PlayでurlFormEncodedなデータを受け取る

after.scala

object PersonController extends Controller with ControllerHelper {
  def create = Action(parse.urlFormEncoded) { implicit req =>
    val personOpt: Option[Person] = for {
      name <- paramOpt[String]("name")
      age <- paramOpt[Int]("age")
      person <- Person.create(name, age)
    } yield person

    // あとはResultを作る
  }
}

before.scala

import scalaz._, Scalaz._

object PersonController extends Controller {
  def create = Action(parse.urlFormEncoded) { implicit req =>
    val personOpt: Option[Person] = for {
      name <- req.body.get("name") map {
        case Seq(s) => s.some
        case _ => none
      }
      age <- req.body.get("age") map {
        case Seq(s) => s.parseInt.toOption
        case _ => none
      }
      person <- Person.create(name, age)
    } yield person

    // あとはResultを作る
  }
}

betterJava.scala

def param(req: Request[Map[String, Seq[String]]], key: String): Option[String] =
  req.body.get(key) map {
    case Seq(s) => s.some
    case _ => none
  }

ControllerHelper.scala

import scalaz._, Scalaz._

trait ControllerHelper {

  // Seq[String]から型Tのデータを抽出する型クラス
  trait Extractor[T] {
    def extract(data: Seq[String]): Option[T]
  }

  // Extractorを簡単に生成できるようにする
  def extractor[T](f: Seq[String] => Option[T]): Extractor[T] = new Extractor[T] {
    def extract(data: Seq[String]) = f(data)
  }

  // 他の型のExtractorとの連携も簡単にできるように
  def extractorBy[T, B](f: B => Option[T])(implicit extB: Extractor[B]): Extractor[T] =
    extractor[T] { extB.extract(_) >>= f }

  // こいつがControllerで実際に呼び出す関数
  def paramOpt[T](key: String)(implicit req: Request[Map[String, Seq[String]]], ext: Extractor[T]): Option[T] =
    req.body.get(key) >>= ext.extract

  // OptionじゃなくてValidationで受け取りたい時用
  def paramVld[E, T](key: String)(err: => E)(implicit req: Request[Map[String, Seq[String]]], ext: Extractor[T]): Validation[E, T] =
    paramOpt[T](key).toSuccess(err)

  // よく使う型のExtractorは予め作っておきやしょう
  implicit lazy val StringExtractor = extractor {
    case Seq(s) => s.some
    case _ => none
  }

  // Extractor[String]とString => Option[Int]を組み合わせてExtractor[Int]を作る
  implicit lazy val IntExtractor = extractorBy[Int, String] { _.parseInt.toOption }
}