An example of how to customize the field mapping in spray-json to do generic transformation, in this case translating between camelcased Scala attributes and snakecase JSON attributes

SnakifiedSprayJsonSupport.scala

/**
 * The MIT License (MIT)
 * 
 * Copyright (c) 2013-2015 Andrew Snare, Age Mooij
 * 
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 * of this software and associated documentation files (the "Software"), to deal
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 * furnished to do so, subject to the following conditions:
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 * The above copyright notice and this permission notice shall be included in all
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package com.scalapenos.spray

import spray.json._

/**
 * A custom version of the Spray DefaultJsonProtocol with a modified field naming strategy
 */
trait SnakifiedSprayJsonSupport extends DefaultJsonProtocol {
  import reflect._

  /**
   * This is the most important piece of code in this object!
   * It overrides the default naming scheme used by spray-json and replaces it with a scheme that turns camelcased
   * names into snakified names (i.e. using underscores as word separators).
   */
  override protected def extractFieldNames(classTag: ClassTag[_]) = {
    import java.util.Locale

    def snakify(name: String) = PASS2.replaceAllIn(PASS1.replaceAllIn(name, REPLACEMENT), REPLACEMENT).toLowerCase(Locale.US)

    super.extractFieldNames(classTag).map { snakify(_) }
  }

  private val PASS1 = """([A-Z]+)([A-Z][a-z])""".r
  private val PASS2 = """([a-z\d])([A-Z])""".r
  private val REPLACEMENT = "$1_$2"
}

object SnakifiedSprayJsonSupport extends SnakifiedSprayJsonSupport

This code was adapted by me from an original idea and implementation by @asnare

Thank you, this was immensely helpful!

Awesome! Thanks!

So, a few minutes ago I wanted to do this once more and no longer had access to my original implementation. Amusingly Googling to see if there was a better way of doing this by now led me here…

Thanks for preserving this. :)

Now officially licensed with the MIT license

Thanks. Really helpful.

what a great code! thank you so much

great code! will use this

What about combined json field names(I mean fields with underscore and not underscore)? for example I have following json:

{ "requestId": "sdsdsdsdsd", "_links": { "self": { "href": "https://ecom2.nbu.uz/v1/Orders/f963d8c1-fe19-44e6-8441-e6e496b399b5" }, "redirectToCheckout": { "href": "https://ecom2.nbu.uz/Checkout/f963d8c1-fe19-44e6-8441-e6e496b399b5" } } }

Your solution not works here, because spray json will asks "request_id" field. Can you give any suggestions by that situation?

@sm-tester this code is ancient and nowadays I would not use it myself since spray-json has explicit support for defining the exact field names you want to map to.

Use something like this:

val input = """{ "requestId": "sdsdsdsdsd", "_links": { "self": { "href": "https://ecom2.nbu.uz/v1/Orders/f963d8c1-fe19-44e6-8441-e6e496b399b5" }, "redirectToCheckout": { "href": "https://ecom2.nbu.uz/Checkout/f963d8c1-fe19-44e6-8441-e6e496b399b5" } } }"""

case class Input(...)

implicit val format = jsonFormat(Input, "requestId", "_links")

e.g. you can map the original fields to whatever you call your fields in the case class by just specifying the names explicitly.

So please do not use this ancient code and instead use the standard spray-json features.