I'm new to Scala and I'm trying to do my first Play 2.0 application. I'm using:
Scala 2.9.3
Play 2.0.4
SalatWithPlay2 1.1
I have this in my conf/routes file:
PUT /newVenue controllers.Application.createNewVenue
I have this in my Application.scala file:
def createNewVenue = Action(parse.json) { request =>
val newVenue = Venue.fromJSON(request.body.toString)
Venue.insert(newVenue)
Ok("New Venue Created")
}
And this is the code for Venue.scala:
import play.api.Play.current
import com.novus.salat._
import com.novus.salat.global._
import com.novus.salat.annotations._
import com.novus.salat.dao._
import com.mongodb.casbah.Imports._
import se.radley.plugin.salat._
object Venue extends ModelCompanion[Venue, ObjectId] {
val collection = mongoCollection("venues")
val dao = new SalatDAO[Venue, ObjectId](collection = collection) {}
}
case class Venue(
#Key("_id") val venueId:ObjectId,
var playlist:Playlist,
var isPlaying:Boolean = false)
To test if this is working I send a PUT request to localhost:9000/newVenue with this JSON as a body:
{"venueId": 3,"playlist":{"playlistId":2,"currentSongPosition":5},"isPlaying":false}
And then I get this error:
[error] application -
! #6d7oco1hf - Internal server error, for request [PUT /newVenue] ->
play.core.ActionInvoker$$anonfun$receive$1$$anon$1: Execution exception [[NoSuchMethodException: model.Venue$.apply$default$1()]]
at play.core.ActionInvoker$$anonfun$receive$1.apply(Invoker.scala:134) [play_2.9.1.jar:2.0.4]
at play.core.ActionInvoker$$anonfun$receive$1.apply(Invoker.scala:115) [play_2.9.1.jar:2.0.4]
at akka.actor.Actor$class.apply(Actor.scala:318) [akka-actor.jar:2.0.2]
at play.core.ActionInvoker.apply(Invoker.scala:113) [play_2.9.1.jar:2.0.4]
at akka.actor.ActorCell.invoke(ActorCell.scala:626) [akka-actor.jar:2.0.2]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:197) [akka-actor.jar:2.0.2]
Caused by: java.lang.NoSuchMethodException: model.Venue$.apply$default$1()
at java.lang.Class.getMethod(Class.java:1605) ~[na:1.6.0_37]
at com.novus.salat.ConcreteGrater.defaultArg(Grater.scala:350) ~[salat-core_2.9.1-1.9.1.jar:1.9.1]
at com.novus.salat.ConcreteGrater.safeDefault(Grater.scala:360) ~[salat-core_2.9.1-1.9.1.jar:1.9.1]
at com.novus.salat.ConcreteGrater$$anonfun$6$$anonfun$apply$7.apply(Grater.scala:319) ~[salat-core_2.9.1-1.9.1.jar:1.9.1]
at com.novus.salat.ConcreteGrater$$anonfun$6$$anonfun$apply$7.apply(Grater.scala:319) ~[salat-core_2.9.1-1.9.1.jar:1.9.1]
at scala.Option.orElse(Option.scala:218) ~[scala-library.jar:0.11.3]
I think the line triggering the error is val newVenue = Venue.fromJSON(request.body.toString).
Does anyone have a clue of what's wrong?
I followed the tutorial in SalatWithPlay2 page and also followed some advices in similar problems), but I had no luck so far.
UPDATE:
I found a workaround, although it's not exactly a solution, but maybe it's helpful for somebody else and for understanding what is the actual solution.
If I remove the annotation #Key, the code of the case class Venue looks like this:
case class Venue(
val venueId:ObjectId,
var playlist:Playlist,
var isPlaying:Boolean = false)
And then I get this other error:
[RuntimeException: in: unexpected OID input class='net.liftweb.json.JsonAST$JInt', value='3']
And if instead of using ObjectId I use Long for example, the code looks like this:
case class Venue(
val venueId:Long,
var playlist:Playlist,
var isPlaying:Boolean = false)
And I get no error!
