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kotlinlang

What do you think about providing a json serialization/deserialization library?
I mean that is a solution to solve this issue <https://github.com/FasterXML/jackson-module-kotlin/issues/58>

Basically I tried to fix that for Kotlin validation should return all validation failure, not just first error regarding to null.
```
class SignUpDto(val email: String, val password: String)

@Post("/signup")
fun signup(@Body @Valid dto: SignUpDto): String {
    return "OK"
}
```
If we will send `{ "email": null, "password": null }` or `{}` to the endpoint, kotlin will throw an exception that ONE field is null, so we will be able in response only say that ONE field can not be null. What I want to achieve is that we should return in response that BOTH/ALL fields can not be null.
So, this can be done if validation will be done before object creation.

Maybe Micronaut can provide own solution for json serialization/deserialization? It can be based on existing solution, like <https://github.com/square/moshi>
In this case also can be fixed Jackson limitation regarding deserializing nested polymorphic types <https://github.com/FasterXML/jackson-databind/issues/2000>
But swagger supports it by _anyOf_, even multilevel.