Milestones.scala

import org.scalatra.ScalatraServlet
import org.scalatra.json.JacksonJsonSupport
import java.util.Date

import com.novus.salat.annotations._
import com.novus.salat.dao.SalatDAO
import com.novus.salat.global._
import com.novus.salat.grater

import com.mongodb.casbah.Imports._

import org.json4s.{CustomSerializer, Extraction, DefaultFormats}
import org.json4s.JsonAST.{JValue, JString}
import org.json4s.mongo.ObjectIdSerializer

case class Milestone(@Key("_id") id: Object = new ObjectId, name: String, date: Date)

object MilestoneDao extends SalatDAO[ Milestone , ObjectId](collection = MongoConnection()("my_db")("milestones"))

class MongoSample extends ScalatraServlet with JacksonJsonSupport {

  // add support for ObjectId serialization
  implicit val jsonFormats = DefaultFormats + new ObjectIdSerializer

  before("/") {
    contentType = formats("json")
  }

  get("/milestones") {
    val id = new ObjectId
    MilestoneDao.save(Milestone(id, "asd", new Date))

    val m = MilestoneDao.findOneById(id).get

    // 1. use json4s' Extraction + ObjectIdSerializer from json4s-mongo
    val v: JValue = Extraction.decompose(m)

    // 2. use salat's grater
    // following https://github.com/novus/salat/wiki/JSON
    val v2: JValue = grater[Milestone].toJSON(m)

    // 3. set content type to application/json and return Milestone
    // the render pipeline handles the conversion
    contentType = formats("json")
    m
  }

}