Question

当我运行我的应用程序时，浏览器会显示

[ExecutionException: Boxed Error]

它没有说明行号等等。

在控制台中，我有以下

! @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对在Error内投掷的Future的回复。在Java中，因此Scala，类型Error的子类具有致命错误的特殊含义。见Differences between Exception and Error。简而言之，javadoc说：

错误是Throwable的子类，表示严重问题一个合理的应用程序不应该试图抓住。最多的错误是异常情况。

与将来抛出其他Throwable不同，当抛出Error的子类时，默认的Scala解析器会将Error包裹在java.util.concurrent.ExecutionException中，消息字符串“Boxed Error”，并在失败时完成您的承诺。

引用期货文件http://docs.scala-lang.org/overviews/core/futures.html w.r.t. Error被抛出：

[错误]在执行失败的线程中重新抛出异常异步计算。这背后的理由是防止通常传播关键和控制流相关的异常不是由客户端代码处理，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，可以通过Error

提取抛出的原始ExecutionException#getCause()（但不是特别适合模式匹配的方式）

Answer 2

我不知道这是Boxed Error，但根据您的堆栈跟踪，根问题来自factorie max2Double来自/**Returns both the maximum element and the second-to-max element */ def max2ByDouble(extractor: A => Double): (A, A) = { val s1 = t.toSeq assert(s1.length > 1) // <<<== HERE var best1 = Double.NegativeInfinity ... method at line 95。

从源代码中提取：

Traversable

您的{{1}}似乎是空的。

什么是Scala中的盒装错误？

2 个答案: