title: Play 2.x Json transform json keys to camelCase from underscore case
body: <p>I want to transform a json with underscore case keys to camel case keys.</p>
  
  <pre><code>"{\"first_key\": \"first_value\", \"second_key\": {\"second_first_key\":\"second_first_value\"}}"
  </code></pre>
  
  <p>to </p>
  
  <pre><code> "{\"firstKey\": \"first_value\", \"secondKey\": {\"secondFirstKey\":\"second_first_value\"}}"
  </code></pre>
  
  <p>This is partial code:</p>
  
  <pre><code>val CamelCaseRegex = new Regex("(_.)")
  val jsonTransformer = (__).json.update(
    //converts json camel_case field names to Scala camelCase field names  
  )
  val jsonRet = Json.parse(jsonStr).transform(jsonTransformer)
  </code></pre>
  
  <p>I have tried several ways in the update method without success.</p>