Question

我有一个如下所示的cassandra键空间和表：

CREATE KEYSPACE animals WITH replication = {'class':'SimpleStrategy', 'replication_factor' : 1};
--
USE animals;

CREATE TABLE alpakka (
  id int PRIMARY KEY,
  name text,
  animal_type text
  );

我正在尝试使用datastax和Alpakka这样从此表中检索所有结果：

object CassandraService {

    def selectFromCassandra()(): Future[Seq[Row]] = {

      val statement: Statement = new SimpleStatement(s"SELECT * FROM animals.alpakka")

      val rows: Future[immutable.Seq[Row]] = CassandraSource(statement).runWith(Sink.seq)
    rows

}

当我得到结果时，我想使用Circe将它们转换为case类，就像这样：

import io.circe.{Decoder, Encoder}

import io.circe.generic.semiauto._


object Alpakka {
  implicit val jsonDecoder: Decoder[Alpakka] = deriveDecoder[Alpakka]
  implicit val jsonEncoder: Encoder[Alpakka] = deriveEncoder[Alpakka]
}

case class Alpakka(id:Int,name:String,animal_type:String)

然后我按照以下路线调用服务：

object Routes {

val routes: Route = path("routes"){

  onSuccess(CassandraService.selectFromCassandra()) { seq =>
    complete(seq.head.asInstanceOf[Alpakka].name)

  }
}

但是，当我这样做时，出现以下错误：

Error during processing of request: 'com.datastax.driver.core.ArrayBackedRow cannot be cast to com.nk.map.model.Alpakka'. Completing with 500 Internal Server Error response. To change default exception handling behavior, provide a custom ExceptionHandler.
java.lang.ClassCastException: com.datastax.driver.core.ArrayBackedRow cannot be cast to com.nk.map.model.Alpakka

我不确定自己在做什么错-感谢您提供任何指导！

将datastax行转换为案例类？

0 个答案: