Scala 2.10.0 generates a class-not-found error for scala.reflect.ClassManifest

[glsil...@pssd.com]

I created a maven project using the camel-scala-archetype archetype. Running mvn exec:java works fine out-of-the box, but when I change the scala version to 2.10.0 in the pom.xml file, I get the following error:

Caused by: java.lang.NoClassDefFoundError: scala/reflect/ClassManifest

at com.dsi.mytest.MyRouteMain$.main(MyRouteMain.scala:31)

at com.dsi.mytest.MyRouteMain.main(MyRouteMain.scala)

... 6 more

Caused by: java.lang.ClassNotFoundException: scala.reflect.ClassManifest

at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

... 8 more

I haven't found anything on other forums or searching through the various Google results on this error that is helpful in resolving it. Does anyone have a solution? 

[Eugene Burmako]

Could you please show full stack trace? Also it'd be helpful if you published the pom.xml file, namely the dependency section.

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[glsil...@pssd.com]

Yes, here is the pom.xml (the dependencies and build sections):

<properties>

<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

<camel.version>2.10.0</camel.version>

</properties>

<dependencies>

<dependency>

<groupId>org.apache.camel</groupId>

<artifactId>camel-core</artifactId>

<version>${camel.version}</version>

</dependency>

<dependency>

<groupId>org.apache.camel</groupId>

<artifactId>camel-scala</artifactId>

<version>${camel.version}</version>

</dependency>

<!-- scala -->

<dependency>

<groupId>org.scala-lang</groupId>

<artifactId>scala-library</artifactId>

<version>2.10.0</version>

</dependency>

<!-- logging -->

<dependency>

<groupId>org.slf4j</groupId>

<artifactId>slf4j-api</artifactId>

<version>1.6.6</version>

</dependency>

<dependency>

<groupId>org.slf4j</groupId>

<artifactId>slf4j-log4j12</artifactId>

<version>1.6.6</version>

</dependency>

<dependency>

<groupId>log4j</groupId>

<artifactId>log4j</artifactId>

<version>1.2.16</version>

</dependency>

<!-- testing -->

<dependency>

<groupId>org.apache.camel</groupId>

<artifactId>camel-test</artifactId>

<version>${camel.version}</version>

<scope>test</scope>

</dependency>

</dependencies>

<build>

<defaultGoal>install</defaultGoal>

<sourceDirectory>src/main/scala</sourceDirectory>

<testSourceDirectory>src/test/scala</testSourceDirectory>

<plugins>

<!-- the Maven compiler plugin will compile Java source files -->

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

<version>2.5</version>

<configuration>

<source>1.6</source>

<target>1.6</target>

</configuration>

</plugin>

<!-- the Maven Scala plugin will compile Scala source files -->

<plugin>

<groupId>net.alchim31.maven</groupId>

<artifactId>scala-maven-plugin</artifactId>

<version>3.1.3-SNAPSHOT</version>

<executions>

<execution>

<goals>

<goal>compile</goal>

<goal>testCompile</goal>

</goals>

</execution>

</executions>

</plugin>

<!-- configure the eclipse plugin to generate eclipse project descriptors 

for a Scala project -->

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-eclipse-plugin</artifactId>

<version>2.8</version>

<configuration>

<projectnatures>

<projectnature>ch.epfl.lamp.sdt.core.scalanature</projectnature>

<projectnature>org.eclipse.jdt.core.javanature</projectnature>

</projectnatures>

<buildcommands>

<buildcommand>ch.epfl.lamp.sdt.core.scalabuilder</buildcommand>

</buildcommands>

<classpathContainers>

<classpathContainer>ch.epfl.lamp.sdt.launching.SCALA_CONTAINER</classpathContainer>

<classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER</classpathContainer>

</classpathContainers>

</configuration>

</plugin>

<!-- allows the route to be run via 'mvn exec:java' -->

<plugin>

<groupId>org.codehaus.mojo</groupId>

<artifactId>exec-maven-plugin</artifactId>

<version>1.2.1</version>

<configuration>

<mainClass>com.dsi.mytest.MyRouteMain</mainClass>

</configuration>

</plugin>

</plugins>

</build>

 

And here is the full stack trace:

[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project mytest: An exception occured while executing the Java class. null: InvocationTargetException: scala/reflect/ClassManifest: scala.reflect.ClassManifest -> [Help 1]

org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project mytest: An exception occured while executing the Java class. null

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:217)

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)

at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)

at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)

at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)

at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)

at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)

at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)

at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)

at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)

at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)

at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)

at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)

at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)

Caused by: org.apache.maven.plugin.MojoExecutionException: An exception occured while executing the Java class. null

at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:352)

at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)

... 19 more

Caused by: java.lang.reflect.InvocationTargetException

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:297)

at java.lang.Thread.run(Thread.java:662)

Caused by: java.lang.NoClassDefFoundError: scala/reflect/ClassManifest

at com.dsi.mytest.MyRouteMain$.main(MyRouteMain.scala:31)

at com.dsi.mytest.MyRouteMain.main(MyRouteMain.scala)

... 6 more

Caused by: java.lang.ClassNotFoundException: scala.reflect.ClassManifest

at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

... 8 more

[ERROR] 

[ERROR] Re-run Maven using the -X switch to enable full debug logging.

[ERROR] 

[ERROR] For more information about the errors and possible solutions, please read the following articles:

[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

[                      Thread-1] MainSupport$HangupInterceptor  INFO  Received hang up - stopping the main instance.

[                      Thread-1] MainSupport                    INFO  Apache Camel 2.10.0 stopping

[                      Thread-1] MainSupport$HangupInterceptor  WARN  Error during stopping the main instance.

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

at java.util.ArrayList.RangeCheck(ArrayList.java:547)[:1.6.0_26]

at java.util.ArrayList.get(ArrayList.java:322)[:1.6.0_26]

at org.apache.camel.main.Main.doStop(Main.java:114)[camel-core-2.10.0.jar:2.10.0]

at org.apache.camel.support.ServiceSupport.stop(ServiceSupport.java:91)[camel-core-2.10.0.jar:2.10.0]

at org.apache.camel.main.MainSupport$HangupInterceptor.run(MainSupport.java:80)[camel-core-2.10.0.jar:2.10.0]

[Eugene Burmako]

Could you please expand this part of the stack trace?

Caused by: java.lang.ClassNotFoundException: scala.reflect.ClassManifest

at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

... 8 more

Looks like one of your dependencies is incompatible with 2.10, but I can't yet see which one exactly from the stack trace.

[Sonnenschein]

This is probably because you have some dependencies compiled against Scala 2.9.x.
Peter

[glsil...@pssd.com]

How can I expand the stack trace. I'm just running mvn exec:java. Running it with -e or -X option doesn't expand the trace any. Is there some other command or option I can use?

[Clint Gilbert]

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This is almost certainly the culprit. I'd run

mvn dependency:tree

To see what's getting pulled in transitively. Something in there
somewhere depends on Scala 2.9.x.

I'd also check the build output carefully. Recent(ish) versions of
the Scala Maven plugin will warn if there are dependencies on more
than one version of Scala.

On 01/30/2013 04:04 AM, Sonnenschein wrote:
> This is probably because you have some dependencies compiled
> against Scala 2.9.x. Peter
>

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[Lanny Ripple]

scala-reflect is packaged as its own jar.

Include org.scala-lang:scala-reflect:2.10.0 in your dependencies.

[Eugene Burmako]

ClassTag (the replacement for ClassManifest) resides in scala-library.jar, so there's no need to depend on scala-reflect.jar unless you're using the newly introduced reflection framework.

Having someone requiring a classfile for scala.reflect.ClassManifest is a clear sign of that someone being compiled against Scala 2.9. In Scala 2.10 ClassManifest is an alias for ClassTag and, as such, doesn't have an underlying classfile.

[glsil...@pssd.com]

scala-reflect jar doesn't include a scala.relect.ClassManifest class. The documentation for scala.reflec.ClassManifest says it is deprecated, since v 2.10.0. So I guess org.apache.camel.scala.dsl.builder.RouteBuilderSupport is incompatible with scala v 2.10.0. That means you can't write Camel routes using the Scala Camel DSL if you want to include the most recent Scala release. Not good, guys!

[Eugene Burmako]

Looks like camel-scala isn't going to work with the new release of Scala for quite a while: http://camel.465427.n5.nabble.com/Scala-DSL-with-Scala-2-10-td5724331.html.

[Simon Ochsenreither]

Starting from version 2.11 Camel Scala DSL is compiled against Scala 2.10.
Support for Scala 2.9 is deprecated and will be removed starting from the Camel 2.12 and 3.0.
— http://camel.apache.org/scala-dsl.html

[Eugene Burmako]

Oh wait I was too quick and misunderstood what's going on. It looks like the upcoming release of camel-scala 2.11 will be compiled against scala 2.10: https://issues.apache.org/jira/browse/CAMEL-6011.