Module Layers and platform architectures

[David Lloyd]

On Fri, Dec 20, 2024 at 7:52 AM Alan Bateman <alan.bateman at oracle.com>
wrote:

> On 19/12/2024 20:54, David Lloyd wrote:
>
> I wonder: would this also allow services to be found across the layer
> boundaries? For example, an API from a layer that the application can see
> uses a service provided by an implementation in a layer that the
> application cannot see?
>
>
> Service loading is specified to work across module layers. Code in a child
> layer might invoke ServiceLodaer to locate providers in its own and parent
> layer, assuming the service is in the parent layer. Code in the parent
> layer might invoke ServiceLoader to locate providers in the child layer. If
> everyone were in the same room in front of a white board then this would be
> easy to draw.
>
> An important point about service providers is that they be fully
> encapsulated. So while many modules can "see" the service provider module,
> where "see" means visibility, then nobody can access.
>
> -Alan
>

I see, so it seems that there still would have to be a parent-child
relationship (possibly transitive) between the layer containing the service
consumer and the layer containing the service provider, correct? And the
provider must be in a parent layer. I.e. using `jlink` doesn't magically
make this constraint disappear, which is what I thought was being implied.

Thanks.

-- 
- DML • he/him
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