RFR 7183985: Class.getAnnotation() throws an ArrayStoreException when the annotation class not present

[Joel Borggrén-Franck]

Hi Liam,

Sorry for the delay,

On Sat, 30 Jan 2016 at 04:45 Liam Miller-Cushon <cushon at google.com> wrote:

> On Thu, Jan 28, 2016 at 11:50 AM, Joel Borggrén-Franck <
> joel.borggren.franck at gmail.com> wrote:
>
> But, the reason we didn't fix this the last two times we looked at it
>> (that I am aware of) is the compatibility story. In order to fix his
>> you need to figure out two things:
>>
>> - Is this is a spec change, that is, can we get away with throwing an
>> AnnotationFormatError where we would now do? Should we clarify the
>> spec?
>>
>
> Can you clarify which parts of the spec might need to be updated? I can't
> find anything relevant in the jls or jvms. The javadoc for AnnotatedElement
> mentions some conditions under which TypeNotPresentException is thrown:
>
> "If an annotation returned by a method in this interface contains
> (directly or indirectly) a Class-valued member referring to a class that is
> not accessible in this VM, attempting to read the class by calling the
> relevant Class-returning method on the returned annotation will result in a
> TypeNotPresentException."
>
> So throwing TypeNotPresentException when an array-valued annotation
> indirectly references an inaccessible class sounds like the right
> behaviour, and is consistent with how the implementation currently handles
> similar cases.
>

I think you answered my concerns. By the spec I meant either the Java
Language Specification or the normative parts of the javadoc. This seems to
be in line with what is currently specified.


> - Since this is a behaviorally incompatible change, how big is the
>> impact? This is of course a hard question to answer, but if one could
>> do a corpus analysis over a large code base and look for catches of
>> ArrayStoreExceptions when reflecting over annotations, that could be
>> useful. If it turns out that "a lot" of users have adopted to this
>> bug, perhaps it isn't worth fixing? On the other hand I can imagine
>> that this is so uncommon that no one catches either type of error.
>>
>
> I'm working on evaluating the impact. A review of our code base showed
> that handling ArrayStoreException is fairly uncommon. Of the instances I
> found, none of them were in code that was inspecting annotations.
>
> The next step is to start using the patch internally and see if anything
> breaks. I'll update the thread when I have results on that.
>

Great, if the experiment works out I'll help formulate a change request for
compatibility review.

cheers
/Joel