Mongodb 萨拉特磨碎机故障ClassNotFoundException

我在Salat方面遇到了一个奇怪的问题，尤其是当我运行PlayWeb应用程序时

以下是stacktrace：

Caused by: java.util.concurrent.ExecutionException: Boxed Error
at scala.concurrent.impl.Promise$.resolver(Promise.scala:52) ~[scala-library.jar:na]
at scala.concurrent.impl.Promise$.scala$concurrent$impl$Promise$$resolveTry(Promise.scala:44) ~[scala-library.jar:na]
at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:116) [scala-library.jar:na]
... 9 common frames omitted

原因：com.novus.salat.util.GraterGlitch：

  GRATER GLITCH - unable to find or instantiate a grater using supplied path name

  REASON: Very strange!  Path='domain.content.Exam' from pickled ScalaSig causes ClassNotFoundException

  Context: 'global'
  Path from pickled Scala sig: 'domain.content.Exam'



at com.novus.salat.Context$class.lookup(Context.scala:213) ~[salat-core_2.10-1.9.2.jar:1.9.2]
at com.novus.salat.global.package$$anon$1.lookup(global.scala:29) ~[salat-core_2.10-1.9.2.jar:1.9.2]
at com.novus.salat.package$.grater(package.scala:62) ~[salat-core_2.10-1.9.2.jar:1.9.2]
at com.novus.salat.dao.SalatDAO.<init>(SalatDAO.scala:48) ~[salat-core_2.10-1.9.2.jar:1.9.2]
at domain.content.ExamDAO$.<init>(Exam.scala:31) ~[classes/:na]
at domain.content.ExamDAO$.<clinit>(Exam.scala) ~[classes/:na]
at domain.content.Exam$.getAllExamsForTechnology(Exam.scala:22) ~[classes/:na]
at core.ContentService.allExamsForTechnology(ContentService.scala:30) ~[classes/:na]
at controllers.content.ExamController$$anonfun$allExamsForTechnology$1.apply(ExamController.scala:24) ~[classes/:na]
at controllers.content.ExamController$$anonfun$allExamsForTechnology$1.apply(ExamController.scala:22) ~[classes/:na]
at play.api.mvc.ActionBuilder$$anonfun$apply$10.apply(Action.scala:221) ~[play_2.10.jar:2.2.1]
at play.api.mvc.ActionBuilder$$anonfun$apply$10.apply(Action.scala:220) ~[play_2.10.jar:2.2.1]
at play.api.mvc.Action$.invokeBlock(Action.scala:357) ~[play_2.10.jar:2.2.1]
at play.api.mvc.ActionBuilder$$anon$1.apply(Action.scala:309) ~[play_2.10.jar:2.2.1]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:109) ~[play_2.10.jar:2.2.1]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:109) ~[play_2.10.jar:2.2.1]
at play.utils.Threads$.withContextClassLoader(Threads.scala:18) ~[play_2.10.jar:2.2.1]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:108) ~[play_2.10.jar:2.2.1]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:107) ~[play_2.10.jar:2.2.1]
at scala.Option.map(Option.scala:145) ~[scala-library.jar:na]
at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:107) ~[play_2.10.jar:2.2.1]
at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:100) ~[play_2.10.jar:2.2.1]
at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:481) ~[play-iteratees_2.10.jar:2.2.1]
at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:481) ~[play-iteratees_2.10.jar:2.2.1]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:517) ~[play-iteratees_2.10.jar:2.2.1]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:517) ~[play-iteratees_2.10.jar:2.2.1]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:493) ~[play-iteratees_2.10.jar:2.2.1]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:493) ~[play-iteratees_2.10.jar:2.2.1]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library.jar:na]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library.jar:na]
... 6 common frames omitted

