Json4s scala json API cookbook as unit test cases. / published by https://github.com/dacr/code-examples-manager #b2de4720-2d03-44bf-92cf-1c4f67ac1864/a2291e1b8aa90f83b7f415fc7a99d9ac39199411

json-json4s.sc

// summary : Json4s scala json API cookbook as unit test cases.
// keywords : scala, scalatest, json4s, json, @testable, @fail
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : b2de4720-2d03-44bf-92cf-1c4f67ac1864
// created-on : 2018-07-10T08:11:54Z
// managed-by : https://github.com/dacr/code-examples-manager
// execution : scala ammonite script (http://ammonite.io/) - run as follow 'amm scriptname.sc'
// run-with : scala-cli $file

// ---------------------
//> using scala  "3.3.0"
//> using dep "org.scalatest::scalatest:3.2.16"
//> using dep "org.json4s::json4s-native:4.0.6"
//> using dep "org.json4s::json4s-jackson:4.0.6"
//> using dep "org.json4s::json4s-ext:4.0.6"
//> using dep "com.fasterxml.jackson.core:jackson-databind:2.15.1"
//> using objectWrapper
// ---------------------


import org.scalatest._, flatspec._, matchers._, OptionValues._

import java.time.{OffsetDateTime, ZonedDateTime}
import com.fasterxml.jackson.databind.node.ObjectNode



case class Someone(name:String, age:Int)
case class Event(when:OffsetDateTime, who:Someone, what:String)

trait Pet {
  val name:String
  val birthYear:Int
}
case class Dog(name:String, birthYear:Int) extends Pet
case class Cat(name:String, birthYear:Int, lifeCount:Int) extends Pet
case class Animals(animals:List[Pet])

case class Something[T](that:T)



case class CheckedValue[NUM](
  value: NUM,
  isPrime: Boolean,
  digitCount: Long,
  nth: NUM) //(implicit numops: Integral[NUM])


case class Truc(msg:String)
case class Muche[A](data:A)

case class DocTree(name:String,size:String)
case class DocReport(tree:DocTree)
case class Doc(report:DocReport)


class JsonJson4sCookBook extends AnyFlatSpec with should.Matchers {
  override def suiteName = "JsonJson4sCookBook"

  "json4s" should "work with literals (jackson)" in  {
    implicit val formats = org.json4s.DefaultFormats
    import org.json4s.jackson.JsonMethods.{parse}
    import org.json4s._
    parse(""" "truc" """).extract[String] shouldBe """truc"""
  }

  it should "work with literals (native)" ignore  {
    implicit val formats = org.json4s.DefaultFormats
    import org.json4s._
    intercept[Exception] { // :(
      import org.json4s.native.JsonMethods.{parse}
      parse(""" "truc" """).extract[String] shouldBe """truc"""
    }
    fail("not supported")
  }

  it should "parse json strings" in {
    import org.json4s.jackson.JsonMethods.{parse}
    import org.json4s._
    implicit val formats = org.json4s.DefaultFormats
    val json = """{"name":"John Doe", "age":42}"""
    val doc = parse(json)
    (doc \ "name").extract[String] should equal("John Doe")
  }

  it should "provide easy way to query and extract data" in {
    import org.json4s._
    import org.json4s.Extraction.decompose
    implicit val formats = org.json4s.DefaultFormats
    val people = List(
      Someone(name="John Doe", age=22),
      Someone(name="Sarah Connors", age=84),
      Someone(name="John Connors", age=42)
    )
    val jvalue = decompose(people)

    (jvalue \\ "name").children.map(_.extract[String])
    (jvalue \\ "name").children.flatMap(_.extractOpt[String])
    (jvalue \\ "age").children.map(_.extract[Int]).sum shouldBe 148
  }

  it should "be easy easy to move from its json AST to a user friendly data structure" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{parse}
    implicit val formats = org.json4s.DefaultFormats
    val json = parse(""" { "truc":[{"a":1},{"a":2},{"b":3}] }""") \ "truc"
    // extract alternatives, see how it is powerful to convert complex data structure from its internal AST :)
    json.extract[List[JValue]]
    json.extract[List[JValue]].map(_.extract[Map[String,Int]])
    json.extract[List[Map[String,Int]]] shouldBe List(Map("a" -> 1), Map("a" -> 2), Map("b" -> 3))
  }

  it should "pretty render json" in {
    import org.json4s.jackson.JsonMethods.{parse,pretty,render}
    implicit val formats = org.json4s.DefaultFormats
    val jvalue = parse("""{"name":"John Doe", "age":42}""")
    val result: String = pretty(render(jvalue))
    result.split("\n") should have size(4)
  }

