ReactiveMongo查詢返回無

Question

我只是學習Scala和相關技術的新手。我遇到了LoadUser應該返回一條記錄但將來空的問題。

我收到以下錯誤： java.util.NoSuchElementException：None.get

我明白這是不理想的Scala，所以隨時提出改進我。

class MongoDataAccess extends Actor { 
    val message = "Hello message" 

    override def receive: Receive = { 
    case data: Payload => { 
     val user: Future[Option[User]] = MongoDataAccess.loadUser(data.deviceId) 
     val twillioApiAccess = context.actorOf(Props[TwillioApiAccess], "TwillioApiAccess") 
     user onComplete { 
     case Failure(exception) => println(exception) 
     case p: Try[Option[User]] => p match { 
      case Failure(exception) => println(exception) 
      case u: Try[Option[User]] => twillioApiAccess ! Action(data, u.get.get.phoneNumber, message) 
     } 
     } 
    } 

    case _ => println("received unknown message") 
    } 
} 

object MongoDataAccess extends MongoDataApi { 
    def connect(): Future[DefaultDB] = { 
    // gets an instance of the driver 
    val driver = new MongoDriver 
    val connection = driver.connection(List("192.168.99.100:32768")) 

    // Gets a reference to the database "sensor" 
    connection.database("sensor") 
    } 

    def props = Props(new MongoDataAccess) 

    def loadUser(deviceId: UUID): Future[Option[User]] = { 
    println(s"Loading user from the database with device id: $deviceId") 
    val query = BSONDocument("deviceId" -> deviceId.toString) 

    // By default, you get a Future[BSONCollection]. 
    val collection: Future[BSONCollection] = connect().map(_.collection("profile")) 

    collection flatMap { x => x.find(query).one[User] } 
    } 
} 

感謝

Answer 1

，我們無法保證您的數據庫查找一（.one[T]）匹配至少一個文件，所以你得到一個Option[T]。

然後由您來考慮（或不），發現沒有文檔是失敗的（或不是）;例如

val u: Future[User] = x.find(query).one[User].flatMap[User] { 
    case Some(matchingUser) => Future.successful(matchingUser) 
    case _ => Future.failed(new MySemanticException("No matching user found")) 
} 

Using .get on Option is a bad idea anyway.