bartdag/Java

## Java
package p1;

import py4j.GatewayServer;

public class MyApplication {

    public static void main(String[] args) {
        GatewayServer server = new GatewayServer(null);

        // This will start the Py4J server and now, the JVM is ready to receive Python commands.
        // Once gateway.shutdown is called on the Python side, this call will return, and the Java program
        // will exit.
        // Obviously, this can be way more complex, but it's a good start :-)
        server.start();
    }

}

## Starting Java from python
import subprocess
import py4j.java_gateway import JavaGateway

def start_java():
    # Note: I assume that my_library.jar contains the library you want to expose with your CLI program.
    ARGS = ['java', '-cp', '/path/to/my_library.jar:/path/to/my/class_dir:/path/to/py4j-java.jar', 'p1.MyApplication']
    p = subprocess.Popen(ARGS)
    print('Java Started: {0}'.format(p.pid))

def stop_java():
    gateway = JavaGateway()
    gateway.shutdown()
    # Two alternatives:
    # (1) You could call a method on the Java side that calls System.exit(0);
    # (2) You could save the pid from start_java and kill the process, but you need to handle mac, linux, and
    #     windows...
	package p1;

	import py4j.GatewayServer;

	public class MyApplication {

	public static void main(String[] args) {
	GatewayServer server = new GatewayServer(null);

	// This will start the Py4J server and now, the JVM is ready to receive Python commands.
	// Once gateway.shutdown is called on the Python side, this call will return, and the Java program
	// will exit.
	// Obviously, this can be way more complex, but it's a good start :-)
	server.start();
	}

	}
	import subprocess
	import py4j.java_gateway import JavaGateway

	def start_java():
	# Note: I assume that my_library.jar contains the library you want to expose with your CLI program.
	ARGS = ['java', '-cp', '/path/to/my_library.jar:/path/to/my/class_dir:/path/to/py4j-java.jar', 'p1.MyApplication']
	p = subprocess.Popen(ARGS)
	print('Java Started: {0}'.format(p.pid))

	def stop_java():
	gateway = JavaGateway()
	gateway.shutdown()
	# Two alternatives:
	# (1) You could call a method on the Java side that calls System.exit(0);
	# (2) You could save the pid from start_java and kill the process, but you need to handle mac, linux, and
	# windows...