clojure: ExceptionInInitializerError in Namespace.<init> loading from a non-default classpath - clojure

Question

In attempting to load an AOT-compiled class from a non-default classpath, I receive the following exception:
Traceback (innermost last):
File "test.jy", line 10, in ?
at clojure.lang.Namespace.<init>(Namespace.java:34)
at clojure.lang.Namespace.findOrCreate(Namespace.java:176)
at clojure.lang.Var.internPrivate(Var.java:149)
at aot_demo.JavaClass.<clinit>(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
java.lang.ExceptionInInitializerError: java.lang.ExceptionInInitializerError
I'm able to reproduce this with the following trivial project.clj:
(defproject aot-demo "0.1.0-SNAPSHOT"
:dependencies [[org.clojure/clojure "1.3.0"]]
:aot [aot-demo.core])
...and src/aot_demo/core.clj defined as follows:
(ns aot-demo.core
(:gen-class
:name aot_demo.JavaClass
:methods [#^{:static true} [lower [java.lang.String] java.lang.String]]))
(defn -lower [str] (.toLowerCase str))
The following Jython script is then sufficient to trigger the bug:
#!/usr/bin/jython
import java.lang.Class
import java.net.URLClassLoader
import java.net.URL
import os
customLoader = java.net.URLClassLoader(
[java.net.URL('file://%s/target/aot-demo-0.1.0-SNAPSHOT-standalone.jar'
% (os.getcwd()))])
java.lang.Class.forName('aot_demo.JavaClass', True, customLoader)
However, the exception does not occur if the test script is started with the uberjar already in the CLASSPATH variable.
What's going on here? I'm trying to write a plugin for the BaseX database in Clojure; the above accurately represents how their plugin-loading mechanism works for the purpose of providing a SSCE for this problem.

Answer 1

The plugin-loading mechanism used by BaseX should be extended to modify the current thread's context classloader. For the given sample code (in Jython), this would look something like the following:
currentThread = java.lang.Thread.currentThread()
oldLoader = currentThread.getContextClassLoader()
currentThread.setContextClassLoader(customLoader)
try:
cls = java.lang.Class.forName('aot_demo.JavaClass', True, customLoader)
finally:
currentThread.setContextClassLoader(oldLoader)