Re: Import Python class from Java

Julian,

That's probably me in the video you mention (so likely
https://www.youtube.com/watch?v=hLm3garVQFo)

In that video, I was referencing the Clamp project, which builds on new
functionality in Jython 2.7 such that we can *precisely* generate the Java
bytecode produced for Python classes that implement Java interfaces and/or
extend a Java class. By doing this precise generation, we can ensure
aspects like Java serializability, construction, and the specific naming,
so that you can import and use in Java (or other JVM languages).

So this means you would have to modify your class A such that it does the
requisite implementation/extension. In turn, this implementation/extension
allows Java code to import and use your Python class - it knows how to call
your code.

Clamp is demoed here, https://github.com/jimbaker/clamped, and is under
sporadic development at https://github.com/jythontools/clamp

There are other things to be done, but I see two major missing features:

   - Java annotations. Python classes should be able to support Java
   annotations on classes and methods, ideally use @-notation - so treating
   Java annotations as if they are Python decorators. This is just an
   extension of the precise bytecode generation I mentioned.
   - Maven jars. Clamp currently supports using sys.path for loading jars,
   via a jar.pth file in site-packages. (See
   https://docs.python.org/2/library/site.html on .pth file processing.)
   Clamp should be able to resolve Maven coordinates, as specified in your
   package's setup.py, to get jar artifacts, install in site-packages, and
   thereby place on sys.path. No more telling people, you need to put
   x.y.z.jar on CLASSPATH.

In my experience, Clamp works well enough, except when building jars on
Windows, but it needs unit testing and refactoring. (The existing Clamp
codebase is a good example of a prototype to try out ideas that proved to
be too successful.) The metaclass approach we use, as inspired by
SqlAlchemy, has shown itself to be a nice API and we will certainly keep.
Other aspects are still subject to change, but I suspect any changes will
be minor at most for users.

- Jim

On Thu, Sep 10, 2015 at 6:37 AM, Julian Kennedy <[email protected]>
wrote:

> Hi Guys
>
> I somehow remember seeing a recent video showing directly importing a
> python class from java. Something along the lines of:
>
> import some.python.module.MyClass
>
> class A {
>     // Some java code
>
>     MyClass a = new MyClass();
>
>     // More java code
> }
>
> Is this correct? Or did I see wrong?
>
> Regards
>
>
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