Issue

• A Maven build is failing with an error like

ERROR: Failed to parse POMs 
...
Caused by: java.lang.UnsupportedClassVersionError: org/apache/maven/eventspy/EventSpy : 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)
...

Environment

• CloudBees CI (CloudBees Core) on modern cloud platforms - Managed Master
• CloudBees CI (CloudBees Core) on traditional platforms - Client Master
• CloudBees Jenkins Enterprise - Managed Master
• CloudBees Jenkins Platform - Client Master
• CloudBees Jenkins Distribution
• Jenkins LTS

Resolution

Apache Maven 3.3.x requires a minimum of Java 7 and your build is configured to use Java 6.

Either install and configure your job to use a version of Maven < 3.3 or install and configure your job to use a version of JDK > 6 to solve the issue. The Configuration Slicing Plugin will help you to easily change the version of Apache Maven or the JDK used in several jobs in one step.