Instrumentation.redefineModule -- extraPackages argument?

Remi Forax forax at
Sat Mar 11 13:56:06 UTC 2017

Hi Mickael,
i do not think you can use addPackage() directly because Module.getResourceAsStream() will not work on the resources associated with a package added by addPackage.

The code of Module.getResourceAsStream() currently supposes that only proxies can add private packages, and proxies can not add new resources.


----- Mail original -----
> De: "Michael Rasmussen" <michael.rasmussen at>
> À: "jigsaw-dev" <jigsaw-dev at>
> Envoyé: Samedi 11 Mars 2017 14:31:08
> Objet: Re: Instrumentation.redefineModule -- extraPackages argument?

> Looking a bit closer in the source, and not just the public API, I did find
> addPackage in the private API part of Module (and the corresponding
> native JVM_AddModulePackage).
> So the capability for dynamically evolving a named module is present,
> supported, and utilized by Proxy!
> Adding a new package isn't just for use-cases of development, modules that
> dynamically expand have other use cases as well, for instance classes
> dynamically created at runtime based on factors that cannot be determined
> at compile time (well, proxy is a good example of that, and as mentioned
> already does exactly this!).
> Also, as Jochen pointed out, setting up a new classloader with new layers
> and modules etc, is a non-trivial task, just for adding a new package --
> especially considering the functionality is present, just not public.
> sure, from JRebel's point of view, a method being non-public isn't exactly
> an obstacle for us; but "normal" frameworks don't have that luxury.
> /Michael

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