scala - Play 2.3 implicit json conversion causes null pointer exception -

I am trying to parse json in my case class delphormim

  case class DealFormMap (range: option [Int], filter option [DealFormFilterMap]) case square DealFormFilterMap (on option [string] code: option [string]) built Val dealFormMapReads: Books [DealFormMap] = ((JsPath \ "border") readNullable [int] and (JsPath \ "filter") readNullable [DealFormFilterMap]) (DealFormMap) Built-in Val dealFormFilterMapReads: ... Reads [DealFormFilterMap] = (JsPath \ "date") readNullable [string]  

JSON in question and parsing attempt

  val str = "" " {"Limit": 10, "Filter": {"Date": "2014-10-27"}} "" "Val FRM = Jason. PRSE (SR). [Delfermmap]  

a Cryptic error which I think causes stack that

  play.api.Application $$ $ $ anon $: execution exception [[NullPointerException: null]] to play. API.App $ class.handError (application.scala: 296) ~ [play_2.11-2.3.5. If: 2.3.5] play.api.DefaultApplication.handleError (application.scala: 4 02) [play_2.11- 2.3.5.jar: [play_2.11-2.3.5.jar: 2.3.5] play.core.server.netty.PlayDefaultUpstreamHandler $$ anonfun $ 14 $$ anonfun $ $ 1 applyOrElse (205 PlayDefaultUpstreamHandler.scala) are: scala on 2.3.5]: [play_2.11-2.3.5.jar: 2.3.5] $$ on play.core.server.netty.PlayDefaultUpstreamHandler anonfun $ 14 $$ apply anonfun $ $ 1.applyOrElse (202 PlayDefaultUpstreamHandler.scala) apply .runtime.AbstractPartialFunction.apply (AbstractPartialFunction.scala: 36) [scala-library -2.11.2. jar: na]: java.lang.NullPointerException: due to play .api.libs.json.PathReads Do null ineligible to apply $ 1 $ $ $ $ $ $ $ $ to $$ anonfun $ apply $ $ $ 9apply (JsConstraints.scala: 65) ~ [play-json_2.11-2.3. 5.jar: 2.3.5] at play.api.libs.json. PathReads $$ $ $ Cancel $ 1 $ $ $ $ $ $ $ Apply $ $ $ $ Apply $ 9apply (JsConstraints.scala: 63) ~ [play-json_2.11-2.3.5.jar: 2.3 5] .l Ibs.json.JsResult at play.api $ class.fold (JsResult.scala: 76) ~ [play-json_2.11-2.3.5. If: 2.3.5] at play.api.libs.json .JsSuccess.fold (JSRSalt Scholle): 9) ~ [Play-json_2.11-2.3.5. If: 2.3.5] play.api.libs.json.PathReads $$ at $ $ $ $ 1 $ $ Exclusive $ $ Apply $ .apply (JsConstraints.scala: 61) ~ [play-json_2.11-2.3.5.jar: 2.3.5]  

I'm going out of ideas here What can be the problem?

The problem is the initial order dealFormMapReads underlying dealFormFilterMapReads Depending on which, which is not defined by then it will be compiled as it is found to be contained, even if it has not been started, therefore the form of dealFormMapReads as null , Which ultimately causes the NPE.

Lazily loading will fix it:

  Built-in Val dealFormMapReads: .. Reads [DealFormMap] = ((JsPath \ "border") readNullable [Int] and (JsPath \ "filter") lazyReadNullable  

or just Can swap the order in which read is defined.

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The NPE is thrown here is similar to this example:

  Case class A (i: IT) object test {val test = a.toString val a = A (1)} // compiles throws Test.test // NPE here, because `A` was not started before` Test`