Strange serialization property name internal

[entrery]

Hi experts,
I am new to Kotlin and I am trying to use Jackson for a simple (de)serialization scenario of a Kotlin class with the Jackson Kotlin module. However when I serialize the object I see a strange property pattern for the high-level object. For example if my class is called Account and it has a property transactions instead of "transactions:[]" in the json output I see transactions$":[]. Why is that ? I presume it is pretty straightforward to answer. Thanks in advance!

[cowtowncoder]

@entrery Please include relevant class definition(s) instead of verbal explanation of the same.

[entrery]

Apologies @cowtowncoder I thought it is a simple issue on my side. I deep dived a bit more into the issue. It turns out the strange behaviour is caused by the internal keyword in Kotlin. Here is a simple definition of a class and the json output:

class A {
    internal var number: Int? = null
}

fun main() {
   val v = A().apply {
        number = 100
    };
    val mapper = jacksonObjectMapper()
    val timeModule = JavaTimeModule()
    timeModule.addSerializer(LocalDate::class.java, LocalDateSerializer(DateTimeFormatter.ISO_LOCAL_DATE))
    timeModule.addSerializer(LocalDateTime::class.java, LocalDateTimeSerializer(DateTimeFormatter.ISO_LOCAL_DATE_TIME))
    mapper.registerModule(timeModule)
    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL)

    println(mapper.writeValueAsString(v))
}

Actual Output:

{"number$<NAME_OF_MY_MAVEN_MODULE>":100}

Expected Output:

{"number":100}

Any hint is appreciated, thanks!

[cowtowncoder]

Ok I don't know enough about Kotlin or this module to know but I hope someone else can help more.

My only guess is that somehow Polymorphic deserialization was enabled for value class, using "as-wrapper-object" style -- output looks like that, so that key is simple class name of an inner class. But your declaration does not use @JsonTypeInfo nor enable default typing on mapper which would be the usual ways to enable it.

[entrery]

Hi @cowtowncoder, First thanks for your reply. I continued with the investigation... It turned out you were already involved in a discussion about this issue in 2017. Here is the thread #71. I don't understand at all what the guys are talking about there because I am new to Kotlin but tomorrow when I weak up I will read it carefully :). You can also have a look and give me a hint if the provided solution at the end seems ok. Thanks!

[cowtowncoder]

Oh. :)

I had fogotten about this. Work-arounds suggested may work but aren't really the proper solution.

[k163377]

@entrery
As you say, the issue is a duplicate of issue #71, so this issue is closed.
Progress on the kotlin-module modifications will be reported in #71 (or #630 ).