Proposal: Allow illegal reflective access by default in JDK 9

Uwe Schindler uschindler at
Thu May 18 16:08:21 UTC 2017

Hi Mark,

To me this proposal is a Desaster. I'd not do this. Buggy software may use the big kill switch.

Sorry Red Hat guys: that's what you triggered with your "no". Bravo! I am impressed!

Sorry Gradle, the worst design in software about environment variables made the whole world again as unsafe as before. We will again see ongoing security updates in Java just fix fix holes that are opened by default. When I have read the mails yesterday, I thought: do you really want to build your software with such a broken tool and it's ecosystem? Can you not just tell the plug-in authors to fix their shit and fix your API to work correct?

Amazon S3 software dilettantes: Fix your EC2 security software to not undermine the Java security system! I can bring many more: Don't do that in security relevant tools or build systems many people rely on!

Today is the worst day in Java history.


Am 18. Mai 2017 16:48:40 MESZ schrieb mark.reinhold at
>Over time, as we've gotten closer and closer to the JDK 9 GA date, more
>and more developers have begun paying attention the actual changes in
>this release.  The strong encapsulation of JDK-internal APIs has, in
>particular, triggered many worried expressions of concern that code
>works on JDK 8 today will not work on JDK 9 tomorrow, yet no advance
>warning of this change was given in JDK 8.
>To help the entire ecosystem migrate to the modular Java platform at a
>more relaxed pace I hereby propose to allow illegal reflective access
>from code on the class path by default in JDK 9, and to disallow it in
>a future release.
>In short, the existing "big kill switch" of the
>option [1] will become the default behavior of the JDK 9 run-time
>though without as many warnings.  The current behavior of JDK 9, in
>illegal reflective-access operations from code on the class path are
>permitted, will become the default in a future release.  Nothing will
>change at compile time.
>In detail, the recently-introduced `--permit-illegal-access` option
>be replaced by a more-general option, `--illegal-access`.  This option
>will take a single keyword parameter, as follows:
>  `--illegal-access=permit`
>    This will be the default mode for JDK 9.  It opens every package in
>    every explicit module to code in all unnamed modules, i.e., code on
>    the class path, just as `--permit-illegal-access` does today.
>   The first illegal reflective-access operation causes a warning to be
>  issued, as with `--permit-illegal-access`, but no warnings are issued
>    after that point.  This single warning will describe how to enable
>    further warnings.
>  `--illegal-access=warn`
>    This causes a warning message to be issued for each illegal
>    reflective-access operation.  This is equivalent to the current
>    `--permit-illegal-access` option.
>  `--illegal-access=debug`
>    This causes both a warning message and a stack trace to be shown
>    for each illegal reflective-access operation.  This is equivalent
>    to combining today's `--permit-illegal-access` option with
>    `-Dsun.reflect.debugModuleAccessChecks`.
>  `--illegal-access=deny`
>    This disables all illegal reflective-access operations except for
>    those enabled by other command-line options, such as `--add-opens`.
>    This will become the default mode in a future release.
>  - The proposed default mode enables the run-time system to issue a
>    warning message, possibly at some time long after startup, without
>    having been explicitly requested to do so.  This may be a surprise
>    in production environments, since it's extremely unusual for the
>  run-time system to issue any warning messages at all.  If the default
>   mode permits illegal reflective access, however, then it's essential
>    to make that known so that people aren't surprised when this is no
>    longer the default mode in a future release.
>  - Warning messages in any mode can be avoided, as before, by the
>    judicious use of the `--add-exports` and `--add-opens` options.
>  - This proposal will, if adopted, require adjustments to JEP 260,
>   "Encapsulate Most Internal APIs" [2].  APIs that are internal to the
>    JDK will still be strongly encapsulated from the standpoint of code
>  in modules, whether those modules are automatic or explicit, but they
>  will not appear to be encapsulated at run time from the standpoint of
>    code on the class path.
>- When `deny` becomes the default mode then I expect `permit` to remain
>    supported for at least one release, so that developers can continue
>  to migrate their code.  The `permit`, `warn`, and `debug` modes will,
>   over time, be removed, as will the `--illegal-access` option itself.
>    (For launch-script compatibility the unsupported modes will most
>    likely just be ignored, after issuing a warning to that effect.)
>  - This change will not magically solve every JDK 9 adoption problem.
>  The concrete types of the built-in class loaders are still different,
>  `rt.jar` is still gone, the layout of a system image is still not the
>    same, and the version string still has a new format.
>- Mark

More information about the jigsaw-dev mailing list