Broken Scala Map to JSON

JacksonMapTest.scala

package test

import org.codehaus.jackson.map.ObjectMapper
import com.fasterxml.jackson.module.scala.DefaultScalaModule

object JacksonMapTest {

  def main(args: Array[String]): Unit = {
    val map = Map((2, 3) -> "Horsey")
    val mapper = new ObjectMapper()
    mapper.registerModule(DefaultScalaModule)
    val writer = new java.io.StringWriter()
    mapper.writeValue(writer, map)
    println(map)
    println(writer)
    val result = mapper.readValue(writer.toString, classOf[Map[Tuple2[Int, Int], String]])
    result.foreach(e => println(e._1.getClass))
  }
}