Plugin leaks classloaders when using in-process strategy

[marcphilipp]

When scanning for bindings in dependencies, the plugin creates a URLClassLoader that is never closed:

https://github.com/highsource/maven-jaxb2-plugin/blob/3c15b7ee35940859ab75e503ea1bbab89400b9fc/plugin-core/src/main/java/org/jvnet/jaxb2/maven2/RawXJC2Mojo.java#L810

As a result, the underlying JARs in that classloader remain open and cannot be deleted. Also, their content can be stale when opened using java.util.ZipFile.

This is a problem when running Maven integration tests using Embedded3xLauncher. We are developing a Maven extension and want to make sure it works well with this plugin. This classloader leak means we have to use a forking launcher instead, which slows down our tests considerably.

[highsource]

I wonder how one would safely close the class loader.

[marcphilipp]

I may be missing sth. but since the method only returns URIs, I don't see why it would not be safe to close it.

[marcphilipp]

@highsource I've submitted a PR to fix this in #169.