[MNG-6506] Mojos are unable to load package annotations on Java >= 9

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.6.0
• Fix Version/s: 3.6.1
• Component/s: Class Loading
• Labels: up-for-grabs
• Assignee: Sylwester Lachiewicz
• Reporter: Andreas Veithen
• Created: 04/Nov/18 15:00
• Updated: 28/Mar/20 15:03
• Resolved: 29/Mar/19 06:42

Description

On Java 9 and above, calls to java.lang.Package.getAnnotation(Class) from within a Mojo always return null (unless the package-info class has been loaded by some other means before).

The reason appears to be an incompatibility between Java 9 and Plexus Classworlds:

• Java 9 ultimately calls findClass (instead of loadClass) to get the package-info class.
• The findClass implementation in ClassRealm always throws ClassNotFoundException: https://github.com/codehaus-plexus/plexus-classworlds/blob/master/src/main/java/org/codehaus/plexus/classworlds/realm/ClassRealm.java#L275.

This in particular affects plugins that interact with the JAXB API because it relies on package annotations.

A workaround is to preload the required package-info classes using loadClass; see e.g. http://svn.apache.org/viewvc?rev=1845026&view=rev.

Issue Links

• is duplicated by: MNG-6543 Upgrade plexus classworld to support java 9+ ClassLoader.findClass(String moduleName, String name) in Mojos
• links to: #3 plexus-classworlds
• links to: GitHub Pull Request #43