How to serialize JSON with json4s with UTF-8 characters?

@0__, it is not clear what answer you want to get with your bounty. The bug mentioned in the original question has already been fixed, so you can customize whether you want Unicode characters to be encoded or not. You just need to build with a current version, e.g. with a build.sbt like this:

name := "SO_ScalaJson4sUnicodeChars"version := "1.0"scalaVersion := "2.12.1"libraryDependencies += "org.json4s" %% "json4s-native" % "3.5.1"

As @kriegaex mentioned in his comment, UTF-8 is the default encoding for JSON according to RFC 7159, so encoding is not strictly necessary. This is why by default json4s does not encode, just as the OP requested:

package soimport org.json4s.JsonDSL._import org.json4s._import org.json4s.native.JsonMethods._object SOTest extends App {  val json = ("english" -> JString("serialization")) ~ ("japanese" -> JString("シリアライゼーション"))  println(pretty(render(json)))}

Console log:

{  "english":"serialization",  "japanese":"シリアライゼーション"}

However if for some compatibility reason you need the output to be encdeded, json4s supports that as well. If you add your own customJsonFormats like this, you get encoded output:

package soimport org.json4s.JsonDSL._import org.json4s._import org.json4s.native.JsonMethods._object SOTest extends App {  val json = ("english" -> JString("serialization")) ~ ("japanese" -> JString("シリアライゼーション"))  implicit val customJsonFormats = new DefaultFormats {    override def alwaysEscapeUnicode: Boolean = true  }  println(pretty(render(json)))}

Console log:

{  "english":"serialization",  "japanese":"\u30b7\u30ea\u30a2\u30e9\u30a4\u30bc\u30fc\u30b7\u30e7\u30f3"}

Update by @kriegaex: I decided to edit this answer, merging in some information from my own one and fixing a few minor issues. I did this so as to avoid redundancy. I am more interested in a good, consistent answer than in the bounty. I am going to delete mine now.