JEP 330 and MemoryClassLoader.getResourceAsStream

[John Rose]

On Aug 24, 2018, at 5:47 PM, Jonathan Gibbons <jonathan.gibbons at oracle.com> wrote:
> 
> The worker class that performs the source-file launcher work is
> passed the name of the source file as an argument, but it is not
> passed down to the source code or class file in any way.
> 
> 
OK, so that's not a workaround anyway.

As a general matter regarding script files, they often make
use of $0 to either refer to themselves (for error reporting)
or to access side files.  The JEP points out that a shell script
wrapper can be used to adjust the launching of the JVM,
and it occurs to me that (1) this can be used to push the
origin (shell "$0") into the Java program, and (2) the JEP
allows a single file to be launched by both /bin/sh and the
JVM—with a little finicking.  Here's a proof of concept:

http://cr.openjdk.java.net/~jrose/scripts/myshebang.txt

The trick is to make the initial segment of the shebang file
acceptable to both /bin/sh and the JVM's source-file reader.
I was mildly surprised to find that it can be done with a mix
of quotes and comment delimiters (in both languages).

Anyway, the above POC might be useful to someone
who wants to use the JVM's new source-file mode for
a script that needs to refer to itself. 

I also believe that this shouldn't require a workaround at all,
but should be somehow native to the JVM, as $0 is to
the shell.  So I also filed JDK-8209963 to track this RFE.

— John

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