java.lang.ClassNotFoundException：scala.Serializable

Question

我试图建立一个测试scala作业，以使用flink流连接器从kafka流数据中读取数据，但收到以下错误

java.lang.ClassNotFoundException：scala.Serializable

import java.util.Properties

import org.apache.flink.api.common.typeinfo.TypeInformation
import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer
import org.apache.flink.api.common.serialization.SimpleStringSchema

object kafka_int_s3 {

  def main(args: Array[String]): Unit = {

    implicit val typeInfo = TypeInformation.of(classOf[(String)])
    val env: StreamExecutionEnvironment = 
    StreamExecutionEnvironment.getExecutionEnvironment

    val properties = new Properties()
    properties.setProperty("bootstrap.servers", "localhost:9092")
    properties.setProperty("zookeeper.connect", "localhost:2181")
    properties.setProperty("group.id", "test")
    properties.setProperty("auto.offset.reset", "earliest")

    val kkConsumer = new FlinkKafkaConsumer[String](
      "testtopic",
      new SimpleStringSchema(),
      properties)

    val stream = env
      .addSource(kkConsumer)
      .print()

  }

}