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Richard S. Hall2cd5bed2007-07-16 20:32:41 +0000[diff] [blame]28 <div class="main">
29<h1><a name="LaunchingandEmbeddingApacheFelix-LaunchingandEmbeddingApacheFelix"></a>Launching and Embedding Apache Felix</h1>
30
31<ul>
32 <li><a href="#LaunchingandEmbeddingApacheFelix-introduction" title="introduction on Launching and Embedding Apache Felix">Introduction</a></li>
33 <li><a href="#LaunchingandEmbeddingApacheFelix-overview" title="overview on Launching and Embedding Apache Felix">API Overview</a></li>
34 <li><a href="#LaunchingandEmbeddingApacheFelix-launching" title="launching on Launching and Embedding Apache Felix">Launching Felix</a>
35 <ul>
36 <li><a href="#LaunchingandEmbeddingApacheFelix-standardlauncher" title="standard-launcher on Launching and Embedding Apache Felix">Standard Felix Launcher</a></li>
37 <li><a href="#LaunchingandEmbeddingApacheFelix-customlauncher" title="custom-launcher on Launching and Embedding Apache Felix">Custom Felix Launcher</a></li>
38 </ul>
39 </li>
40 <li><a href="#LaunchingandEmbeddingApacheFelix-embedding" title="embedding on Launching and Embedding Apache Felix">Embedding Felix</a>
41 <ul>
42 <li><a href="#LaunchingandEmbeddingApacheFelix-configproperty" title="config-property on Launching and Embedding Apache Felix">Embedded Execution Configuration Property</a></li>
43 <li><a href="#LaunchingandEmbeddingApacheFelix-hostinteraction" title="host-interaction on Launching and Embedding Apache Felix">Host/Felix Interaction</a></li>
44 <li><a href="#LaunchingandEmbeddingApacheFelix-hostservices" title="host-services on Launching and Embedding Apache Felix">Providing Host Application Services</a></li>
45 <li><a href="#LaunchingandEmbeddingApacheFelix-hostserviceusage" title="host-service-usage on Launching and Embedding Apache Felix">Using Services Provided by Bundles</a>
46 <ul>
47 <li><a href="#LaunchingandEmbeddingApacheFelix-servicereflection" title="service-reflection on Launching and Embedding Apache Felix">Using Bundle Services via Reflection</a></li>
48 </ul>
49 </li>
50 </ul>
51 </li>
52 <li><a href="#LaunchingandEmbeddingApacheFelix-caveat" title="caveat on Launching and Embedding Apache Felix">Caveat</a></li>
Karl Pauls7bca0de2007-09-16 20:38:10 +0000[diff] [blame]53 <li><a href="#LaunchingandEmbeddingApacheFelix-feedback" title="feedback on Launching and Embedding Apache Felix">Feedback</a></li>
Richard S. Hall2cd5bed2007-07-16 20:32:41 +0000[diff] [blame]54</ul>
55
56
57<p><a name="LaunchingandEmbeddingApacheFelix-introduction"></a></p>
58
59<h1><a name="LaunchingandEmbeddingApacheFelix-Introduction"></a>Introduction</h1>
60
61<p>The Apache Felix OSGi framework is intended to be easily launchable
62and embeddable. For example, Felix avoids the use of system properties
63for configuration, since these are globals that can cause interference
64if multiple framework instances are created in the same VM. Felix is
65also implemented to multiplex singleton facilities, like the URL stream
66handler factory. The goal is to make it possible to use Felix in as
67many scenarios as possible; however, this is still just a goal. In
68other words, this is a work in progress and if any issues arise, it
69would be greatly appreciated if they are brought to the attention of
70the Felix community. The next section provides a Felix API overview,
71while the remainder of the document is divided into two sections, one
72focusing on how to launch Felix and one focusing on how to embed Felix
73into a host application.</p>
74
75<p><a name="LaunchingandEmbeddingApacheFelix-overview"></a></p>
76
77<h1><a name="LaunchingandEmbeddingApacheFelix-APIOverview"></a>API Overview</h1>
78
79<p>The Felix class that implements the OSGi framework is <tt>org.apache.felix.framework.Felix</tt> or just <tt>Felix</tt> for short. The OSGi specification defines a special bundle, called the <em><b>System Bundle</b></em>,
80that represents the framework at run time and appears like any other
81bundle in the list of installed bundles. To make this notion even more
82intuitive, the <tt>Felix</tt> class implements the <tt>org.osgi.framework.Bundle</tt> interface, which is reiterated here:</p>
83
84<div class="code"><div class="codeContent">
85<pre class="code-java"><span class="code-keyword">public</span> <span class="code-keyword">interface</span> Bundle
86{
87 <span class="code-keyword">public</span> BundleContext getBundleContext();
88 <span class="code-keyword">public</span> <span class="code-object">long</span> getBundleId();
