Example JSon transform and get configuration from Controller.

app/application/API.scala

@@ -3,6 +3,7 @@ import play.api.mvc._
 import play.api.libs.json._
 import play.api.libs.functional.syntax._
 import javax.inject._
+import play.api.Configuration
 
 case class Location(lat: Double, long: Double)
 
@@ -25,7 +26,7 @@ object Place {
     list = list ::: List(place)
   }
 }
-class ApiApplication @Inject() (cc: ControllerComponents) extends AbstractController(cc) {
+class ApiApplication @Inject() (cc: ControllerComponents, config: Configuration) extends AbstractController(cc) {
   implicit val locationWrites: Writes[Location] = (
     (__ \ "lat").write[Double] and
     (__ \ "long").write[Double]
@@ -46,6 +47,9 @@ class ApiApplication @Inject() (cc: ControllerComponents) extends AbstractContro
     (__ \ "location").read[Location]
   )(Place.apply _)
 
+  // implicit val placeWrites = Json.writes[Place]
+  // implicit val placeReads = Json.reads[Place]
+
   def listPlaces = Action {
     val json = Json.toJson(Place.list)
     Ok(json)
@@ -63,4 +67,14 @@ class ApiApplication @Inject() (cc: ControllerComponents) extends AbstractContro
       }
     )
   }
+
+  def playTransform = Action { request =>
+    val json = Json.obj("key1" -> "value1", "key2" -> Json.obj("key21" -> "value21", "key22" -> "value22"))
+    val jsonTransformer = (__ \ "key2").json.pick
+    Ok(json.transform(jsonTransformer).toString)
+  }
+
+  def getConfiguration = Action { request =>
+    Ok(config.get[String]("db.default.username"))
+  }
 }

conf/routes

@@ -14,6 +14,8 @@ POST        /login                 application.AccountApplication.login
 
 GET   /places               application.ApiApplication.listPlaces
 POST  /places               application.ApiApplication.savePlace
+GET  /transform               application.ApiApplication.playTransform
+GET  /getconfig               application.ApiApplication.getConfiguration
 
 # Map static resources from the /public folder to the /assets URL path
 GET         /assets/*file          controllers.Assets.versioned(path="/public", file: Asset)