Question

我是Scala的新手，我的问题是有关使用play（2.5）获得Joda可选值的Json序列化我的输入： 1。

first <- c("andrea","luis","mike","thomas")
last <- c("robinson", "trout", "rice","snell")
email <- c("andrea@gmail.com", "lt@gmail.com", "mr@gmail.com", "tom@gmail.com")



first <- c("mike","steven","mark","john", "martin")
last <- c("rice", "berry", "smalls","sale", "arnold")
email <- c("mr@gmail.com", "st@gmail.com", "ms@gmail.com", "js@gmail.com", "ma@gmail.com)
alz <- c(1,2,NA,3,4)
der <- c(0,2,3,NA,3)

all_emails <- data.frame(first,last,email)
no_contact_emails <- data.frame(first,last,email,alz,der)

df <- merge(no_contact_emails, all_emails, all = TRUE)

df <- df$email[!duplicated(df$email) & !duplicated(df$email, fromLast = TRUE)]

序列化器

import org.joda.time.LocalDateTime
     case class User(
                     name: String, 
                     lastLogin: Option[LocalDateTime])
    object User {
      implicit val serializers = JsonSerializers
      implicit val UserFormat: Format[User] = Format(serializers.UserReads, serializers.UserWrites)
    }

测试对象：

import com.dtos.{User}
import org.joda.time.LocalDateTime
import org.joda.time.format.DateTimeFormat
import play.api.libs.json._
import play.api.libs.functional.syntax._
object JsonSerializers {
  val dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS"

  implicit val UserReads: Reads[User] = (
    (JsPath \ "name").read [String] and
      (JsPath \ "active").read [Boolean] and
      (JsPath \\ "$ldt").read[LocalDateTime]
    )(User.apply _)

  implicit val UserWrites: Writes[User] = (
    (JsPath \ "name").write [String] and
      (JsPath \ "active").write [Boolean] and
      (JsPath \ "lastLogin" \ "$ldt") .write [LocalDateTime]
    )(unlift (User.unapply))
}

问题： 1.如何在UserReads / UserWrites期间管理Option值？我收到以下错误：

重载的方法值适用于替代方法： [B]（f：B =>（String，Boolean，org.joda.time.LocalDateTime））（隐式fu：play.api.libs.functional.ContravariantFunctor [play.api.libs.json.Reads]）播放。 api.libs.json.Reads [B] [B]（f：（String，Boolean，org.joda.time.LocalDateTime）=> B）（隐式fu：play.api.libs.functional.Functor [play.api.libs.json.Reads]）播放。 api.libs.json.Reads [B] 不能应用于（（（String，Boolean，Option [org.joda.time.LocalDateTime]）=> com.dtos.User）（JsPath \“活动”）。阅读[Boolean]和

不能使其适用于用户的输入Json结构：

object MainTest extends App {    
  val value: JsValue = Json.parse("{ \"name\" : \"hello\" , \"lastLogin\" : {\"$ldt\":\"2018-09-09T11:06:27.655\"} }")
  println("First Output:")
  println(Json.toJson(new MyUser("user", LocalDateTime.now)))
  println("Second Output:")
  println(Json.fromJson(value))    
}

Answer 1

我认为您缺少的是串行器Format[LocalDateTime]。

开箱即用地支持

Option。

来自另一个Stackoverflow答案：

import org.joda.time.LocalDateTime
import org.joda.time.format.ISODateTimeFormat

implicit val readsJodaLocalDateTime = Reads[LocalDateTime](js =>
  js.validate[String].map[LocalDateTime](dtString =>
    LocalDateTime.parse(dtString, ISODateTimeFormat.basicDateTime())
  )
)

请参阅完整答案：custom-jodatime-serializer-using-play-frameworks-json-library

通过案例类，您可以添加一个序列化器，如下所示：

object User {
  implicit val jsonFormat: Format[User] = Json.format[User]
}

Scala，使用play 2.5将joda.LocalDateTime转换为json

1 个答案: