Patch-module with dynamic layer creating.

[Alan Bateman]

On 12/10/2018 21:57, Alex Sviridov wrote:
> Hi Alan,
>
> Thank you for detailed explanation. It is great that we have API that allows to implement
> such features. However, what I suggest is a little different. I am speaking about using
> existing code for such features.
>
> I think this way - firstly, we can do write the same code many times. We can, but we
> don't want. Secondly if we pass parameters to JPMS via JVM options to configure boot
> layer, it would be great if we had possibility to pass the same parameters to configure a
> custom layer without writing a line of code and use existing JDK code.
>
> Of course this is my person opinion. It is interesting to hear what other developers think.
>
I'm skeptical on both the feasibility and desirability of going there. 
If a container is creating module layers at runtime then it is arranging 
which modules are observable, e.g. it may choose one version of JAX-RS 
for one configuration/layer, and another version for another 
configuration/layer. In your scenario it may want to patch or augment 
one of these modules. I don't think you can easily express this on the 
command line as there isn't anything to identify the layer than you want 
to adjust. Also module names may not be sufficient in the face of a 
container wanting to make available different versions. It's also 
possible that a container would want to opt out from this as it would 
want full control of which modules to resolve.

-Alan