Implement Json4s CustomKeySerializer (#127)

lloydmeta · Mar 16, 2017 · f1e9c5d · f1e9c5d
1 parent 91426ac
commit f1e9c5d
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Showing 2 changed files with 57 additions and 2 deletions.
diff --git a/enumeratum-json4s/src/main/scala/enumeratum/Json4s.scala b/enumeratum-json4s/src/main/scala/enumeratum/Json4s.scala
@@ -1,6 +1,6 @@
 package enumeratum
 
-import org.json4s.CustomSerializer
+import org.json4s.{CustomSerializer, CustomKeySerializer}
 import org.json4s.JsonAST.JString
 
 @SuppressWarnings(Array("org.wartremover.warts.Any"))
@@ -44,4 +44,43 @@ object Json4s {
           }
       ))
 
+  /**
+    * Returns a Json [[CustomKeySerializer]] for the given Enumeratum enum
+    *
+    * {{{
+    * scala> import enumeratum._
+    * scala> import org.json4s._
+    * scala> import org.json4s.native.Serialization
+    *
+    * scala> sealed trait ShirtSize extends EnumEntry
+    * scala> case object ShirtSize extends Enum[ShirtSize] {
+    *      |  case object Small  extends ShirtSize
+    *      |  case object Medium extends ShirtSize
+    *      |  case object Large  extends ShirtSize
+    *      |  val values = findValues
+    *      | }
+    *
+    * scala> implicit val formats = Serialization.formats(NoTypeHints) + Json4s.keySerializer(ShirtSize)
+    *
+    * scala> val valueMap = ShirtSize.values.zipWithIndex.toMap
+    *
+    * scala> Serialization.write(valueMap)
+    * res0: String = {"Small":0,"Medium":1,"Large":2}
+    *
+    * scala> Serialization.read[Map[ShirtSize,Int]]("""{"Small":0,"Medium":1,"Large":2}""") == valueMap
+    * res1: Boolean = true
+    * }}}
+    *
+    * @param enum the enum you want to generate a Json4s key serialiser for
+    */
+  def keySerializer[A <: EnumEntry: Manifest](enum: Enum[A]): CustomKeySerializer[A] =
+    new CustomKeySerializer[A](
+      _ =>
+        (
+          {
+            case s: String if enum.withNameOption(s).isDefined => enum.withName(s)
+          }, {
+            case x: A => x.entryName
+          }
+      ))
 }
diff --git a/enumeratum-json4s/src/test/scala/enumeratum/Json4sSpec.scala b/enumeratum-json4s/src/test/scala/enumeratum/Json4sSpec.scala
@@ -6,10 +6,12 @@ import org.scalatest.{FunSpec, Matchers}
 
 class Json4sSpec extends FunSpec with Matchers {
 
-  implicit val formats = DefaultFormats + Json4s.serializer(TrafficLight)
+  implicit val formats = DefaultFormats + Json4s.serializer(TrafficLight) + Json4s.keySerializer(
+      TrafficLight)
 
   case class Data(tr: TrafficLight)
   case class DataOpt(tr: Option[TrafficLight])
+  case class DataMap(tr: Map[TrafficLight, Int])
 
   describe("to JSON") {
     it("should serialize plain value to entryName") {
@@ -27,6 +29,13 @@ class Json4sSpec extends FunSpec with Matchers {
     it("should serialize None to nothing") {
       Serialization.write(DataOpt(tr = None)) shouldBe """{}"""
     }
+
+    it("should serialize value to key") {
+      TrafficLight.values.foreach { value =>
+        val name = value.entryName
+        Serialization.write(DataMap(tr = Map(value -> 0))) shouldBe s"""{"tr":{"$name":0}}"""
+      }
+    }
   }
 
   describe("from JSON") {
@@ -47,6 +56,13 @@ class Json4sSpec extends FunSpec with Matchers {
       Serialization.read[DataOpt]("""{}""").tr shouldBe None
     }
 
+    it("should parse enum members into keys") {
+      TrafficLight.values.foreach { value =>
+        val name = value.entryName
+        Serialization.read[DataMap](s"""{"tr":{"$name":0}}""").tr shouldBe Map(value -> 0)
+      }
+    }
+
     it("should parse invalid value into None") {
       Serialization.read[DataOpt]("""{"tr":"bogus"}""").tr shouldBe None
       Serialization.read[DataOpt]("""{"tr":17}""").tr shouldBe None