IncompatibleClassChangeError in Scala Spring-Boot application

问题

I am currently experiencing a weird exception when testing my Scala - Spring Boot application with JUnit Vintage.

java.lang.IncompatibleClassChangeError: org.myapp.SampleWebApplication and org.myapp.SampleWebApplication$delayedInit$body disagree on InnerClasses attribute

    at java.lang.Class.getDeclaringClass0(Native Method)
    at java.lang.Class.getDeclaringClass(Class.java:1235)
    at java.lang.Class.getEnclosingClass(Class.java:1277)
    at java.lang.Class.getSimpleBinaryName(Class.java:1443)
    at java.lang.Class.isMemberClass(Class.java:1433)
    at org.junit.internal.builders.AnnotatedBuilder.getEnclosingClassForNonStaticMemberClass(AnnotatedBuilder.java:94)
    at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:83)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
    at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
    at org.junit.vintage.engine.discovery.DefensiveAllDefaultPossibilitiesBuilder.runnerForClass(DefensiveAllDefaultPossibilitiesBuilder.java:56)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
    at org.junit.vintage.engine.discovery.TestClassRequestResolver.createRunnerTestDescriptor(TestClassRequestResolver.java:55)
    at org.junit.vintage.engine.discovery.VintageDiscoverer.lambda$discover$0(VintageDiscoverer.java:53)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.Iterator.forEachRemaining(Iterator.java:116)
    at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312)
    at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:742)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
    at org.junit.vintage.engine.discovery.VintageDiscoverer.discover(VintageDiscoverer.java:55)
    at org.junit.vintage.engine.VintageTestEngine.discover(VintageTestEngine.java:61)
    at org.junit.platform.launcher.core.DefaultLauncher.discoverEngineRoot(DefaultLauncher.java:130)
    at org.junit.platform.launcher.core.DefaultLauncher.discoverRoot(DefaultLauncher.java:117)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:90)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

This is the entrypoint and it's the class that throws the error.

object SampleWebApplication extends App{
  SpringApplication.run(classOf[Application])
}

HOWEVER! If I change the code to this (without extending app) the error stops appearing.

object SampleWebApplication {
  def main(args : Array[String]) : Unit = {
    SpringApplication.run(classOf[Application])
  }
}

Do you have any suggestions on why I am experiencing this error? Why does removing "extends App" solve my issue? Any help really appreciated.

回答1:

I found out the issue. There is a bug in Scala 2.12.6 (fixed in 2.13.x). Because of the project I'm currently working on I can't bump the versions.

Workarounds if you cant update your Scala version:

1.One workaround is to update the test framework from JUnit Vintage -> JUnit Jupiter.
2.The second workaround (the one I did) is to change the Entrypoint of your application (see below).

object SampleWebApplication {
  def main(args : Array[String]) : Unit = {
    SpringApplication.run(classOf[Application])
  }
}

来源：https://stackoverflow.com/questions/52252527/incompatibleclasschangeerror-in-scala-spring-boot-application