Richard S. Hall wrote:
> Bill Shannon wrote:
>> Richard S. Hall wrote:
>>>> Since ServiceLoader is loading the class, and ServiceLoader isn't in
>>>> the
>>>> same bundle/module as the class, seems to me it shouldn't be able to
>>>> access the class. If the JVM were enforcing module boundaries,
>>>> wouldn't
>>>> this fail if the implementation class isn't exported?
>>>
>>> Conceptually, that is accurate, but OSGi cannot do such enforcement.
>>> For OSGi, there is only one class loader that is used to load classes
>>> from a bundle, so if you get a reference to the class loader then you
>>> can load any class from the bundle that is on its bundle class path.
>>> Typically, bundles should not be loading classes this way and should
>>> only use their own class loader which will delegate appropriately.
>>>
>>> In the long run, if we get VM support for module visibility, then yes
>>> this could be an issue, but for me it is probably more a sign of how
>>> the META-INF/services approach is broken with respect to modularity.
>>
>> That's why I suggested "should" rather than "must". Even if you don't
>> export it today, it will probably work.
>>
>> But if you envision a future where the JVM supports modules, I think
>> you're
>> going to need to export such classes.
>
> Right. Hypothetically, if ClassLoader.loadClass() is modified in the
> future to return a module private class to member classes of the module
> and an exception for non-member classes, then you would have an issue.
So, are we back to ... you *should* export such implementation classes
so that ServiceLoader can load them?
>> If ServiceLoader isn't the right approach, what would be a more modular
>> approach?
>
> Well, I won't claim to have a full grasp of all of the issues around
> this, since I have only looked at it in passing. I think the
> ServiceLoader concept is an improvement in Java 6, since it at least
> attempts to centralize lookups, but I am not sure about its capabilities
> for hooking into the lookup.
It's all class loader based.
> I think this would be a great topic about which to have a detailed
> discussion.
Great! When and where? :-) Let's include the JDK guys...
(I know, this is not a high priority item right now...)