我试图在Play中为传入的Json添加简单验证。基于this question,我尝试写作:
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 _)
这不会编译,产生错误:
type mismatch;
[error] found : String => ApiData
[error] required: play.api.libs.json.Reads[?]
[error] )(ApiData.apply _)
[error] ^
[error] one error found
但如果我添加第二个字段,它会编译:
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 _)
如果只使用一个字段,我需要做什么?
答案 0 :(得分:6)
由于您只有一个字段,因此您不需要使用组合子语法来创建读取,您只需使用Reads
上已定义的函数来构建所需的函数。
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 _)
}
您从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富类型(map
)。