![Persistence using Traits
import play.api.libs.json.Json
case class User
( id : Option[BSONObjectID]
, firstName: String
, lastName : String
, email : String
, password : String)
object User extends DataAccess[User] {
def collectionName = “user”
implicit val format = Json.format[User]
}](https://image.slidesharecdn.com/playscalareactivemongo-130920133126-phpapp02/85/Play-scala-reactive-mongo-9-320.jpg)
![The Data Access Trait
trait DataAccess[M] {
def collectionName: String
implicit val format: Format[M]
private def db = ReactiveMongoPlugin.db
private def collection = db[JSONCollection](collectionName)
def insert(instance: M): (BSONObjectID, Future[LastError]) = {
val id = BSONObjectID.generate
(id, collection.insert(Json.toJson(instance) ++ id))
}](https://image.slidesharecdn.com/playscalareactivemongo-130920133126-phpapp02/85/Play-scala-reactive-mongo-10-320.jpg)
![The Data Access Trait (cont’d)
def update(instance: M): Future[LastError] = {
instance.id map { id =>
collection.update(id, Json.toJson(instance))
} getOrElse Future.successful(LastError(err = Some("Invalid
ID"))
}
def byId(id: BSONObjectID): Future[Option[M]] = {
collection.find(id).cursor.headOption map {
_ flatMap { doc: JsObject =>
doc.asOpt[M]
}
}
}](https://image.slidesharecdn.com/playscalareactivemongo-130920133126-phpapp02/85/Play-scala-reactive-mongo-11-320.jpg)
![Cons (cont’d)
case class Book
( name : String
, author: Author)
case class author(name: String) {
lazy val books: Seq[Book] = Book.byAuthor(this)
}
lazy val books: Future[Seq[Book]] = Book.byAuthor(this)
val books = author.books
author.books map { books =>
...
}](https://image.slidesharecdn.com/playscalareactivemongo-130920133126-phpapp02/85/Play-scala-reactive-mongo-14-320.jpg)
![The End
Thanks for listening
Future[Option[Applause]]
max@trialfire.com marconi@trialfire.com
We’re hiring!](https://image.slidesharecdn.com/playscalareactivemongo-130920133126-phpapp02/85/Play-scala-reactive-mongo-16-320.jpg)
![[1D1]신개념 N스크린 웹 앱 프레임워크 PARS](https://cdn.slidesharecdn.com/ss_thumbnails/1d1n-screenpars-140928071352-phpapp01-thumbnail.jpg?width=560&fit=bounds)
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Play + scala + reactive mongo
- 1. Play + Scala + Reactive Mongo Building a “reactive” data-access layer to mongoDB
- 2. About Us Max Kremer Trialfire - co-founder founded in June 2013 Autodesk - cloud solutions architect Datastay - co-founder Acquired by Autodesk 2011 Marconi Lanna Trialfire - lead developer founded in June 2013 Too many startups since 1996 to list here
- 3. Why “reactive” Classic Synchronous Model: With a traditional synchronous database driver, each operation blocks the current thread until a response is received. More requests = more threads waiting = poor scalability
- 4. What is “reactive” Fully non-blocking and asynchronous I/O operations
- 5. Play and async I/O • Java NIO • Non-blocking, asynchronous IO • Process multiple HTTP requests with a single thread • Large number of concurrent requests can be handled with a few threads
- 6. Example •A Play controller using a Future result: package controllers import play.api.mvc.{Action, Controller} import concurrent.{ExecutionContext, Future} import ExecutionContext.Implicits.global object StuffController extends Controller { def doStuff( ) = Action { val someStuff = scala.concurrent.future { models.Stuff.fetch( ) } Async { someStuff.map(value => Ok(value)) } } }
- 7. A word about Futures •Represents a value that will be available later •Execution contexts - think “thread pools” •Futures are Monads •Layer of abstraction over multi-threading
- 8. Data Access Layer •Active Record Design Pattern •Based on Futures •Model = Case Class + Companion Object •Stackable Traits
- 9. Persistence using Traits import play.api.libs.json.Json case class User ( id : Option[BSONObjectID] , firstName: String , lastName : String , email : String , password : String) object User extends DataAccess[User] { def collectionName = “user” implicit val format = Json.format[User] }
- 10. The Data Access Trait trait DataAccess[M] { def collectionName: String implicit val format: Format[M] private def db = ReactiveMongoPlugin.db private def collection = db[JSONCollection](collectionName) def insert(instance: M): (BSONObjectID, Future[LastError]) = { val id = BSONObjectID.generate (id, collection.insert(Json.toJson(instance) ++ id)) }
- 11. The Data Access Trait (cont’d) def update(instance: M): Future[LastError] = { instance.id map { id => collection.update(id, Json.toJson(instance)) } getOrElse Future.successful(LastError(err = Some("Invalid ID")) } def byId(id: BSONObjectID): Future[Option[M]] = { collection.find(id).cursor.headOption map { _ flatMap { doc: JsObject => doc.asOpt[M] } } }
- 12. Pros •easy compared to sql •no schemas •no queries •no migration •it just works conversion from/to json automatically handled by play json api macros
- 13. Cons •Futures all the way down… •Futures all the way up, too... •No joins
- 14. Cons (cont’d) case class Book ( name : String , author: Author) case class author(name: String) { lazy val books: Seq[Book] = Book.byAuthor(this) } lazy val books: Future[Seq[Book]] = Book.byAuthor(this) val books = author.books author.books map { books => ... }
- 15. Links reactive mongo driver: http://reactivemongo.org/ Play ReactiveMongo plugin: https://github.com/ReactiveMongo/Play-eactiveMongo
- 16. The End Thanks for listening Future[Option[Applause]] [email protected] [email protected] We’re hiring!