How can I write dates to ISO 8601 format using JSON Writes?

Question

I've got a case calss

import java.sql.Date
case class GetMilestoneLanguage(
                               ...
                   due_date: Option[Date],
                                ...
                   )
object GetMilestoneLanguage {
  implicit val writes = Json.writes[GetMilestoneLanguage]
}

Its outputting the JSON in UTC - and I need it to be iso 8601. I'm NOT use Joda time.

What the easiest way to achieve getting the date in iso 8601?

Thanks

Answer 1

import play.api.libs.json.{Json, Writes}
import play.api.libs.json.Writes.dateWrites // do not import everything here, especially DefaultDateWrites

case class GetMilestoneLanguage(param1: String, dueDate: Option[java.sql.Date])

object GetMilestoneLanguage {
  implicit val customDateWrites: Writes[java.util.Date] = dateWrites("yyyy-MM-dd'T'HH:mm:ss'Z'")

  implicit val writes =  Json.writes[GetMilestoneLanguage]
}

The key here is to define your own implicit Writes[java.util.Date]. If you import DefaultDateWrites your customDateWrites will be silently ignored (I wonder why there is no ambiguous implicit warning).