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?

Answer 1

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

Answer 2

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.