我是新来Scala和阿卡所以请原谅我,如果这是对于新手的问题,但我找不到答案其他地方...为什么Scala无法实例化Companion对象?
对于我使用Scala的2.9.0-1和阿卡记录1.1.3,并包含了我的SBT 0.10.1设置。
我已经写下了这封邮件的代码,作为Akka的实验;它是用户数据库和注册设施的玩具版本。基本思想是有一个UserPool Actor ActorPool,每个ActorPool都有一个MemoryUserDatabase的实例,它使用STM与用户的电子邮件地址关联的用户图进行交互 - 非常简单,对吧?
该问题可以通过编译文件并运行在两个单独的控制台以下再现:
控制台#1:
进口toy.service.user._; ServiceRunner.run
控制台#2:
进口toy.service.user._; ClientRunner.run
这是从服务器控制台输出(#1)
Aug 31, 2011 5:21:29 PM org.multiverse.api.GlobalStmInstance <clinit>
INFO: Initializing GlobalStmInstance using factoryMethod 'org.multiverse.stms.alpha.AlphaStm.createFast'.
Aug 31, 2011 5:21:29 PM org.multiverse.stms.alpha.AlphaStm <init>
INFO: Created a new AlphaStm instance
Aug 31, 2011 5:21:29 PM org.multiverse.api.GlobalStmInstance <clinit>
INFO: Successfully initialized GlobalStmInstance using factoryMethod 'org.multiverse.stms.alpha.AlphaStm.createFast'.
[ERROR] [8/31/11 5:21 PM] [akka:event-driven:dispatcher:global-3] [LocalActorRef] Availability(foo)
java.lang.NoClassDefFoundError: Could not initialize class toy.service.user.memory.MemoryUserDatabase$
at toy.service.user.memory.MemoryUserDatabase$$anonfun$getUser$1.apply(Registration.scala:96)
at toy.service.user.memory.MemoryUserDatabase$$anonfun$getUser$1.apply(Registration.scala:96)
at toy.service.user.memory.MemoryUserDatabase$$anonfun$getUser$2.apply(Registration.scala:96)
at toy.service.user.memory.MemoryUserDatabase$$anonfun$getUser$2.apply(Registration.scala:96)
at akka.stm.Stm$$anon$1.call(Stm.scala:51)
at org.multiverse.templates.TransactionBoilerplate.executeWithTransaction(TransactionBoilerplate.java:279)
at org.multiverse.templates.TransactionBoilerplate.executeChecked(TransactionBoilerplate.java:218)
at org.multiverse.templates.TransactionBoilerplate.execute(TransactionBoilerplate.java:169)
at akka.stm.Stm$class.atomic(Stm.scala:50)
at akka.stm.package$.atomic(package.scala:10)
at akka.stm.Stm$class.atomic(Stm.scala:47)
at akka.stm.package$.atomic(package.scala:10)
at toy.service.user.memory.MemoryUserDatabase.getUser(Registration.scala:95)
at toy.service.user.UserDatabase$class.available(Registration.scala:88)
at toy.service.user.memory.MemoryUserDatabase.available(Registration.scala:92)
at toy.service.user.UserServer$$anonfun$receive$1.apply(Registration.scala:77)
at toy.service.user.UserServer$$anonfun$receive$1.apply(Registration.scala:76)
at akka.actor.Actor$class.apply(Actor.scala:478)
at toy.service.user.UserServer.apply(Registration.scala:74)
at akka.actor.LocalActorRef.invoke(ActorRef.scala:860)
at akka.dispatch.MessageInvocation.invoke(MessageHandling.scala:26)
at akka.dispatch.ExecutableMailbox$class.processMailbox(ExecutorBasedEventDrivenDispatcher.scala:214)
at akka.dispatch.ExecutorBasedEventDrivenDispatcher$$anon$4.processMailbox(ExecutorBasedEventDrivenDispatcher.scala:120)
at akka.dispatch.ExecutableMailbox$class.run(ExecutorBasedEventDrivenDispatcher.scala:186)
at akka.dispatch.ExecutorBasedEventDrivenDispatcher$$anon$4.run(ExecutorBasedEventDrivenDispatcher.scala:120)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
at akka.dispatch.MonitorableThread.run(ThreadPoolBuilder.scala:181)
错误是使用稍微更有趣的Scala 2.9.1.final:
Aug 31, 2011 5:38:35 PM org.multiverse.api.GlobalStmInstance <clinit>
INFO: Initializing GlobalStmInstance using factoryMethod 'org.multiverse.stms.alpha.AlphaStm.createFast'.
