json-what-else.md

title	type	description	num	previous-page	next-page
What else can uPickle do?	section	An incomplete list of features of uPickle	22	json-files	http-client-intro

{% include markdown.html path="_markdown/install-upickle.md" %}

Construct a new JSON structure with uJson

{% tabs construct%} {% tab 'Scala 2 and Scala 3' %}

val obj: ujson.Value = ujson.Obj(
  "library" -> "upickle",
  "versions" -> ujson.Arr("1.6.0", "2.0.0", "3.1.0"),
  "documentation" -> "https://com-lihaoyi.github.io/upickle/",
)

{% endtab %} {% endtabs %}

Learn more about constructing JSON in the uJson documentation.

Defining custom JSON serialization

You can customize the ReadWriter of your data type by mapping the ujson.Value, like this:

{% tabs custom-serializer class=tabs-scala-version %} {% tab 'Scala 2' %}

import upickle.default._

case class Bar(i: Int, s: String)

object Bar {
  implicit val barReadWriter: ReadWriter[Bar] = readwriter[ujson.Value]
    .bimap[Bar](
      x => ujson.Arr(x.s, x.i),
      json => new Bar(json(1).num.toInt, json(0).str)
    )
}

val bar = Bar(5, "bar")
val json = upickle.default.write(bar)
println(json)
// prints: [5, "bar"]

{% endtab %} {% tab 'Scala 3' %}

import upickle.default.*

case class Bar(i: Int, s: String)

object Bar:
  given ReadWriter[Bar] = readwriter[ujson.Value]
    .bimap[Bar](
      x => ujson.Arr(x.s, x.i),
      json => new Bar(json(1).num.toInt, json(0).str)
    )

val bar = Bar(5, "bar")
val json = upickle.default.write(bar)
println(json)
// prints: [5, "bar"]

{% endtab %} {% endtabs %}

Learn more about custom JSON serialization in the uPickle documentation.