  it should "serialize case classes to json" in {
    import org.json4s.jackson.Serialization.{read, write}
    implicit val formats = org.json4s.DefaultFormats
    val someone = Someone(name="John Doe", age=42)
    val json: String = write(someone)
    read[Someone](json) should equal(someone)
  }

  it should "manage java8 time" in {
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.DefaultFormats
    import org.json4s.ext.JavaTimeSerializers
    implicit val formats = DefaultFormats ++ JavaTimeSerializers.all // Warning : by default it doesn't manage milliseconds ! See next test, and lossless method
    val when = OffsetDateTime.parse("2042-01-01T01:42:42Z")
    val event = Event(when, Someone("John Doe", 42), "future birth")
    val json:String = write(event)
    val eventBack = read[Event](json)
    eventBack should equal(event)
  }

  it should "extract ZonedDateTime/OffsetDatetime with milliseconds" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{parse,render,compact}
    import org.json4s.DefaultFormats
    import org.json4s.ext.JavaTimeSerializers

    implicit val formats = DefaultFormats.lossless ++ JavaTimeSerializers.all // USE .lossless for milliseconds to ba taken into account !
    val timestamp = "2042-01-01T01:42:42.042Z"
    val json = s"""{"when":"$timestamp"}"""
    val jvalue = parse(json)
    (jvalue \ "when").extract[ZonedDateTime] // Human readable date time, do not use for equals, comparison...
    (jvalue \ "when").extract[OffsetDateTime] should equal(OffsetDateTime.parse(timestamp))
    compact(render(jvalue)) should equal(json)
  }
  it should "support ISO8601 datetime timezone with offset" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{parse,render,compact}
    import org.json4s.DefaultFormats
    import org.json4s.ext.JavaTimeSerializers
    import java.text.SimpleDateFormat
    def customDefaultFormats:DefaultFormats = new DefaultFormats {
      override def dateFormatter =  new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX")
    }
    implicit val formats = customDefaultFormats ++ JavaTimeSerializers.all
    val timestamp = "2042-01-01T01:42:42.042+01:00"
    val json = s"""{"when":"$timestamp"}"""
    val jvalue = parse(json)
    (jvalue \ "when").extract[ZonedDateTime] // Human readable date time, do not use for equals, comparison...
    (jvalue \ "when").extract[OffsetDateTime] should equal(OffsetDateTime.parse(timestamp))
    compact(render(jvalue)) should equal(json)
  }

  it should "have a way to detect empty object" in {
    import org.json4s.jackson.JsonMethods.{parse,render,compact,pretty}
    import org.json4s._

    implicit val formats = DefaultFormats
    implicit val serialization = jackson.Serialization

    val json = """{"emptyObject":{}, "value":4242, "notEmptyObject":{"that":42} } """
    val jvalue = parse(json)

    val notFound1 = (jvalue \ "somethingNotHere")
    notFound1 should be(JNothing)

    val notFound2 = (jvalue \\ "somethingNotHere")
    notFound2 should be(JObject())

    val emptyObject = (jvalue \ "emptyObject").extract[JObject]
    emptyObject.values.isEmpty should be(true)
    emptyObject.children.isEmpty should be(true)
    emptyObject.children.size should be(0)

    val notEmptyObject = (jvalue \ "notEmptyObject").extract[JObject]
    notEmptyObject.values.isEmpty should be(false)
    notEmptyObject.children.isEmpty should be(false)
    notEmptyObject.children.size should be >(0)

    val aValue = (jvalue \ "value")
    aValue should not be(JNothing)
    aValue should not be(JObject())
    aValue.extractOpt[Int] should be(Some(4242))
  }

  it should "provide a high level pragmatic DSL" in {
    import org.json4s.jackson.JsonMethods.{parse,render,compact,pretty}
    import org.json4s.jackson.Serialization
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.JsonDSL._
    import org.json4s._
    import Extraction.decompose

    implicit val formats = DefaultFormats
    implicit val serialization = Serialization

    val truc = decompose(Truc("Hello"))
    val muche = decompose(Muche("world"))
    val reference = ("x"-> 24) ~ ("y"->42) ~ ("z1" -> truc) ~ ("z2" -> muche)

    write(reference) shouldBe """{"x":24,"y":42,"z1":{"msg":"Hello"},"z2":{"data":"world"}}"""
  }


  it should "be possible to work with POJO objects" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{parse,render,compact,pretty}
    import org.json4s.jackson.Serialization
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.JsonDSL._
    import java.awt.Point

    implicit val formats:Formats = DefaultFormats + FieldSerializer[Point]()
    implicit val serialization = Serialization

    val reference = ("x"-> 24) ~ ("y"->42)

    val point = new Point(24, 42)

    val jsonString = write(point)
    val json = parse(jsonString)
    json should equal(reference)

