"Scanning" module contents

[Alan Bateman]

On 30/12/2014 17:18, Roman Shevchenko wrote:
> Hi Rémi,
>
> do you by any chance know if there is a legitimate way of doing the 
> same from another JVM, not the one the scanning code is loaded into? 
> I've seen your jigsaw-jrtfs, but that patch() part of it feels hacky 
> and (if I got it right) does not scale to more then one JDK instance.
>
At this time you can get a reference to jrt:/ for the current runtime 
(as per Remi's reply and example).

It is also possible for a tool running on JDK 8 to create a jrt:/ that 
provides access to the contents of a JDK 9 runtime image. For this to 
work then it requires putting $JDK9/jrt-fs.jar on the class path 
(jrt-fs.jar is intended to be a supported interface, see JEP 220 [1]). 
Alternatively, for the IDE-like case where you target a runtime image 
selected by the user then you can use code such as following:

          String jdkHome = "/yonder/jdk9";

          URL url = Paths.get(jdkHome, "jrt-fs.jar").toUri().toURL();
          URLClassLoader loader = new URLClassLoader(new URL[] { url });
          FileSystem fs = FileSystems.newFileSystem(URI.create("jrt:/"),
Collections.emptyMap(),
                                                    loader);
          Path top = fs.getPath("/");
Files.walk(top).filter(Files::isRegularFile).forEach(System.out::println);

In time then we expect to improve on this so that jrt-fs.jar is loaded 
automatically from the target runtime image. That will allow a tool 
running on one JDK 9 runtime image to access the contents of another JDK 
9 runtime image for example. There are a few issues to sort out before 
we can get there.

-Alan

[1] http://openjdk.java.net/jeps/220