Kotlin Extensions for Jackson Json (and spring-boot): e.g. ParameterizedTypeReference, TypeReference

Jackson.kt

package example.util.jackson

import com.fasterxml.jackson.core.type.TypeReference
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.kotlin.readValue
import org.springframework.core.ParameterizedTypeReference
import java.lang.reflect.Type

interface ToJson {
    val objectMapper: ObjectMapper
    fun Any?.toJson(): String = objectMapper.encode(value = this)
}

fun ObjectMapper.encode(value: Any?): String = writeValueAsString(value)

inline fun <reified T : Any> ObjectMapper.decode(content: String): T = readValue(content)
inline fun <reified T : Any> ObjectMapper.decode(content: String, valueTypeRef: TypeReference<T>): T =
        readValue(content, valueTypeRef)

inline fun <reified T : Any> ObjectMapper.decode(content: String, parameterizedTypeRef: ParameterizedTypeReference<T>): T =
        readValue(content, parameterizedTypeRef.toJacksonTypeRef())

/**
 * see: 
 * - https://stackoverflow.com/questions/47360082/converting-spring-parameterizedtypereference-to-jackson-typereference
 * - https://github.com/FasterXML/jackson-core/blob/master/src/main/java/com/fasterxml/jackson/core/type/TypeReference.java#L33-L44
 */
inline fun <reified T : Any> parameterizedTypeRef(): ParameterizedTypeReference<T> =
        object : ParameterizedTypeReference<T>() {}

inline fun <reified T : Any> ParameterizedTypeReference<T>.toJacksonTypeRef(): TypeReference<T> {
    val theType: Type = this.type
    return object : TypeReference<T>() {
        override fun getType(): Type = theType
    }
}

JacksonCodecExample.kt

class JacksonCodecExample {
  companion object : ToJson {
        override val objectMapper: ObjectMapper get() = TODO()
  }
  
  fun encode() {
    val json:String=listOf(
                "A", "B", 3, 4, null,
                Instant.parse("2018-11-13T07:19:05.555Z"),
                SomeEnum.FOO, SomeEnum.BAR
        ).toJson()
  }
  
  fun decode() {
    val json = """["A","B"]"""
    val decoded1 :List<String> = objectMapper.decode(json)
    
    val jacksonTypeRef:TypeReference<List<String>> = jacksonTypeRef()
    val decoded2:List<String> = objectMapper.decode(json, jacksonTypeRef)
    
    val parameterizedTypeRef:ParameterizedTypeReference<List<String>> = parameterizedTypeRef()
    val decoded3:List<String> = objectMapper.decode(json, parameterizedTypeRef)
  }
  
}