modulepath spec

Alan Bateman Alan.Bateman at
Mon Dec 7 19:46:51 UTC 2015

On 07/12/2015 17:18, Stephane Epardaud wrote:
> Hi,
> When there is a -modulepath argument, is it a path in the Unix sense?
> With a list of File.pathSeparator-separated folders?
> Ceylon produces `.car` files instead of `.jar` files, but they're really
> zip files like jars. Will Java examine the file type to determine that
> it's a zip file, or will it give up at its name?
> Will there be support for module folder trees? Otherwise it pretty much
> forces Maven/Ceylon users to copy modules from a tree to a flat folder.
> That's an extra step, and it's possible, but it'd be nice if it weren't
> mandatory. I know there are several tree mappings that don't entirely
> correspond, with Ant, Maven, OSGi and Ceylon possibly differring
> slightly, so this may be difficult.
> Worst case I'll add a "ceylon export-java-mlib my.module/2.0" to create
> that mlib folder and populate it flatly and rename `.car` files to `.jar`.
Module path is conceptually very simple, it's just a sequence of sets of 

As things currently stand then the -mp argument to javac and java is a 
sequence of directories, with File.pathSeparator as the separator. The 
current implementations just looks for exploded modules or files ending 
with ".jar" files in those directories. So ".car" files will be ignored. 
There are also ".jmod" files that are also zip format but with a 
different internal structure.

The layout issue is something that Robert Scholte brought up in the last 
few days too (in the context of Maven). There are a couple of ideas 
floating around but no conclusions yet. In Robert's thread then the 
suggestion is that it allow file paths to JAR files (like class path). I 
don't think there is any conclusion on this topic yet so feedback in 
this area is timely.


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