Add better JSON encoding support

play-ws-standalone-json/src/main/scala/play/api/libs/ws/JsonBodyReadables.scala

@@ -5,6 +5,9 @@
 package play.api.libs.ws
 
 /**
+ * Provides implicit for converting a response to JsValue.
+ *
+ * See https://github.com/playframework/play-json for details of Play-JSON.
  */
 trait JsonBodyReadables {
 
@@ -18,7 +21,20 @@ trait JsonBodyReadables {
    * }}}
    */
   implicit val readableAsJson: BodyReadable[JsValue] = BodyReadable { response =>
-    Json.parse(response.body)
+    val body = response.bodyAsBytes
+    Json.parse(body.decodeString(detectEncoding(body)))
+  }
+
+  // Leverage Jackson's RFC-4627 / 7159 JSON encoding support.
+  private[ws] def detectEncoding(in: akka.util.ByteString): String = {
+    // https://github.com/FasterXML/jackson-core/blob/master/src/main/java/com/fasterxml/jackson/core/json/ByteSourceJsonBootstrapper.java
+    // Also see https://stackoverflow.com/a/38036753 if this is insufficient
+    import com.fasterxml.jackson.core.io.IOContext
+    import com.fasterxml.jackson.core.json.ByteSourceJsonBootstrapper
+    import com.fasterxml.jackson.core.util.BufferRecycler
+    val ctx = new IOContext(new BufferRecycler, null, false)
+    val strapper = new ByteSourceJsonBootstrapper(ctx, in.toArray, 0, 4)
+    strapper.detectEncoding.getJavaName
   }
 }
 

play-ws-standalone-json/src/test/scala/play/api/libs/ws/JsonBodyReadablesSpec.scala

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2009-2017 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package play.api.libs.ws
+
+import akka.util.ByteString
+import org.specs2.matcher.MustMatchers
+import org.specs2.mutable.Specification
+
+class JsonBodyReadablesSpec extends Specification with MustMatchers {
+
+  "decode" should {
+
+    "read an encoding of UTF-32BE" in {
+      // 00 00 00 xx - it's UTF-32BE
+      val readables = new JsonBodyReadables() {}
+      val encoding = readables.detectEncoding(ByteString.fromArray(Array[Byte](0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x20)))
+      encoding must beEqualTo("UTF-32BE")
+    }
+
+    "read an encoding of UTF-32LE" in {
+      // xx 00 00 00 - it's UTF-32LE
+      val readables = new JsonBodyReadables() {}
+      val encoding = readables.detectEncoding(ByteString.fromArray(Array[Byte](0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20)))
+      encoding must beEqualTo("UTF-32LE")
+    }
+
+    "read an encoding of UTF-16BE" in {
+      // 00 xx 00 xx - it's UTF-16BE
+      val readables = new JsonBodyReadables() {}
+      val encoding = readables.detectEncoding(ByteString.fromArray(Array[Byte](0x00, 0x20, 0x00, 0x20, 0x00, 0x00, 0x00, 0x20)))
+      encoding must beEqualTo("UTF-16BE")
+    }
+
+    "read an encoding of UTF-16LE" in {
+      // xx 00 xx 00 - it's UTF-16LE
+      val readables = new JsonBodyReadables() {}
+      val encoding = readables.detectEncoding(ByteString.fromArray(Array[Byte](0x00, 0x20, 0x00, 0x20, 0x00, 0x00, 0x00, 0x20)))
+      encoding must beEqualTo("UTF-16BE")
+    }
+
+    "read an encoding of UTF-8" in {
+      // xx xx xx xx - it's UTF-8
+      val readables = new JsonBodyReadables() {}
+      val encoding = readables.detectEncoding(ByteString.fromArray(Array[Byte](0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0x20)))
+      encoding must beEqualTo("UTF-8")
+    }
+  }
+
+}