[External] : Re: Inconsistency with service loading by layer or by class loader

[David Lloyd]

On Tue, Dec 17, 2024 at 10:57 AM Alan Bateman <alan.bateman at oracle.com>
wrote:

> On 17/12/2024 14:21, David Lloyd wrote:
>
> :
>
>
> However, to give a counter-example, `Module` has `addUses` as well. But if
> I want to call `addUses` on behalf of a module I've defined, there is no
> corresponding `ModuleLayer.Controller` method so I do have to define the
> extra class, and that's a bit silly. This is an example of an easy
> enhancement that would not affect the integrity of the platform, would not
> significantly increase maintenance burden (since the logic would be nearly
> identical to its sibling methods), and would be easy to achieve.
>
>
> Module::addUses is for cases where code may need to create a SL that loads
> a service that wasn't known to this module at compile time.
>
> ML.Controller is the equivalent of the --add-exports, --add-opens,
> --add-reads command line options for the boot layer. There was little
> motive to work through the implications of --add-uses and --add-provides
> and the ML.Controller equivalents at the time. The exception is the agent
> case where instrumentation may augment the services used (or provided).
>
> Time has passed and I can only think of one request for --add-uses has
> come up. That request didn't go very far because service binding augments
> the module graph during resolution. A CLI option (or ML.Controller
> equivalent) can only work reflectively, which is post-resolution. This is
> of course too late for what the group requesting this wanted. It hasn't
> been re-examined since then at least not to my knowledge.
>

I was using it as more of an example about how a thing may be possible and
allowed by the platform, and thus is achievable, yet not specifically
presented with a convenient API. That said, I've opened
https://bugs.openjdk.org/browse/JDK-8346439 as a way to continue the
discussion, framed as a specific feature request which covers what we need,
and it does in fact include an `addUses` method. Hopefully the conversation
there will be more productive, being based on specific capabilities rather
than hypotheticals.

-- 
- DML • he/him
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