Scala Pickling for Json serialization and deserialization?

Question

For my project, dijon, I was wondering if it is possible to use Scala pickling for JSON serialization and deserialization. Specifically, I want something like this def toJsonString(json: JSON, prettyPrint: Boolean = false): String and def fromJsonString(json: String): JSON. How can I use pickling to create these two helper methods?

[This](http://stackoverflow.com/questions/18725699/scala-pickling-and-type-parameters) may be your answer. — David Weber, May 19 '14 at 09:11
You get either `fromJsonString[A]` and compile time macros, or `fromJsonString` untyped with runtime reflection. See @DavidWeber's suggestion. Not sure Pickling works with Scala 2.11 yet. — DCKing, May 20 '14 at 13:26
FYI, there is a Scala 2.11 version of scala-pickling on maven central. — David Weber, May 22 '14 at 11:02

score 7 · Accepted Answer · answered May 21 '14 at 09:11

It really depends on what is most convenient for your use. These are rough sketches of the choices you have:

 import scala.pickling._, json._    

 // Uses macros implicitly on Scope
 def toJSONString[A](obj: A, prettyPrint: Boolean = false)(implicit pickler: A => JSONPickle) = {
    val json = pickler(obj)
    myPrettyPrinter.print(json.value, prettyPrint)
 }

 // Uses macros defined elsewhere
 def toJSONString(obj: Any, prettyPrint: Boolean = false) = {
    val json = classToPicklerMap(obj.getClass)(obj)
    myPrettyPrinter.print(json.value, prettyPrint)
 }

 // Uses runtime reflection
 def toJSONString(obj: Any, prettyPrint: Boolean = false) = {
    val json = obj.pickle
    myPrettyPrinter.print(json.value, prettyPrint)
 }

 // Uses macros implicitly on scope
 def fromJSONString[A](json: String)(implicit unpickler: JSONPickle => A): A = {
    unpickler(JSONPickle(json))
 }

 // Uses macros defined elsewhere #1
 def fromJSONString[A](json: String)(implicit c: ClassTag[A]) = {
    classnameToUnpicklerMap(c.runtimeClass.getName)(json).asInstanceOf[A]
 }

 // Uses macros defined elsewhere #2
 def fromJSONString(json: String): Any = {
    val className = parseClassName(json) // Class name is stored in "tpe" field in the JSON    
    classnameToUnpicklerMap(className)(json)
 }

 // Uses runtime reflection
 def fromJSONString(json: String) = JSONPickler(json).unpickle

score 0 · Answer 2 · answered May 14 '14 at 10:45

0

I haven't used Scala Pickling, but it says on its Github repo that it's in its early dev stages. You may also want to try out Spray JSON. It supports the things you need as well.

answered May 14 '14 at 10:45

Haris Osmanagić

1,249
12
28

I am aware that it is early stage. I am not looking for a canonical JSON serializer - there is plenty out there (argonaut, json-4s, rapture.io) to use if I wanted to. I am specifically interested in how pickling can be used since it seems to be the future and is developed by the core Scala group itself and has some interesting concepts (compile time macros for serialization). – pathikrit May 14 '14 at 16:41

Scala Pickling for Json serialization and deserialization?

2 Answers2