Question

How is it possible to export a java method or object using dbus?

I am writing this because the official documentation is very poor and it took me hours to figure out how to do it.

Ideally the DBus interface should go in a java package

Answer 1

DBus.java

import org.freedesktop.dbus.DBusInterface;
import org.freedesktop.dbus.DBusInterfaceName;    

@DBusInterfaceName("org.printer")
public interface DBus extends DBusInterface {
    //Methods to export
    public void Print(String message);
}

Main.java

import org.freedesktop.dbus.DBusConnection;
import org.freedesktop.dbus.exceptions.DBusException;

public class Main {    
    public static void main(String[] args) {
        Printer p = new Printer();

        try {
            DBusConnection conn = DBusConnection.getConnection(DBusConnection.SESSION);
            //Creates a bus name, it must contain some dots.
            conn.requestBusName("org.printer");
            //Exports the printer object
            conn.exportObject("/org/printer/MessagePrinter", p);
       } catch (DBusException DBe) {
           DBe.printStackTrace();
           conn.disconnect();
           return;
       }
    }
}

//Printer object, implements the dbus interface and gets
//called when the methods are invoked.
class Printer implements DBus {
    public boolean isRemote() {
        return false;
    }

    public void Print(String message) {
        System.out.println(message);
    }
}

You can try this out with qdbus from the shell, running:

qdbus org.printer /org/printer/MessagePrinter org.printer.Print test