sonar-maven-plugin stopped working in jenkins - maven

Question

A week ago, all our code analysis jobs stopped working with the error message you see at the end of this post. We have not upgraded anything, it simply stopped working. The only difference I see in the jenkins logs is, that a different version of the sonar-maven-plugin ist used. It was 2.6 before and it is 2.7.1 now. And we don't know, where the information comes from.
Our infrastucture:
Jenkins 1.565.3
Jenkins Sonar Plugin 2.1
Sonarqube 3.1.1
Maven 3.0.3
We have no information about sonar-maven-plugin placed in the pom. Everything is handled by the Jenkins Sonar Plugin.
I noticed a difference between the last build, where the code analysis was working and the first build where it faild:
Working logmessing:
Downloading: https://artifactory.nepatec.de/repo/org/codehaus/mojo/sonar-maven-plugin/2.6/sonar-maven-plugin-2.6.pom
Message the failed build:
Downloading: https://artifactory.nepatec.de/repo/org/codehaus/mojo/sonar-maven-plugin/2.7.1/sonar-maven-plugin-2.7.1.pom
We don't know where the version change comes from, because it is not defined in the jenkins sonar plugin and we also did not find a way to configure it.
Does anyone know, why the version jump comes from and what we can do, to revert it?
The Build always fails with the following Exception:
05.11.2015 09:08:35 org.sonatype.guice.bean.reflect.NamedClass
WARNUNG: Error injecting: org.codehaus.mojo.sonar.SonarMojo
java.lang.TypeNotPresentException: Type org.codehaus.mojo.sonar.SonarMojo not present
at org.sonatype.guice.bean.reflect.URLClassSpace.loadClass(URLClassSpace.java:100)
at org.sonatype.guice.bean.reflect.NamedClass.load(NamedClass.java:45)
at org.sonatype.guice.bean.reflect.AbstractDeferredClass.get(AbstractDeferredClass.java:47)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:40)
at com.google.inject.internal.InjectorImpl$4$1.call(InjectorImpl.java:968)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1014)
at com.google.inject.internal.InjectorImpl$4.get(InjectorImpl.java:964)
at com.google.inject.Scopes$1$1.get(Scopes.java:59)
at org.sonatype.guice.bean.locators.LazyBeanEntry.getValue(LazyBeanEntry.java:79)
at org.sonatype.guice.plexus.locators.LazyPlexusBean.getValue(LazyPlexusBean.java:53)
at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:243)
at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:235)
at org.apache.maven.plugin.internal.DefaultMavenPluginManager.getConfiguredMojo(DefaultMavenPluginManager.java:455)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:92)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
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:319)
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: java.lang.UnsupportedClassVersionError: org/codehaus/mojo/sonar/SonarMojo : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(ClassRealm.java:386)
at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:42)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:244)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:230)
at org.sonatype.guice.bean.reflect.URLClassSpace.loadClass(URLClassSpace.java:96)
... 33 more

Answer 1

The latest release of the Maven SonarQube Plugin requires Java 7 at least, see MSONAR-126.
So you have to update your Jenkins configuration to eun (at least) the SonaQube analyses using Java 7+.