How to fix “java.lang.ClassNotFoundException: org.apache.maven.model.io.xpp3.MavenXpp3WriterEx” for mvn help evaluate

Question

I am trying to get modules in my pom.xml by using below command. This was working till yesterday. Maven artfiact is stored in artifactory and am using .m2/settings.xml to connect to central and download artifacts. I am sure there was not interaction in jenkins and artifactory but suddenly stared seeing failures

I have tried changing M2_HOME/MAVEN_HOME to M3_home. Tried to delete .m2/repository and ran mvn command to download again

Apache Maven 3.5.3 (3383c37e1f9e9b3bc3df5050c29c8aff9f295297; 2018-02-24T14:49:05-05:00) Maven home: /Users/jenkins/Downloads/apache-maven-3.5.3 Java version: 1.8.0_172, vendor: Oracle Corporation Java home: /Library/Java/JavaVirtualMachines/jdk1.8.0_172.jdk/Contents/Home/jre Default locale: en_US, platform encoding: UTF-8 OS name: "mac os x", version: "10.14.2", arch: "x86_64", family: "mac"

mvn help:evaluate -Dexpression=project.modules -B

Expected

[Info] Downloading ....
[Info] Downloaded ....
[Info]....
[Info]....
[Info]....
[Info]....
<modules>
  <module>example-mod1</module>
  <module>example-mod2</module>
  <module>example-mod3</module>
</modules>
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 31.185 s
[INFO] Finished at: 2019-04-17T16:52:52-04:00
[INFO] ------------------------------------------------------------------------

Actual

[Info] Downloading ....
[Info] Downloaded ....
[Info]....
[Info]....
[Info]....
[Info]....
[ERROR]
java.lang.ClassNotFoundException: org.apache.maven.model.io.xpp3.MavenXpp3WriterEx
    at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass (SelfFirstStrategy.java:50)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass (ClassRealm.java:271)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:247)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:239)
    at java.lang.Class.forName0 (Native Method)
    at java.lang.Class.forName (Class.java:348)
    at org.apache.commons.lang3.ClassUtils.getClass (ClassUtils.java:993)
    at org.apache.commons.lang3.ClassUtils.getClass (ClassUtils.java:1059)
    at org.apache.commons.lang3.ClassUtils.getClass (ClassUtils.java:1042)
    at org.apache.maven.plugins.help.EvaluateMojo.addAlias (EvaluateMojo.java:542)
    at org.apache.maven.plugins.help.EvaluateMojo.addAlias (EvaluateMojo.java:491)
    at org.apache.maven.plugins.help.EvaluateMojo.getXStream (EvaluateMojo.java:455)
    at org.apache.maven.plugins.help.EvaluateMojo.toXML (EvaluateMojo.java:420)
    at org.apache.maven.plugins.help.EvaluateMojo.handleResponse (EvaluateMojo.java:381)
    at org.apache.maven.plugins.help.EvaluateMojo.execute (EvaluateMojo.java:214)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:208)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:290)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:194)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
[INFO]
<strings>
  <string>example-mod1</string>
  <string>example-mod2</string>
  <string>example-mod3</string>
</strings>
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 31.185 s
[INFO] Finished at: 2019-04-17T16:52:52-04:00
[INFO] ------------------------------------------------------------------------

Merou Placide Merou Placide · Accepted Answer · 2019-06-26T14:56:11

The class MavenXPP3writerEx seems to be available only in Maven 3.6.1 API.

If you are using Maven 3.3.9, or any release prior to 3.6.1, then you will have this message: you try to use the latest version of the maven-help-plugin (designed to be compatible with Maven 3.6.1), but not retro-compatible with earlier versions.

Then, to use a compatible version you must restrain the version of the maven-help-plugin in order to use it without errors. To do so, define a pluginManagement section in you POM and declare the maven-help-plugin with version 3.1.0 (for Maven 3.3.9). I did not try with another Maven configuration.

How to fix “java.lang.ClassNotFoundException: org.apache.maven.model.io.xpp3.MavenXpp3WriterEx” for mvn help evaluate

1 Answers