Play Framework DynamoDB Json

DynamoJson.scala

object DynamoReader {
  def typeReader[A](f: (JsObject => JsResult[A])) = new Reads[A] {
    def reads(json: JsValue): JsResult[A] = json match {
      case obj: JsObject => f(obj)
      case _ => JsError(Seq(JsPath() -> Seq(ValidationError("error.expected.jsobject"))))
    }
  }
}

object DynamoString {
  val reads: Reads[String] = DynamoReader.typeReader[String](x => (x \ "S").validate[String])
  val writes = new Writes[String] {
    override def writes(o: String): JsValue = Json.obj("S" -> o)
  }
}

object DynamoNumber {
  val longReads: Reads[Long] = DynamoReader.typeReader[Long](x => (x \ "N").validate[String].map(_.toLong))
  val longWrites = new Writes[Long] {
    override def writes(o: Long): JsValue = Json.obj("N" -> JsString(o.toString))
  }
}

object DynamoBoolean {
  val reads: Reads[Boolean] = DynamoReader.typeReader[Boolean](x => (x \ "BOOL").validate[Boolean])
  val writes = new Writes[Boolean] {
    override def writes(o: Boolean): JsValue = Json.obj("BOOL" -> o)
  }
}

SampleModel.scala

case class Sample(someString: String, someLong: Long, optionalBoolean: Option[Boolean])

object Sample {
  implicit val reads: Reads[Sample] = (
    (JsPath \ "some_string").read[String](DynamoString.reads) and
      (JsPath \ "some_long").read[Long](DynamoNumber.longReads) and
      (JsPath \ "optional_bool").readNullable[Boolean](DynamoBoolean.reads)
    )(Sample.apply _)

  implicit val writes: Writes[Sample] = (
    (JsPath \ "some_string").write[String](DynamoString.writes) and
      (JsPath \ "some_long").write[Long](DynamoNumber.longWrites) and
      (JsPath \ "optional_bool").writeNullable[Boolean](DynamoBoolean.writes)
    )(unlift(Sample.unapply))
}

WSHelpers.scala

class DynamoDBWSSample(credProvider: AWSCredentialsProvider, ws: WSAPI, config: Configuration) {

  val conf = config.underlying
  val serviceUrl = conf.getString("dynamoDB.url")
  val serviceName = conf.getString("dynamoDB.serviceName")
  val serviceRegion = conf.getString("dynamoDB.serviceRegion")

  val awsPlayWSSigner = (wsReq: WSRequest, signer: Aws4Signer) => AwsRequestHolder(wsReq, signer).execute()
  //Must be a function so that instances of the class don't cache the credentials from the provider.
  val awsSigner = (credProvider: AWSCredentialsProvider) => {
    val credentials = credProvider.getCredentials
    new Aws4Signer(AwsCredentials(credentials.getAWSAccessKeyId, credentials.getAWSSecretKey), serviceName, serviceRegion)
  }
  val dynamoWSSigner = (wsReq: WSRequest) => awsPlayWSSigner(wsReq, awsSigner(credProvider))

  val dynamoWSRequest = ws.url(serviceUrl).withHeaders("Content-Type" -> "application/x-amz-json-1.0").withMethod("POST")
  val dynamoPutItem = (data: JsObject) => dynamoWSSigner(dynamoWSRequest.withHeaders("x-amz-target" -> "DynamoDB_20120810.PutItem").withBody(data))
  val dynamoGetItem = (data: JsObject) => dynamoWSSigner(dynamoWSRequest.withHeaders("x-amz-target" -> "DynamoDB_20120810.GetItem").withBody(data))
  val dynamoDeleteItem = (data: JsObject) => dynamoWSSigner(dynamoWSRequest.withHeaders("x-amz-target" -> "DynamoDB_20120810.DeleteItem").withBody(data))
  val dynamoQueryItem = (data: JsObject) => dynamoWSSigner(dynamoWSRequest.withHeaders("x-amz-target" -> "DynamoDB_20120810.Query").withBody(data))

  //Once the DynamoFunction Helpers are created, executing signed dynamo requests is not much harder than using the SDK itself...
  def findSample(someString: String): Future[Option[Sample]] = {
    val req = Json.obj(
      "TableName" -> "sample.table.name",
      "Key" -> Json.obj("some_string" -> Json.obj("S" -> someString)),
      "ReturnConsumedCapacity" -> "NONE",
      "ConsistentRead" -> true
    )

    dynamoGetItem(req).map { response =>
      if (response.status == 200) {
        (response.json \ "Item").as[JsObject].validate[Sample].asOpt
      } else {
        //TODO: ....
      }
    }
  }
}

The goal of this gist is to show how one might integrate with DynamoDB using the WS library and this library to sign the requests: https://github.com/Kaliber/play-s3/tree/master/src/main/scala/fly/play/aws

I've provided a couple of read / writers for the different dynamo types. This list is by no means complete - but it shows you how you can handle the different dynamo types while still using Play's built in read / write converters into scala case classes with ease.