How I can sort list of JObject (Scala, json4s)

Question

I read a JSON file and use json4s to parse JSON.

How I can sort an array of JObject that I read from the file?

package org.example

import org.json4s._
import org.json4s.native.JsonMethods._

object Main extends App {
  val file = scala.io.Source.fromURL("https://raw.githubusercontent.com/mledoze/countries/master/countries.json")
  val text = file.mkString

  val json = parse(text)

  val countries = json.children

  countries.sortBy(...)

}

Each country has a field "area" and I need to sort the list by this field. I don't know how to use sortBy in this situation because the country is not just an object of some class. This is JObject and the field "area" has a type JInt.

Can you help me? Or maybe do you know other solution?

Hint: how would you access the int value of that "area" field given a single `JObject`? — Gaël J, Jan 01 '22 at 18:43
BEWARE: [json4s is vulnerable under DoS/DoW attacks!](https://github.com/json4s/json4s/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+denial) — Andriy Plokhotnyuk, Jul 04 '22 at 08:39

score 1 · Answer 1 · answered Jan 01 '22 at 19:19

Thanks, Gaël J for Hint.

I solved my problem as follows:

package org.example

import org.json4s._
import org.json4s.native.JsonMethods._

object Main extends App {
  val file = scala.io.Source.fromURL("https://raw.githubusercontent.com/mledoze/countries/master/countries.json")
  val text = file.mkString

  val json = parse(text)

  val countries = json.children

  val countriesSorted = countries.sortWith((x: JValue, y: JValue) => {

    //File has a few countries with area that has type of Double
    def getValue(value: JValue): Double = {
      value \ "area" match {
        case JDouble(value) => value
        case JInt(value) => value.toDouble
        case _ => 0
      }
    }

    val xValue = getValue(x)
    val yValue = getValue(y)

    xValue > yValue

  })

  for (country <- countriesSorted)
    println(country \ "area")

}

How I can sort list of JObject (Scala, json4s)

1 Answers1