pyjnius "Class not found" when importing jar file

Question

I'm trying to make pyjnius work with a jar file I built from java application, but I keep getting the "Class not found" error:

>>> import os
>>> os.environ['CLASSPATH'] = "~/workspace/myapp-Tools/Admin/Console/couchdb/myapp-web.jar"
>>> from jnius import autoclass
>>> bla = autoclass('com/myapp/webapp/server/helpers/licensee/CalculationHelper')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/home/sam/workspace/myapp-Tools/Admin/Console/couchdb/virtualenv/local/lib/python2.7/site-packages/jnius/reflect.py", line 150, in autoclass
   c = find_javaclass(clsname)
 File "jnius_export_func.pxi", line 23, in jnius.find_javaclass (jnius/jnius.c:12815)
jnius.JavaException: Class not found 'com/myapp/webapp/server/helpers/licensee/CalculationHelper'
>>> 

of course I've checked:

jar tf myapp-web.jar

and com/myapp/webapp/server/helpers/licensee/CalculationHelper.class is in there

I've also tried setting the classpath this way:

import jnius_config
jnius_config.set_classpath('.', '~/workspace/myapp-Tools/Admin/Console/couchdb/')
#import jnius
from jnius import autoclass

But this gave me the same result. I'm working on a virtualenv btw. I've tried all approaches I could find online, but it is simply not working. I had to manually install pyjnius because using pip got me an old version of it. Any help would be greatly appreciated.

---

Edit: tried this with a jar not created by me and I see a different error

Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import jnius_config
>>> jnius_config.add_classpath('/home/sam/workspace/someproject/*')
>>> jnius_config.expand_classpath()
'/home/sam/workspace/someproject/annotations.jar:/home/sam/workspace/someproject/junit-4.10.jar:/home/sam/workspace/someproject/    postgresql-8.1-408.jdbc3.jar'
>>> import jnius
>>> from jnius import autoclass
>>> test = autoclass('org/postgresql/geometric/PGcircle.class')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/sam/workspace/myapp-Tools/Admin/Console/couchdb/virtualenv/local/lib/python2.7/site-packages/jnius/reflect.py", line 150,     in autoclass
    c = find_javaclass(clsname)
  File "jnius_export_func.pxi", line 23, in jnius.find_javaclass (jnius/jnius.c:12815)
jnius.JavaException: Class not found 'org/postgresql/geometric/PGcircle/class'
>>> test = autoclass('org/postgresql/geometric/PGcircle')
Exception in thread "main" java.lang.NoClassDefFoundError: org/postgresql/geometric/PGcircle/class
Caused by: java.lang.ClassNotFoundException: org.postgresql.geometric.PGcircle.class
  at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
  at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/sam/workspace/myapp-Tools/Admin/Console/couchdb/virtualenv/local/lib/python2.7/site-packages/jnius/reflect.py", line 156,     in autoclass
    for constructor in c.getConstructors():
  File "jnius_export_class.pxi", line 562, in jnius.JavaMethod.__call__ (jnius/jnius.c:19385)
  File "jnius_export_class.pxi", line 649, in jnius.JavaMethod.call_method (jnius/jnius.c:20409)
  File "jnius_utils.pxi", line 43, in jnius.check_exception (jnius/jnius.c:3533)
jnius.JavaException: JVM exception occured
>>> test = autoclass('org/postgresql/geometric/PGcircl')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/sam/workspace/myapp-Tools/Admin/Console/couchdb/virtualenv/local/lib/python2.7/site-packages/jnius/reflect.py", line 150,     in autoclass
    c = find_javaclass(clsname)
  File "jnius_export_func.pxi", line 23, in jnius.find_javaclass (jnius/jnius.c:12815)
jnius.JavaException: Class not found 'org/postgresql/geometric/PGcircl'
>>> 

and here are the contents of jar tf on that jar:

sam@lambda ~/workspace$ jar tf ./someproject/postgresql-8.1-408.jdbc3.jar
META-INF/
META-INF/MANIFEST.MF
...
org/postgresql/geometric/PGbox.class
org/postgresql/geometric/PGcircle.class
org/postgresql/geometric/PGline.class
org/postgresql/geometric/PGlseg.class
org/postgresql/geometric/PGpath.class
org/postgresql/geometric/PGpoint.class
org/postgresql/geometric/PGpolygon.class
...
sam@lambda ~/workspace$ 

Again... any help will be greatly appreciated!

Answer 1

tl;dr: make sure the .java files are compiled to (at most) the same Java version .class files as the Java version on the system that will import the file with pyjnius.

Longer version:

I had a very similar problem, with one big difference: some files worked without any problem and others (in the same directory) didn't.

The problem with the files that resulted in the 'Class not found' exception was that I compiled them under Windows, which has Java 8. Ubuntu however currently installs Java 7 when you run "sudo apt-get install default-jdk".

And so, pyjnius couldn't import the Java 8 files on my Java 7 Ubuntu install. It's strange that it throws a 'Class not found' exception, instead of something more descriptive. Changing the target output to 1.7 fixed my problem.