我有以下案例类:
final case class Camel(firstName: String, lastName: String, waterPerDay: Int)
和圆圈配置:
object CirceImplicits {
import io.circe.syntax._
import io.circe.generic.semiauto._
import io.circe.{Encoder, Decoder, Json}
import io.circe.generic.extras.Configuration
implicit val customConfig: Configuration =
Configuration.default.withSnakeCaseMemberNames.withDefaults
implicit lazy val camelEncoder: Encoder[Camel] = deriveEncoder
implicit lazy val camelDecoder: Decoder[Camel] = deriveDecoder
}
可以,对此进行测试:
val camel = Camel(firstName = "Camelbek", lastName = "Camelov", waterPerDay = 30)
private val camelJ = Json.obj(
"firstName" -> Json.fromString("Camelbek"),
"lastName" -> Json.fromString("Camelov"),
"waterPerDay" -> Json.fromInt(30)
)
"Decoder" must "decode camel types" in {
camelJ.as[Camel] shouldBe Right(camel)
}
但是此测试未通过:
val camel = Camel(firstName = "Camelbek", lastName = "Camelov", waterPerDay = 30)
private val camelJ = Json.obj(
"first_name" -> Json.fromString("Camelbek"),
"last_name" -> Json.fromString("Camelov"),
"water_per_day" -> Json.fromInt(30)
)
"Decoder" must "decode camel types" in {
camelJ.as[Camel] shouldBe Right(camel)
}
如何正确配置circe以便能够在蛇形情况下使用键解析json?
我正在使用circe版本0.10.0
答案 0 :(得分:3)
解决方案1
Circe从您的案例类实例中获取字段名称,并使用游标遍历JSON,尝试获取每个字段名称的值并将其转换为所需的类型。
这意味着您的解码器将无法处理这两种情况。
此问题的解决方案是编写两个解码器:
val decoderDerived: Decoder[Camel] = deriveDecoder
val decoderCamelSnake: Decoder[Camel] = (c: HCursor) =>
for {
firstName <- c.downField("first_name").as[String]
lastName <- c.downField("last_name").as[String]
waterPerDay <- c.downField("water_per_day").as[Int]
} yield {
Camel(firstName, lastName, waterPerDay)
}
然后您可以使用Decoder#or
将这两个解码器组合为一个implicit val decoder: Decode[Camel] = decoderDerived or decoderCamelSnake
Decoder#or将尝试使用第一个解码器进行解码,如果失败,则将尝试第二个解码器。
解决方案2
如果只使用camel_case输入是可以的,则可以使用@ConfiguredJsonCodec
包中的"io.circe" %% "circe-generic-extras" % circeVersion
。请注意,要使用此注释,您还需要包括天堂编译器插件。
addCompilerPlugin(
"org.scalamacros" % "paradise" % "2.1.1" cross CrossVersion.full
)
@ConfiguredJsonCodec
case class User(
firstName: String,
lastName: String
)
object User {
implicit val customConfig: Configuration = Configuration.default.withSnakeCaseMemberNames
}
val userJson = User("John", "Doe").asJson
println(userJson)
// { "first_name" : "John", "last_name" : "Doe" }
val decodedUser = decode[User](userJson.toString)
println(decodedUser)
// Right(User("John", "Doe"))
还请注意,您不需要编写自定义解码器和编码器派生程序,因为该配置可以为您完成此工作。