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  • scala的REPL shell的调用

    最近突然对spark的spark-shell发生了兴趣
    它是如何启动scala的REPL的,并且在此前写入了常用的环境变量的呢?
    通过查看spark的源码,找到了SparkILoop.scala

    import scala.tools.nsc.interpreter.{JPrintWriter, ILoop}
    
    /**
     *  A Spark-specific interactive shell.
     */
    class SparkILoop(in0: Option[BufferedReader], out: JPrintWriter)
        extends ILoop(in0, out) {
      def this(in0: BufferedReader, out: JPrintWriter) = this(Some(in0), out)
      def this() = this(None, new JPrintWriter(Console.out, true))
    
      def initializeSpark() {
        intp.beQuietDuring {
          processLine("""
             @transient val sc = {
               val _sc = org.apache.spark.repl.Main.createSparkContext()
               println("Spark context available as sc.")
               _sc
             }
            """)
          processLine("""
             @transient val sqlContext = {
               val _sqlContext = org.apache.spark.repl.Main.createSQLContext()
               println("SQL context available as sqlContext.")
               _sqlContext
             }
            """)
          processLine("import org.apache.spark.SparkContext._")
          processLine("import sqlContext.implicits._")
          processLine("import sqlContext.sql")
          processLine("import org.apache.spark.sql.functions._")
        }
      }
      ...
    }

    可以看出SparkILoop继承自scala.tools.nsc.interpreter.ILoop
    紧接着着看了ILoop的api doc
    终于找到了启动ILoop的方法:

    import scala.tools.nsc.interpreter.ILoop
    import scala.tools.nsc.Settings
    
    val loop = new ILoop
    loop.process(new Settings)
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  • 原文地址:https://www.cnblogs.com/bluejoe/p/5115837.html
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