So the NoSuchMethodException apparently is related to the #Key annotation related to the _id. I also tried to rename venueId to _id and the same NoSuchMethodException error appeared. So the question is: why can't I use the #Key annotation to say which of my attributes maps to the object id of the document in the mongo database?
Besides that, regular Integers cannot be automatically converted to ObjectId instances for some other reason.
Thanks!
Just a shot in the dark, but can you try naming your object class to something else? Maybe to VenueCompanion? It seems it is possible the compiler is getting confused on which object to apply to. IE it is not applying to the case class Venue, that you want. I am curious if the exception is still the same afterwards.
So I found what was the problem.
The attributes of the Json sent in the body of the request must match the names of the attributes of the mongodb's document, not the attributes of the Scala object.
So if my class Venue is defined like this:
case class Venue(
#Key("_id") val venueId:ObjectId,
var playlist:Playlist,
var isPlaying:Boolean = false)
The Json I have to send in the PUT request is:
{"_id": 3,"playlist":{"playlistId":2,"currentSongPosition":5},"isPlaying":false}
And NOT:
{"venueId": 3,"playlist":{"playlistId":2,"currentSongPosition":5},"isPlaying":false}
Related
I have a code like that:
class Object3 (
param1: String
param2: String
)
class Object1 (
param1: String
param2: Object2
) extends Message
class SampleClassSpec extends WordSpec with MockitoSugar {
"A sender" should {
"send a message" in {
val client = mock[Client]
var message = mock[Object1]
var detail = mock[Object2]
when(message.param2).thenReturn(detail)
when(message.param2.toJson).thenReturn(detail.toJson) // give me NPE
val sender = new Sender(client)
sender.prepareandsend(message) // second NPE
verify(client).send(message.param2.toJson.prettyPrint)
}
}
}
the problem is that I got NPE when I want to add the method to get formatted json, I don't want to send the whole Object1, just the Object3; I'm using spray.json._ for this.
if I remove the line that give me NPE, then I got a second NPE on "prepareandsend"
My question is how I can add this method toJson.prettyPrint to a mock?
Or maybe there is another way to do this. I'm a really beginner on this.
I don't know anything about Scala, but I have worked with Mockito before.
It seems to me that the problem is that you haven't set any behavior for detail.
Since it's a mock as well, it doesn't have any behavior, so it won't return anything when you call detail.toJson
You should add some behavior to detail with
when(detail.toJson).thenReturn(/* your JSON code */)
Try:
when(param2.toJson).thenReturn(detail.toJson)
instead.
Alternatively, you can look into using Mockitos DEEP_STUBS mechanism.
I am using scalatra and configured my servlet to always return JSON (as described in the respective guide). Using the MongoDB and Salat leads me to the point where I read a MongoDBObject back into my case class - which seems to work great.
My case class:
import org.bson.types.ObjectId
import com.novus.salat.annotations.raw.Key
case class Player(_id: ObjectId, firstName: String, ...)
Printing the case class object outputs this:
Player(547489ee93f4272e548ded63,Peter,...)
As you can see, the objectid is a org.bson.types.ObjectId.
The automatical serialization to JSON sends this to the browser:
{"_id":{},"firstName":"Peter",...}
Where is my ObjectID? What am I doing wrong?
I found the following on the web:
https://gist.github.com/dozed/5631680
After a small test it seems as if all I had to do was changing the code in my servlet from
protected implicit val jsonFormats: Formats = DefaultFormats
to
protected implicit val jsonFormats: Formats = DefaultFormats + new ObjectIdSerializer
and add
import org.json4s.mongo.ObjectIdSerializer
Maybe this will help another Scalatra-NOOB... ;-)
I'm scala newbie and come from a Ruby background so and am having trouble rendering json response in my web service for which I use scalatra, mongodb with liftweb mongo record and argonaut for JSon serialisation and deserialisation.