Aug 31, 2011 5:38:35 PM org.multiverse.api.GlobalStmInstance getMethod
INFO: Failed to initialize GlobalStmInstance through System property 'org.multiverse.api.GlobalStmInstance.factoryMethod' with value 'org.multiverse.stms.alpha.AlphaStm'.'org.multiverse.stms.alpha.AlphaStm.createFast' is not an existing class (it can't be found using the Thread.currentThread.getContextClassLoader).
[ERROR] [8/31/11 5:38 PM] [akka:event-driven:dispatcher:global-3] [LocalActorRef] Availability(foo)
java.lang.ExceptionInInitializerError
at akka.stm.TransactionFactory.<init>(TransactionFactory.scala:172)
at akka.stm.TransactionFactory$.apply(TransactionFactory.scala:122)
at akka.stm.Stm$class.$init$(Stm.scala:44)
at akka.stm.package$.<init>(package.scala:10)
at akka.stm.package$.<clinit>(package.scala)
at toy.service.user.memory.MemoryUserDatabase.getUser(Registration.scala:95)
at toy.service.user.UserDatabase$class.available(Registration.scala:88)
at toy.service.user.memory.MemoryUserDatabase.available(Registration.scala:92)
at toy.service.user.UserServer$$anonfun$receive$1.apply(Registration.scala:77)
at toy.service.user.UserServer$$anonfun$receive$1.apply(Registration.scala:76)
at akka.actor.Actor$class.apply(Actor.scala:478)
at toy.service.user.UserServer.apply(Registration.scala:74)
at akka.actor.LocalActorRef.invoke(ActorRef.scala:860)
at akka.dispatch.MessageInvocation.invoke(MessageHandling.scala:26)
at akka.dispatch.ExecutableMailbox$class.processMailbox(ExecutorBasedEventDrivenDispatcher.scala:214)
at akka.dispatch.ExecutorBasedEventDrivenDispatcher$$anon$4.processMailbox(ExecutorBasedEventDrivenDispatcher.scala:120)
at akka.dispatch.ExecutableMailbox$class.run(ExecutorBasedEventDrivenDispatcher.scala:186)
at akka.dispatch.ExecutorBasedEventDrivenDispatcher$$anon$4.run(ExecutorBasedEventDrivenDispatcher.scala:120)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
at akka.dispatch.MonitorableThread.run(ThreadPoolBuilder.scala:181)
Caused by: java.lang.IllegalArgumentException: Failed to initialize GlobalStmInstance through System property 'org.multiverse.api.GlobalStmInstance.factoryMethod' with value 'org.multiverse.stms.alpha.AlphaStm'.'org.multiverse.stms.alpha.AlphaStm.createFast' is not an existing class (it can't be found using the Thread.currentThread.getContextClassLoader).
at org.multiverse.api.GlobalStmInstance.getMethod(GlobalStmInstance.java:82)
at org.multiverse.api.GlobalStmInstance.<clinit>(GlobalStmInstance.java:38)
... 22 more
Caused by: java.lang.ClassNotFoundException: org.multiverse.stms.alpha.AlphaStm
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at org.multiverse.api.GlobalStmInstance.getMethod(GlobalStmInstance.java:76)
... 23 more
该执行部分的代码是:
class MemoryUserDatabase extends UserDatabase {
import MemoryUserDatabase._
def getUser(email: String) = atomic {
users.get.get(email)
}
def register(user: User) = atomic {
getUser(user.email) match {
case None =>
users alter (_ + (user.email -> user))
true
case Some(found) => false
}
}
}
object MemoryUserDatabase {
import scala.collection.mutable.{ Map => MutMap }
private val users = Ref(MutMap[String, User]())
}
我不明白为什么Companion对象无法初始化。最奇怪的是,你可以做同样的事情,但如果在服务器控制台(#1)你第一次访问协同对象:
运行ServerRunner之前它只是初始化
MemoryUserDatabase罚款,随后一切都只是花花公子。
任何人都可以解释为什么这是?
