> On 16 Dec 2024, at 14:01, David Lloyd <david.ll...@redhat.com> wrote: > > > No, they don't, because the users we are talking about are generally using a > packaging solution of some sort. They have *some* control. They don't have > *full* control unless they're ready to break things. It's like saying they > have full control over what native libraries the JDK is using. It's > *technically* true. But in practice they're not going to mess with low level > stuff like that.
Ah, so that’s what I was looking for. Clearly, -p is no more low level than -cp. But what you’re saying is that there is something that mediates between the application author and the runtime configuration — let's call that a build tool — and that build tool knows how to output -cp but not -p, even though, from the design of the JDK, the two are equally easy. That is as I suspected, and the build tool problem is one we’re aware of. We have some ideas in mind, but they don’t concern modules’ design directly. > > Yes, we are in fact talking about regular libraries, or at least, that's what > I'm talking about: regular libraries which use ServiceLoader running within > dynamic containers. According to what Alan said, a regular library that uses ServiceLoader that runs within a dynamic container would work just fine if the container uses ModuleLayers. It is only the container itself that would need to require being put on the module path. > > The application author is not using `-cp X.jar` or `-p X.jar` because in most > cases, the application author is either not launching with Java at all (i.e. > they're launching a container startup script), or they're going to launch an > uberjar or some special launcher that sets up a class loading environment and > bootstraps the application, following the instructions provided by the > container (today this might just be e.g. `java -jar startup.jar` but again, > in most cases this will be wrapped up in a script of some sort). But a script contains -p just as easily as it does -cp. Anyway, we’re getting back to the build tool problem. > > You could, and that might work in many cases, maybe even most cases. Few > third party library authors are going to do that though, especially if there > isn't a standard blob of code to do that for them. Very, very, few library authors would ever need to do this. We’re talking about, at most, one in ten thousand libraries. Only containers, really. — Ron
