How to convert JSON to a type in Scala

Question

My problem is I receive an JSON text from say, twitter. Then I want to convert this text to an native object in scala. Is there a standard method to do this? I\'m also using Pla

Answer 1

I suggest to use Jackson JSON processor. It works both for Java and Scala. You just add annotations to your classes which describe how you want to map JSON data to your native objects.

An example:

import scala.reflect.BeanProperty
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.annotate._

class User {
  @BeanProperty var gender: String = null
  @BeanProperty var verified: Boolean = false
  @BeanProperty var userImage: Array[Byte] = null
  @BeanProperty var name: Name = null
}

case class Name {
  @BeanProperty var first: String = null;
  @BeanProperty var last: String = null;
}

object Json {
  def main(argv: Array[String]) {
    val input = """{
  "name" : { "first" : "Joe", "last" : "Sixpack" },
  "verified" : false,
  "userImage" : "Rm9vYmFyIQ=="
}""";

    val mapper = new ObjectMapper(); // can reuse, share globally
    val user: User = mapper.readValue(input, classOf[User]);

    print(user.name.first);
  }
}

This solution has a slight hassle that you have to annotate every field with @BeanProperty, but I don't know a simpler way.

---

Remark: As far as I know, Jackson doesn't use javax.bean.Introspector, it tries to find getters/setters by examining the methods by itself. If it did, things would have been easier, it would be possible to write just

@scala.reflect.BeanInfo
case class Name {
    var first: String;
    var last: String;
}