Flink Scala API"没有足够的参数"

Question

我在使用Apache Flink Scala API时遇到了麻烦

例如,即使我从官方文档中获取示例,scala编译器也会给我带来大量的编译错误.

码:

object TestFlink {

  def main(args: Array[String]) {
    val env = ExecutionEnvironment.getExecutionEnvironment
    val text = env.fromElements(
      "Who's there?",
      "I think I hear them. Stand, ho! Who's there?")

    val counts = text.flatMap { _.toLowerCase.split("\\W+") filter { _.nonEmpty } }
      .map { (_, 1) }
      .groupBy(0)
      .sum(1)

    counts.print()

    env.execute("Scala WordCount Example")
  }
}

Scala IDE为该行输出以下内容 val text = env.fromElements

Multiple markers at this line
  - not enough arguments for method fromElements: (implicit evidence$14: scala.reflect.ClassTag[String], implicit evidence$15: 
   org.apache.flink.api.common.typeinfo.TypeInformation[String])org.apache.flink.api.scala.DataSet[String]. Unspecified value parameter evidence$15.
  - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[String]
  - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[String]
  - not enough arguments for method fromElements: (implicit evidence$14: scala.reflect.ClassTag[String], implicit evidence$15: 
   org.apache.flink.api.common.typeinfo.TypeInformation[String])org.apache.flink.api.scala.DataSet[String]. Unspecified value parameter evidence$15.

这不仅仅是fromElements方法:即使我从文件中读取然后尝试做一些简单的事情ds.map(r => r),我也会得到非常相似的东西

Multiple markers at this line
    - not enough arguments for method map: (implicit evidence$4: org.apache.flink.api.common.typeinfo.TypeInformation[K], implicit 
     evidence$5: scala.reflect.ClassTag[K])org.apache.flink.api.scala.DataSet[K]. Unspecified value parameters evidence$4, evidence$5.
    - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[K]
    - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[K]
    - not enough arguments for method map: (implicit evidence$4: org.apache.flink.api.common.typeinfo.TypeInformation[K], implicit 
     evidence$5: scala.reflect.ClassTag[K])org.apache.flink.api.scala.DataSet[K]. Unspecified value parameters evidence$4, evidence$5.

我尝试了两个版本的Flink:来自Maven Central的0.8.1和来自github存储库的最新版本.

我正在运行Windows 7,scala 2.10.4,jdk 1.7.0_25,Scala IDE版本是3.0.3-20140327-1716-Typesafe在Eclipse 4.3.0之上

我究竟做错了什么？

Answer 1

您需要在代码中添加以下导入:

import org.apache.flink.api.scala._ 

然后该示例有效.