uJSON library to manipulate JSON source and Data Structures

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uJson is uPickle’s JSON library, which can be used to easily manipulate JSON source and data structures without converting them into Scala case-classes. It comes bundled with uPickle json serializer but it can be used standalone as well. You may refer to my previous blog to known more about uPickle.

We can perform the following operations with uJson:

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	package object ujson{
	def transform[T](t: Transformable, v: Visitor[_, T]) = t.transform(v)

	def read(s: Transformable): Js.Value = transform(s, Js)

	def copy(t: Js.Value): Js.Value = transform(t, Js)

	def write(t: Js.Value, indent: Int = -1): String = {
	transform(t, StringRenderer(indent)).toString
	}

	def writeTo(t: Js.Value, out: java.io.Writer, indent: Int = -1): Unit = {
	transform(t, Renderer(out, indent))
	}

	def validate(s: Transformable): Unit = transform(s, NoOpVisitor)

	def reformat(s: Transformable, indent: Int = -1): String = {
	transform(s, StringRenderer(indent)).toString
	}

	def reformatTo(s: Transformable, out: java.io.Writer, indent: Int = -1): Unit = {
	transform(s, Renderer(out, indent)).toString
	}
	// End ujson
	}

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Add the following to the build.sbt

libraryDependencies += "com.lihaoyi" %% "ujson" % "0.6.5"

Now let’s see the syntax.

We will use the following ujson array for all the examples.

import ujson.Js
val json = Js.Arr(
  Js.Obj("brand" -> "Samsung", "model" -> "EGIR34"),
  Js.Obj("brand" -> "Nokia", "model" -> "JHKL56")
)

Output:
json: ujson.Js.Arr = [{"brand":"Samsung","model":"EGIR34"},{"brand":"Nokia","model":"JHKL56"}]

Now we can get the value from the json like this:

val brand = json(0)("brand").str    //Output: brand: String = Samsung
val model = json(0)("model").str    //Output: model: String = EGIR34

To remove an element we can use:

val jsValue = json.arr.remove(1)  //Output: jsValue: ujson.Js.Value = {"brand":"Nokia","model":"JHKL56"}

Transformations

uJson allows you seamlessly convert between any of the following forms you may find your JSON in:

Case classes & Scala data-types
ujson.Js ASTs
Strings
CharSequences
Array[Byte]s
Third-party JSON ASTs (Argonaut, Circe, Json4s, Play-Json)

String

val jsonString = ujson.transform(json, StringRenderer()).toString //Output: jsonString: String = [{"brand":"Samsung","model":"EGIR34"},{"brand":"Nokia","model":"JHKL56"}]

Array[Byte]

val jsonJson = ujson.transform(json, BytesRenderer()).toBytes
Output:
jsonJson: Array[Byte] = Array(91, 123, 34, 98, 114, 97, 110, 100, 34, 58, 34, 83, 97, 109, 115, 117, 110, 103, 34, 44, 34, 109, 111, 100, 101, 108, 34, 58, 34, 69, 71, 73, 82, 51, 52, 34, 125, 44, 123, 34, 98, 114, 97, 110, 100, 34, 58, 34, 78, 111, 107, 105, 97, 34, 44, 34, 109, 111, 100, 101, 108, 34, 58, 34, 74, 72, 75, 76, 53, 54, 34, 125, 93)

Transformation

We can every transform the json to third-party JSON library.

We will now convert ujson array that be have taken earlier to the third party libraries and convert that to the json string.

Libraries

Argonaut

To use ujson with Argonaut we need to add the following dependency:

libraryDependencies += "com.lihaoyi" %% "ujson-argonaut" % "0.6.5"

Now, transforming ujson to Argonaut:

import ujson.argonaut.ArgonautJson

val argJson: argonaut.Json = ArgonautJson(
  json
)

Output:
argJson: argonaut.Json = [{"brand":"Samsung","model":"EGIR34"},{"brand":"Nokia","model":"JHKL56"}]

val argonautString = ArgonautJson.transform(argJson, StringRenderer()).toString
Output:
argonautString: String = [{"brand":"Samsung","model":"EGIR34"},{"brand":"Nokia","model":"JHKL56"}]

2. Circe

To use ujson with Circe we need to add the following dependency:

libraryDependencies += "com.lihaoyi" %% "ujson-circe" % "0.6.5"

Now, transforming ujson to Circe:

import ujson.circe.CirceJson

val circeJson: io.circe.Json = CirceJson(
  json
)
Output:
circeJson: io.circe.Json = [
 {
 "brand" : "Samsung",
 "model" : "EGIR34"
 },
 {
 "brand" : "Nokia",
 "model" : "JHKL56"
 }
]

val circeString = CirceJson.transform(circeJson, StringRenderer()).toString
Output:
circeString: String = [{"brand":"Samsung","model":"EGIR34"},{"brand":"Nokia","model":"JHKL56"}]

3. Json4s

To use ujson withJson4s we need to add the following dependency:

libraryDependencies += "com.lihaoyi" %% "ujson-json4s" % "0.6.5"

Now, transforming ujson to Json4s:

import ujson.json4s.Json4sJson
import org.json4s.JsonAST
val json4sJson: JsonAST.JValue = Json4sJson(
  json
)
Output:
json4sJson: org.json4s.JsonAST.JValue = JArray(List(JObject(List((brand,JString(Samsung)), (model,JString(EGIR34)))), JObject(List((brand,JString(Nokia)), (model,JString(JHKL56))))))

val json4sString = Json4sJson.transform(json4sJson, StringRenderer()).toString
Output:
json4sString: String = [{"brand":"Samsung","model":"EGIR34"},{"brand":"Nokia","model":"JHKL56"}]

Reference:

uPickle Documentation