could not find implicit value for evidence parameter of type JsonSupport.this.JF[org.joda.time.LocalDateTime]

Question

I am beginner with spray json application and I am using LocalDateTime as one of the parameter types in the case class.

import scala.collection.JavaConverters._
import org.apache.commons.imaging.Imaging
import org.joda.time.format.{DateTimeFormat, DateTimeFormatter}
import org.joda.time.{DateTime, LocalDateTime}
import spray.json.DefaultJsonProtocol
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport
import JodaDateTimeFormats._
import spray.json._

case class ExifMetadata(docName:String, exifOffset:Int, gpsInfo:Int, dateTimeOriginal:LocalDateTime,
                        gpsLatitudeRef:String, gpsLatitude:Double, gpsLongitudeRef:String, gpsLongitude:Double, gpsDateStamp:LocalDateTime)

trait JsonSupport extends SprayJsonSupport with DefaultJsonProtocol {
  implicit val exifMetadataFormat = jsonFormat9(ExifMetadata)
}

However I keep getting the following error

could not find implicit value for evidence parameter of type JsonSupport.this.JF[org.joda.time.LocalDateTime]

Does that object extend App with your JsonSupport? It should. — László van den Hoek
Yes, it does. object ExifExtractor extends App with JsonSupport {} — binshi
Ah, you still need to provide a JsonFormat for the LocalDateTime. Will write up an answer for that. — László van den Hoek

László van den Hoek László van den Hoek · Accepted Answer · 2018-02-15T08:22:24

First off: using JodaTime nowadays is discouraged by the authors:

Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.

If you're still stuck on JDK 7 (you poor bastard), you should still prefer using ThreeTenBP, which provides an API almost identical to JSR-310. This would minimize upgrade friction.

With that out of the way: Spray does not provide JsonFormat instances for JodaTime classes out of the box. You will have to write your own. Fortunately, that's not so hard.

How exactly you want to represent your LocalDateTime in JSON depends on your use case, but a standard ISO 8601 format makes sense.

import spray.json._

//prevent confusion with java.time.LocalDateTime
import org.joda.time.{LocalDateTime => JodaLocalDateTime}

implicit val jodaLocalDateTimeFormat: JsonFormat[JodaLocalDateTime] = 
  new JsonFormat[JodaLocalDateTime] {
    override def write(obj: JodaLocalDateTime): JsValue = JsString(obj.toString)

    override def read(json: JsValue): JodaLocalDateTime = json match {
      case JsString(s) => Try(JodaLocalDateTime.parse(s)) match {
        case Success(result) => result
        case Failure(exception) => 
          deserializationError(s"could not parse $s as Joda LocalDateTime", exception)
      }
      case notAJsString => 
        deserializationError(s"expected a String but got a $notAJsString")
    }
  }

Inspiration

Make sure that you define this JsonFormat at the top of your JsonSupport trait. That way, it will be available to your other format(s).

could not find implicit value for evidence parameter of type JsonSupport.this.JF[org.joda.time.LocalDateTime]

1 Answers