无法组装 scala/akka 项目

Question

我是 sbt 和 scala 的新手。只想在服务器上将 jar 文件制作成运行，但是当我尝试编译 jar 文件时出现错误。程序代码很简单，只有一个class（这里不能post，Whosebug不允许）。当我运行它在 Intellij 中时，一切都很好。但是 sbt 程序集引发了这个错误：

[info] Merging files...
[error] scala.MatchError: akka\stream\OverflowStrategies$.class (of class java.lang.String)
[error]         at $a019333dc409d47a4d92$.$anonfun$$sbtdef(D:\workspace_scala\TestSbt2\build.sbt:25)
[error]         at sbtassembly.Assembly$.$anonfun$applyStrategies(Assembly.scala:115)
[error]         at scala.collection.TraversableLike.$anonfun$map(TraversableLike.scala:234)
[error]         at scala.collection.Iterator.foreach(Iterator.scala:929)
[error]         at scala.collection.Iterator.foreach$(Iterator.scala:929)
[error]         at scala.collection.AbstractIterator.foreach(Iterator.scala:1417)
[error]         at scala.collection.IterableLike.foreach(IterableLike.scala:71)
[error]         at scala.collection.IterableLike.foreach$(IterableLike.scala:70)
[error]         at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
[error]         at scala.collection.TraversableLike.map(TraversableLike.scala:234)
[error]         at scala.collection.TraversableLike.map$(TraversableLike.scala:227)
[error]         at scala.collection.AbstractTraversable.map(Traversable.scala:104)
[error]         at sbtassembly.Assembly$.applyStrategies(Assembly.scala:114)
[error]         at sbtassembly.Assembly$.x$lzycompute(Assembly.scala:26)
[error]         at sbtassembly.Assembly$.x(Assembly.scala:24)
[error]         at sbtassembly.Assembly$.stratMapping$lzycompute(Assembly.scala:24)
[error]         at sbtassembly.Assembly$.stratMapping(Assembly.scala:24)
[error]         at sbtassembly.Assembly$.inputs$lzycompute(Assembly.scala:68)
[error]         at sbtassembly.Assembly$.inputs(Assembly.scala:58)
[error]         at sbtassembly.Assembly$.apply(Assembly.scala:85)
[error]         at sbtassembly.Assembly$.$anonfun$assemblyTask(Assembly.scala:249)
[error]         at scala.Function1.$anonfun$compose(Function1.scala:44)
[error]         at sbt.internal.util.$tilde$greater.$anonfun$$u2219(TypeFunctions.scala:39)
[error]         at sbt.std.Transform$$anon.work(System.scala:66)
[error]         at sbt.Execute.$anonfun$submit(Execute.scala:262)
[error]         at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error]         at sbt.Execute.work(Execute.scala:271)
[error]         at sbt.Execute.$anonfun$submit(Execute.scala:262)
[error]         at sbt.ConcurrentRestrictions$$anon.$anonfun$submitValid(ConcurrentRestrictions.scala:174)
[error]         at sbt.CompletionService$$anon.call(CompletionService.scala:36)
[error]         at java.util.concurrent.FutureTask.run(Unknown Source)
[error]         at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
[error]         at java.util.concurrent.FutureTask.run(Unknown Source)
[error]         at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
[error]         at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
[error]         at java.lang.Thread.run(Unknown Source)
[error] (assembly) scala.MatchError: akka\stream\OverflowStrategies$.class (of class java.lang.String)
[error] Total time: 1 s, completed Jun 20, 2018 1:20:02 PM

built.sbt

name := "TestSbt2"
version := "0.1"
scalaVersion := "2.12.4"

libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.5.13"
libraryDependencies += "com.typesafe.akka" %% "akka-stream" % "2.5.13"
libraryDependencies += "com.typesafe.akka" %% "akka-http" % "10.1.0"

assemblyMergeStrategy in assembly := {
  case PathList("reference.conf") => MergeStrategy.concat
}

project/assembly.sbt

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.6")

程序代码：

import akka.actor._
import akka.http.scaladsl._
import akka.http.scaladsl.model.ws.{Message, TextMessage}
import akka.http.scaladsl.server.Directives._
import akka.stream._
import akka.stream.scaladsl._

import scala.io.StdIn

object Server2 {
  def main(args: Array[String]): Unit = {
    implicit val system = ActorSystem()
    implicit val materializer = ActorMaterializer()

    def echoFlow: Flow[Message, Message, Any] =
      Flow[Message].map {
        case tm: TextMessage.Strict => TextMessage.Strict("Test " + tm.text)
        case _ => TextMessage("Message type unsupported")
      }

    val websocketRoute =
      path("chat") {
        handleWebSocketMessages(echoFlow)
      }

    val bindingFuture = Http().bindAndHandle(websocketRoute, "127.0.0.1", 8080)

    // the rest of the sample code will go here
    println("- Started server at 127.0.0.1:8080, press enter to kill server")
    StdIn.readLine()
    system.terminate()
  }
}

Answer 1

不太确定发生了什么，但是如果您在 assemblyMergeStrategy 定义中添加一个 default 案例，它应该可以正常工作。

例如：

assemblyMergeStrategy in assembly := {
  case "reference.conf" => MergeStrategy.concat
  case x =>
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}

稍作编辑：

实际上在回购协议上它说

assemblyMergeStrategy in assembly expects a function. You can't do assemblyMergeStrategy in assembly := MergeStrategy.first

Answer 2

它说的是 "MatchError"，它是在 build.sbt 文件中找到的，而你的 sbt 文件说的是

assemblyMergeStrategy in assembly := {
  case PathList("reference.conf") => MergeStrategy.concat
}

告诉我，您想使用后备案例。

将此添加为同一场比赛中的第二个案例（在您的 case PathList 之后）

case x =>
  val oldStrategy = (assemblyMergeStrategy in assembly).value
  oldStrategy(x)

（从 GitHub-sbt-assembly 复制）

Answer 3

谢谢大家！

这有帮助：

mainClass in assembly := Some("chat.Server2")

assemblyMergeStrategy in assembly := {
  case "reference.conf" => MergeStrategy.concat
  case x =>
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}

无法组装 scala/akka 项目

Can't assembly scala/akka project

scala

sbt

akka

akka-stream