How to avoid scientific notation in circe JSON serialization

bigdecimal, circe, json, scala

Solution

I assume that you use `scala.math.BigDecimal`, for `java.math.BigDecimal` code is similar. The way to change how objects are serialized is to provide corresponding implicit `Encoder` object. Unfortunately both `Json` and `JsonNumber` hierachies are sealed, so there is no very clean solution but you still can use `JsonNumber.fromDecimalStringUnsafe` that implements `toString` to just return any string you passed in. So you can do something like this:

case class Person(id: String, money: BigDecimal)

object Person {
  implicit final val bigDecimalAsPlainStringEncoder: Encoder[BigDecimal] = new Encoder[BigDecimal] {
    final def apply(value: BigDecimal): Json = Json.fromJsonNumber(JsonNumber.fromDecimalStringUnsafe(value.bigDecimal.toPlainString))
  }

  implicit val encoder: Encoder[Person] = Encoder.forProduct2("ID", "Money")(u => (u.id, u.money))

}

Problem

Let's say I have the next case class: ``` case class Person(id: String, money: BigDecimal) object Person { implicit val encoder: Encoder[Person] = Encoder.forProduct2("ID", "Money")(u => (u.id, u.money)) ``` I want to serialize instances of the Person class to JSON, so when I evaluate the `asJson` from circe, I get the result in scientific notation: ``` { "ID" : "123", "VALOR_SAP" : 2.7E+7 } ``` Why do this happens? I think the reason is because the default to string of `BigDecimal` automatically format to scientific notation. What could I do to avoid this? May be creating another type which extends from `BigDecimal` and overriding the `toString`?

Original source