Basic usage

Bus connectivity

When using this library all communication between your application and the systemd daemon is done via D-Bus. Thus at first a connection to either the system or the user (session) daemon is required. Both can be achieved via the 'Systemd' class.

The following code establishes a connection to the system daemon and disconnects at the end. An exception of type 'DBusException' is thrown in case the connection can't be established.

import de.thjom.java.systemd.Systemd;
import org.freedesktop.dbus.exceptions.DBusException;

Systemd systemd = new Systemd();

try {
    systemd.connect();
}
catch (DBusException e) {
    // ...
}

systemd.disconnect();

Calling the constructor method with the DBusConnection.SYSTEM argument does the same:

import de.thjom.java.systemd.Systemd;
import org.freedesktop.dbus.DBusConnection;
import org.freedesktop.dbus.exceptions.DBusException;

Systemd systemd = new Systemd(DBusConnection.SYSTEM);

try {
    systemd.connect();
}
catch (DBusException e) {
    // ...
}

systemd.disconnect();

Likewise it is possible to establish a connection to the user (session) daemon:

import de.thjom.java.systemd.Systemd;
import org.freedesktop.dbus.DBusConnection;
import org.freedesktop.dbus.exceptions.DBusException;

Systemd systemd = new Systemd(DBusConnection.SESSION);

try {
    systemd.connect();
}
catch (DBusException e) {
    // ...
}

systemd.disconnect();

try-with-resource variant

The 'Systemd' class implements the 'AutoClosable' interface hence it allows the try-with-resource pattern like shown below which omits the explicit call to disconnect from the bus.

Connection to system daemon:

import de.thjom.java.systemd.Systemd;
import org.freedesktop.dbus.exceptions.DBusException;

try (Systemd systemd = Systemd.createAndConnect()) {
    // ...
}
catch (DBusException e) {
    // ...
}

Connection to user (session) daemon:

import de.thjom.java.systemd.Systemd;
import org.freedesktop.dbus.DBusConnection;
import org.freedesktop.dbus.exceptions.DBusException;

try (Systemd systemd = Systemd.createAndConnect(DBusConnection.SESSION)) {
    // ...
}
catch (DBusException e) {
    // ...
}