Examples for Lift and Mongo Post

animals-2.scala

import net.liftweb.mongodb._
  import BsonDSL._

trait Animal {
  def makeNoise(): String
}

case class Dog(name: String, breed: String) extends Animal {
  def makeNoise() = {
    "Woof"
  }
}

case class Cat(name: String, furPattern: String) extends Animal {
  def makeNoise() = {
    "Meow"
  }
}

// Define AnimalInfo as a mongo model.
case class AnimalInfo(animals: List[Animal], _id: ObjectId = ObjectId.get)
    extends MongoDocument[AnimalInfo] {
  val meta = AnimalInfo
}
object AnimalInfo extends MongoDocumentMeta[AnimalInfo] {
  override def formats = allFormats ++ ShortTypeHints(
    classOf[Dog] ::
    classOf[Cat] ::
    Nil
  )
}

// Create and save an animal info.
AnimalInfo(
  Dog("Shadow", "Collie") ::
  Dog("Beamer", "Collie") ::
  Cat("Mittens", "Zig-Zag") ::
  Nil
).save

//And your data is in Mongo!

animals.scala

trait Animal {
  def makeNoise(): String
}

case class Dog(name: String, breed: String) extends Animal {
  def makeNoise() = {
    "Woof"
  }
}

case class Cat(name: String, furPattern: String) extends Animal {
  def makeNoise() = {
    "Meow"
  }
}

case class AnimalInfo(animals: List[Animal])

lift-json-example-2-executionresult.txt

scala> val jvalueAnimals: JValue = decompose(animals)
jvalueAnimals: net.liftweb.json.package.JValue = JObject(List(JField(animals,JArray(List(JObject(List(JField(name,JString(Shadow)), JField(breed,JString(Collie)))), JObject(List(JField(name,JString(Beamer)), JField(breed,JString(Collie)))), JObject(List(JField(name,JString(Mittens)), JField(furPattern,JString(Zig-Zag)))))))))

scala> val extractedAnimals = jvalueAnimals.extract[AnimalInfo]
net.liftweb.json.MappingException: No usable value for animals
No constructor for type interface Animal, JObject(List(JField(name,JString(Shadow)), JField(breed,JString(Collie))))
  at net.liftweb.json.Meta$.fail(Meta.scala:191)
	at net.liftweb.json.Extraction$.mkValue$1(Extraction.scala:357)
	at net.liftweb.json.Extraction$.build$1(Extraction.scala:317)
	at net.liftweb.json.Extraction$$anonfun$12.apply(Extraction.scala:253)
	at net.liftweb.json.Extraction$$anonfun$12.apply(Extraction.scala:253)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:233)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:233)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:76)
	at scala.collection.TraversableLike$class.map(TraversableLike.scala:233)
	at scala.collection.immutable.List.map(List.scala:76)
	at net.liftweb.json.Extraction$.instantiate$1(Extraction.scala:253)

lift-json-example.scala

// Import lift-json
import net.liftweb.json._
  import Extraction._

// Declare a set of serializers and type hints to use.
implicit val formats = DefaultFormats

// Produce a JValue representation of a dog. This can
// be serialized to actual JSON and manipulated with
// queries and transforms.
val jvalueDog: JValue = decompose(Dog("Shadow", "Collie"))

lift-json-example2.scala

// Import lift-json
import net.liftweb.json._
  import Extraction._

// Declare a set of serializers and type hints to use.
implicit val formats = DefaultFormats

// Create an animal info instance with a list of animals.
val animals = AnimalInfo(
  Dog("Shadow", "Collie") ::
  Dog("Beamer", "Collie") ::
  Cat("Mittens", "Zig-Zag") ::
  Nil
)

// Produce a JValue representation of the animals.
// Would render to the following JSON:
// { animals: [ {name: "Shadow", breed: "Collie"}, ... ] }
val jvalueAnimals: JValue = decompose(animals)

// Attempt to extract the animals, which will fail with
// a no constructor error because Animals is a trait that
// can't be directly instantiated.
val extractedAnimals = jvalueAnimals.extract[AnimalInfo]

lift-json-example3.scala

// Import lift-json
import net.liftweb.json._
  import Extraction._

// Declare a set of serializers and type hints to use.
implicit val formats = DefaultFormats ++ ShortTypeHints(
  classOf[Dog] ::
  classOf[Cat] ::
  Nil
)

// Create an animal info instance with a list of animals.
val animals = AnimalInfo(
  Dog("Shadow", "Collie") ::
  Dog("Beamer", "Collie") ::
  Cat("Mittens", "Zig-Zag") ::
  Nil
)

// Produce a JValue representation of the animals.
// Would render to the following JSON:
// { animals: [ {jsonClass: "Dog", name: "Shadow", breed: "Collie"}, ... ] }
val jvalueAnimals: JValue = decompose(animals)

// Attempt to extract the animals, which will succeed because the jsonClass
// parameter tells lift-json which actual instance fitting Animal it should
// instatiate.
val extractedAnimals = jvalueAnimals.extract[AnimalInfo]