How to convert Scala Document to JSON in Scala

Question

I want to convert variable message which is of type scala.Seq[Scala.Document] to JSON format in following code:

path("getMessages"){
          get {
            parameters('roomname.as[String]) {
              (roomname) =>
                try {
                  val messagesByGroupName = MongoDatabase.collectionForChat.find(equal("groupChatName",roomname)).toFuture()
                  val messages = Await.result(messagesByGroupName,60.seconds)
                  println("Messages:"+messages)
                  complete(messages)
                }
                catch {
                  case e:TimeoutException =>
                    complete("Reading file timeout.")
            }
          }
        }

But it is giving me error on complete(messages) line. It is not accepting message of that type.

I tried to convert it into JSON by using following :

import play.api.libs.json._

object MyJsonProtocol{
  implicit object ChatFormat extends Format[Chat] {
    def writes(c: Chat) : JsValue = {
      val chatSeq = Seq (
        "sender" -> JsString(c.sender),
        "receiver" -> JsString(c.receiver),
        "message" -> JsString(c.message),
        "groupChatName" -> JsString(c.groupChatName),
      )
      JsObject(chatSeq)
    }


    def reads(value: JsValue) = {
      JsSuccess(Chat("","","",""))
    }
  }
}

But it is not working.

My Chat.scala class is as follows:

import play.api.libs.json.{Json, Reads, Writes}

class Chat(var sender:String,var receiver:String,var message:String, var groupChatName:String){
  def setSenderName(senderName:String) = {
    sender = senderName
  }
  def setReceiverName(receiverName:String) = {
    receiver = receiverName
  }
  def setMessage(getMessage:String) = {
    message = getMessage
  }
  def setGroupChatName(chatName:String) = {
    groupChatName = chatName
  }
}

object Chat {
  def apply(sender: String, receiver: String, message: String, groupname: String): Chat
  = new Chat(sender, receiver, message,groupname)

  def unapply(arg: Chat): Option[(String, String, String,String)] = ???
  implicit val requestReads: Reads[Chat] = Json.reads[Chat]
  implicit val requestWrites: Writes[Chat] = Json.writes[Chat]
}

I am also not able to figure out what to write in unapply method. I am new to scala and akka.

EDIT: My MongoDatabase.scala which has collection is as follows:

object MongoDatabase {
  val chatCodecProvider = Macros.createCodecProvider[Chat]()

  val codecRegistry = CodecRegistries.fromRegistries(
    CodecRegistries.fromProviders(chatCodecProvider),
    DEFAULT_CODEC_REGISTRY
  )
  implicit val system = ActorSystem("Scala_jwt-App")
  implicit val executor: ExecutionContext = system.dispatcher
  val mongoClient: MongoClient = MongoClient()
  val databaseName = sys.env("database_name")
  // Getting mongodb database
  val database: MongoDatabase = mongoClient.getDatabase(databaseName).withCodecRegistry(codecRegistry)
  val registrationCollection = sys.env("register_collection_name")
  val chatCollection = sys.env("chat_collection")
  // Getting mongodb collection
  val collectionForUserRegistration: MongoCollection[Document] = database.getCollection(registrationCollection)
  collectionForUserRegistration.drop()
  val collectionForChat: MongoCollection[Document] = database.getCollection(chatCollection)
  collectionForChat.drop()
}

And if try to change val collectionForChat: MongoCollection[Document] = database.getCollection(chatCollection)

to

val collectionForChat: MongoCollection[Chat] = database.getCollection[Chat](chatCollection)

then I get error on in saveChatMessage() method below:

def saveChatMessage(sendMessageRequest: Chat) : String = {
    val senderToReceiverMessage : Document = Document(
      "sender" -> sendMessageRequest.sender,
      "receiver" -> sendMessageRequest.receiver,
      "message" -> sendMessageRequest.message,
      "groupChatName" -> sendMessageRequest.groupChatName)
    val chatAddedFuture = MongoDatabase.collectionForChat.insertOne(senderToReceiverMessage).toFuture()
    Await.result(chatAddedFuture,60.seconds)
    "Message sent"
  }

on val chatAddedFuture = MongoDatabase.collectionForChat.insertOne(senderToReceiverMessage).toFuture() this line since it accepts data of type Seq[Document] and I am trying to add data of type Seq[Chat]

Check the following link: https://lansalo.com/2018/05/07/custom-json-serializer/ — Zvi Mints, Jan 14 '21 at 07:28
messageByGroupName is of type Future [ scala.Seq [ scala.Document ] ] — Ruchir Dixit, Jan 14 '21 at 18:37
When you say "But it is not working", how is it not working? — Levi Ramsey, Jan 14 '21 at 18:58

Tomer Shetah · Answer 1 · 2021-01-14T10:28:41.770

0

I am going to assume that MongoDatabase.collectionForChat.find(equal("groupChatName",roomname)) returns either Seq[Chat], or Chat. Both of them are the same for play.

You have 2 options:

Adding the default format on the companion object:
```
object Chat {
    implicit val format: Format[Chat] = Json.format[Chat]
}
```
In this case you can delete the object MyJsonProtocol which is not used.
In case you want to keep your own serializers(i.e. MyJsonProtocol), you need to rename MyJsonProtocol into Chat. This way the complete route will be able to find the implicit Format.

edited Jan 14 '21 at 10:28

answered Jan 14 '21 at 10:22

Tomer Shetah

8,413
7
27
35

My **MongoDatabase.collectionForChat.find(equal("groupChatName",roomname))** line is actually return **Seq[Document]** – Ruchir Dixit Jan 14 '21 at 18:49
@RuchirDixit, so does my answer help you? – Tomer Shetah Jan 14 '21 at 19:00
No. Because it would work perfectly if my code would have retuned Seq[Chat] or Chat but it ain't. – Ruchir Dixit Jan 14 '21 at 19:08
@RuchirDixit, Are you sure? Did you try to rename `MyJsonProtocol` into `Chat`? What is the error you are getting? – Tomer Shetah Jan 14 '21 at 19:12
yes I tried that but it is not able to get access to Chat class. – Ruchir Dixit Jan 15 '21 at 05:36

score 0 · Answer 2 · answered Jan 14 '21 at 11:44

0

create case class for the message object you want to send for example:

case class MyMessage(sender: String, receiver: String, message: String, groupChatName: String)

You should create Format for the type of case class

implicit val MessageTypeFormat = Json.format[MyMessage]

if complete should get JSON type - then call complete myMessage when myMessage is an instance of MyMessage.

complete(Json.toJson(myMessage))

answered Jan 14 '21 at 11:44

Zvi Mints

1,072
1
8
20

I don't think this will help the PO, since he deliberately implemented a class where the fields are mutables. Therefore I think that defining a case class is not what he meant. – Tomer Shetah Jan 14 '21 at 12:31
Yes exactly. Here I need to use setter methods so I cant use case class. – Ruchir Dixit Jan 14 '21 at 18:30
You can make it with class also, or define some `var` variables – Zvi Mints Jan 14 '21 at 18:40
Which is anyway a bad practice – cchantep Jan 14 '21 at 23:51

How to convert Scala Document to JSON in Scala

2 Answers2