什么是Scala中的盒装错误？

Question

当我运行我的应用程序时,浏览器显示

[ExecutionException: Boxed Error]

它没有说明行号等.

在控制台中,我有以下内容

! @6elaah0c8 - Internal server error, for (GET) [/testlearn] ->

play.api.Application$$anon$1: Execution exception[[ExecutionException: Boxed Error]]
    at play.api.Application$class.handleError(Application.scala:289) ~[play_2.10.jar:2.1.1]
    at play.api.DefaultApplication.handleError(Application.scala:383) [play_2.10.jar:2.1.1]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$17$$anonfun$apply$24.apply(PlayDefaultUpstreamHandler.scala:326) [play_2.10.jar:2.1.1]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$17$$anonfun$apply$24.apply(PlayDefaultUpstreamHandler.scala:324) [play_2.10.jar:2.1.1]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) [play_2.10.jar:2.1.1]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) [play_2.10.jar:2.1.1]
java.util.concurrent.ExecutionException: Boxed Error
    at scala.concurrent.impl.Promise$.resolver(Promise.scala:52) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at scala.concurrent.impl.Promise$.scala$concurrent$impl$Promise$$resolveTry(Promise.scala:44) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:116) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at scala.concurrent.Promise$class.complete(Promise.scala:55) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:58) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:23) [factorie-1.0.0-M4-jar-with-dependencies.jar:na]
Caused by: java.lang.AssertionError: assertion failed
    at scala.Predef$.assert(Predef.scala:165) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at cc.factorie.util.TraversableExtras$class.max2ByDouble(TraversableExtras.scala:95) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at cc.factorie.package$$anon$2.max2ByDouble(package.scala:148) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at cc.factorie.optimize.SampleRankExample.accumulateExampleInto(SampleRank.scala:31) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at cc.factorie.optimize.OnlineTrainer$$anonfun$processExamples$3.apply(Trainer.scala:72) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]
    at cc.factorie.optimize.OnlineTrainer$$anonfun$processExamples$3.apply(Trainer.scala:63) ~[factorie-1.0.0-M4-jar-with-dependencies.jar:na]

Answer 1

"盒装错误"是Scala对一个Error被抛出的回应Future.在Java中,因此Scala,类型的子类Error具有特殊含义作为致命错误.请参阅异常和错误之间的差异.简而言之,javadoc说:

Error是Throwable的子类,表示合理的应用程序不应该尝试捕获的严重问题.大多数此类错误都是异常情况.

与Throwable在未来抛出其他s 不同,当Error抛出一个子类时,默认的Scala解析器将使用消息字符串"Boxed Error" 包装Error在a中java.util.concurrent.ExecutionException,并以失败完成您的承诺.

引用期货文档http://docs.scala-lang.org/overviews/core/futures.html wrt Error被抛出:

[错误]在执行失败的异步计算的线程中重新抛出异常.这背后的基本原理是防止通常不由客户端代码处理的关键和控制流相关异常的传播,同时通知客户端计算失败的未来.

如果你想对失败做一些特别的事情,Error可以提取抛出的原始文件(但不是特别适合模式匹配的方式),ExecutionException#getCause()