GRATER故障-无法使用提供的路径名找到或实例化GRATER
理由：很奇怪！pickled ScalaSig中的Path='domain.content.Exam'导致ClassNotFoundException
背景：“全球”
pickled Scala sig的路径：“domain.content.Exam”
在com.novus.salat.Context$class.lookup（Context.scala:213）~[salat-core_2.10-1.9.2.jar:1.9.2]
在com.novus.salat.global.package$$anon$1.lookup（global.scala:29）~[salat-core_2.10-1.9.2.jar:1.9.2]
在com.novus.salat.package$.grater（package.scala:62）~[salat-core_2.10-1.9.2.jar:1.9.2]
在com.novus.salat.dao.SalatDAO.（SalatDAO.scala:48）~[salat-core_2.10-1.9.2.jar:1.9.2]
在domain.content.ExamDAO$（Exam.scala:31）~[classes/:na]
在domain.content.ExamDAO$（Exam.scala）~[classes/:na]
在domain.content.Exam$.getAllExamsForTechnology（Exam.scala:22）~[classes/:na]
在core.ContentService.allExamsForTechnology（ContentService.scala:30）~[classes/:na]
在controllers.content.ExamController$$anonfun$allExamsForTechnology$1.apply（ExamController.scala:24）~[classes/:na]
在controllers.content.ExamController$$anonfun$allExamsForTechnology$1.apply（ExamController.scala:22）~[classes/:na]
在play.api.mvc.ActionBuilder$$anonfun$apply$10.apply（Action.scala:221）~[play_2.10.jar:2.2.1]
在play.api.mvc.ActionBuilder$$anonfun$apply$10.apply（Action.scala:220）~[play_2.10.jar:2.2.1]
在play.api.mvc.Action$.invokeBlock（Action.scala:357）~[play_2.10.jar:2.2.1]
在play.api.mvc.ActionBuilder$$anon$1.apply（Action.scala:309）~[play_2.10.jar:2.2.1]
在play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply（Action.scala:109）~[play_2.10.jar:2.2.1]
在play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply（Action.scala:109）~[play_2.10.jar:2.2.1]
在play.utils.Threads$.withContextClassLoader（Threads.scala:18）~[play_2.10.jar:2.2.1]
在play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply（Action.scala:108）~[play_2.10.jar:2.2.1]
在play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply（Action.scala:107）~[play_2.10.jar:2.2.1]
在scala.Option.map（Option.scala:145）~[scala library.jar:na]
在play.api.mvc.Action$$anonfun$apply$1.apply（Action.scala:107）~[play_2.10.jar:2.2.1]
在play.api.mvc.Action$$anonfun$apply$1.apply（Action.scala:100）~[play_2.10.jar:2.2.1]
在play.api.libs.iteratee.iteratee$$anonfun$mapM$1.apply（iteratee.scala:481）~[play-iteratees_2.10.jar:2.2.1]
在play.api.libs.iteratee.iteratee$$anonfun$mapM$1.apply（iteratee.scala:481）~[play-iteratees_2.10.jar:2.2.1]
在play.api.libs.iteratee.iteratee$$anonfun$flatMapM$1.apply（iteratee.scala:517）~[play-iteratees_2.10.jar:2.2.1]
在play.api.libs.iteratee.iteratee$$anonfun$flatMapM$1.apply（iteratee.scala:517）~[play-iteratees_2.10.jar:2.2.1]
在play.api.libs.iteratee.iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply（iteratee.scala:493）~[play-iteratees_2.10.jar:2.2.1]
在play.api.libs.iteratee.iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply（iteratee.scala:493）~[play-iteratees_2.10.jar:2.2.1]
在scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1（Future.scala:24）[scala library.jar:na]
在scala.concurrent.impl.Future$PromiseCompletingRunnable.run（Future.scala:24）[scala library.jar:na]
... 省略了6个公共框架

---

这个奇怪错误的原因是什么？

我添加了一个自定义包对象，如下所示：

import com.novus.salat.Context
import play.api.Play

package object CustomPlaySalatContext {
  implicit val ctx = new Context {
    val name = "Custom_Classloader"
  }
  ctx.registerClassLoader(Play.classloader(Play.current))
}

---

在DAO对象中导入上面的包，问题就消失了

我在Play 2.4.x中遇到了同样的问题。但sparkr的解决方案还不够，因为Play会在每次代码更改时不断创建新的类加载器。以下黑客（在

Globals.scala

中）似乎解决了这个问题：

import play.api.{Play, Application, GlobalSettings}
import com.novus.salat.global.{ctx => SalatGlobalContext}

object Global extends GlobalSettings {
  override def onStart(app: Application) = {
    SalatGlobalContext.clearAllGraters()
    SalatGlobalContext.registerClassLoader(Play.classloader(Play.current))
  }
}

---

我使用的是SalatCore1.9.2、Casbah2.5.1和Scala2.10。我能做些什么来消除这个错误？有了这个方法，似乎还有另一个问题。我不能再对我的实体进行单元测试了。原因是它需要一个播放应用程序启动并运行。这是一个非常丑陋的解决方案，原因是我将我的DAO类与一个UI/REST框架（如Play）绑定在一起。我可能会考虑使用卡斯巴，没有萨拉河！有一种在Play中运行假的应用程序的方法，我也遇到过这种情况。但是我不喜欢在数据库层上使用playapi的想法。我来自JavaEE背景，是松耦合设计原理的铁杆粉丝。