lift-json trait for scalatra

lift-json.scala

package org.scalatra
package liftjson

import scala.xml.XML
import net.liftweb.json._
import net.liftweb.json.Xml.toXml

trait JsonSupport extends ApiFormats {

  /**
   * If a request is made with a parameter in jsonpCallbackParameterNames it will
   * be assumed that it is a JSONP request and the json will be returned as the
   * argument to a function with the name specified in the corresponding parameter.
   *
   * By default no parameterNames will be checked
   */
  def jsonpCallbackParameterNames: Iterable[String] = Nil

  override protected def renderPipeline = ({
    case jv: JValue if format == "xml" =>
      contentType = "application/xml"
      XML.write(response.writer, <resp>{toXml(jv)}</resp>, response.characterEncoding.get, true, null)
    case jv : JValue =>
      contentType = "application/json"
      // JSON should always be utf8
      response.characterEncoding = Some("UTF-8")

      val jsonpCallback = for {
        paramName <- jsonpCallbackParameterNames
        callback <- params.get(paramName)
      } yield callback

      val writer = response.writer

      jsonpCallback match {
        case some::_ =>
          // Status must always be 200 on jsonp, since its loaded in a <script> tag.
          status = 200
          writer write some
          writer write '('
          Printer.compact(render(jv), writer)
          writer write ");"
        case _ =>
          Printer.compact(render(jv), writer)
      }
    () // Done writing response.
  }: RenderPipeline) orElse super.renderPipeline
}