Idiomatic JAR file load for Jython does no longer work in 5.3

[prof-spock]

Dear all,

in older versions of Modelio (e.g. 4.1) it was possible in a script to load necessary external JAR-files via a URLClassLoader as follows:

from java.net import URL, URLClassLoader
from java.lang import ClassLoader
from java.io import File

jarFilePath = "/path_to/xxx.jar"

if jarFilePath not in sys.path:
    sys.path.append(jarFilePath)

# add the jar to the ClassLoader
m = URLClassLoader.getDeclaredMethod("addURL", [URL])
m.accessible = 1
m.invoke(ClassLoader.getSystemClassLoader(),
               [File(jarFilePath).toURL()])

import <<some class from xxx.jar>>

This no longer works, because the underlying JRE implementation has changed for Java 11 (the system class loader is no URL class loader any longer). The error message is

java.lang.IllegalArgumentException: java.lang.IllegalArgumentException: object is not an instance of declaring class in <script> at line number 13
Traceback (most recent call last):
  File "<script>", line 13, in <module>
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
java.lang.IllegalArgumentException: java.lang.IllegalArgumentException: object is not an instance of declaring class

Is there any trick to get this problem solved in the Jython engine of Modelio?

Best regards,
Prof. Spock