Hi Emanuel, Thanks for your reply.
On Tue, 2019-01-22 at 09:17 +0100, Emmanuel Bourg wrote: > Hi Bill, > > Le 22/01/2019 à 01:09, Bill Zaumen a écrit : > > > the following commands will cause java to crash: > > > > java -p /usr/share/java --list-modules > > java -p /usr/share/java --describe-module MODULE > > I don't think this is a use case we can reasonably support. Even if > there were no symlinks in /usr/share/java it isn't rare to see two > incompatible versions of the same jar there. If such jars are modular > 'java --list-modules' would complain too (modules aren't versioned > unfortunately). You can tag modular jar files with a version number that the command java --list-modules recognizes, but that version number is set when the JAR file is created (a jar option named --module-version sets this value). In the listing, the version number appears after an '@' symbol, but it is not used when an application is running or during compilation. Unfortunately, the java --list-modules and --describe-module options are broken: java exits after an exception is thrown instead of merely noting a conflict or listing both versions. I mentioned this as an indication of why one might want a directory for the most recent versions of these jar files. > > > > The question is whether there is a standard location for modular > > JAR files. I found a PDF file suggesting /usr/share/java/modules > > but that document is quite a few years old and I couldn't find any > > other documents corroborating that suggestion. > > What would be the benefit of installing modular jars in a common > directory such as /usr/share/java/modules? What one could put into such a directory would be symbolic links to the latest version of a modular jar file in /usr/share/java. Then that directory can appear on an application's module path. It would save application developers the effort of having to track down which jar files to use and then setting up symbolic links from some application- specific directory. If you don't want to do that, it is worth pointing out that such directories should be set up by application developers or package maintainers - otherwise people can end up spending a lot of time trying to make sure they didn't miss something. Bill
