Illegal access reflection

[aelgn]

Javers uses reflection setAccessible on types, see JaversMember:95. If you want to diff a class with non-public fields of a java.lang type (like String, Locale etc...) setAccessible is considered an illegal access operation.
This has just resulted in runtime warnings but with java 16 out the default is to deny these operations. It is still possible to override this behavior with the vm arg --illegal-access=warn, but this will be removed in a future JVM release.

A more granular way is to add the module import with vm args for each sub module in java.base --add-open.
But this will require all downstream projects to change their runtime config, which is much more cumbersome than to declare the modules in a module-info.java file in javers.

#911

Steps To Reproduce

• create diffable dto class with a private final Locale member
• launch with java 16
• diff it
  -> exception: java.lang.reflect.InaccessibleObjectException: Unable to make field private static final java.util.Map java.util.Locale.CONSTANT_LOCALES accessible: module java.base does not "opens java.util" to unnamed module @1c53fd30

static class Qwop {
    private final Locale l;
    Qwop(final Locale l) {
        this.l = l;
    }
}
...
final Javers javers = JaversBuilder.javers().build();
javers.compare(new Qwop(Locale.US), new Qwop(Locale.CHINA));

Javers' Version
5.14.0 & 6.1.0

[bartoszwalacik]

already fixed in Javers 6.0, see #911

[bartoszwalacik]

ok, I see that you have referenced #911 in your report, so why this issue?

[aelgn]

@bartoszwalacik hi, ah yes. I tested it with 6.1.0 too but still reproduced - will update the issue to reflect this

[dmitry-weirdo]

Most probably is an issue with Java 16, I have exactly the same bug, also on 6.1.0. The same code is working under Java 15.

See https://openjdk.java.net/jeps/396 for more details on the change in the JDK.

[bartoszwalacik]

Could be, it would be nice if you guys come up with a PR to fix this issue with Java 16.

[bartoszwalacik]

@dmitry-weirdo how to reproduce this issue with Java 16?

[aelgn]

@bartoszwalacik see reproducible steps in the issue above. It is using Locale as an example, but any Type from the java std lib will have the same issue if it contains private members, since javers tries to .setAccessible on them and java16 prevents that as a default. Maybe leverage the jackson serialization lib? I guess they solved it by creating custom serializers for alot of the data types in java std lib, and they also have extnesion modules for eg. Guava types.

[bartoszwalacik]

confirmed, javers doesn't work on java 16

java.lang.reflect.InaccessibleObjectException: Unable to make field private static final long java.time.LocalDate.serialVersionUID accessible: module java.base does not "opens java.time" to unnamed module @59dfd65b

[bartoszwalacik]

fixed in 6.2.1