Applications for --limit-modules?

Alan Bateman Alan.Bateman at
Sat Jan 28 17:22:31 UTC 2017

On 28/01/2017 14:34, Nicolai Parlog wrote:

>   Hi!
> I'm experimenting with --limit-modules and am not quite sure what
> exactly it is good for.
It's wonderful for testing.  Think `java --limit-module java.base -cp 
...` to test an application running with just java.base rather than 
creating a minimal run-time image with jlink.

> But before I come to that I want to make sure
> I got it right, because I had to figure this out by trial and error
> (the current output of java -? is not that helpful)
     --limit-modules <modulename>[,<modulename>...]
                   limit the universe of observable modules

I guess this could be expanded a bit but it might be too much to attempt 
to include text on how it interacts with other options.

> I came to the conclusion that only the modules given to
> --limit-modules will be root modules for the resolution process. This
> explicitly excludes the initial module so unless it is listed as well
> or a transitive dependency of one of the ones that were, the command
> will fail right away.
The set of observable modules is the the transitive closure of the 
modules you specify to --limit-modules plus any modules that you specify 
to --add-modules or -m (for the main/initial module). There's more on 
JEP 261 on this if you need it.


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