Title: JSR223: NullPointerException in Eclipse following wiki instructions
Type: Severity: normal
Components: Documentation Versions:
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: eaaltonen
Priority: Keywords:

Created on 2015-04-24.14:49:29 by eaaltonen, last changed 2015-04-27.10:14:01 by eaaltonen.

File name Uploaded Description Edit Remove eaaltonen, 2015-04-27.07:55:37 Test program
msg9954 (view) Author: (eaaltonen) Date: 2015-04-24.14:49:29
Following the wiki instructions at

After fixing Eclipse setting @issue2222, I get a NullPointerException. Jython is included as a Maven dependency, but is apparently not found.
msg9979 (view) Author: (eaaltonen) Date: 2015-04-27.07:55:37
This seems to be some sort of classloading issue that occurs both when running the sample program in the Eclipse IDE and with "mvn exec:java..."

Running (in Linux) with jython.jar in the boot classpath works without problems.

Manually registering the PyScriptEngineFactory to the ScriptEngineManager will make PyScriptEngineFactory.getScriptEngine() fail with a ClassNotFoundException.

Calling getScriptEngine() manually before calling scriptEngineManager.getEngineByName("python") will make the classloaders happy again, but the next failure is

Exception in thread "main" ImportError: Cannot import site module and its dependencies: No module named site
msg9980 (view) Author: (eaaltonen) Date: 2015-04-27.10:14:00
Looking at the sys.path solved this issue
sys.path: ['C:\\Users\\myuser\\.m2\\repository\\org\\python\\jython\\2.7-rc3\\Lib', '__classpath__', '__pyclasspath__/']

the 'jython' artifact was trying to import packages from a non-existent directory.

Changing the dependency to 'jython-standalone' fixed all issues.

So this is probably something that should just be more visibly documented.
Date User Action Args
2015-04-27 10:14:01eaaltonensetmessages: + msg9980
components: + Documentation
2015-04-27 07:55:38eaaltonensetfiles: +
messages: + msg9979
2015-04-24 14:49:29eaaltonencreate