However based on the examples given at http://argonaut.io/ I'm unable to figure out how this would work when using the net.liftweb.mongo.record library.
On compiling this i get a error which says a type mismatch. The error description follows the code snippet.
package firstscalatraapp
import org.scalatra
import net.liftweb.mongodb._
import net.liftweb.mongodb.record.MongoRecord
import net.liftweb.mongodb.record.field.ObjectIdPk
import net.liftweb.record.field.StringField
import net.liftweb.record.field.IntField
import net.liftweb.record.field.PasswordField
import net.liftweb.record.field.DateTimeField
import net.liftweb.mongodb.record.MongoMetaRecord
import argonaut._
import Argonaut._
case class Person private extends MongoRecord[Person] with ObjectIdPk[Person] {
def meta = Person
object age extends IntField(this, 3)
object name extends StringField(this, 29)
object created_at extends DateTimeField(this)
object password extends PasswordField(this)
}
object Person extends Person with MongoMetaRecord[Person] {
implicit def PersonCodecJson: CodecJson[Person] =
casecodec3(Person.apply, Person.unapply)("name", "age", "things")
}
The Error i get is
[error] found : () => firstscalatraapp.Person
[error] required: (?, ?, ?) => ?
[error] casecodec3(Person.apply, Person.unapply)("name", "age", "things")
[error] ^
[error] one error found
[error] (compile:compile) Compilation failed
which seems logical because the constructor does not accept any parameters and the mongo library seems to be generating the val for the fields that i need for the class (I still don't fully understand what the lift mongo wrapper does yet).
So how do i define the implicit to be able to find serialise an object of type person.
Also how do I define serialisation capabilities when i'm dealing with collections. For instance when I have a List[Person].
Thanks in advance. I would really appreciate any help i can get on this.
I'm just about to start using Argonaut so I'm no expert on that but with that said your initial problem seems obvious.
casecodec3 needs a constructor and a deconstructor for the class you're defining the codec for. In the examples of Argonaut they're using case classes and these have automatically generated companion objects with apply/unapply for the fields defined. Which for casecodec3 needs to be 3. In your case, the case class is of zero-arity - you have no case class fields at all. The fields of the record are defined as inner objects with their own apply-methods (very imperative stuff). That's just the way lifts records are defined. So your apply method is just () => Person.
casecodec3 wants a function from a 3-tuple to Person and from Person to a 3-tuple. I would suggest skipping the case definition if you're going to use lift record. And create functions on the side instead. Something like:
object Person extends Person with MongoMetaRecord[Person] {
implicit def PersonCodecJson: CodecJson[Person] =
casecodec3(parse, serialize)("name", "age", "things")
// Something like
def parse(name: String, age: Int, things: Something) = {
val p = Person.createRecord
p.name(name)
...
}
def serialize(p: Person) = (p.name.get, p.age.get, p.things.get)
}
As for your other questions I think you can head back to argonaut.io again. Their documentation seems quite alright - maybe it was worse when you posted this question as it is kind of old?
I'm going to try to replace all my serialization from lift-json to argonaut right now so if you're still stuck (probably not) I might be able to answer better in a bit.
I am trying to serialize / deserialize using JSON and the Play Framework 2.1.0 and Scala 2.10. I am using Anorm, and I have a pretty simple Object that I want to store in a database. The Order is very simple:
case class Order(id: Pk[Long] = NotAssigned, mfg: String, tp: String)
In my controller, I am trying to build a REST interface to be able to accept and send an Order instance (above) as JSON. In there, I have the following code:
implicit object PkFormat extends Format[Pk[Long]] {
def reads(json: JsValue):Pk[Long] = Id(json.as[Long])
def writes(id: Pk[Long]):JsNumber = JsNumber(id.get)
}
However, this is failing to compile when I run "play test" with the following:
overriding method reads in trait Reads of type (json: play.api.libs.json.JsValue)play.api.libs.json.JsResult[anorm.Pk[Long]];
[error] method reads has incompatible type
[error] def reads(json: JsValue):Pk[Long] = Id(json.as[Long])
Does anyone know why this is happening?
