使用 sbt-spark-package 插件了解 build.sbt

Question

我是新的 scala 和 SBT 构建文件。从介绍性教程中，将 spark 依赖项添加到 scala 项目应该是通过 sbt-spark-package 插件直接进行的，但我收到以下错误：

[error] (run-main-0) java.lang.NoClassDefFoundError: org/apache/spark/SparkContext

请提供资源以详细了解可能导致错误的原因，因为我想更彻底地了解流程。

代码：

trait SparkSessionWrapper {

  lazy val spark: SparkSession = {
    SparkSession
      .builder()
      .master("local")
      .appName("spark citation graph")
      .getOrCreate()
  }

  val sc = spark.sparkContext

}


import org.apache.spark.graphx.GraphLoader

object Test extends SparkSessionWrapper {

  def main(args: Array[String]) {
    println("Testing, testing, testing, testing...")

    var filePath = "Desktop/citations.txt"
    val citeGraph = GraphLoader.edgeListFile(sc, filepath)
    println(citeGraph.vertices.take(1))
  }
}

plugins.sbt

resolvers += "bintray-spark-packages" at "https://dl.bintray.com/spark-packages/maven/"

addSbtPlugin("org.spark-packages" % "sbt-spark-package" % "0.2.6")

build.sbt -- 工作中。为什么 libraryDependencies 运行/工作？

spName := "yewno/citation_graph"

version := "0.1"

scalaVersion := "2.11.12"

sparkVersion := "2.2.0"

sparkComponents ++= Seq("core", "sql", "graphx")

libraryDependencies ++= Seq(
  "org.apache.spark" %% "spark-core" % "2.2.0",
  "org.apache.spark" %% "spark-sql" % "2.2.0",
  "org.apache.spark" %% "spark-graphx" % "2.2.0"
)

build.sbt -- 不工作。希望它能够正确编译和运行

spName := "yewno/citation_graph"

version := "0.1"

scalaVersion := "2.11.12"

sparkVersion := "2.2.0"

sparkComponents ++= Seq("core", "sql", "graphx")

解释奖励 + 资源链接，以了解有关 SBT 构建过程、jar 文件以及任何其他可以帮助我加快速度的信息！

Answer 1

sbt-spark-package plugin 在provided 范围内提供依赖：

sparkComponentSet.map { component =>
  "org.apache.spark" %% s"spark-$component" % sparkVersion.value % "provided"
}.toSeq

我们可以通过从 sbt 运行 show libraryDependencies 来确认这一点：

[info] * org.scala-lang:scala-library:2.11.12
[info] * org.apache.spark:spark-core:2.2.0:provided
[info] * org.apache.spark:spark-sql:2.2.0:provided
[info] * org.apache.spark:spark-graphx:2.2.0:provided

provided 范围意味着：

依赖项将是编译和测试的一部分，但不包括在 运行时。

因此sbt run 抛出java.lang.NoClassDefFoundError: org/apache/spark/SparkContext

如果我们真的想在 run 类路径上包含 provided 依赖项，那么 @douglaz 建议：

run in Compile := Defaults.runTask(fullClasspath in Compile, mainClass in (Compile, run), runner in (Compile, run)).evaluated