greyplane / jsonpath4s   0.0.1

MIT License GitHub

Compile JsonPath to Monocle optics, pass and use it freely.

Scala versions: 3.x
Scala.js versions: 1.x


Compile JsonPath to Monocle optics, pass and use it freely.


  • Support filter and function extension.


  1. Add core dependency.
libraryDependencies ++= Seq(
 "io.github.greyplane" %% "jsonpath4s-core" % "version",
 "io.github.greyplane" %% "jsonpath4s-optics" % "version"
  1. Add JSON library support as you needed, currently we supported circe and spray-json.
libraryDependencies ++= Seq(
 "io.github.greyplane" %% "jsonpath4s-circe" % "version",
 // or if you're using spray-json
 "io.github.greyplane" %% "jsonpath4s-spray-json" % "version"
  1. If you're using Scala 2, here's the extra config required for Scala 2 to use Scala 3 artifact.
ThisBuild / scalacOptions ++= Seq("-Ytasty-reader")

// add cross config for every artifact
("io.github.greyplane" %% "jsonpath4s-core" % "version").cross(CrossVersion.for2_13Use3)
  1. Add imports as needed, for typical usage the following should suffice.
import jsonpath4s._
import jsonpath4s.optics._
// if you're using spray-json, import jsonpath4s.json.spray._
import jsonpath4s.json.circe._

if you're using scala 3

import jsonpath4s.*
import jsonpath4s.optics.*
import jsonpath4s.json.circe.given


For simplest usage you could just utilizing the string interpolation functionality.

// This would throw RuntimeException if parsing failed!
val nodeLists: List[Json] = jsonpath"$$.a".compile.getAll(json)

For safer option, you should use JsonPathParser directly.

val maybeJsonPath: Either[JsonPathError, JsonPath] = JsonPathParser.parse("""$.a""")

If you'd like use one JsonPath multiple times, you could just compile it and pass it around, after all, it's just a normal optic!

// make sure you've import json support library
val a: Fold[Json, Json] = jsonpath"$$.a".compile

Interesting(Advanced) Usage

Compose JsonPath

Since they're just normal optics, there's nothing prevent you to compose them!

val a = jsonpath"$$.a".compile
val b = jsonpath"$$.b".compile

// it's equivalent to jsonpath"$$.a.b"

Use as setter

// number of Traversal equals to the product of all segments' segment.selectors.size
// in this case there's only 1 Traversal
val ts: Seq[Traversal] = summon[Compiler[Json]].compileSegments(jsonpath"$$.a.*")

// this will modify for example { "a": { "b": 1, "c": 2 } } to { "a": { "b": "test", "c": "test" } } => Json.fromString("test"))(json))

But there's one gotcha, if your JsonPath contains descendants segment(..), it cannot be used as setter, since we use uniplate's cosmos combinator, which should be a Fold rather than Traversal, but we implemented it as a Traversal to make use others as setter possible.