播放Json单字段读取验证器 [英] Play Json Single Field Reads Validator
问题描述
我正在尝试为传入的Json Play添加简单的验证.基于这个问题,我尝试编写:
I'm trying to add simple validation to incoming Json in Play. Based on this question, I tried writing:
case class ApiData(data: String)
def maxLengthValidator = Reads.StringReads.filter(ValidationError("Error"))(_.length < 100)
implicit val ApiDataReads: Reads[ApiData] = (
(JsPath \ "data").read[String](maxLengthValidator)
)(ApiData.apply _)
这不能编译,产生错误:
This does not compile, producing the error:
type mismatch;
[error] found : String => ApiData
[error] required: play.api.libs.json.Reads[?]
[error] )(ApiData.apply _)
[error] ^
[error] one error found
但是如果我添加第二个字段,它将编译:
But if I add a second field, it does compile:
case class ApiData(data: String, __doNotUse: Option[Int])
implicit val ApiDataReads: Reads[ApiData] = (
(JsPath \ "data").read[String](maxLengthValidator) and
(JsPath \ "__doNotUse").readNullable[Int]
)(ApiData.apply _)
我需要做什么才能使它仅在单个字段中起作用?
What do I need to do to get this working with just a single field?
推荐答案
由于您只有一个字段,因此不需要使用组合语法来创建读取,因此可以使用已经在Reads
上定义的函数建立你想要的那个.
Since you only have a single field, you don't need the combinator syntax to create a reads, you can just use the functions already defined on Reads
to build the one you want.
def maxLengthValidator = Reads.of[String].filter(ValidationError("Error"))(_.length < 100)
case class ApiData(data: String)
object ApiData {
implicit val reads: Reads[ApiData] = (__ \ "data").read(maxLengthValidator).map(ApiData.apply _)
}
从Reads[String]
开始,添加一些验证(filter
),然后将有效结果转换为您自己的丰富类型(map
).
You start with a Reads[String]
, add some validation (filter
) and then transform valid results to your own rich type (map
).
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