[英]Play Json: custom reads one field
假设我必须为Person
类编写自定义Reads[Person]
:
import play.api.libs.functional.syntax._
implicit val personReads: Reads[Person] = (
(__ \ "name").read[String] and // or ~
(__ \ "age").readNullable[Int]
) ((name, age) => Person(name = name, age = age))
它就像一个魅力,真的(不)。
但是当json对象中只有一个字段时,我该怎么办?
Reads
and Writes
的核心是转换这些“解析”步骤的函数式语法。
以下不编译:
import play.api.libs.functional.syntax._
implicit val personReads: Reads[Person] = (
(__ \ "name").read[String]
)(name => Person(name))
你能建议如何处理吗?
选项 1: Reads.map
import play.api.libs.json._
case class Person(name: String)
object PlayJson extends App {
implicit val readsPeson: Reads[Person] =
(__ \ "name").read[String].map(name => Person(name))
val rawString = """{"name": "John"}"""
val json = Json.parse(rawString)
val person = json.as[Person]
println(person)
}
选项 2: Json.reads
import play.api.libs.json._
case class Person(name: String)
object Person {
implicit val readsPerson = Json.reads[Person]
}
object PlayJson extends App {
val rawString = """{"name": "John"}"""
val json = Json.parse(rawString)
val person = json.as[Person]
println(person)
}
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