我是Flink的新手。我正在尝试使用flink1.3.2来读取我们的kinesis流，并将输出写入cassandra表。这个程序能够从动觉中输入数据。
问题是，当我执行“cassandrasink.addsink（countsstreaming）”时，它会导致“类型不匹配”。应为：datastream[notinferredin]，实际为：datastream[（string，long）]'。我浏览了文档和源代码，注意到addsink接受datastream[in]。
有人能帮我理解“in”类型是什么以及如何解决这个问题吗？
提前谢谢！

val env = StreamExecutionEnvironment.getExecutionEnvironment
val mapper = new ObjectMapper
val kinesis = env.addSource(new FlinkKinesisConsumer[String](
  "kinesis-stream", new SimpleStringSchema, ConsumerConfig))

//DataStream[(String, Long)]
val countsStreaming: DataStream[(String, Long)] = kinesis.map(x => mapper.readValue(x,classOf[java.util.Map[String,String]]))
  .map(x => x.get("game_name"))
  .map({x => (x,1L) })
  .keyBy(0)
  .timeWindow(Time.seconds(5))
  .sum(1)

countsStreaming.print()

CassandraSink.addSink(countsStreaming)
  .setQuery("INSERT INTO example.values (id, counter) values (?, ?);")
.setClusterBuilder(new ClusterBuilder() {
  override def buildCluster(builder: Cluster.Builder): Cluster = {
    builder.addContactPoint("0.0.0.0").build()
  }
}).build()

env.execute("StreamingExample")