Summary

Changing the jlink --compress flags to align with the jmod tool.

Problem

The jlink compression flags are currently arbitrary values (0|1|2) and correspond to unrelated types of compression (none, string sharing, zip). This is out of alignment with the jmod tool, which uses standard unix-style zip compression levels.

Solution

Deprecate the existing "none" (0), "string sharing" (1), and zip (2) flag values. Add support for UNIX-style zip-[0-9] flags. Newly supported values will be prepended by "zip-" and be in the numeric range 0-9. Eg "zip-0, zip-1, zip-2, ... etc."

Specification

Standard usage from --list-plugins

  --compress <compress>             Compression to use in compressing resources:
                                    Accepted values are:
                                    zip-[0-9], where zip-0 provides no compression,
                                    and zip-9 provides the best compression.
                                    Default is zip-6.

Help Usage:

  --compress <compress>             Compression to use in compressing resources:
                                    Accepted values are:
                                    zip-[0-9], where zip-0 provides no compression,
                                    and zip-9 provides the best compression.
                                    Default is zip-6.
                                    Deprecated values to be removed in a future release:
                                    0:  No compression. Equivalent to zip-0.
                                    1:  Constant String Sharing
                                    2:  Equivalent to zip-6.

When jlink is invoked with --compress 0 or 1 or 2 option, a warning will be emitted about this deprecated value may be removed in a future release.