如何在Play 2.x中强制对JSON进行严格序列化 [英] How to enforce strict serialization of JSON in Play 2.x

问题描述

从JSON序列化为case类时，默认情况下允许Play的JSON序列化.例如.

Play's JSON serialization is by default permissive when serializing from JSON into a case class. For example.

case class Stuff(name: String, value: Option[Boolean])

implicit val stuffReads: Reads[Stuff] = (
  ( __ \ 'name).read[String] and
  ( __ \ 'value).readNullable[Boolean]
)(Stuff.apply _)

如果收到以下JSON:

If the following JSON was received:

{name: "My Stuff", value: true, extraField: "this shouldn't be here"}

它将以'JsSuccess'成功，并丢弃'extraField'.

It will succeed with a 'JsSuccess' and discard the 'extraField'.

如果存在未处理的"字段，是否可以构造Json Reads函数以使其返回JsError?

Is there a way to construct the Json Reads function to have it return a JsError if there are 'unhandled' fields?

推荐答案

您可以在执行自己的解码之前验证对象不包含多余的键:

You can verify that the object doesn't contain extra keys before performing your own decoding:

import play.api.data.validation.ValidationError

def onlyFields(allowed: String*): Reads[JsObject] = Reads.filter(
  ValidationError("One or more extra fields!")
)(_.keys.forall(allowed.contains))

或者如果您不关心错误消息(无论如何也不是很有帮助):

Or if you don't care about error messages (and that one's not very helpful, anyway):

def onlyFields(allowed: String*): Reads[JsObject] =
  Reads.verifying(_.keys.forall(allowed.contains))

然后:

implicit val stuffReads: Reads[Stuff] = onlyFields("name", "value") andThen (
  (__ \ 'name).read[String] and
  (__ \ 'value).readNullable[Boolean]
)(Stuff)

重复不是很好，但是可以.

The repetition isn't very nice, but it works.

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