JDK 8 (initial) RFR for JDK-8005294 : Consider default methods for additions to AnnotatedElement

[Peter Levart]

Hi Joe,

I propose some "premature" optimization for 
AnnotatedElement.getDeclaredAnnotationsByType(). This implementation 
calls either getDeclaredAnnotatios() once or 
getDeclaredAnnotation(Class) once, depending on whether the annotation 
type is repeatable or not respectively (this check also requires a 
getDeclaredAnnotation() call, but I propose to extend AnnotationType in 
the future to provide with cached containerClass directly). Also, it is 
about 7x faster to use annotationClass.isInstance(ann) to check for the 
type of annotation instead of ann.annotationType() == annotationClass 
which goes through annotation Proxy, etc...

Here it is:

     default <T extends Annotation> T[] 
getDeclaredAnnotationsByType(Class<T> annotationClass) {
         Objects.requireNonNull(annotationClass);
         Repeatable repeatable = 
annotationClass.getDeclaredAnnotation(Repeatable.class);

         // non-repeatable: just delegate to getDeclaredAnnotation and 
return wrapped result
         if (repeatable == null) {
             T ann = getDeclaredAnnotation(annotationClass);
             @SuppressWarnings("unchecked")
             T[] result = (T[]) Array.newInstance(annotationClass, ann 
== null ? 0 : 1);
             if (ann != null) result[0] = ann;
             return result;
         }

         // repeatable: iterate all declared annotations, find directly 
and indirectly present
         // and also determine the order (directlyPresentFirst)...
         Class<? extends Annotation> containerClass = repeatable.value();
         T directlyPresent = null;
         T[] indirectlyPresent = null;
         boolean directlyPresentFirst = false;
         for (Annotation ann : getDeclaredAnnotations()) {
             if (directlyPresent == null && 
annotationClass.isInstance(ann)) {
                 directlyPresent = annotationClass.cast(ann);
                 if (indirectlyPresent != null) {
                     break;
                 }
             } else if (indirectlyPresent == null && 
containerClass.isInstance(ann)) {
                 indirectlyPresent = AnnotationSupport.getValueArray(ann);
                 if (directlyPresent != null) {
                     directlyPresentFirst = true;
                     break;
                 }
             }
         }

         // concatenate directlyPresent and indirectlyPresent annotations
         @SuppressWarnings("unchecked")
         T[] result = (directlyPresent == null && indirectlyPresent != null)
                      ? indirectlyPresent
                      : (T[]) Array.newInstance(annotationClass,
                          (directlyPresent == null ? 0 : 1) +
                          (indirectlyPresent == null ? 0 : 
indirectlyPresent.length));

         if (directlyPresent != null) {
             if (indirectlyPresent == null || indirectlyPresent.length 
== 0) {
                 result[0] = directlyPresent;
             } else {
                 result[directlyPresentFirst ? 0 : 
indirectlyPresent.length] = directlyPresent;
                 System.arraycopy(indirectlyPresent, 0, result,
                     directlyPresentFirst ? 1 : 0, 
indirectlyPresent.length);
             }
         }

         return result;
     }



Regards, Peter

On 10/25/2013 10:40 AM, Joe Darcy wrote:
> Hi Joel and Peter,
>
> On 10/24/2013 07:10 AM, Peter Levart wrote:
>> Hi Joe,
>>
>> I see two problems with the implementation in 
>> *AnnotatedElementSupport*. The first is the treatment of 
>> declared-only annotations where the code returns either directly 
>> present or in-directly present repeatable annotations, but not both. 
>> So in the following example:
>>
>> @Ann(1)
>> @AnnCont({@Ann(2), @Ann(3)})
>>
>> it will only return [@Ann(1)], but I think it should return all of 
>> them [@Ann(1), @Ann(2), @Ann(3)] - does the spec. define that?
>>
>
> [snip]
>
> From your feedback (and a closer reading of the specifciation), I've 
> reworked the specifications and implemenations of the default methods 
> for get[Declared]AnnotationsByType:
>
> http://cr.openjdk.java.net/~darcy/8005294.2/
>
> Tests still need to be written, but this implementation should be much 
> closed to what is needed.
>
> Thanks,
>
> -Joe