Question

我试图强制执行验证规则，输入Json中的时间戳必须使用格式-ffloat-store Do not store floating-point variables in registers, and inhibit other options that might change whether a floating-point value is taken from a register or memory. This option prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a "double" is supposed to have. Similarly for the x86 architecture. For most programs, the excess precision does only good, but a few programs rely on the precise definition of IEEE floating point. Use -ffloat-store for such programs, after modifying them to store all pertinent intermediate computations into variables.指定时区。当输入不正确时，我想返回一条表示格式错误的消息。

此代码段用于解析预期格式的数据：

DateTimeFormatter.ISO_OFFSET_DATE_TIME

但如果格式错误则抛出implicit val instantReads = Reads[Instant] { js => js.validate[String].map[Instant](tsString => Instant.from(OffsetDateTime.parse(tsString, DateTimeFormatter.ISO_OFFSET_DATE_TIME)) ) }。

如何修复它以返回DateTimeParseException而不是抛出异常？

Answer 1

您可以改为使用Read.flatMap。

implicit val instantReads = Reads[Instant] {
  _.validate[String].flatMap[Instant] { tsString =>
    try { // or Try [T]
      JsSuccess (Instant.from(OffsetDateTime.parse(tsString, DateTimeFormatter.ISO_OFFSET_DATE_TIME)))
    } catch {
      case cause: Throwable =>
        JsError("Wrong datetime format")
    }
  }
}

Play-Json解析日期时间字符串为Reads [Instant]

1 个答案: