Multiple versions of a non-exported dependency
Alan.Bateman at oracle.com
Thu Sep 1 13:59:27 UTC 2016
On 01/09/2016 13:29, David M. Lloyd wrote:
> It seems like there is no good reason why the application modules
> aren't loaded with classloader-per-module now. The platform stuff
> could all be in one, but the application stuff? Problems like this
> are going to come up a lot otherwise; let's consider making that change.
If we were just dealing with a graph of explicit modules they it may be
an option, assuming you get over all the issues that arise when
arranging visibility this way. You might remember "module mode" in the
original exploratory phase of Project Jigsaw for example.
The issue is of course that there is lot more in picture, esp. when you
have the unnamed module (= class path) reading all modules, also
automatic modules that bridge to the class path (and so read the unnamed
module). Then add upgradable modules into the picture, ... and you will
quickly start to see there is a lot more to this, not to mind the risk
of circular delegation.
So I think what we have ended up with sane and not difficult to explain.
It favors migration and good interop over green field. Sure, there will
be periodic complaints when people try to deploy modules with
overlapping packages on the application module path. Anyone using Maven
Shade Plugin and the like can continue to do this. Finally, it's not
hard to create your own "launcher" that instantiates the configuration
with Layer.defineModulesWithManyLoaders if you really want.
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