I have a issue about LENS. when I use

Map<String, Any?>>

as input json, to get map from req. it parse json number 5 to

java.math.BigIntger

rather than

<http://kotlin.Int|kotlin.Int>

. any one knows why? or How can I fix it?

JSON doesn't really have type information, and most marshallers can barely differentiate between integers and decimals. There's no way for the marshaller to know the maximum size of the number, so my best guess is that it chose the safest option, which is BigInteger. You wouldn't want it to return an Int one time, and then a Long another time, would you?

Ok, I see. so I need to handle the BigIntger myself. got it.

If you're using Jackson, that can be configured centrally (i.e. you don't have to handle BigIntegers yourself). Here's an example:

import com.fasterxml.jackson.databind.DeserializationFeature
import com.fasterxml.jackson.module.kotlin.KotlinModule
import org.http4k.format.ConfigurableJackson
import org.http4k.format.asConfigurable

data class Foo(val bar: Int)

object CustomJackson : ConfigurableJackson(
    KotlinModule.Builder().build()
        .asConfigurable()
        .done()
        .configure(DeserializationFeature.USE_BIG_INTEGER_FOR_INTS, false)
)

fun main() {
    val jsonExample = """{"bar":123}"""

    val foo = CustomJackson.asA<Foo>(jsonExample)
    println(foo)
}