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<h3 class="sectionHead"><span class="titlemark">2 </span> <a
id="x9-130002"></a>DBusConnection</h3>
<!--l. 121--><p class="noindent" >The <span
class="cmtt-12">DBusConnection</span><span class="footnote-mark"><a
href="dbus-java10.html#fn4x0"><sup class="textsuperscript">4</sup></a></span><a
id="x9-13001f4"></a>
class provides methods for connecting to the bus, exporting objects, sending signals and getting
references to remote objects.
</p><!--l. 126--><p class="indent" > <span
class="cmtt-12">DBusConnection </span>is a singleton class, multiple calls to <span
class="cmtt-12">getConnection </span>will return the same
bus connection.
</p>
<div class="verbatim" id="verbatim-1">
conn = DBusConnection.getConnection(DBusConnection.SESSION);
</div>
<!--l. 131--><p class="nopar" >
</p><!--l. 133--><p class="indent" > This creates a connection to the session bus, or returns the existing connection.
</p>
<div class="verbatim" id="verbatim-2">
conn.addSigHandler(TestSignalInterface.TestSignal.class,
 <br />                   new SignalHandler());
</div>
<!--l. 139--><p class="nopar" >
</p><!--l. 141--><p class="indent" > This sets up a signal handler for the given signal type. SignalHandler.handle will be called
in a new thread with an instance of TestSignalInterface.TestSignal when that signal is
recieved.
</p>
<div class="verbatim" id="verbatim-3">
conn.sendSignal(new TestSignalInterface.TestSignal(
 <br />                     "/foo/bar/com/Wibble",
 <br />                     "Bar",
 <br />                     new UInt32(42)));
</div>
<!--l. 150--><p class="nopar" >
</p><!--l. 152--><p class="indent" > This sends a signal of type <span
class="cmtt-12">TestSignalInterface.TestSignal</span>, from the object
<span
class="cmti-12">“/foo/bar/com/Wibble” </span>with the arguments <span
class="cmti-12">“Bar” </span>and <span
class="cmtt-12">UInt32(42)</span>.
</p>
<div class="verbatim" id="verbatim-4">
conn.exportObject("/Test", new testclass());
</div>
<!--l. 158--><p class="nopar" >
</p><!--l. 160--><p class="indent" > This exports the <span
class="cmtt-12">testclass </span>object on the path <span
class="cmti-12">“/Test”</span>
</p>
<div class="verbatim" id="verbatim-5">
Introspectable intro = (Introspectable) conn.getRemoteObject(
 <br />                              "foo.bar.Test", "/Test",
 <br />                              Introspectable.class);
</div>
<!--l. 166--><p class="nopar" >
</p><!--l. 168--><p class="indent" > This gets a reference to the <span
class="cmti-12">“/Test” </span>object on the process with the name <span
class="cmti-12">“foo.bar.Test” </span>.
The object implements the <span
class="cmtt-12">Introspectable </span>interface, and calls may be made to methods in
that interface as if it was a local object.
</p>
<div class="verbatim" id="verbatim-6">
String data = intro.Introspect();
</div>
<!--l. 175--><p class="nopar" >
</p><!--l. 177--><p class="indent" > The Runtime Exception <span
class="cmtt-12">DBusExecutionException </span>may be thrown by any remote method if
any part of the execution fails.
</p>
<h4 class="subsectionHead"><span class="titlemark">2.1 </span> <a
id="x9-140002.1"></a>Asynchronous Calls</h4>
<!--l. 182--><p class="noindent" >Calling a method on a remote object is synchronous, that is the thread will block until it has a
reply. If you do not want to block you can use an asynchronous call.
</p><!--l. 186--><p class="indent" > There are two ways of making asynchronous calls. You can either call the
<span
class="cmtt-12">callMethodAsync </span>function on the connection object, in which case you are returned a
<span
class="cmtt-12">DBusAsyncReply</span><span class="footnote-mark"><a
href="dbus-java11.html#fn5x0"><sup class="textsuperscript">5</sup></a></span><a
id="x9-14001f5"></a>
object which can be used to check for a reply and get the return value. This is demonstrated in
figure <a
href="#x9-140021">1<!--tex4ht:ref: fig:async --></a>.
</p>
<hr class="figure" /><div class="figure"
>
<a
id="x9-140021"></a>
<div class="center"
>
<!--l. 194--><p class="noindent" >
</p>
<div class="verbatim" id="verbatim-7">
DBusAsyncReply<Boolean> stuffreply =
 <br />   conn.callMethodAsync(remoteObject, "methodname", arg1, arg2);
 <br />...
 <br />if (stuffreply.hasReply()) {
 <br />   Boolean b = stuffreply.getReply();
 <br />   ...
 <br />}
</div>
<!--l. 203--><p class="nopar" ></p></div>
<br /> <div class="caption"
><span class="id">Figure 1: </span><span
class="content">Calling an asynchronous method</span></div><!--tex4ht:label?: x9-140021 -->
</div><hr class="endfigure" />
<!--l. 209--><p class="indent" > Alternatively, you can register a callback with the connection using the <span
class="cmtt-12">callWithCallback</span>
function on the connection object. In this case, your callback class (implementing the
<span
class="cmtt-12">CallbackHandler</span><span class="footnote-mark"><a
href="dbus-java12.html#fn6x0"><sup class="textsuperscript">6</sup></a></span><a
id="x9-14003f6"></a>
interface will be called when the reply is returned from the bus.
</p>
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