How to prohibit accepting values other than true and false in request for Kotlin Spring Boot

Issue

What decorator can I put on the class field so that values other than true and false are not accepted in the request.

Now, any values can go into the request, including boolean.

I can send false, 0 and an empty string – it will be interpreted as false.

I can send true, all positive and negative numbers and it will be interpreted as true.

What can I do to accept only true and false?

open class KdInfo : Info {

    @Min(0)
    var brutto: Long = 0

    @NotNull
    var isRefund: Boolean = false  // this field can get not only boolean values from request
}

Solution

I found solution. Make custom JsonDeserializer and add it as decorator to field.:

import com.fasterxml.jackson.core.JsonParser
import com.fasterxml.jackson.databind.DeserializationContext
import com.fasterxml.jackson.databind.JsonDeserializer

class JsonBooleanDeserializer : JsonDeserializer<Boolean>() {

    override fun deserialize(parser: JsonParser, context: DeserializationContext): Boolean {
        return when (parser.text.toLowerCase()) {
            "true" -> true
            "false" -> false
            else -> throw Exception()
        }
    }
}

open class KdInfo : Info {

    @Min(0)
    var brutto: Long = 0

    @NotNull
    @JsonProperty("refund")
    @JsonDeserialize(using = JsonBooleanDeserializer::class)
    var isRefund: Boolean = false  // this field can get not only boolean values from request
}

Answered By - Anton Zotin