Why the annotation processing API ?

[joe darcy]

On 5/25/2016 9:32 PM, Stéphane NICOLAS wrote:
> Hi folks,
>
> I know a simple mail like this generally has very minimal value. But 
> still, it's been around 2-3 years now that I work on Android, doing a 
> lot of work around reflection and annotation processing.
>
> I don't like the annotation processing API. I still find every concept 
> hard to remember, and it is always taking time to get immersed into it 
> for a new project.
>
> Thus, I don't understand, very humbly and very honestly, why this API 
> even exists. Why can't we simply use reflection-like APIs ? It would 
> not be that complex to expose an API that looks like reflection 
> (read-only of course, no new instance of classes, to method calls or 
> setting/getting field values, just the discovery part).
>

The core reflection API has a number of serious design flaws, for a 
detailed discussion see

Gilad Bracha and David Ungar. Mirrors: Design Principles for Meta-level 
Facilities of Object-Oriented Programming Languages.  In Proc. of the 
ACM Conf. on Object-Oriented Programming, Systems, Languages and 
Applications, October 2004.
http://www.bracha.org/mirrors.pdf

With the benefit of hindsight, these problems were avoided in the 
language model portion of the annotation processing API, javax.lang.model.

Cheers,

-Joe