Fehlermeldung: Versuchen Sie ein implizites Schreiben oder Format für diesen Typ zu implementieren

Question

Ich habe die folgende JSON-Zeichenfolge. In scala möchte ich einige Felder extrahieren und sie in einem neuen json speichern.

{"query":"doi:10.1186/s13612-016-0045-3","result":[{"total":"1","start":"1","pageLength":"10"}],"records":[{"identifier":"doi:10.1186/s13612-016-0045-3","url":[{"format":"","platform":"","value":" http://dx.doi.org/10.1186/s13612-016-0045-3 "}],"title":"Technology and Reflection: Mood and Memory Mechanisms for Well-Being","creators":[{"creator":"Konrad, Artie"},{"creator":"Tucker, Simon"},{"creator":"Crane, John"},{"creator":"Whittaker, Steve"}],"publicationName":"Psychology of Well-Being","issn":"2211-1522","openaccess":"true","journalid":"13612","doi":"10.1186/s13612-016-0045-3","publisher":"Springer","publicationDate":"2016-06-15","volume":"6","number":"1","issuetype":"","topicalCollection":"","startingPage":"1","copyright":"©2016 The Author(s)","genre":"OriginalPaper","abstract":"AbstractBackgroundWe report a ..."}],"facets":[{"name":"subject","values":[{"value":"Biological Psychology","count":"1"},{"value":"Health Psychology","count":"1"},{"value":"Neuropsychology","count":"1"},{"value":"Positive Psychology","count":"1"},{"value":"Psychology","count":"1"},{"value":"Quality of Life Research","count":"1"}]},{"name":"pub","values":[{"value":"Psychology of Well-Being","count":"1"}]},{"name":"year","values":[{"value":"2016","count":"1"}]},{"name":"country","values":[{"value":"United States","count":"1"},{"value":"USA","count":"1"}]},{"name":"type","values":[{"value":"Journal","count":"1"}]},{"name":"keyword","values":[{"value":"Emotion","count":"1"},{"value":"Memory","count":"1"},{"value":"Mood","count":"1"},{"value":"Reflection","count":"1"},{"value":"Reminiscence","count":"1"},{"value":"Technology mediated reflection","count":"1"},{"value":"Well-being","count":"1"}]}]}

Insbesondere möchte ich die folgende neue JSON-Objekt erhalten (dh Extrakt Felder „Schöpfer“, „Publica“ und „abstrakt“, und umbenennen entsprechend):

{"creators":[{"creator":"Konrad, Artie"},{"creator":"Tucker, Simon"},{"creator":"Crane, John"},{"creator":"Whittaker, Steve"}],"pubTitle":"Psychology of Well-Being","pubAbstract":"AbstractBackgroundWe report ..."}

Diese Ist mein aktueller Code, aber ich habe die Fehlermeldung Error:(137, 27) No Json serializer found for type play.api.libs.json.JsResult[org.test.Publication]. Try to implement an implicit Writes or Format for this type. val json = Json.toJson(processedPubl).

import play.api.libs.json._ 
import play.api.libs.functional.syntax._ 
import play.api.data.validation.ValidationError 
import play.api.libs.json.Reads._ 

case class Creator(creator: String) 
case class Publication(pubTitle: String, creators: Seq[Creator], pubAbstract: String) 

val jsonstring = ... // this is the raw string provided 
        // at the beginning of this post 

implicit val publReads: Reads[Publication] = (
     (JsPath \ "publicationName").read[String] and 
     (JsPath \ "creators").read[Seq[Creator]] and 
     (JsPath \ "abstract").read[String] 
    ) (Publication.apply _) 

val processedPubl = Json.parse(jsonstring).validate[Publication](publReads) 

val json = Json.toJson(processedPubl) 

Answer 1

Sie sollten dies versuchen:

import play.api.libs.functional.syntax._ 
import play.api.libs.json._ 

case class Creator(creator: String) 
case class Publication(pubTitle: String, creators: Seq[Creator], pubAbstract: String) 

val jsonString = ... 

implicit val creatorFormat = Json.format[Creator] 
implicit val publWrites = Json.writes[Publication] 
implicit val publReads: Reads[Publication] = (
    (JsPath \ "publicationName").read[String] and 
    (JsPath \ "creators").read[Seq[Creator]] and 
    (JsPath \ "abstract").read[String] 
)(Publication.apply _) 

val input = Json.parse(jsonString).as[Publication] 
val output = Json.toJson(input) 

Reads ist etwas, das während des Lesens von JSON verwendet wird (input diese verwendet) und Writes ist etwas, das während des Schreibens zu JSON verwendet wird (output verwendet es) . Zusammen bilden sie etwas, das Format genannt wird. Da Sie in Ihrem Code Fallklassen verwenden, können Sie diese Lese-/Schreibvorgänge/Formate mithilfe von json-Methoden von play automatisch generieren.