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How to Encode and Decode JSON with Scala-Circeby@seeni
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How to Encode and Decode JSON with Scala-Circe

by SeeniNovember 14th, 2021
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This is a TLDR; article. If you are a beginner to Scala-Circe library and you want to know how to decode/encode JSON, do as below. You need to encode objects and decode text using Circe and use them as per Business Logic. Sample app is below and runnable version of this code can be found at [scastie.org/sy4s1aISQTqX60uUCSlErA) If you want a run version of the code, use [scasterie.scala-lang].

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If you are new to the Scala-Circe library and you want to know how to decode/encode JSON, follow the method below.

Your Classes

Assume your application has a nested class named Person which has a member named address of class Address.


case class Address(doorNo: Int, street: String, city: String, zipCode: String)
case class Person(name: String, age: Int, address: Address)

Your Task

You need to encode objects and decode text using Circe and use them following some business logic.

What to do?

I will give you a simple straightforward approach that will work for 95% of your use cases.


  1. Add implicit codec in companion objects for your case classes.

  2. Add encode and decode method in the companion object.


import io.circe._, io.circe.generic.semiauto._, io.circe.syntax._

case class Address(doorNo: Int, street: String, city: String, zipCode: String)
object Address {
  implicit val codec = deriveCodec[Address]
}

case class Person(name: String, age: Int, address: Address)

object Person {
  implicit val codec = deriveCodec[Person]
  def encode(person: Person): String = {
    person.asJson.toString
  }

  def decode(jsonString: String): Person = {
    parser.decode[Person](jsonString).toOption.get
  }
}


That’s it. You can now use the Person.encode and Person.decode methods.


The sample app is below.


import io.circe._, io.circe.generic.semiauto._, io.circe.syntax._

val johnDoe = Person("John Doe", 24, Address(5, "Times Square Street", "New York", "12345"))
println(Person.encode(johnDoe))


val encodedText = """
{
  "name" : "Fin",
  "age" : 21,
  "address" : {
    "doorNo" : 7,
    "street" : "Staten Island",
    "city" : "New York",
    "zipCode" : "23456"
  }
}
"""
val decodedJohnDoe = Person.decode(encodedText)

println(decodedJohnDoe)


If you want to access the runnable version of this code, along with imports and library version, use scastie link.


First published here