What JSON library to use in Scala? [closed]

Question

Unfortunately writing a JSON library is the Scala community's version of coding a todo list app.

There are quite a variety of alternatives. I list them in no particular order, with notes:

1. parsing.json.JSON - Warning this library is available only up to Scala version 2.9.x (removed in newer versions)
2. spray-json - Extracted from the Spray project
3. Jerkson ± - Warning a nice library (built on top of Java Jackson) but now abandonware. If you are going to use this, probably follow the Scalding project's example and use the backchat.io fork
4. sjson - By Debasish Ghosh
5. lift-json - Can be used separately from the Lift project
6. json4s 💣 § ± - An extraction from lift-json, which is attempting to create a standard JSON AST which other JSON libraries can use. Includes a Jackson-backed implementation
7. Argonaut 💣 § - A FP-oriented JSON library for Scala, from the people behind Scalaz
8. play-json ± - Now available standalone, see this answer for details
9. dijon - A handy, safe and efficient JSON library, uses jsoniter-scala under hood.
10. sonofjson - JSON library aiming for a super-simple API
11. Jawn - JSON library by Erik Osheim aiming for Jackson-or-faster speed
12. Rapture JSON ± - a JSON front-end which can use 2, 4, 5, 6, 7, 11 or Jackson as back-ends
13. circe 💣 - fork of Argonaut built on top of cats instead of scalaz
14. jsoniter-scala - Scala macros for compile-time generation of ultra-fast JSON codecs
15. jackson-module-scala - Add-on module for Jackson to support Scala-specific datatypes
16. borer - Efficient CBOR and JSON (de)serialization in Scala

💣 = has not fixed security vulnerabilities, § = has Scalaz integration, ± = supports interop with Jackson JsonNode

In Snowplow we use json4s with the Jackson back-end; we've had good experiences with Argonaut too.

Lift-json is at version 2.6 and it works really well (and is also very well supported, the maintainer is always ready to fix any bugs users may find. You can find examples using it on the github repository

The maintainer (Joni Freeman) is always reachable on the Lift mailing list. There are also other users on the mailing list who are very helpful as well.

As @Alexey points out, if you want to use the library with other Scala version, say 2.11.x, change scalaVersion and use %% as follows:

scalaVersion := "2.11.5" 

"net.liftweb" %% "lift-json" % "2.6"

You can check the liftweb.net site to find out the latest version as time goes by.

I suggest using jerkson, it supports most basic type conversions:

scala> import com.codahale.jerkson.Json._

scala> val l = List( 
                 Map( "id" -> 1, "name" -> "John" ),
                 Map( "id" -> 2, "name" -> "Dani")
               )

scala> generate( l )

res1: String = [{"id":1,"name":"John"},{"id":2,"name":"Dani"}]

Number 7 on the list is Jackson, not using Jerkson. It has support for Scala objects, (case classes etc).

Below is an example of how I use it.

object MyJacksonMapper extends JacksonMapper
val jsonString = MyJacksonMapper.serializeJson(myObject)
val myNewObject = MyJacksonMapper.deserializeJson[MyCaseClass](jsonString)

This makes it very simple. In addition is the XmlSerializer and support for JAXB Annotations is very handy.

This blog post describes it's use with JAXB Annotations and the Play Framework.

http://krasserm.blogspot.co.uk/2012/02/using-jaxb-for-xml-and-json-apis-in.html

Here is my current JacksonMapper.

trait JacksonMapper {

  def jsonSerializer = {
    val m = new ObjectMapper()
    m.registerModule(DefaultScalaModule)
    m
  }

  def xmlSerializer = {
    val m = new XmlMapper()
    m.registerModule(DefaultScalaModule)
    m
  }

  def deserializeJson[T: Manifest](value: String): T = jsonSerializer.readValue(value, typeReference[T])
  def serializeJson(value: Any) = jsonSerializer.writerWithDefaultPrettyPrinter().writeValueAsString(value)
  def deserializeXml[T: Manifest](value: String): T = xmlSerializer.readValue(value, typeReference[T])
  def serializeXml(value: Any) = xmlSerializer.writeValueAsString(value)

  private[this] def typeReference[T: Manifest] = new TypeReference[T] {
    override def getType = typeFromManifest(manifest[T])
  }

  private[this] def typeFromManifest(m: Manifest[_]): Type = {
     if (m.typeArguments.isEmpty) { m.erasure }
     else new ParameterizedType {
       def getRawType = m.erasure

       def getActualTypeArguments = m.typeArguments.map(typeFromManifest).toArray

       def getOwnerType = null
     }
  }
}   

Maybe I've late a bit, but you really should try to use json library from play framework. You could look at documentation. In current 2.1.1 release you could not separately use it without whole play 2, so dependency will looks like this:

val typesaferepo  = "TypeSafe Repo" at "http://repo.typesafe.com/typesafe/releases"
val play2 = "play" %% "play" % "2.1.1"

It will bring you whole play framework with all stuff on board.

But as I know guys from Typesafe have a plan to separate it in 2.2 release. So, there is standalone play-json from 2.2-snapshot.