Exporting - the wrong default?

[Remi Forax]

----- Mail original -----
> De: "dalibor topic" <dalibor.topic at oracle.com>
> À: jigsaw-dev at openjdk.java.net
> Envoyé: Mercredi 27 Juillet 2016 14:39:05
> Objet: Re: Exporting - the wrong default?

> On 26.07.2016 18:42, Stephen Colebourne wrote:
>> In many projects
>> packages change names frequently during development, everything is
>> open and locking stuff down is the last thing on peoples minds. While
>> this of course leads to slightly less secure software, it does achieve
>> *business value*.
> 
> I would recommend Cristina Cifuentes presentation "Are We Ready for
> Secure Languages?" from the recent Curry On conference, of which a
> recording is available at https://www.youtube.com/watch?v=-fC975HLhyc
> for some less anecdotal thoughts on the business value of slightly more
> secure software.
> 
> It even touches briefly on the utility of modules in JDK 9.

Interesting talk !

to get back to our issue,
there are 4 possibilities when exporting a package, for a public type,
(1) don't see it at compile time, don't see it at runtime (can't reflect on it)
(2) don't see it at compile time, see it at runtime (this is the OSGI/JBoss model for not exported)
(3) see it at compile time, may not exist at runtime (so be prepared to get an exception then)
(4) see it at compile time and see it at runtime

The default can not be (3) because it's a corner case, it can not be (4) because in that case we lost the 'strong encapsulation' that a module should provide by default, so the default can be either (1), either (2) or to force the user to choose between (1) and (2) when declaring a module.

The problem with (1) is that:
 - it makes most of the code that use reflection not working (and as Stephen said, at lot of codes use reflection (or bytecode generation)),
 - it will slow down the adoption of jigsaw (not jdk9 which will be run with a -classpth) but the modularization of the already existing jars, so we will end up with a module system which will be not used or worst, some jars will be modularized, some will not and we will be in the same sad state of Python now with 2 mostly compatible worlds *. 

The problem of letting users to choose is that the hope to educate them by forcing them to make their own choices will be destroyed because in practice IDEs will chose for them (e.printStackTrace() anyone ?)

So the only valid choice seem to be (2), which
- still enable JDK and application server implementation modules to not export some types at runtime, so the security will improve and by example, it will avoid most of the access control bugs Christina talk about.
- the default behavior will make the move to convert their jars to modularized jars easier because people will not conflate the problem of the modularization itself with the problem of the access control at runtime.
- everybody will be happy and we will not see angry ponies on slides about Java 9. 

> 
> cheers,
> dalibor topic

cheers,
Rémi

* Or, at some point, someone will also find that by using jlink and creating its own module Layer, he can have a 'Java' launcher with its own defaults.