Dependancy Injection and Anorm

Moving from Play Framework 2.4.x to 2.5.x requires to drop global variables. Specifically in this case play.api.Play.current and play.api.db.DB.

Most of my models using Anorm have a simple form:

case class Model(id:Long, name:String, …)

case object Model {

  val model=get[Long]("id")~get[String]("name")~ … map {

    case id~name~ … => Model(id, name, …)

  }

  def findById(id:Long):Option[Model]=DB.withConnection { implicit c=>

    SQL"SELECT * FROM models WHERE modelId=$id".as(model*).headOption

  }

}

In 2.5.x, DB is now deprecated. It is recommended to use dependancy injection.

Here's a minimum to support 2.5.x:

1. Instead of changing much (such as not using a case object), change DB to implicit.

    def findById(id:Long)(implicit db:Database):Option[Model]=db.withConnection { implicit c=>

       SQL"SELECT * FROM models WHERE modelId=$id".as(model*).headOption

    }  

2. For every controller using models, add @Inject()(db: Database), e.g., 

       class Application @Inject()(db: Database) extends Controller {

          implicit val dbImplicitVal=db

3. For every AKKA actor using models, add (db:Database), e.g., 

      class Logger(db:Database) extends Actor {

     and by calling props with a valid database when requesting an actor, e.g., 

       val logger=actorSystem.actorOf(Props(new Logger(db)))

Simple and minimal.