Re: [Jython-users] Can we use Jython with just the jython.jar file?

[Paul G. <pau...@so...>]

Forgive me for not replying to this sooner, but it took while for me to 
sort through code and actually find the relevant answers. We have dealt 
with most of common Jython embedding issues, and a few less-common ones. 
This effort was completed a while ago, so the answers are not fresh in 
my mind.

First, let me say that it is unfortunate that the mailing list archives 
are not searchable, as this theme keeps popping up from time to time, 
and most of the answers are already there. But I would have a hard time 
finding the relevant postings myself :-(

You can pack python library modules in a jar file. The most compact 
deployments that I have seen distribute 2 jar files: jython.jar, plus 
one containing the libraries. It is conceivable that both of these could 
be packed into a single jar, but I have not tried it.
To access python module in a directory "Lib" contained in file 
JythonLib.jar used this syntax:

          "/path/JythonLib.jar!Lib"

Here is is code that one of my colleagues used to deduce the location of 
the libraries in the CLASSPATH. It requires no mods to jython, but may 
not be 100% reliable:


            // jar:file:$ABSOLUTE_PATH_TO_JYTHON_LIB!/Lib/string.py
            final URL url = ClassLoader.getSystemResource("Lib/string.py");

            //      file:$ABSOLUTE_PATH_TO_JYTHON_LIB!/Lib/string.py
            final StringBuffer pythonpath = new StringBuffer(url.getFile());

            //           $ABSOLUTE_PATH_TO_JYTHON_LIB!/Lib/string.py
            pythonpath.delete(0, 5);

            //           $ABSOLUTE_PATH_TO_JYTHON_LIB!/Lib
            final int len = pythonpath.length();
            pythonpath.delete(len - 10, len);

            //           $ABSOLUTE_PATH_TO_JYTHON_LIB!Lib
            pythonpath.deleteCharAt(pythonpath.length() - 4);



Some other things things that you my find useful is to set the cachedir 
to some directory that you know you have write access to, and to load a 
jython registry file and perhaps also include jython properties via 
system properties. Below, I combined some code snippets that demonstrate 
these thing. Use it as a guide, I am not sure that I pasted all the 
pieces together properly:

       HashMap properties = new HashMap();
       properties .put("python.path", "/path/JythonLib.jar!Lib");
       properties .put("python.cachedir", "/tmp/my_python_cachedir");

        InputStream registryFile = 
ClassLoader.getSystemResourceAsStream("jython.registry");

        // registryPre remains empty
        Properties registryPre = new Properties();

        // values in registryPost override those in registryPre
        Properties registryPost = new Properties();

        // load properties into registryPost from file
         registryPost.load(registryFile);
     

        // System properties override the file values
        registryPost.putAll(System.getProperties());

        // more properties are appended here:
        registryPost.putAll(properties);

        PythonInterpreter.initialize(registryPre, registryPost, new 
String[]{});

Hope this helps,

-Paul

>I would prefer putting the .py files into a jar file and loading
>them from the classpath, but from the discussion so far that may
>only be available to me if I modify Jython itself which I am
>somewhat reluctant to do due to the maintenance problem associated
>with future releases of Jython.  Although, it doesn't seem too big
>a problem to overcome at present....
>

-- 
Paul Giotta  Software Architect
Technoparkstrasse 1, CH-8005 Zurich. Email: pau...@So...

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