D-Bus examples

Here are some code snippets for various programming languages (complete with completely unnecessary comments) showing how you can interface with Apertium by means of D-Bus. You'll need to install the D-Bus service for Apertium.

Python

#!/usr/bin/python
# coding=utf-8
# -*- encoding: utf-8 -*-

import dbus, sys, codecs;

sys.stdin = codecs.getwriter('utf-8')(sys.stdin);
sys.stdout = codecs.getwriter('utf-8')(sys.stdout);

mode_name = 'en-af'; # The name of the installed mode
dbus_mode_name = '/' + '_'.join(pair_name.split('-')); # Some mandatory mangling

bus = dbus.SessionBus(); # Create a new session bus

translator = dbus.Interface(bus.get_object('org.apertium.mode', dbus_mode_name), 'org.apertium.Mode'); # Get the translator

input = sys.stdin.read(); # Read the data

print translator.translate({}, input); # Print the translation

Java

Installing the Java D-Bus bindings

First you will need to download the D-Bus bindings for Java; the latest version can be found on the D-Bus project site. The bindings use libmatthew by the same author; the latest version can be downloaded from his site.

1. Compile and install libmatthew.
2. Compile and install the Java D-Bus bindings (ignore errors about invalid JAR paths - if it compiles and installs, everything will work.)

The Java binding build process should install the following binaries on your machine:

1. CreateInterface
2. DBusCall
3. DBusDaemon
4. DBusViewer
5. ListDBus

You can make sure that everything works by executing:

DBusCall org.apertium.info / org.apertium.Info modes

If you get a message such as

ParseException: Bus address is blank

it means that the environment variable $DBUS_SESSION_BUS_ADDRESS isn't set. You can get around it by using dbus-launch --exit-with-session to execute the program:

dbus-launch --exit-with-session DBusCall org.apertium.info / org.apertium.Info modes.

You should get output that looks something like this:

[[en-af, af-en]]

Using D-Bus from Java

Now that everything is working, it's time to create a Java program which uses an Apertium D-Bus object.

Since both D-Bus and Java use statically typed systems, Java needs to have the D-Bus interface descriptions of the objects it will use available at compile time. The 'CreateInterface' program in the Java D-Bus distribution creates Java interfaces by introspecting D-Bus objects.

We will create a Java interface corresponding to the info.apertium.Info interface and we will store it under the file org/apertium/Info.java. To do this, execute:

CreateInterface org.apertium.info / > org/apertium/Info.java

(and remember to use dbus-launch --exit-with-session if this does not work).

The contents out the newly created file should look something like:

/* File: org/apertium/Info.java */
package org.apertium;
import java.util.List;
import org.freedesktop.dbus.DBusInterface;
public interface Info extends DBusInterface
{

  public String directory();
  public List<List<String>> get_pipeline(String mode);
  public List<String> get_filters(String _type);
  public List<String> modes();
  public String mode_directory();

}

The next step is to create our minimal Java program. Create a file called TestDBus with the following contents:

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

import org.apertium.Info; // The interface we use to access org.apertium.info/

class TestDBus {

        public static void main(String[] args) throws org.freedesktop.dbus.exceptions.DBusException {
                DBusConnection bus = null;
                Info info = null;

                bus = DBusConnection.getConnection(DBusConnection.SESSION);
                info = bus.getRemoteObject("org.apertium.info", "/", Info.class);

                for (String s : info.modes()) {
                        System.out.println(s);
                }

                bus.disconnect();
        }
}

To compile this program, we need to include the current path on the class path as well as the jar files needed by the Java D-Bus binding. To compile, execute (you should modify the directories to suit your installation):

javac -cp .:/usr/local/share/java/dbus.jar:/usr/local/share/java/unix.jar:\
/usr/local/share/java/debug-disable.jar  TestDBus.java

To run the program, you need to specify the class paths specified above, as well as the JNI code (which installs to /usr/local/lib/jni by default (if you are using TCP instead of UNIX domain sockets for transport, then this won't be needed). You can run the program using:

java -cp .:/usr/local/share/java/dbus.jar:\
/usr/local/share/java/unix.jar:/usr/local/share/java/debug-disable.jar\
-Djava.library.path=/usr/local/lib/jni TestDBus

(and if it does not work, prefix the command with dbus-launch --exit-with-session).

Of course, if you are writing an application, you would hide all of these flags in a wrapper script.