使用sbt-spark-package插件理解build.sbt

Question

我是新的scala和SBT构建文件。从入门教程中可以直接通过sbt-spark-package插件向scala项目添加spark依赖项，但我得到了以下错误：

[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))
  }
}

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

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

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"
)

spName := "yewno/citation_graph"

version := "0.1"

scalaVersion := "2.11.12"

sparkVersion := "2.2.0"

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

额外的解释+参考资料链接，以了解更多关于SBT构建过程、jar文件和任何其他可以帮助我跟上速度的东西！

Answer 1

sbt-spark-package插件在provided作用域中提供依赖项：

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

提供的作用域表示：

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