modjy

h1. Trouble shooting modjy installations

By far the best way to get modjy running is to use the demo modjy application, distributed with jython, in the *Demo* directory, sub-directory *modjy_webapp*.

Don't forget to place the *jython.jar* file in the *WEB-INF/lib* directory!

If you're deploying a Django application, I highly recommend using the war packaging tool built, described on the [[ModjyAndDjango|Modjy and Django]] page: it configures everything correctly and prevents possible problems.

Similarly, the [[ModjyAndPylons|modjy and Pylons]] page describes the "snakefight":http://pypi.python.org/pypi/snakefight war-building tool, which does a similar job for Pylons.

h2(#noclassdef). java.lang.NoClassDefFoundError: com/xhaus/modjy/ModjyJServlet.

If you see this error, this means that your servlet container cannot find the java class *com.xhaus.modjy.ModjyJServlet*, which is the only java class used in modjy.

The likely cause of this issue is one of the following

 # The container cannot find the *jython.jar* file, which contains the class file.

 # The container cannot load the class from the *jython.jar* file, either for permissions or security reasons.

I recommend reading the documentation on [[ModjyDeployment#Placing-the-jythonjar-file|placing the jython.jar file]] 

h2(#importerror). ImportError: no module named modjy

There are two parts to modjy: a java part (actually a single java class) and a jython part. The majority of modjy is implemented in jython, with the entry point in a file called *modjy.py*. The java servlet component of modjy tries to import this module: if it fails, you will see the error above.

Obviously, you have to configure things such that modjy can find the *modjy.py* module and supporting modules. Which you can do by

 # Setting the *python.home* property. See the [[ModjyDeployment#Configuring-modjy|modjy deployment documentation]] for how to do this.

 # You can also copy the contents of the jython *Lib* directory into the *WEB-INF/lib-python* directory. This directory is automatically added to *sys.path* and any modules contained in it can be imported. To do this, copy every file and directory from the *Lib* directory of your jython installation into *WEB-INF/lib-python*, and that should solve your import problem.

 # It is also possible to package the entire jython *Lib* directory into a single file, which you then copy into *WEB-INF/lib-python*. This process is described on the [[ModjyGoogleAppEngine|running modjy on google appengine]] page, under the heading "Making the jython library accessible".

h2(#endswithnone). Caught AttributeError while rendering: 'NoneType' object has no attribute 'endswith'

This error appears to occur when running "Django on Jython":http://code.google.com/p/django-jython/, as described in this bug report: "Problem with Websphere Application Server 6.1":http://code.google.com/p/django-jython/issues/detail?id=64 .

As described in that bug report, the underlying error is reported from the "gettext module":http://docs.python.org/library/gettext.html , which needs to find data files in the jython home directory in order to do its job.

The real cause of the problem is that gettext uses the value in *sys.prefix* to find the location of the jython home directory. If the value of *sys.prefix* is None, then its attempt to load data files will fail with the "'NoneType' object has no attribute 'endswith'" error.

To fix this problem, there must be a value of *sys.prefix*. For further information on what *sys.prefix* means and how its value is set, read "Finding the registry file":http://wiki.python.org/jython/UserGuide#finding-the-registry-file .

The quickest way to solve this problem is to set a value for the *python.home* property in the *web.xml* for your modjy application. Read [[ModjyConfiguration|Modjy Configuration]] for how to set the value of this property.

h2(#other). Other problems.

If you experience other problems deploying WSGI applications with modjy, then please either file a bug on the "Jython bug tracker":http://bugs.jython.org or send an email to the "Jython Users":https://lists.sourceforge.net/lists/listinfo/jython-users mailing list.