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<h3 class="sectionHead"><span class="titlemark">1 </span> <a
id="x5-40001"></a>Introduction</h3>
<!--l. 50--><p class="noindent" >This document describes how to use the Java implementation of D-Bus. D-Bus is an IPC
mechanism which at a low level uses message passing over Unix Sockets or IP. D-Bus
models its messages as either function calls on remote objects, or signals emitted from
them.
</p><!--l. 55--><p class="indent" > Java is an object-oriented language and this implementation attempts to match the D-Bus
IPC model to the Java object model. The implementation also make heavy use of threads and
exceptions. The programmer should be careful to take care of synchronisation issues in their
code. All method calls by remote programs on exported objects and all signal handlers are run
in new threads. Any calls on remote objects may throw <span
class="cmtt-12">DBusExecutionException</span>,
which is a runtime exception and so the compiler will not remind you to handle
it.
</p><!--l. 63--><p class="indent" > The Java D-Bus API is also documented in the
JavaDoc<span class="footnote-mark"><a
href="dbus-java6.html#fn1x0"><sup class="textsuperscript">1</sup></a></span><a
id="x5-4001f1"></a> , D-Bus is described
in the specification<span class="footnote-mark"><a
href="dbus-java7.html#fn2x0"><sup class="textsuperscript">2</sup></a></span><a
id="x5-4002f2"></a> and
the API documentation<span class="footnote-mark"><a
href="dbus-java8.html#fn3x0"><sup class="textsuperscript">3</sup></a></span><a
id="x5-4003f3"></a> .
</p>
<h4 class="subsectionHead"><span class="titlemark">1.1 </span> <a
id="x5-50001.1"></a>Protocol Implementation</h4>
<!--l. 70--><p class="noindent" >This library is a native Java implementation of the D-Bus protocol and not a wrapper around
the C reference implementation.
</p><!--l. 73--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">1.2 </span> <a
id="x5-60001.2"></a>Dependencies</h4>
<!--l. 75--><p class="noindent" >This library requires Java 1.5-compatible VM and compiler (either Sun, or ecj+jamvm with
classpath-generics newer than 0.19) and the unix socket, debug and hexdump libraries from
<a
href="http://www.matthew.ath.cx/projects/java/" class="url" ><span
class="cmtt-12">http://www.matthew.ath.cx/projects/java/</span></a>.
</p><!--l. 79--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">1.3 </span> <a
id="x5-70001.3"></a>D-Bus Terminology</h4>
<!--l. 81--><p class="noindent" >D-Bus has several notions which are exposed to the users of the Java implementation.
</p><!--l. 84--><p class="noindent" >
</p>
<h5 class="subsubsectionHead"><span class="titlemark">1.3.1 </span> <a
id="x5-80001.3.1"></a>Bus Names</h5>
<!--l. 86--><p class="noindent" >Programs on the bus are issued a unique identifier by the bus. This is guaranteed
to be unique within one run of the bus, but is assigned sequentially to each new
connection.
</p><!--l. 90--><p class="indent" > There are also so called well-known bus names which a device can request on the bus. These
are of the form <span
class="cmti-12">“org.freedesktop.DBus”</span>, and any program can request them if they are not
already owned.
</p><!--l. 94--><p class="noindent" >
</p>
<h5 class="subsubsectionHead"><span class="titlemark">1.3.2 </span> <a
id="x5-90001.3.2"></a>Interfaces</h5>
<!--l. 96--><p class="noindent" >All method calls and signals are specified using an interface, similar to those in Java. When
executing a method or sending a signal you specify the interface the method belongs to. These
are of the form <span
class="cmti-12">“org.freedesktop.DBus”</span>.
</p><!--l. 101--><p class="noindent" >
</p>
<h5 class="subsubsectionHead"><span class="titlemark">1.3.3 </span> <a
id="x5-100001.3.3"></a>Object Paths</h5>
<!--l. 103--><p class="noindent" >A program may expose more than one object which implements an interface. Object paths of
the form <span
class="cmti-12">“/org/freedesktop/DBus” </span>are used to distinguish objects.
</p><!--l. 107--><p class="noindent" >
</p>
<h5 class="subsubsectionHead"><span class="titlemark">1.3.4 </span> <a
id="x5-110001.3.4"></a>Member Names</h5>
<!--l. 109--><p class="noindent" >Methods and Signals have names which identify them within an interface. D-Bus does
not support method overloading, only one method or signal should exist with each
name.
</p><!--l. 113--><p class="noindent" >
</p>
<h5 class="subsubsectionHead"><span class="titlemark">1.3.5 </span> <a
id="x5-120001.3.5"></a>Errors</h5>
<!--l. 115--><p class="noindent" >A reply to any message may be an error condition. In which case you reply with an error
message which has a name of the form <span
class="cmti-12">“org.freedesktop.DBus.Error.ServiceUnknown”</span>.
</p>
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