解析一个 JSON 给出 JsResultException

Question

我正在尝试解析可能有也可能没有字段的 JSON。所以我做了字段选项。但是当我尝试解析 JSON 时，它会导致 JsResultException

import java.nio.charset.StandardCharsets

import play.api.libs.json
import play.api.libs.json.Json


case class Test(field1: String , field2: Seq[String] = Seq.empty[String])

object Test{

  implicit val format = Json.format[Test]
}

val t = Test("1")

println(s"here = ${t.field2}")


val test  = """""{"field1":"test1"}"""""""

//Json.fromJson[Test](Json.parse(test), T)
Json.parse(test).as[Test]

异常：

play.api.libs.json.JsResultException: JsResultException(errors:List((/field1,List(ValidationError(List(error.path.missing),WrappedArray()))), (/field2,List(ValidationError(List(error.path.missing),WrappedArray())))))
    at play.api.libs.json.JsReadable$$anonfun.apply(test2.sc:19)
    at play.api.libs.json.JsReadable$$anonfun.apply(test2.sc:19)
    at play.api.libs.json.JsResult$class.fold(test2.sc:69)
    at play.api.libs.json.JsError.fold(test2.sc:9)
    at play.api.libs.json.JsReadable$class.as(test2.sc:17)
    at play.api.libs.json.JsString.as(test2.sc:42)
    at com.rallyhealth.healthvault.files.dao.A$A1$A$A1.get$$instance$$res0(test2.sc:21)
    at #worksheet#.#worksheet#(test2.sc:54)

试过这个

import play.api.libs.json
import play.api.libs.json.Json

case class Test(field1: String = "", field2: Seq[String] = Seq.empty[String])

object Test {


  def main(args: Array[String]): Unit ={
    implicit val jsonFormat: json.Format[Test] = Json.using[Json.WithDefaultValues].format[Test]


    val test = """""{"field1":"test1"}"""""""

    //Json.fromJson[Test](Json.parse(test), T)
    val value = Json.parse(test).as[Test]
    println(value)
  }
}

我仍然低于异常

Exception in thread "main" play.api.libs.json.JsResultException: JsResultException(errors:List((,List(JsonValidationError(List(error.expected.jsobject),WrappedArray())))))
    at play.api.libs.json.JsReadable.$anonfun$as(JsReadable.scala:25)
    at play.api.libs.json.JsError.fold(JsResult.scala:56)
    at play.api.libs.json.JsReadable.as(JsReadable.scala:24)
    at play.api.libs.json.JsReadable.as$(JsReadable.scala:23)
    at play.api.libs.json.JsString.as(JsValue.scala:86)
    at kavya.Test$.main(GetOrElse.scala:18)
    at kavya.Test.main(GetOrElse.scala)

Answer 1

问题是参数必须是 Option 类型，才能正常工作。

case class Test(field1: Option[String], field2: Option[Seq[String]])

如果不想更改签名，最简单的解决方案是设置默认值：

case class Test(field1: String = "", field2: Seq[String] = Seq.empty[String])

implicit val jsonFormat: Format[Test] = Json.using[Json.WithDefaultValues].format[Test]

解析一个 JSON 给出 JsResultException

Parse a JSON gives JsResultException

json

scala

playframework