Question

我有一个Akka actor，它以大约1500字节的块的形式读取文件的内容。当actor收到 NextBlock 消息时，它会回复包含在ByteString中的下一个数据块。几个非常简单的测试和手动眼球数据表明演员正在正常工作。我使用的是Scala 2.11.5，Akka 2.3.9，ScalaTest 2.2.1和SBT 0.13.5。

我遇到了设置更大测试的问题。我想将大约10kB左右的测试模式数据写入文件，然后验证Actor的输出是我所期望的。我通过ByteStringBuilder创建测试模式。当我将测试数据写入文件时，我得到了NullPointerExceptions。以下是显示问题的测试的条带化版本的代码：

import java.nio.ByteOrder
import java.nio.file.StandardOpenOption._
import java.nio.file.{Files, Paths}

import akka.actor.ActorSystem
import akka.testkit.TestKit
import akka.util.{ByteString, ByteStringBuilder}
import org.scalatest.{BeforeAndAfterAll, Matchers, WordSpecLike}

class ByteBufferTest extends TestKit(ActorSystem("ByteBufferTest"))
with WordSpecLike with Matchers with BeforeAndAfterAll {

  implicit val byteOrder = ByteOrder.BIG_ENDIAN
  val file = Paths.get("test.data")

  Files.deleteIfExists(file)
  createTestFile()

  "A ByteBufferTest" must { "work" in { assert(true) } }

  def createTestFile(): Unit = {
    val out = Files.newByteChannel(file, CREATE, WRITE)
    out.write(contents.toByteBuffer) // Here is where the NPE occurs
    out.close()
  }

  val contents: ByteString = {
    val builder = new ByteStringBuilder
    (0 to 255).foreach(builder.putInt)
    builder.result()
  }

  override protected def afterAll(): Unit = {
    Files.delete(file)
    system.shutdown()
  }
}

我尝试过这种不同的方式

将ByteString转换为ByteBuffer并通过ByteChannel编写（上面显示）
将ByteString的单个字节写入BufferedOutputStream
将ByteString转换为Array [Byte]并通过BufferedOutputStream写入

无论我尝试什么，我都会按照

的方式结束

[debug] Running TaskDef(demo.ByteBufferTest, org.scalatest.tools.Framework$$anon$1@40fbf2c, false, [SuiteSelector])
java.lang.NullPointerException at demo.ByteBufferTest.createTestFile(ByteBufferTest.scala:32)
  at demo.ByteBufferTest.<init>(ByteBufferTest.scala:21)
  at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
  at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
  at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
  at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
  at java.lang.Class.newInstance(Class.java:374)
  at org.scalatest.tools.Framework$ScalaTestTask.execute(Framework.scala:641)
  at sbt.TestRunner.runTest$1(TestFramework.scala:84)
  at sbt.TestRunner.run(TestFramework.scala:94)
  at sbt.TestFramework$$anon$2$$anonfun$$init$$1$$anonfun$apply$8.apply(TestFramework.scala:219)
  at sbt.TestFramework$$anon$2$$anonfun$$init$$1$$anonfun$apply$8.apply(TestFramework.scala:219)
  at sbt.TestFramework$.sbt$TestFramework$$withContextLoader(TestFramework.scala:207)
  at sbt.TestFramework$$anon$2$$anonfun$$init$$1.apply(TestFramework.scala:219)
  at sbt.TestFramework$$anon$2$$anonfun$$init$$1.apply(TestFramework.scala:219)
  at sbt.TestFunction.apply(TestFramework.scala:224)
  at sbt.Tests$$anonfun$7.apply(Tests.scala:196)
  at sbt.Tests$$anonfun$7.apply(Tests.scala:196)
  at sbt.std.Transform$$anon$3$$anonfun$apply$2.apply(System.scala:45)
  at sbt.std.Transform$$anon$3$$anonfun$apply$2.apply(System.scala:45)
  at sbt.std.Transform$$anon$4.work(System.scala:64)
  at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:237)
  at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:237)
  at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:18)
  at sbt.Execute.work(Execute.scala:244)
  at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:237)
  at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:237)
  at sbt.ConcurrentRestrictions$$anon$4$$anonfun$1.apply(ConcurrentRestrictions.scala:160)
  at sbt.CompletionService$$anon$2.call(CompletionService.scala:30)
  at java.util.concurrent.FutureTask.run(FutureTask.java:262)
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
  at java.util.concurrent.FutureTask.run(FutureTask.java:262)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
  at java.lang.Thread.run(Thread.java:745)

任何人都有任何想法，我做错了吗？

我已将示例项目放在github

上

Answer 1

我没有找到确切的根本原因，但似乎它与从scala测试启动测试类时的初始化有关。

我建议将createTestFile()放在beforeAll（）的方法中。经过测试并且有效。

override def beforeAll {
    createTestFile()
}

将ByteString写入导致NullPointerException的文件

1 个答案: