Deserializing complex nested JSON into Scala objects

Question

Scala 2.12 here. I'm trying to use Lift-JSON to deserialize some JSON into a Scala object and am having trouble navigating the Lift API. Please note: I'm not married to Lift-JSON, any other working solution will be accepted so long as I don't have to bring any heavy/core Play dependencies into my project.

Here's the JSON file I'm trying to read:

{
  "fizz" : "buzz",
  "foo" : [
    "123",
    "456",
    "789"
  ],
  "bar" : {
    "whistle" : 1,
    "feather" : true
  }
}

Here's my Scala object hierarchy:

case class Bar(whistle : Integer, feather : Boolean)
case class MyConfig(fizz : String, foo : Array[String], bar : Bar)

And finally my best attempt at the codeup for this:

def loadConfig(configFilePath : String) : MyConfig = {
  val configJson = Source.fromFile(configFilePath)

  val parsedJson = parse(configJson.mkString)

  MyConfig(???)
}

I need validation in place so that if the JSON is not valid an exception is thrown. Any ideas how I can extract fields out of parsedJson and use them to set values for my MyConfig instance? And how to perform the validation?

Karl Bielefeldt · Accepted Answer · 2018-05-15 18:32:35Z

1

Have you tried parsedJson.extract[MyConfig]? That is straight out of the Extracting values documentation. If you haven't already, you will need to specify an implicit reference to the default formats:

implicit val formats = DefaultFormats

edited May 15, 2018 at 18:32

answered May 15, 2018 at 16:58

Karl Bielefeldt

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1 Comment

hotmeatballsoup Over a year ago

Thanks @Karl (+1) but adding that yields a compiler error:

/Users/myuser/workspace/myapp/src/main/scala/com/myapp/MyConfigLoader.scala:13: could not find implicit value for parameter formats: net.liftweb.json.Formats

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