Discussion: #MutableConfigurations

[David M. Lloyd]

Yes, and that means new modules, which means new classes.

On 07/13/2016 03:32 PM, Paul Benedict wrote:
> Question: If Configurations aren't mutable, would that necessitate
> rebuilding the Layer if you want a modified Configuration? And by
> rebuilding, I mean obtaining a new Layer instance.
>
> Cheers,
> Paul
>
> On Wed, Jul 13, 2016 at 9:30 AM, <mark.reinhold at oracle.com
> <mailto:mark.reinhold at oracle.com>> wrote:
>
>     Reference:
>     http://openjdk.java.net/projects/jigsaw/spec/issues/#MutableConfigurations
>
>     2016/3/2 18:11:34 -0800, david.lloyd at redhat.com
>     <mailto:david.lloyd at redhat.com>:
>     > It appears from what I can see in the Jigsaw code, that once a
>     > Configuration is calculated, it cannot be changed in any way,
>
>     That's true.
>
>     The overall model in the present design is that, given a set of modules,
>     you first compute a configuration, which captures the resolution of all
>     the modules' dependences in a consistent fashion.  You then instantiate
>     that as a Layer (or even more than one Layer, if you want).
>
>     This model is motivated by one of our primary goals, namely reliable
>     configuration.  Resolving a complete configuration, rather than doing
>     so incrementally, allows the early detection of missing, duplicate,
>     and conflicting dependencies.
>
>     >                                                               which
>     > makes them unsuitable for use in containers which add and remove modules
>     > at run time.  It is not clear how such containers are expected to
>     > function.
>
>     They're expected to create Layers, which can be related
>     hierarchically as
>     needed (or perhaps more generally, cf. #NonHierarchicalLayers [1]).
>
>     >            If there is a deliberate intention that the Jigsaw system
>     > will not support dynamic modification of layers/configurations
>     > (including the dynamic addition and removal of modules at run time),
>     > then that should be explicitly stated.
>
>     I don't think it makes sense for Configurations to be mutable, for the
>     reasons stated above.  It may be that the Layer concept needs to be made
>     more dynamic in certain ways, but that's a different matter.
>
>     I intend to close this issue unless there are strong objections from
>     other EG members.
>
>     - Mark
>
>
>     [1]
>     http://openjdk.java.net/projects/jigsaw/spec/issues/#NonHierarchicalLayers
>
>

-- 
- DML