当我在Java Flink中运行Scala REPL时，为什么会出现“缺少参数类型错误”的情况？

Question

当我在Java中运行flink scala REPL脚本时，无法编译。

我尝试使用此Java代码运行Flink scala REPL进行测试，但始终会出现bug。

Settings settings = new Settings();
    ((MutableSettings.BooleanSetting) settings.usejavacp()).value_$eq(true);
    IMain main = new IMain(settings, new PrintWriter(System.out));
    // Thread.currentThread().setContextClassLoader(main.classLoader());
    for (String imp : imports) {
        main.interpret(MessageFormat.format("import {0}", imp));
    }
    ExecutionEnvironment env = ExecutionEnvironment.createLocalEnvironment();
    String script = FileUtils.readFileToString(new File("/opt/project/security-detection/sappo/src/sappo-interpreter/src/test/resources/demo.txt"), StandardCharsets.UTF_8);
    main.bind(new NamedParamClass("env", ExecutionEnvironment.class.getName(), env));
    main.interpret(script);

标量文字

val text = env.fromElements("Who's there?", "I think I hear them. Stand, ho! Who's there?")

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

    // result 2
    val counts = text.map((x:String) => 1)
    counts.print()

    // result 3
    text.print()

结果1

import org.apache.flink.core.fs._
    import org.apache.flink.core.fs.local._
    import org.apache.flink.api.common.io._
    import org.apache.flink.api.common.aggregators._
    import org.apache.flink.api.common.accumulators._
    import org.apache.flink.api.common.distributions._
    import org.apache.flink.api.common.operators._
    import org.apache.flink.api.common.operators.base.JoinOperatorBase.JoinHint
    import org.apache.flink.api.common.functions._
    import org.apache.flink.api.java.io._
    import org.apache.flink.api.java.aggregation._
    import org.apache.flink.api.java.functions._
    import org.apache.flink.api.java.operators._
    import org.apache.flink.api.java.sampling._
    import org.apache.flink.api.scala._
    import org.apache.flink.api.scala.utils._
    import org.apache.flink.streaming.api.scala._
    import org.apache.flink.streaming.api.windowing.time._
    env: org.apache.flink.api.java.ExecutionEnvironment = Local Environment (parallelism = 8) : ee335d29eefca69ee5fe7279414fc534
    console:67: error: missing parameter type for expanded function ((x$1) => x$1.toLowerCase.split("\\W+").filter(((x$2) => x$2.nonEmpty)))
           val counts = text.flatMap { _.toLowerCase.split("\\W+") filter { _.nonEmpty } } map { (_, 1) } groupBy(0) sum(1)

结果2

import org.apache.flink.core.fs._
    import org.apache.flink.core.fs.local._
    import org.apache.flink.api.common.io._
    import org.apache.flink.api.common.aggregators._
    import org.apache.flink.api.common.accumulators._
    import org.apache.flink.api.common.distributions._
    import org.apache.flink.api.common.operators._
    import org.apache.flink.api.common.operators.base.JoinOperatorBase.JoinHint
    import org.apache.flink.api.common.functions._
    import org.apache.flink.api.java.io._
    import org.apache.flink.api.java.aggregation._
    import org.apache.flink.api.java.functions._
    import org.apache.flink.api.java.operators._
    import org.apache.flink.api.java.sampling._
    import org.apache.flink.api.scala._
    import org.apache.flink.api.scala.utils._
    import org.apache.flink.streaming.api.scala._
    import org.apache.flink.streaming.api.windowing.time._
    env: org.apache.flink.api.java.ExecutionEnvironment = Local Environment (parallelism = 8) : 5cbf8e476ebf32fd8fdf91766bd40af0
    console:71: error: type mismatch;
     found   : String => Int
     required: org.apache.flink.api.common.functions.MapFunction[String,?]
           val counts = text.map((x:String) => 1)

结果3

import org.apache.flink.core.fs._
    import org.apache.flink.core.fs.local._
    import org.apache.flink.api.common.io._
    import org.apache.flink.api.common.aggregators._
    import org.apache.flink.api.common.accumulators._
    import org.apache.flink.api.common.distributions._
    import org.apache.flink.api.common.operators._
    import org.apache.flink.api.common.operators.base.JoinOperatorBase.JoinHint
    import org.apache.flink.api.common.functions._
    import org.apache.flink.api.java.io._
    import org.apache.flink.api.java.aggregation._
    import org.apache.flink.api.java.functions._
    import org.apache.flink.api.java.operators._
    import org.apache.flink.api.java.sampling._
    import org.apache.flink.api.scala._
    import org.apache.flink.api.scala.utils._
    import org.apache.flink.streaming.api.scala._
    import org.apache.flink.streaming.api.windowing.time._
    env: org.apache.flink.api.java.ExecutionEnvironment = Local Environment (parallelism = 8) : ee335d29eefca69ee5fe7279414fc534
    Who's there?
    I think I hear them. Stand, ho! Who's there?
    text: org.apache.flink.api.java.operators.DataSource[String] = org.apache.flink.api.java.operators.DataSource@53e28097
    PASSED: testIMain
    PASSED: testIMainScript

Answer 1

尝试使用Flink随附的Scala REPL：

$ bin/start-scala-shell.sh local

我尝试了您共享的三个示例（使用Flink 1.7.0），它们都工作正常。