将类型安全配置解析为案例 class

Question

什么是适合案例class解析：

input {
    foo {
      bar = "a"
      baz = "b"
    }

    bar {
      bar = "a"
      baz = "c"
      other= "foo"
    }
}

来自类型安全的 HOCON 配置，通过 https://github.com/kxbmap/configs?

如何通过 ADT 读取它？查看他们的示例，我不确定如何构建一个 class 层次结构，其中一些 class 具有不同数量的字段 - 但可以继承一些。

sealed trait Tree
case class Branch(value: Int, left: Tree, right: Tree) extends Tree
case object Leaf extends Tree

我这里的样本：

import at.tmobile.bigdata.utils.config.ConfigurationException
import com.typesafe.config.ConfigFactory
import configs.syntax._

val txt =
  """
    |input {
    |    foo {
    |      bar = "a"
    |      baz = "b"
    |      type = "foo"
    |    }
    |
    |    bar {
    |      bar = "a"
    |      baz = "c"
    |      other= "foo"
    |      type="bar"
    |    }
    |}
  """.stripMargin

val config = ConfigFactory.parseString(txt)
config

sealed trait Input{ def bar: String
  def baz:String }
case class Foo(bar: String, baz: String) extends Input
case class Bar(bar:String, baz:String, other:String)extends Input

config.extract[Input].toEither match {
  case Right(s) => s
  case Left(l) =>
    throw new ConfigurationException(
      s"Failed to start. There is a problem with the configuration: " +
        s"${l.messages.foreach(println)}"
    )
}

失败：

No configuration setting found for key 'type'

Answer 1

如果 input 配置将始终包含 2 字段（如示例中的 txt 值；即仅 foo 和 bar），那么你可以这样做：

val txt =
  """
    |input {
    |    foo {
    |      bar = "a"
    |      baz = "b"
    |      type = "foo"
    |    }
    |
    |    bar {
    |      bar = "a"
    |      baz = "c"
    |      other = "foo"
    |      type = "bar"
    |    }
    |}
  """.stripMargin

sealed trait Input {
  def bar: String
  def baz: String
}
case class Foo(bar: String, baz: String) extends Input
case class Bar(bar: String, baz: String, other:String) extends Input

case class Inputs(foo: Foo, bar: Bar)

val result = ConfigFactory.parseString(txt).get[Inputs]("input")
println(result)

输出：

Success(Inputs(Foo(a,b),Bar(a,c,foo)))

--

如果您打算设置一个序列通用输入，那么您应该在配置中反映这一点并解析 Seq[Input]：

val txt =
  """
    |inputs = [
    |    {
    |      type = "Foo"
    |      bar = "a"
    |      baz = "b"
    |    }
    |
    |    {
    |      type = "Bar"
    |      bar = "a"
    |      baz = "c"
    |      other= "foo"
    |    }
    |]
  """.stripMargin

sealed trait Input {
  def bar: String
  def baz: String
}
case class Foo(bar: String, baz: String) extends Input
case class Bar(bar: String, baz: String, other: String) extends Input

val result = ConfigFactory.parseString(txt).get[Seq[Input]]("inputs")
println(result)

输出：

Success(Vector(Foo(a,b), Bar(a,c,foo)))

将类型安全配置解析为案例 class

Parsing Typesafe configuration to a case class

scala

adt

case-class

typesafe-config