Support jrt protocol

[oliverlietz]

https://openjdk.org/jeps/220

#47

[oliverlietz]

When support for bundleresource protocol was added in PAXTB-26 (#35), the case for unsupported protocols was removed (commented):

//        throw new IllegalStateException( "unsupported protocol " + classUrl.getProtocol() );

Which would have caught jrt protocol. Instead a misleading exception is thrown: Unsupported woven or system package classes.

[oliverlietz]

An additional fix for JDK 9, 10, 11 and 12 is required to remove the /modules part from the URI of a class.

See https://bugs.openjdk.org/browse/JDK-8227076

Problem

Consider the file "/modules/java.base/java/lang/Object.class" in the jrt file system. If a tool has a Path to this file then invoking its toUri method should create the URI "jrt:/java.base/java/lang/Object.class". Unfortunately, due to a bug (the bug exists in JDK 9, 10, 11, 12), it yields the URI "jrt:/modules/java.base/java/lang/Object.class". This URI cannot be used with the jrt protocol handler (URL::openStream will fail with an IOException because module "modules" is not found).

Now consider the URI "jrt:/java.base/java/lang/Object.class". If Path.of(URI) is used to create a java.nio.file.Path from this URI then the resulting jrt file path will be "/java.base/java/lang/Object.class" and so will not locate a file in the jrt file system.