future
>> Java version? As pointed out, it'd be very helpful to Bean Validation
>> and I reckon other cases, too.
>>
>> Thanks,
>>
>> --Gunnar
>>
>>
>>
>> 2017-01-18 3:13 GMT+01:00 Joseph D. Darcy <joe.darcy at oracle.com>:
>>>
>>> Hello,
>>>
>>> Following up on Joel's message, IIRC this ordering issue did come up
>>> during
>>> the design and testing of repeating annotations.
>>>
>>> As noted previously in the thread, while the ordering of the annotations
>>> in
>>> a container annotation is guaranteed, there is *not* a general ordering
>>> constraint on the annotations returned by the methods of the
>>> AnnotatedElement interface.
>>>
>>> HTH,
>>>
>>> -Joe
>>>
>>>
>>> On 1/13/2017 1:16 PM, Gunnar Morling wrote:
>>>>
>>>> Hi Yuri,
>>>>
>>>> Thanks for the pointer.
>>>>
>>>> But do you see any clear description of an order mandated for
>>>> getDeclaredAnnotations()? The only references to an order I can find
>>>> there are for repeatable annotations (where source code order is
>>>> maintained when retrieving them via the container annotation type).
>>>> But I cannot find any guaranteed order when obtaining all declared
>>>> annotations from an element.
>>>>
>>>> The reason why I'm asking is Bean Validation, where we've seen
>>>> requests of people that wish to validate the constraints of an element
>>>> in a fixed order, aborting after the first failed constraint:
>>>>
>>>>       @NotNull
>>>>       @Email
>>>>       String email;
>>>>
>>>> Here one may want to first validate @NotNull and don't proceed with
>>>> validating @Email if the field is null.
>>>>
>>>> Relying on source order would be a very natural way to express the
>>>> order of constraints. Without a guaranteed ordering of annotations
>>>> we'd have to add some other means of ordering, e.g. an attribute with
>>>> the index (@NotNull(order=0) @Email(order=1)) which is more verbose of
>>>> course.
>>>>
>>>> --Gunnar
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> 2017-01-13 21:15 GMT+01:00 Yuri Gaevsky <ygaevsky at azulsystems.com>:
>>>>>
>>>>> Hi Gunnar,
>>>>>
>>>>> Please take a look at JDK-8010679 'Clarify "present" and annotation
>>>>> ordering in Core Reflection for Annotations' [*].
>>>>>
>>>>> Best regards,
>>>>> -Yuri
>>>>>
>>>>> [*] https://bugs.openjdk.java.net/browse/JDK-8010679
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: core-libs-dev [mailto:core-libs-dev-bounces at openjdk.java.net] On
>>>>> Behalf Of Gunnar Morling
>>>>> Sent: Friday, January 13, 2017 08:14 PM
>>>>> To: core-libs-dev at openjdk.java.net
>>>>> Subject: Guaranteed order of annotations?
>>>>>
>>>>> Hi,
>>>>>
>>>>> Is there any order guaranteed in which an element's annotations are
>>>>> returned by AnnotatedElement#getDeclaredAnnotations()? Specifically,
>>>>> is this the order in which the annotations are given in the source
>>>>> code?
>>>>>
>>>>> Section 9.7.5. of the JLS ("Multiple Annotations of the Same Type")
>>>>> makes a statement of the source order being considered by the array of
>>>>> the implicit container annotation created for a repeatable annotation
>>>>> ("[...] all the base annotations in the left-to-right order in which
>>>>> they appeared in the context").
>>>>>
>>>>> But I couldn't find any authoritative description on the ordering
>>>>> behaviour of getDeclaredAnnotations(). Should we assume that we cannot
>>>>> rely on the order in the source?
>>>>>
>>>>> Thanks for any pointers,
>>>>>
>>>>> --Gunnar
>>>
>>>
>