Proposal: Allow illegal reflective access by default in JDK 9

Peter Levart peter.levart at
Fri May 19 12:02:38 UTC 2017

Hi Alan,

On 05/19/2017 01:05 PM, Alan Bateman wrote:
> On 19/05/2017 10:48, Volker Simonis wrote:
>> :
>>  From my understanding, at run-time, "open" implicates "exports" (i.e.
>> if a module M1 opens a package P for some other module M2 it also,
>> implicitly exports P to M2). The  "big kill switch" in both, its old
>> and in the newly proposed form, usually only refers to "enabling
>> reflective access" but doesn't explicitly mentions that it will also,
>> implicitly export the respective packages. Also, the usage of the
>> "kill switch" only produces warnings for reflective accesses which are
>> enabled by the option itself (and not at the same time, explicitly
>> allowed by --add-opens directives). But it doesn't warn about the
>> simple, non-reflective accesses to packages which are implicitly
>> exported by the kill switch as well.
> You are correct. If the package is opened at run-time:
> 1. All public members of public types in the package are accessible. 
> This includes both static and reflective access.
> 2. All members of all types in the package can be reflected on when 
> using setAccessible or privateLookupIn.
> The reason you don't get warnings with the static references is 
> because access checking in the VM is very low level and we 
> deliberately decided to avoid the invasive changes needs to report 
> warnings here. The latest proposal does not change this, it's just too 
> late in JDK 9 to take on this surgery.
> -Alan

Ok, I can understand that such interpretation of "opens" is necessary 
for JDK 8 compatibility story. If something is "open" then it behaves 
exactly like in JDK 8 or before (apart from compilation) regardless of 
packages being exported or not. But from consistency perspective, 
explicit "exports" should be required just like "public" modifiers are 
required to access members without .setAccessible(true) or without 

This would not hinder the ability for frameworks to access members. It 
would just require them to call .setAccessible(true)/.privateLookupIn() 
in more places, but would be safer too as "suppressAccessChecks" 
permission would be required for non-exported package access like it is 
required for "private" members.

I'm sorry I haven't noticed this before. It is probably to late to 
change this now. Was this deliberate choice (to promote compatibility 
with existing code)?

Regards, Peter

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