Shapelaysson = Shapeless + Play-Json

Do you like Shapeless, this great API developed by Miles Sabin studying generic/polytypic programming in Scala?

Do you like Play-json, the Play Json 2.1 Json API developed for Play 2.1 framework and now usable as stand-alone module providing functional & typesafe Json validation and Scala conversion?

Here is Shapelaysson an API interleaving Play-Json with Shapeless to be able to manipulate Json from/to Shapeless HList

HList are heterogenous polymorphic lists able to contain different types of data and able to keep tracks of these types

Shapelaysson takes part in my reflexions around manipulating pure data structures from/to JSON.

A few pure Json from/to HList samples

import play.api.libs.json._
import shapeless._
import HList._
import Tuples._
import shapelaysson._

// validates + converts a JsArray into HList
scala> Json.arr("foo", 123L).validate[ String :: Long :: HNil ]
res1: play.api.libs.json.JsResult[shapeless.::[String,shapeless.::[Long,shapeless.HNil]]] = 
JsSuccess(foo :: 123 :: HNil,)

// validates + converts a JsObject into HList
scala> Json.obj("foo" -> "toto", "bar" -> 123L).validate[ String :: Long :: HNil ]
res3: play.api.libs.json.JsResult[shapeless.::[String,shapeless.::[Long,shapeless.HNil]]] = 
JsSuccess(toto :: 123 :: HNil,)

// validates + converts imbricated JsObject into HList
scala> Json.obj(
     |   "foo" -> "toto", 
     |   "foofoo" -> Json.obj("barbar1" -> 123.45, "barbar2" -> "tutu"),
     |      "bar" -> 123L,
     |      "barbar" -> Json.arr(123, true, "blabla")
     |   ).validate[ String :: (Float :: String :: HNil) :: Long :: (Int :: Boolean :: String :: HNil) :: HNil ]
res4: play.api.libs.json.JsResult[shapeless.::[String,shapeless.::[shapeless.::[Float,shapeless.::[String,shapeless.HNil]],shapeless.::[Long,shapeless.::[shapeless.::[Int,shapeless.::[Boolean,shapeless.::[String,shapeless.HNil]]],shapeless.HNil]]]]] = 
JsSuccess(toto :: 123.45 :: tutu :: HNil :: 123 :: 123 :: true :: blabla :: HNil :: HNil,)

// validates with ERROR JsArray into HList
scala> Json.arr("foo", 123L).validate[ Long :: Long :: HNil ] must beEqualTo( JsError("validate.error.expected.jsnumber") )
<console>:23: error: value must is not a member of play.api.libs.json.JsResult[shapeless.::[Long,shapeless.::[Long,shapeless.HNil]]]
                    Json.arr("foo", 123L).validate[ Long :: Long :: HNil ] must beEqualTo( JsError("validate.error.expected.jsnumber") )

// converts HList to JsValue
scala> Json.toJson(123.45F :: "tutu" :: HNil)
res6: play.api.libs.json.JsValue = [123.44999694824219,"tutu"]

A few Json Reads/Writes[HList] samples

import play.api.libs.functional.syntax._

// creates a Reads[ String :: Long :: (String :: Boolean :: HNil) :: HNil]
scala> val HListReads2 = (
     |    (__ \ "foo").read[String] and
     |    (__ \ "bar").read[Long] and
     |    (__ \ "toto").read(
     |      (
     |        (__ \ "alpha").read[String] and
     |        (__ \ "beta").read[Boolean]
     |      ).tupled.hlisted
     |    )
     | ).tupled.hlisted
HListReads2: play.api.libs.json.Reads[shapeless.::[String,shapeless.::[Long,shapeless.::[shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]],shapeless.HNil]]]] = play.api.libs.json.Reads$$anon$8@7e4a09ee

// validates/converts JsObject to HList
scala> Json.obj(
     |   "foo" -> "toto", 
     |   "bar" -> 123L,
     |   "toto" -> Json.obj(
     |      "alpha" -> "chboing",
     |      "beta" -> true
     |   )
     | ).validate(HListReads2)
res7: play.api.libs.json.JsResult[shapeless.::[String,shapeless.::[Long,shapeless.::[shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]],shapeless.HNil]]]] = 
JsSuccess(toto :: 123 :: chboing :: true :: HNil :: HNil,)

// Create a Writes[String :: Long :: HNil]
scala> implicit val HListWrites: Writes[ String :: Long :: HNil ] = (
     |         (__ \ "foo").write[String] and
     |         (__ \ "bar").write[Long]
     |       ).tupled.hlisted
HListWrites: play.api.libs.json.Writes[shapeless.::[String,shapeless.::[Long,shapeless.HNil]]] = play.api.libs.json.Writes$$anon$5@7c9d07e2

// writes a HList to JsValue
scala> Json.toJson("toto" :: 123L :: HNil)
res8: play.api.libs.json.JsValue = {"foo":"toto","bar":123}

Adding shapelaysson in your dependencies

In your Build.scala, add:

import sbt._
import Keys._

object ApplicationBuild extends Build {

  val mandubianRepo = Seq(
    "Mandubian repository snapshots" at "https://github.com/mandubian/mandubian-mvn/raw/master/snapshots/",
    "Mandubian repository releases" at "https://github.com/mandubian/mandubian-mvn/raw/master/releases/"
  )

  val sonatypeRepo = Seq(
    "Sonatype OSS Releases" at "http://oss.sonatype.org/content/repositories/releases/",
    "Sonatype OSS Snapshots" at "http://oss.sonatype.org/content/repositories/snapshots/"    
  )

  lazy val playJsonAlone = Project(
    BuildSettings.buildName, file("."),
    settings = BuildSettings.buildSettings ++ Seq(
      resolvers ++= mandubianRepo ++ sonatypeRepo,
      libraryDependencies ++= Seq(
        "org.mandubian"  %% "shapelaysson"  % "0.1-SNAPSHOT",
        "org.specs2"     %% "specs2"        % "1.13" % "test",
        "junit"           % "junit"         % "4.8" % "test"
      )
    )
  )
}

More to come maybe in this draft project... Suggestions are welcome too

Have fun!