使用json4s

Question

如何解析YYYY-MM-dd到java.time.LocalDate的字符串？目前我尝试了以下方法：

1. 导入JavaTimeSerializers

  

抛出错误JString无法转换为LocalDate

case class Dates(createdAt: LocalDate, updatedAt: LocalDate, startDate: LocalDate, endDate: LocalDate )
implicit val formats =  defaultFormats ++ org.json4s.ext.JavaTimeSerializers.all

implicit val formats =  defaultFormats ++ org.json4s.ext.JavaTimeSerializers.all

val input =
  """
    |{
    |  "createdAt": "1999-12-10",
    |  "updatedAt": "1999-12-16",
    |  "startDate": "2000-01-02",
    |  "endDate": "200-01-16"
    |}
  """.stripMargin

val result = read[Dates] { input }

1. 覆盖DefaultFormats：

  

抛出错误发现java.time.format.DateTimeFormatter期望java.text.SimpleDateFormat

implicit val formats = new org.json4s.DefaultFormats {
  override def dateFormatter = DateTimeFormatter.ofPattern("YYYY-MM-dd")
}

val input =
  """
    |{
    |  "createdAt": "1999-12-10",
    |  "updatedAt": "1999-12-16",
    |  "startDate": "2000-01-02",
    |  "endDate": "200-01-16"
    |}
  """.stripMargin

val result = read[Dates] { input }

1. 尝试根据此处的示例定义CustomFormatter

  

错误预期类型是：（PartialFunction [org.json4s.JValue，java.time.LocalDate]，PartialFunction [Any，org.json4s.JValue]）

object LocalDateSerializer extends CustomSerializer[LocalDate](
  format => (
{
  case JString(str) => LocalTime.parse(str)
  case JNull => null
}
))

implicit val formats =  org.json4s.DefaultFormats ++ new LocalDateSerializer

Answer 1

对于您的第三个错误，您缺少第二个部分功能，请参阅：

ser: Formats => (PartialFunction[JValue, A], PartialFunction[Any, JValue])

所以你可能想要这样做，比如：

  object LocalDateSerializer extends CustomSerializer[LocalDate](format => ({
    case JString(str) =>
      LocalDate.parse(str)
  }, {
    case date: LocalDate => JString(date.toString)
  }))

由于LocalDate默认模式为yyyy-MM-dd，因此"200-01-16"这不是合法时间，您可能希望将其更改为2000-01-16。