Support for jrt-fs.jar in JDK 7 would be very helpful in allowing FindBugs to run under Java 9

[mark.reinhold at oracle.com]

2014/11/20 6:23 -0800, alan.bateman at oracle.com:
> On 17/11/2014 20:23, Andrey Loskutov wrote:
>> :
>> 
>> If FindBugs needs to read the bytecode of the java.sql.Array class from JDK 9,
>> how we can address it *without* knowledge to which module it belongs? We would
>> never know the module names, but only class names from bytecode, or I'm wrong
>> here?
>> 
>> At the end, the *only* reliable way to get the bytecode of the class file for
>> a given class name from JDK 9 classes would be to use the
>> Classloader.getSystemResource("full/qualified/class/Name.class") and this will
>> mean: to analyze JDK 9 we *must* run on JDK 9?
>> 
>> I'm missing something trivial?
> 
> There is some TBD here, most likely the file system will need to provide 
> file paths to get to the class files without knowing the module name.

Yes.  Here's what we're thinking.  Paths in the "jrt:/" NIO filesystem
are currently of this form:

  /$MODULE/$PATH

where $MODULE is a module name (e.g., "java.base") and $PATH is the name
of a resource, most often the binary name of a class.

Let's add a directory level, and support two forms:

  /modules/$MODULE/$PATH
  /packages/$PACKAGE/$MODULE

where $PACKAGE is a package name (e.g., "java.lang").  A path of the
second form names a symbolic link which, in turn, points to the
directory under /modules that contains a module that defines that
package.  Example:

  /packages/java.lang/java.base -> /modules/java.base

To find java/sql/Array.class without knowing its module you look up
/packages/java.sql, which is a directory, and enumerate its entries.
In this case there will be just one entry, a symbolic link named
"java.sql", which will point to /modules/java.sql, which will contain
java/sql/Array.class.

The reason for having /package/$PACKAGE be a directory of symbolic links
to module directories rather than such a symbolic link itself is that in
some scenarios multiple modules will contain packages of the same name.

- Mark