I have a lot of experience with JAXB, but I am realtively new to Play and Scala, and I haven't been able to find any answers so far. This seems like a pretty simple use case, actually I was hoping there would be a simpler solution (like Annotations), but I wasn't able to find one (at least not yet)
Any help is greatly appreciated!
Thanks
play.api.libs.json.Reads trait defines reads method as:
def reads(json : play.api.libs.json.JsValue) : play.api.libs.json.JsResult[A]
Therefore, the response of reads method is expected to be JsResult[A], not A; that is, JsResult[Pk[Long]] and not Pk[Long]. In a case of success, you'll want to return this:
implicit object PkFormat extends Format[Pk[Long]] {
def reads(json: JsValue):JsResult[Pk[Long]] = JsSuccess(Id(json.as[Long]))
def writes(id: Pk[Long]):JsNumber = JsNumber(id.get)
}
What do i need to do to extract the value for friends_count. i noticed that screen_name are already define in the Status object and case class. Do still require to extends Js or JsObject different
object TweetDetails extends Js { val friends_count = 'friends_count ? num }
and then pattern match it against each json object in the list of JsObjects as represented below. The symbols are confusing:
scala> val friends_count = 'friends_count ! num // I wish SO understood Scala's symbols
val twtJsonList = http(Status("username").timeline)
twtJsonList foreach {
js =>
val Status.user.screen_name(screen_name) = js
val Status.text(text) = js
val friends_counts(friends_count) = js //i cannot figure out how to extract this
println(friends_count)
println(screen_name)
println(text)
}
Normally, Scala symbols can be thought of as a unique identifier which will always be the same. Every symbol that is lexi-graphically identical refers to the exact same memory space. There's nothing else that's special about them from Scala's point of view.
However, Dispatch-Json pimps out symbols making them JSON property extractors. To see the code which is responsible for the pimping, check out the SymOp class and the rest of the JsonExtractor.scala code.
Let's write some code which solves the problem you are looking at and then analyze what's going on:
trait ExtUserProps extends UserProps with Js {
val friends_count = 'friends_count ! num
}
object ExtUser extends ExtUserProps with Js
val good_stuff = for {
item <- http(Status("username").timeline)
msg = Status.text(item)
user = Status.user(item)
screen_name = ExtUser.screen_name(user)
friend_count = ExtUser.friends_count(user)
} yield (screen_name, msg, friend_count)
The first thing that we're doing is extending the UserProps trait in the Dispatch-Twitter module to give it a friends_count extractor and then defining a ExtUser object which we can use to get access to that extractor. Because the ExtUserProps extends UserProps, which also extends Js, we get the method sym_add_operators in scope which turns our symbol 'friends_count into a SymOp case class. We then call the ! method on that SymOp which we then pass the Extractor num to, which creates an Extractor that looks for a property "friends_count" on a JSON object and then parses it as a number before returning. Quite a bit going on there for such a small bit of code.
The next part of the program is just a for-comprehension that calls out to the Twitter timeline for a user and parses it into JsObjects which represent each status item, them we apply the Status.text extractor to pull out the status message. Then we do the same to pull out the user. We then pull the screen_name and friend_count out of the user JsObject and finally we yield a Tuple3 back with all of the properties we were looking for. We're then left with a List[Tuple3[String,String,BigDecimal]] which you could then iterate on to print out or do whatever with.
I hope that clears some things up. The Dispatch library is very expressive but can be a little tough to wrap your head around as it uses a lot of Scala tricks which someone just learning Scala won't get right away. But keep plugging around and playing with, as well as looking at the tests and source code, and you'll see how to create powerful DSL's using Scala.