farmdawgnation / liftjson-scalajson-interop Edit

A utility for Lift JSON and Scala JSON interop.

Version Matrix

LiftJSON / Scala JSON AST Interop

Build Status

This package implements interoperability between lift-json's AST and the Scala JSON AST that is being proposed for inclusion in the Scala language. The motivation of the new Scala AST that has been proposed is to provide true interoperability between all libraries that talk in JSON across the Scala language.

In the current ecosystem, you're not guaranteed compatibility between json4s, play-json, spay-json, and any other library. This is particularly problematic as applications grow and evolve in complexity because they could transitively pull in multiple JSON libraries. The result is that when this happens engineers are having to manually deal with converting ASTs from one half of their application to the other. Libraries like databinder-dispatch require users to think about what JSON library they might be using. And ensuring the correctness of conversions between ASTs is sometimes nontrivial and, if done in application code, likely not well documented.


This library requires Java 8 because Lift requies Java 8.

To use this library in your application, simply include it along with your Lift and scala-json-ast dependency.

libraryDependencies ++= Seq(
  "net.liftweb"                %% "lift-json"                  % "3.1.0",
  "org.scala-lang.platform"    %% "scalajson"                  % "1.0.0-M3",
  "me.frmr.jsonutils"          %% "liftjson-scalajson-interop" % "0.2.0"

After this is included, you can start converting between the Standard and Unsafe AST and Lift's AST using simple converter functions.

// Bring the methods into scope.
import me.frmr.jsonutils.JsonConverters._

// Convert Lift to Standard AST.
liftJsonObj.toStandardScalaAST        // => Option[scalajson.ast.JValue]

// Convert Lift to Unsafe AST.
liftJsonObj.toUnsafeScalaAST          // => Option[scalajson.ast.unsafe.JValue]

// Convert standard AST to Lift AST
standardObj.toLiftAST                 // => net.liftweb.json.JValue

// Convert unsafe AST to Lift AST
unsafeObj.toLiftAST                   // => net.liftweb.json.JValue

On JNothing

You'll notice that converting the Lift AST to the Scala AST will produce an Option. This is because Lift's AST includes the concept of a JNothing in its AST. This is effectively the same as no value, and disappears during the conversion.

About Me

My name is Matt Farmer. I'm a developer in Atlanta, GA, with passions for beer, coffee, and Scala. You can find me on Twitter or at my blog.