谢谢! Idan
PS。这是我的第一个Scala代码,所以尽量不要太难以发笑......并且欢迎任何其他建议(风格,哲学,神学......)。
package toy.service.user import scala.collection.mutable.HashMap import akka.actor.{ Actor, ActorRef } import akka.config.Supervision.{ OneForOneStrategy, Permanent } import Actor._ import akka.routing._ import akka.stm._ import akka.actor.TypedActor import akka.event.EventHandler class User(var email: String, var password: String) extends Serializable /** Registration message types. */ sealed trait RegistrationMessage case class Availability(email: String) extends RegistrationMessage case class GetUser(email: String) extends RegistrationMessage case class Register(user: User) extends RegistrationMessage // Client --------------------------------------- class UserClient(defaultTimeout: Int = 1000) { val userService = Actor.remote.actorFor(UserService.USER_SERVICE_ID, "localhost", UserService.USER_SERVICE_PORT) EventHandler.info(this, "remote UserService: id(" + userService.id + "), uuid(" + userService.uuid + ")") def getUser(email: String, timeout: Int = defaultTimeout): Option[User] = (userService !! (GetUser(email), timeout)).as[User] def available(email: String, timeout: Int = defaultTimeout): Boolean = (userService !! (Availability(email), timeout)).as[Boolean].getOrElse(throw new RuntimeException("Oi!")) def register(user: User, timeout: Int = defaultTimeout): Boolean = (userService !! (Register(user), timeout)).as[Boolean].getOrElse(throw new RuntimeException("Got bogus (None) response from " + UserService.USER_SERVICE_ID)) } // Service Pool --------------------------------- object UserService { val USER_SERVICE_ID = "user:service" val USER_SERVICE_PORT = 2662 val host = "localhost" } class UserService extends Actor with DefaultActorPool with BoundedCapacityStrategy with MailboxPressureCapacitor with SmallestMailboxSelector with BasicFilter { import toy.service.user.memory._ def receive = _route // DefaultActorPool's receive def lowerBound = 1 def upperBound = 5 def pressureThreshold = 1 def partialFill = true // never send duplicate messages to same actor (only meaningful if selectionCount > 1) def selectionCount = 1 // How many in pool should receive each message def rampupRate = 0.1 // increase by 10% capacity (# num actors) def backoffRate = 0.50 // halve capacity once backoffThreshold is reached def backoffThreshold = 0.50 def instance = actorOf(new UserServer(new MemoryUserDatabase)) override def preStart() { import UserService.{ host, USER_SERVICE_ID, USER_SERVICE_PORT } remote.start(host, UserService.USER_SERVICE_PORT); remote.register(UserService.USER_SERVICE_ID, self) //Register the actorPool with the specified service id EventHandler.info(this, "Prestart: Started UserService(" + self.uuid + ") on %s:%s".format(host, UserService.USER_SERVICE_PORT.toString())) } } // Service -------------------------------------- class UserServer(db: UserDatabase) extends Actor { def receive = { case Availability(email) => self.reply(db.available(email)) case GetUser(email) => self.reply(db.getUser(email)) case Register(user) => self.reply(db.register(user)) } } // Database ------------------------------------- trait UserDatabase { def getUser(email: String): Option[User] def register(user: User): Boolean def available(email: String): Boolean = getUser(email) == None } package memory { class MemoryUserDatabase extends UserDatabase { import MemoryUserDatabase._ def getUser(email: String) = atomic { users.get.get(email) } def register(user: User) = atomic { getUser(user.email) match { case None => users alter (_ + (user.email -> user)) true case Some(found) => false } } } object MemoryUserDatabase { import scala.collection.mutable.{ Map => MutMap } private val users = Ref(MutMap[String, User]()) } } object ServerRunner { def run() { actorOf[UserService].start() } } object ClientRunner { def run { val client = new UserClient EventHandler.info(this, client.available("foo")) } }
最近发布了Scala 2.9.1。也许在那里拍一下? –
我认为你需要添加更多的堆栈跟踪以供任何使用。 –
另外,你正在使用共享的,unthreadsafe状态,这是一个很大的禁止 –