ClassCastException: MissingProperty cannot be cast to java.lang.Double

[mdii]

Hello, we have a use case that needs a custom comparator for Double values. However in some cases we get the following exception:

java.lang.ClassCastException: org.javers.core.metamodel.property.MissingProperty cannot be cast to java.lang.Double
	at org.javers.core.metamodel.type.CustomValueComparatorNullSafe.equals(CustomValueComparatorNullSafe.java:29)
	at org.javers.core.metamodel.type.PrimitiveOrValueType.equals(PrimitiveOrValueType.java:32)
	at org.javers.core.diff.appenders.ValueChangeAppender.calculateChanges(ValueChangeAppender.java:34)
	at org.javers.core.diff.appenders.ValueChangeAppender.calculateChanges(ValueChangeAppender.java:10)
	at org.javers.core.diff.DiffFactory.appendChanges(DiffFactory.java:153)
	at org.javers.core.diff.DiffFactory.appendPropertyChanges(DiffFactory.java:143)
....

I managed to reproduce it in the following test case.

class CustomValueComparatorCase extends Specification {
    class Parent {}

    class Child1 extends Parent {
        String prop1
    }

    class Child2 extends Parent {
        Double prop2
    }

    class Container {
        Map<String, Parent> map = new HashMap<>()
    }

    class CustomDoubleComparator implements CustomValueComparator<Double> {
        @Override
        boolean equals(Double a, Double b) {
            return round(a) == round(b)
        }

        @Override
        String toString(Double value) {
            return round(value).toString()
        }

        private BigDecimal round(Double val) {
            return NumberUtils.toScaledBigDecimal(val, 4, RoundingMode.HALF_UP)
        }
    }

    def "should compare map values using their concrete type"() {
        given:
        def javers = JaversBuilder.javers()
                .registerValue(Double.class, new CustomDoubleComparator())
                .build()

        when:
        Parent c1 = new Child1(prop1: "Hi")
        Parent c2 = new Child2(prop2: 1.2)


        Container container1 = new Container()
        container1.map.put("key", c1)

        Container container2 = new Container()
        container2.map.put("key", c2)

        def diff = javers.compare(container1, container2)

        then:
        diff.changes.size() > 0

        println(diff.changes)
    }
}

It seems that Javers sees the values in the map as Parent type not the concrete type.
If I change Map<String, Parent> map to Map<String, Object> map then the test passes.
If I keep Map<String, Parent> map and compare the maps directly like javers.compare(container1.map, container2.map) then the test passes.

Would it be possible to avoid this exception?

[bartoszwalacik]

Hi, please push this case here , https://github.com/javers/javers/tree/master/javers-core/src/test/groovy/org/javers/core/cases
as a failing test case

[mdii]

Done #936

[bartoszwalacik]

thanks for reporting, fortunately, that's easy to fix

[mdii]

Thanks for the fix. I am still wandering about the behavior that I reported:

It seems that Javers sees the values in the map as Parent type not the concrete type.
If I change Map<String, Parent> map to Map<String, Object> map then the test passes.
If I keep Map<String, Parent> map and compare the maps directly like javers.compare(container1.map, container2.map) then the test passes.

[bartoszwalacik]

Fixed in 5.8.9, try now (map was not the cause) but handling MISSING_PROPERTY in CustomValueComparator

[mdii]

Thank you!