Question

I want to be able to call certain methods and such that are contained in a Java jar that is already running (It is guaranteed that it will be running). I have found things like Jython, but those only seem to be able to access Java’s native classes and such.

Answer 1

Check out this: Calling Java from Python

“You could also use Py4J. There is an example on the frontpage and lots of documentation, but essentially, you just call Java methods from your python code as if they were python methods:

from py4j.java_gateway import JavaGateway

gateway = JavaGateway() # connect to the JVM

java_object = gateway.jvm.mypackage.MyClass() # invoke constructor

other_object = java_object.doThat()

other_object.doThis(1,’abc’)

gateway.jvm.java.lang.System.out.println(‘Hello World!’) # call a static method

As opposed to Jython, one part of Py4J runs in the Python VM so it is always “up to date” with the latest version of Python and you can use libraries that do not run well on Jython (e.g., lxml). The other part runs in the Java VM you want to call.

The communication is done through sockets instead of JNI and Py4J has its own protocol (to optimize certain cases, to manage memory, etc.)“