89 <span class="code-keyword">public</span> URL getEntry(<span class="code-object">String</span> name);
90 <span class="code-keyword">public</span> Enumeration getEntryPaths(<span class="code-object">String</span> path);
91 <span class="code-keyword">public</span> Enumeration findEntries(<span class="code-object">String</span> path, <span class="code-object">String</span> filePattern, <span class="code-object">boolean</span> recurse);
92 <span class="code-keyword">public</span> Dictionary getHeaders();
93 <span class="code-keyword">public</span> Dictionary getHeaders(<span class="code-object">String</span> locale);
94 <span class="code-keyword">public</span> <span class="code-object">long</span> getLastModified();
95 <span class="code-keyword">public</span> <span class="code-object">String</span> getLocation();
96 <span class="code-keyword">public</span> URL getResource(<span class="code-object">String</span> name);
97 <span class="code-keyword">public</span> Enumeration getResources(<span class="code-object">String</span> name) <span class="code-keyword">throws</span> IOException;
98 <span class="code-keyword">public</span> ServiceReference[] getRegisteredServices();
99 <span class="code-keyword">public</span> ServiceReference[] getServicesInUse();
100 <span class="code-keyword">public</span> <span class="code-object">int</span> getState();
101 <span class="code-keyword">public</span> <span class="code-object">String</span> getSymbolicName();
102 <span class="code-keyword">public</span> <span class="code-object">boolean</span> hasPermission(<span class="code-object">Object</span> obj);
103 <span class="code-keyword">public</span> <span class="code-object">Class</span> loadClass(<span class="code-object">String</span> name) <span class="code-keyword">throws</span> ClassNotFoundException;
104 <span class="code-keyword">public</span> void start() <span class="code-keyword">throws</span> BundleException;
105 <span class="code-keyword">public</span> void stop() <span class="code-keyword">throws</span> BundleException;
106 <span class="code-keyword">public</span> void uninstall() <span class="code-keyword">throws</span> BundleException;
107 <span class="code-keyword">public</span> void update() <span class="code-keyword">throws</span> BundleException;
108 <span class="code-keyword">public</span> void update(InputStream is) <span class="code-keyword">throws</span> BundleException;
109}</pre>
110</div></div>
111
112<p>When you instantiate the <tt>Felix</tt> class, the resulting object is actually the System Bundle and can be cast to the <tt>Bundle</tt> interface. The <tt>start()</tt> method is used to start the framework instance, while the <tt>stop()</tt> method is used to asynchronously stop the framework instance. The <tt>Felix</tt> class also includes the following two additional public methods:</p>
113
114<div class="code"><div class="codeContent">
115<pre class="code-java"><span class="code-keyword">public</span> class Felix <span class="code-keyword">extends</span> AbstractBundle
116{
117 <span class="code-keyword">public</span> Felix(Map configMutableMap, List activatorList);
118 <span class="code-keyword">public</span> void stopAndWait();
119}</pre>
120</div></div>
121
122<p>The first method is the constructor used to instantiate framework
123instances; the constructor accepts configuration properties and System
124Bundle activators, which are both described in more detail later. The <tt>stopAndWait()</tt> method is a synchronous version of the <tt>stop()</tt> method, used to stop the framework and block the calling thread until the framework is completely stopped.</p>
125
126<p><a name="LaunchingandEmbeddingApacheFelix-launching"></a></p>
127
128<h1><a name="LaunchingandEmbeddingApacheFelix-LaunchingFelix"></a>Launching Felix</h1>
129
130<p>Launching Felix is fairly simple and involves only three steps:</p>
131
132<ol>
133 <li>Defining some configuration properties.</li>
134 <li>Creating an instance of <tt>org.apache.felix.framework.Felix</tt> with the configuration properties.</li>
135 <li>Invoking the <tt>org.apache.felix.framework.Felix.start()</tt> method.</li>
136</ol>
137
138
139<p>The only configuration properties that are actually required to
140start Felix are ones that tell it where/how to locate the bundle cache
141profile directory where installed bundles will be cached. Felix' bundle
142cache implementation allows you to configure the location where bundles
143are cached using configuration properties. At a minimum, either a
