LaunchedURLClassLoader preemptively defines the package for any
classes that it attempts to load so that the manifest from a nested
jar is correctly associated with the package. This can lead to a race
where the package is defined on two threads in parallel, resulting
in an IllegalArgumentException being thrown.
This problem was manifesting itself as a NoClassDefFoundError.
If the initialization of a class failed due to the above-described
IllegalArgumentException, subsequent attempts to use that class
would then fail with a NoClassDefFoundError.
This commit updates LaunchedURLClassLoader to catch the
IllegalArgumentException and then double-check that the package has
already been defined. This approach, including thrown an
AssertionError when the second check fails, is modelled on the
approach taken by URLClassLoader.
Closes gh-5464
1d099035b1