Request for review: 8004698: Implement Core Reflection for Type Annotations (original) (raw)

Peter Levart peter.levart at gmail.com
Sat Jan 19 17:11:48 UTC 2013

Hi Joel,

I see, there is a dilema how to cache type annotations. To satisfy single-annotation-returning methods and repeating annotation logic, a HashMap would be a logical choice, but it has much bigger footprint than simple arrays of annotations...

I experimented with an idea of using a special purpose immutable Map implementation:

https://github.com/plevart/jdk8-tl/blob/anno-map/jdk/src/share/classes/sun/reflect/annotation/UniqueIndex.java

and:

https://github.com/plevart/jdk8-tl/blob/anno-map/jdk/src/share/classes/sun/reflect/annotation/AnnotationMap.java

This is just a preview. I still have to create some tests to see how it compares to HashMap. Being an immutable wrapper for a single array of annotations it has a nice feature that a reference to it can be passed to other threads via a data race with no danger of data inconsistency, which simplifies caching mechanisms and helps scalability. Might even be a space-saving replacement for existing HashMaps of annotations. Depending on performance, of course. What do you think? Is it worth pursuing this further?

Regards, Peter On Jan 17, 2013 5:24 PM, "Joel Borggrén-Franck" <joel.franck at oracle.com> wrote:

Hi,

Here is a webrev for core reflection support for type annotations: http://cr.openjdk.java.net/~jfranck/8004698/webrev.00/ This code is based on the tl/jdk repository, but in order to run the tests you need a javac with type annotations support and also a recent copy of the VM that includes this change set: http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/rev/35431a769282(This also means this code can't be pushed until all supporting pieces are in place.) Type annotations are still a bit of a moving target so there will be follow up work on this. There is no caching of annotations in this version and I am not sure how we want to do the space/time trade of for type annotations. cheers /Joel

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