Question

我一直关注this tutorial以了解如何在Scala中使用Akka HTTP。我没有Scala的经验。我正在使用IntelliJ Idea 2016.3 Ultimate。

我创建了一个项目并配置了as the guide says。

name := "My Project"

version := "1.0"

scalaVersion := "2.9.1"

resolvers += "Typesafe Repository" at "http://repo.typesafe.com/typesafe/releases/"

libraryDependencies += "com.typesafe.akka" % "akka-actor" % "2.0"

我有完全相同的代码as in the guide，但是当我运行SBT命令编译时，我收到以下错误

[info] Updating {file:/Users/Javyer/Testing/Akka-Test/}akka-test...
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
[info] Compiling 1 Scala source to /Users/Javyer/Testing/Akka-Test/target/scala-2.9.1/classes...
[info] 'compiler-interface' not yet compiled for Scala 2.9.1.final. Compiling...
error: error while loading CharSequence, class file '/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home/jre/lib/rt.jar(java/lang/CharSequence.class)' is broken
(bad constant pool tag 18 at byte 10)
error: error while loading AnnotatedElement, class file '/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home/jre/lib/rt.jar(java/lang/reflect/AnnotatedElement.class)' is broken
(bad constant pool tag 18 at byte 76)
error: error while loading Arrays, class file '/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home/jre/lib/rt.jar(java/util/Arrays.class)' is broken
(bad constant pool tag 18 at byte 765)
error: error while loading Comparator, class file '/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home/jre/lib/rt.jar(java/util/Comparator.class)' is broken
(bad constant pool tag 18 at byte 20)
/var/folders/kw/80c0kgzs0b9d06vjrbx0l6g40000gn/T/sbt_139df807/xsbt/ExtractAPI.scala:549: error: java.util.Comparator does not take type parameters
  private[this] val sortClasses = new Comparator[Symbol] {
                                      ^
5 errors found
[info] Resolving org.scala-sbt#interface;0.13.13 ...
[error] (compile:compileIncremental) Error compiling sbt component 'compiler-interface'
[error] Total time: 5 s, completed Mar 22, 2017 11:42:21 AM

如果我将build.sbt更改为更新版本的akka库

name := "Akka-Test"

version := "1.0"

scalaVersion := "2.12.1"

resolvers += "Typesafe Repository" at "http://repo.typesafe.com/typesafe/releases/"

libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-actor" % "2.4.17",
  "com.typesafe.akka" %% "akka-remote" % "2.4.17"
)

再次编译我得到了一个不同的错误

[info] Updating {file:/Users/Javyer/Testing/Akka-Test/}akka-test...
[info] Resolving jline#jline;2.14.1 ...
[info] Done updating.
[info] Compiling 1 Scala source to /Users/Javyer/Testing/Akka-Test/target/scala-2.12/classes...
[error] /Users/Javyer/Testing/Akka-Test/src/main/scala/Pi.scala:5: object RoundRobinRouter is not a member of package akka.routing
[error] import akka.routing.RoundRobinRouter
[error]        ^
[error] /Users/Javyer/Testing/Akka-Test/src/main/scala/Pi.scala:6: object Duration is not a member of package akka.util
[error] import akka.util.Duration
[error]        ^
[error] /Users/Javyer/Testing/Akka-Test/src/main/scala/Pi.scala:7: object duration is not a member of package akka.util
[error] import akka.util.duration._
[error]                  ^
[error] /Users/Javyer/Testing/Akka-Test/src/main/scala/Pi.scala:17: not found: type Duration
[error]   case class PiApproximation(pi: Double, duration: Duration)
[error]                                                    ^
[error] /Users/Javyer/Testing/Akka-Test/src/main/scala/Pi.scala:40: not found: value RoundRobinRouter
[error]     val workerRouter = context.actorOf(Props[Worker].withRouter(RoundRobinRouter(nrOfWorkers)), name = "workerRouter")
[error]                                                                 ^
[error] 5 errors found
[error] (compile:compileIncremental) Compilation failed
[error] Total time: 4 s, completed Mar 22, 2017 11:47:47 AM

我该如何解决这个问题？我不知道如何调试此错误，也不知道从哪里开始解决此问题。正如我所说，这是我对Scala的第一次测试，所以我没有任何先前的经验，所以，请给我详细解答。

谢谢！

Answer 1

第一个错误：Scala 2.9.x需要JVM运行时v 1.6或1.7，而你使用1.8，这是行不通的，因为我们可以从消息中清楚地看到（'broken class'意味着运行时不理解你正在喂它的文件的结构。）

第二个错误需要更多的上下文，你可以发布代码吗？我99％肯定你会遵循一些过时的例子，但是使用新的库版本。例如。 Duration中没有akka.util，RoundRobinRouter中没有akka.routing等。

我建议你花点时间探索/调整available samples，例如这一个：https://github.com/akka/akka-samples/tree/master/akka-sample-main-scala。

另外，请注意akka的发展速度非常快，但是具有可靠的文档版本支持，因此对于每个库版本，网站上都有一个单独的文档部分。当您访问过时的发布文档页面时，您每天都会收到有关此信息的通知。这是他2.4.17文档的链接：http://doc.akka.io/docs/akka/2.4.17/scala.html

Answer 2

有两个选项：

将java 7与scala 2.7.2一起使用
使用另一版本的scala（2.11.4）和java 8：

示例build.sbt

scalaVersion := Option(System.getProperty("scala.version")).getOrElse("2.11.4")

Scala SBT编译错误

2 个答案: