setAccessible() alternative with Jigsaw
manovotn at redhat.com
Mon Apr 3 12:17:21 UTC 2017
Thanks for suggestion!
I'll definitely look at that direction and see if it suffices.
----- Original Message -----
> From: "Alan Bateman" <Alan.Bateman at oracle.com>
> To: "Matej Novotny" <manovotn at redhat.com>, jigsaw-dev at openjdk.java.net
> Cc: "Martin Kouba" <mkouba at redhat.com>
> Sent: Friday, March 31, 2017 4:28:34 PM
> Subject: Re: setAccessible() alternative with Jigsaw
> On 31/03/2017 14:46, Matej Novotny wrote:
> > Hello,
> > I work on Weld, context dependency injection framework.
> > Long story short - we need to generate proxies for classes - bytecode which
> > we then "register" with the class loader using
> > java.lang.ClassLoader#defineClass.
> > Obviously, for this you need reflections - to load java.lang.ClassLoader,
> > then to load the method itself, and most importantly, to make the method
> > accessible cause it's `protected`.
> > In JDK 9, this blows up as soon as you try to make the method accessible
> > (invocation of setAccessible).
> > Fair enough, but what is the "legitimate" alternative?
> > I know I can --add-opens / --add-opens / --permit-illegal-access
> > But all those just bypass the checks and don't really solve it. I am
> > looking for an intended way to do such stuff.
> > I am pretty sure there are many frameworks which need to do this in one way
> > or the other.
> > So far I have found workarounds which involve using `sun.misc.Unsafe`
> > because there (for some reason) you are allowed to invoke setAccessible().
> > Is this the official intended backdoor? Because it sure does not look any
> > safer/cleaner solution than the original one...
> As Claes pointed out, look at Lookup.defineClass. It shouldn't be too
> hard to imagine a future update of the CDI spec where there a select
> variant that includes a Lookup to the target class with the @Inject
> annotation. When using Weld outside of a container then I think there is
> main code that obtains the WeldContainer and selects the types, that
> might be a suitable place to extend to provide the Lookup to the library.
> MethodHandles.privateLookupIn might also be useful to know about, esp.
> starting out when you don't want to make API changes and where the
> user's code is on the class path or in open modules.
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