用sbt火花封装插件理解build.sbt

Question

我是新的scala和SBT构建文件。在入门教程中，将火花依赖项添加到scala项目应该是通过sbt火花包插件直接进行的，但是我得到了以下错误：

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

请提供资源，以了解更多关于什么可能是驱动错误，因为我想更彻底地理解过程。

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。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 -不起作用。应该编译并正确运行。

spName := "yewno/citation_graph"

version := "0.1"

scalaVersion := "2.11.12"

sparkVersion := "2.2.0"

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

奖金的解释+链接到资源，以了解更多关于SBT构建过程，jar文件，以及任何其他可以帮助我提高速度！

Answer 1

sbt-火花塞插件在provided作用域中提供依赖关系：

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：

该依赖项将是编译和测试的一部分，但不包含在运行时。

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

如果我们真的想在provided类路径上包含run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