Scala SBT编译错误

Question

I have been following this tutorial to learn how to use Akka HTTP with Scala. I have no prior experience with Scala. I'm using IntelliJ Idea 2016.3 Ultimate.

I created a project and configured 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"

I have the exactly same code as in the guide but when I run the SBT command compile I get the following error

[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

If I change my build.sbt to a more recent version of the akka libraries

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"
)

and compile again I get a different error

[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

How can I fix this? I don't know how to debug this error nor where to start tackling this problem. As I said, this is my first test with Scala so I don't have any prior experience with it, so, please, give me detail answers.

Thanks!

Answer 1

First error: Scala 2.9.x requires JVM runtime v 1.6 or 1.7, while you are using 1.8, which wouldn't work as we can clearly see from the message ('broken class' means that the runtime doesn't understand the structure of the files you are feeding it).

Second error requires a bit more context, could you post the code? I'm 99% sure you follow some outdated example, but use fresh library releases. Eg there's no Duration in akka.util , no RoundRobinRouter in akka.routing etc.

I would suggest you to spend some time exploring/tweaking available samples , eg this one: https://github.com/akka/akka-samples/tree/master/akka-sample-main-scala .

Also, note that akka evolves pretty fast, but has a solid documentation versioning support, so for each library release there's a separate documentation section on the site. You'll be notified about this at leas once a day when you visit an outdated release documentation page. Here's the link to he 2.4.17 docs: http://doc.akka.io/docs/akka/2.4.17/scala.html

Answer 2

There are 2 options:

1. Using java 7 with scala 2.7.2
2. Using another version of scala (2.11.4), and java 8:

Example build.sbt

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