    // Alternative way
    Extraction.decompose(point) should equal(reference)
  }


  it should "be possible to work with POJO objects even when the class is unknown" ignore { // TODO - shall work with genson
    import org.json4s.jackson.JsonMethods.{parse,render,compact,pretty}
    import org.json4s.jackson.Serialization
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.JsonDSL._
    import org.json4s._

    val reference = ("x"-> 24) ~ ("y"->42)

    //val clazz = Class.forName("java.awt.Point")
    //val cons = clazz.getConstructor(classOf[Int], classOf[Int])
    //val point = cons.newInstance(new java.lang.Integer(24), new java.lang.Integer(42)).asInstanceOf[Object]

    val point = new java.awt.Point(24, 42)
    //val customSerializer = classOf[FieldSerializer].newInstance()

    implicit val formats = DefaultFormats //+ customSerializer //FieldSerializer[java.awt.Point]()
    implicit val serialization = Serialization

    Extraction.decompose(point) should equal(reference)
    // TODO - current status : decompose doesn't introspect dynamically allocated java types
  }


  it should "map a ScalaMap to a json object" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{render,compact,pretty}

    val now = new java.util.Date()
    val nowIso8601 = now.toInstant.toString // ~ 2018-09-25T12:59:21.315Z
    val input = Map("age"->42, "name"->"John Doe", "now"->now)

    implicit val formats = DefaultFormats.lossless // for milliseconds in iso8601 dates...

    val jvalue = Extraction.decompose(input)
    val json = pretty(render(jvalue))
    info(json)
    compact(render(jvalue)) shouldBe s"""{"age":42,"name":"John Doe","now":"${nowIso8601}"}"""
  }

  it should "be possible to extract a Map from a json object" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{render,compact,pretty}
    implicit val formats = DefaultFormats.lossless // for milliseconds in iso8601 dates...

    val someone = Someone("john", 42)
    val jvalue = Extraction.decompose(someone)
    val jmap = jvalue.extract[Map[String,Any]]
    jmap shouldBe Map("name"->"john", "age"->42)
  }

  it should "be possible to serialize java collection types" in {
    import org.json4s._
    import org.json4s.jackson.JsonMethods.{render,compact,pretty}
    implicit val formats = DefaultFormats.lossless
    val jl = new java.util.LinkedList[String]()
    jl.add("Hello1")
    jl.add("Hello2")

    compact(render(Extraction.decompose(jl))) shouldBe """["Hello1","Hello2"]"""
  }

  it should "be possible to rename field during serdes operations" in {
    import org.json4s._
    import org.json4s.FieldSerializer
    import org.json4s.FieldSerializer._
    import org.json4s.jackson.Serialization.{read, write}
    val renamer = FieldSerializer[Someone](
      renameTo("name", "lastName"),
      renameFrom("lastName", "name")
    )
    implicit val format: Formats = DefaultFormats + renamer
    val someone = Someone(name="Connors", age=42)
    val jsontxt = """{"lastName":"Connors","age":42}"""
    write(someone) shouldBe jsontxt
    read[Someone](jsontxt) shouldBe someone
  }

  it should "be possible to rename multiple fields during serdes operations" in {
    import org.json4s._
    import org.json4s.FieldSerializer
    import org.json4s.FieldSerializer._
    import org.json4s.jackson.Serialization.{read, write}
    val renamer = FieldSerializer[Someone](
      renameTo("name", "lastName").orElse(renameTo("age", "ageInYear")),
      renameFrom("lastName", "name").orElse(renameFrom("ageInYear", "age"))
    )
    implicit val format: Formats = DefaultFormats + renamer
    val someone = Someone(name="Connors", age=42)
    val jsontxt = """{"lastName":"Connors","ageInYear":42}"""
    write(someone) shouldBe jsontxt
    read[Someone](jsontxt) shouldBe someone
  }

  it should "be possible to rename inherited field during serdes operations" in {
    import org.json4s._
    import org.json4s.FieldSerializer
    import org.json4s.FieldSerializer._
    import org.json4s.jackson.Serialization.{read, write}
    val renamer = FieldSerializer[Pet](
      renameTo("birthYear", "birth"),
      renameFrom("birth", "birthYear")
    )
    implicit val format: Formats = DefaultFormats + renamer
    val pet = Cat(name="minou", birthYear=1942, lifeCount=7)
    val jsontxt = """{"name":"minou","birth":1942,"lifeCount":7}"""
    write(pet) shouldBe jsontxt
    read[Cat](jsontxt) shouldBe pet
  }

  it should "be possible to add type hints" in {
    import org.json4s._
    import org.json4s.jackson.Serialization
    import org.json4s.jackson.Serialization.{read, write}
    implicit val formats = Serialization.formats(
      FullTypeHints(List(
        classOf[Cat], classOf[Dog]
      ))
    )
    val catClass = classOf[Cat].getName
    val animalsText = s"""{"animals":[{"jsonClass":"$catClass","name":"minou","birthYear":1942,"lifeCount":7}]}"""
    val cat = Cat(name="minou", birthYear=1942, lifeCount=7)
    val animals = read[Animals](animalsText)
    animals shouldBe Animals(List(cat))
    write(read[Animals](animalsText)) shouldBe animalsText
  }

  it should "be possible to use either camel case or snake case" in {
    import org.json4s._
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.jackson.JsonMethods.{parse}
    import org.json4s.DefaultFormats
    import org.json4s.Extraction, Extraction.decompose
    import org.json4s.JValue
    implicit val formats = DefaultFormats
    val json = """{"name":"minou","birth_year":1980,"life_count":7}"""
    val cat = Cat("minou", 1980, 7)

    decompose(cat).camelizeKeys.extractOpt[Cat].value shouldBe cat
    parse(json).camelizeKeys.extractOpt[Cat].value shouldBe cat
    read[JValue](json).camelizeKeys.extractOpt[Cat].value shouldBe cat
  }

  it should "be possible to serialize / deserialize complex types with generics" in {
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.DefaultFormats
    import org.json4s.Extraction, Extraction.decompose
    import org.json4s.JValue
    implicit val formats = DefaultFormats
    val something1 = Something("chisel")
    val jvalue = decompose(something1)
    write(jvalue) shouldBe """{"that":"chisel"}"""
  }

  it should "be possible to serialize / deserialize complex types with implicits" in {
    import org.json4s._
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.DefaultFormats
    import org.json4s.Extraction, Extraction.decompose
    import org.json4s.JValue
    implicit val formats = DefaultFormats
    val something1 = CheckedValue(value=7L, isPrime=true, digitCount=1, nth=4)
    val jvalue = decompose(something1)
    write(jvalue) shouldBe """{"value":7,"isPrime":true,"digitCount":1,"nth":4}"""
  }


  it should "be possible to manipulate json trees flattening" in {
    import org.json4s._
    import org.json4s.jackson.Serialization.{read, write}
    import org.json4s.jackson.JsonMethods.{parse,compact,render}
    import org.json4s.DefaultFormats
    import org.json4s.Extraction, Extraction.decompose
    import org.json4s.JValue
    implicit val formats = DefaultFormats
    val someFile: JValue = parse(
      """
        |{
        | "report": {
        |   "trees": {
        |     "tree": {
        |       "name": "oak",
        |       "size": "5m"
        |     }
        |   }
        | }
        |}
        |""".stripMargin)

    val subtree = (someFile \ "report" \ "trees")
    val fixedtree = someFile.merge( decompose("report"->subtree)).removeField{ case (name,value)=> name == "trees"}
    fixedtree.extractOpt[Doc] shouldBe Option(Doc(DocReport(DocTree("oak", "5m"))))
    compact(render(fixedtree)) shouldBe """{"report":{"tree":{"name":"oak","size":"5m"}}}"""
  }

  "Jackson" should "be interoperable with json4s" in {
    import org.json4s._
    import org.json4s.JsonDSL._
    import org.json4s.jackson.JsonMethods.{asJsonNode, fromJsonNode}
    import com.fasterxml.jackson.databind._
    import org.json4s.DefaultFormats

    implicit val formats = DefaultFormats

    val objectMapper = new ObjectMapper()
    val jsonNode = objectMapper.readTree("""{"name":"joe"}""")
    info("JsonNode is the default AST type for Jackson, as JValue for json4s")
    val jvalue = fromJsonNode(jsonNode)
    (jvalue \ "name").extractOpt[String] shouldBe Some("joe")
    asJsonNode(jvalue) shouldBe jsonNode
  }

  it should "be quite easy to manipulate Json AST" in {
    import org.json4s._
    import org.json4s.JsonDSL._
    import org.json4s.jackson.JsonMethods.{asJsonNode, fromJsonNode}
    import com.fasterxml.jackson.databind._
    import org.json4s.DefaultFormats

    implicit val formats = DefaultFormats

    val objectMapper = new ObjectMapper()
    val jsonNode = objectMapper.readTree("""{"name":"joe"}""")
    val updatedJson = jsonNode match {
      case ob:ObjectNode =>
        val updated = ob.deepCopy()
        updated.put("age", 42)
        val addressNode = updated.putObject("address")
        addressNode.put("town", "dallas")
        updated
      case _ => fail()
    }
    info("But take care, jackson use mutation, so do use deepCopy if needed as within this example")
    objectMapper.writeValueAsString(updatedJson) shouldBe """{"name":"joe","age":42,"address":{"town":"dallas"}}"""
  }
}


org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[JsonJson4sCookBook].getName))