BigDecimal / An illegal reflective access operation has occurred

[buderjoh]

If you register a BigDecimal Type

JaversBuilder builder = JaversBuilder.javers()
.registerValue(BigDecimal.class, new CustomBigDecimalComparator(2));

The following warning occurs upon startup of a spring Service

2019-11-05 15:27:47.706 INFO 22492 --- [ main] org.javers.core.JaversBuilder : mappingStyle: FIELD
2019-11-05 15:27:47.716 INFO 22492 --- [ main] org.javers.core.JaversBuilder : loading JodaAddOns ...
2019-11-05 15:27:47.747 INFO 22492 --- [ main] org.javers.core.JaversBuilder : loading GuavaAddOns ...
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.javers.common.reflection.JaversMember (/.metadata/.m2/org/javers/javers-core/5.8.4/javers-core-5.8.4.jar) to field java.math.BigDecimal.intVal
WARNING: Please consider reporting this to the maintainers of org.javers.common.reflection.JaversMember
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

[YanLinAung]

It is caused of new module system in Java 9+. Before library migrate to module system, add this run time parameter can fix for a while.
--add-opens java.base/java.math=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED

For IDEA user, Run > Edit Configuration > add VM Options.

[bartoszwalacik]

thanks @YanLinAung

[mlubavin-vg]

Hi everyone, is there a plan to address this in the code so that we don't have to add the "--add-opens" exception? Note the warning says "All illegal access operations will be denied in a future release"

[bartoszwalacik]

Could you reproduce this issue in a new test case?

[mlubavin-vg]

It appears on my application startup as soon as I add the BigDecimal line to:
private final static Javers differ = JaversBuilder.javers()
.withListCompareAlgorithm(ListCompareAlgorithm.LEVENSHTEIN_DISTANCE)
.registerValue(BigDecimal.class, new BigDecimalComparatorWithFixedEquals())
.withMappingStyle(MappingStyle.BEAN)
.build();

it will take me some time to get familiar with how to add a test case

[YanLinAung]

Hi everyone, is there a plan to address this in the code so that we don't have to add the "--add-opens" exception? Note the warning says "All illegal access operations will be denied in a future release"

In that case, javers need to implements proper way of java 9 module.
In short, it need to add meta data module file module-info.java in library jar file, which define java.math and java.lang module is needed to run this libray.

module javers-core {
// other module related info
    opens java.lang;
    opens java.math;
}

Ref: Java 9 Modularity

[bartoszwalacik]

this has rather low priority for me, feel free to contribute a PR

[mlubavin-vg]

A bit more info - this happens when Javers is registering the BigDecimal class and ClassAnotationsScan.findAllGetters() goes through all getters and creates JaversGetter objects for them, and for any method that it finds that is private and looks like a getter, it calls JaversMember.setAccessibleIfNecessary() which looks like:

void setAccessibleIfNecessary(Member rawMember) {
        if (!isPublic(rawMember)) {
            ((AccessibleObject) rawMember).setAccessible(true); //that's Java Reflection API ...
        }
    }

the issue specifically with BigDecimal.isPowerOfTen() is not a real getter and Javers doesn't need to do this, ideally it would ignore this method isPowerOfTen(). Is there any way to do this in the Javer's codebase?

[bartoszwalacik]

BigDecimal is mapped to ValueType by default, so its class shouldn't be analyzed to find getters and setters. Did you intentionally mapped it to ValueObejct?

[mlubavin-vg]

Thank you for looking once more!

We register it like this:
.registerValue(BigDecimal.class, new BigDecimalComparatorWithFixedEquals())
as it is documented to do at https://javers.org/documentation/diff-configuration/

[bartoszwalacik]

okay, I will fix it in 6.0