Review request: exports runtime support + jdk modules converted to use exports

[Mandy Chung]

  On 6/10/11 11:23 AM, David M. Lloyd wrote:
> Keeping (additional) maps of every class seems ludicrous to me.  In 
> JBoss Modules, we do everything by package, with additional filters 
> which can be (optionally) applied for the non-common case where you 
> want to only partially export a package.  It is far more 
> memory-efficient, and empirically seems to be very fast.
>
> Note that it is important not to over-promise the contract.  If you 
> tell people that they can and should routinely pick and choose classes 
> within a package to export or not export, you're encouraging a usage 
> pattern that may not be easy to implement efficiently.
>
> By encouraging users to export whole packages only, but give the 
> option of partial package export (at a possible performance cost) you 
> are encouraging much more performant behaviors without reducing your 
> total functionality.

Agree and this is also what I am considering for optimization.  
Exporting whole packages is the common case in which we would only need 
to keep maps of package names and handle individual class exports 
differently.

Mandy