使用sbt程序集创建胖jar时的scala.MatchError

Question

我正试图为我的项目创建一个jar文件。我使用sbt程序集命令生成一个程序集。

但是当它开始合并文件时出错：

spray\http\parser\ProtocolParameterRules$$anonfun$DeltaSeconds$1.class :scala.MatchError(java.lang.String类)

我的build.sbt看起来是这样的：

lazy val commonSettings = Seq(
  name := "SampleSpray",
  version := "1.0",
  scalaVersion := "2.11.7",
  organization := "com.test"

)
mainClass in assembly := Some("com.example.Boot")

lazy val root = (project in file(".")).
  settings(commonSettings: _*).
  settings(
    name := "test",
    resolvers += "spray repo" at "http://repo.spray.io",
    libraryDependencies ++= {
            val akkaV = "2.3.9"
            val sprayV = "1.3.3"
            Seq(
              "io.spray"            %%  "spray-can"     % sprayV,
              "io.spray"            %%  "spray-routing" % sprayV,
              "io.spray"            %%  "spray-json"    % "1.3.2",
              "io.spray"            %%  "spray-testkit" % sprayV  % "test",
              "com.typesafe.akka"   %%  "akka-actor"    % akkaV,
              "com.typesafe.akka"   %%  "akka-testkit"  % akkaV   % "test",
              "org.specs2"          %%  "specs2-core"   % "2.3.11" % "test",
              "com.sksamuel.elastic4s" %% "elastic4s-core" % "2.1.0",
              "com.sksamuel.elastic4s" %% "elastic4s-jackson" % "2.1.0",
              "net.liftweb" %% "lift-json" % "2.6+"
            )
  }
)


assemblyOption in assembly := (assemblyOption in assembly).value.copy(cacheUnzip = false)

assemblyMergeStrategy in assembly := {
  case "BaseDateTime.class"                            => MergeStrategy.first

}

不知道为什么会出现错误。

Answer 1

设置assemblyMergeStrategy in assembly的类型为String => MergeStrategy。

在sbt文件中，您使用的是部分函数。

{
   case "BaseDateTime.class" => MergeStrategy.first
}

这是语法糖

(s:String) => {
  s match {
    case "BaseDateTime.class" => MergeStrategy.first
  }
}

这种表示形式表明，给定函数将不完全匹配所有传递的字符串。在您的示例中，sbt程序集试图将名为spray\http\parser\ProtocolParameterRules$$anonfun$DeltaSeconds$1.class的文件合并到胖jar中，但找不到任何匹配的合并策略。您还需要一个“默认”案例：

(s:String) => {
  s match {
    case "BaseDateTime.class" => MergeStrategy.first
    case x =>
      val oldStrategy = (assemblyMergeStrategy in assembly).value
      oldStrategy(x)
  }
}

或写成部分函数：

{
  case "BaseDateTime.class" => MergeStrategy.first
  case x =>
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}

当sbt-装配的assembly任务由于elasticsearch中的名称冲突及其传递的joda-time依赖项而未能创建胖jar时，我也遇到了同样的问题。Elasticsearch重新定义了类org.joda.time.base.BaseDateTime，该类已经在joda-time库中实现。

assemblyMergeStrategy in assembly := {
  case "org/joda/time/base/BaseDateTime.class" => MergeStrategy.first
  case x =>
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}