Hi, With the introduction of modules in JDK 9, there were changes with regard to how classloading works, and this impacts class realms created in Maven. Today, the parent (as per ClassLoader.getParent()) of a class realm is null, which represents the bootstrap classloader. In JDK 9, the change is that some classes were moved to a named module other than java.base, and they are not loaded with the bootstrap classloader anymore, but with the platform classloader (which was previously the extension classloader, see JDK-814637).
This has consequences, like MANTRUN-200, where locating providers with the ServiceLoader API, using the plugin class realm, will miss JDK internal implementation classes. In the case of MANTRUN-200, it is Nashorn of the jdk.scripting.nashorn module, that cannot be found because of the way ServiceLoader works http://download.java.net/java/jdk9/docs/api/java/util/ServiceLoader.html#load-java.lang.Class-java.lang.ClassLoader-. During the search in named modules, the class realm will not be able to use its strategy since that process relies on parent delegation implemented as explicit calls to ClassLoader.getParent() (http://hg.openjdk.java.net/jdk9/jdk9/jdk/file/f3cf7fd26baa/src/java.base/share/classes/java/util/ServiceLoader.java#l1062), which, for a class realm, corresponds to the base classloader, i.e. the bootstrap classloader. And since the Nashorn script engine factory was loaded with the platform classloader, it is missed. It seems that the fix here would be to make all class realms have as base classloader the platform classloader starting with JDK 9, instead of the bootstrap classloader (there is a new utility method in ClassLoader to obtain the platform classloader). I verified that this solves the problem described in MANTRUN-200, but before I create an MNG issue, I'm wondering if this is the correct approach. What do you think of this change to class realms? The other possibility I can think of would be to have a way in the JDK to override the search in named modules, so that our ClassRealm can also delegate to its parent classloader. It is possible for unnamed modules (since the search process then relies on the ClassLoader.getResources method, that can be overriden) but it doesn't look like (and probably intentionally so) to be possible for named modules. Guillaume --- L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast. https://www.avast.com/antivirus --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org