Karl Pauls7bca0de2007-09-16 20:38:10 +0000[diff] [blame]144bundle cache profile name or directory must be specified; see the <a href="http://felix.apache.org/site/apache-felix-bundle-cache.html" title="Apache Felix Bundle Cache">bundle cache document</a> for more detailed information on configuring the bundle cache.</p>
Richard S. Hall2cd5bed2007-07-16 20:32:41 +0000[diff] [blame]145
Karl Pauls7bca0de2007-09-16 20:38:10 +0000[diff] [blame]146<p>Besides configuration properties for the bundle cache, it is usually necessary to set the <tt>org.osgi.framework.system.packages</tt> configuration property to export packages from the class path, such as the OSGi interface classes (e.g., <tt>org.osgi.framework</tt>) on which all bundles depend. If you are creating a launcher for Felix, then the <tt>felix.auto.start</tt> configuration property may also be used to automatically install and start various bundles; see the <a href="http://felix.apache.org/site/apache-felix-usage-documentation.html#ApacheFelixUsageDocumentation-configuringfelix" title="configuring-felix on Apache Felix Usage Documentation">usage document</a> for more information on configuring Felix and on the various configuration properties.</p>
Richard S. Hall2cd5bed2007-07-16 20:32:41 +0000[diff] [blame]147
148<p>The remainder of this section describes how the standard Felix
149launcher works as well as how to create a custom launcher for Felix.</p>
150
151<p><a name="LaunchingandEmbeddingApacheFelix-standardlauncher"></a></p>
152
153<h2><a name="LaunchingandEmbeddingApacheFelix-StandardFelixLauncher"></a>Standard Felix Launcher</h2>
154
155<p>The standard Felix launcher is very simple and is not intended to
156solve every possible requirement; it is intended to work for most
157standard situations. Most special launching requirements should be
158resolved by creating a custom launcher. This section describes how the
159standard launcher works. The following code represents the complete <tt>main()</tt> method of the standard launcher, each numbered comment will be described in more detail below:</p>
160
161<div class="code"><div class="codeContent">
162<pre class="code-java"><span class="code-keyword">public</span> <span class="code-keyword">static</span> void main(<span class="code-object">String</span>[] argv) <span class="code-keyword">throws</span> Exception
163{
164 <span class="code-comment">// (1) Load system properties.
165</span> Main.loadSystemProperties();
166
167 <span class="code-comment">// (2) Read configuration properties.
168</span> Properties configProps = Main.loadConfigProperties();
169
170 <span class="code-comment">// (3) Copy framework properties from the system properties.
171</span> Main.copySystemProperties(configProps);
172
173 <span class="code-comment">// (4) See <span class="code-keyword">if</span> the profile name property was specified.
174</span> <span class="code-object">String</span> profileName = configProps.getProperty(BundleCache.CACHE_PROFILE_PROP);
175
176 <span class="code-comment">// (4) See <span class="code-keyword">if</span> the profile directory property was specified.
177</span> <span class="code-object">String</span> profileDirName = configProps.getProperty(BundleCache.CACHE_PROFILE_DIR_PROP);
178
179 <span class="code-comment">// Print welcome banner.
180</span> <span class="code-object">System</span>.out.println(<span class="code-quote">"\nWelcome to Felix."</span>);
181 <span class="code-object">System</span>.out.println(<span class="code-quote">"=================\n"</span>);
182
183 <span class="code-comment">// (5) If no profile or profile directory is specified in the
184</span> <span class="code-comment">// properties, then ask <span class="code-keyword">for</span> a profile name.
185</span> <span class="code-keyword">if</span> ((profileName == <span class="code-keyword">null</span>) &amp;&amp; (profileDirName == <span class="code-keyword">null</span>))
186 {
187 <span class="code-object">System</span>.out.print(<span class="code-quote">"Enter profile name: "</span>);
188 BufferedReader in = <span class="code-keyword">new</span> BufferedReader(<span class="code-keyword">new</span> InputStreamReader(<span class="code-object">System</span>.in));
189 <span class="code-keyword">try</span>
190 {
191 profileName = in.readLine();
192 }
193 <span class="code-keyword">catch</span> (IOException ex)
194 {
195 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not read input."</span>);
196 <span class="code-object">System</span>.exit(-1);
197 }
198 <span class="code-object">System</span>.out.println("");
199 <span class="code-keyword">if</span> (profileName.length() != 0)
200 {
201 configProps.setProperty(BundleCache.CACHE_PROFILE_PROP, profileName);
202 }
203 }
204
205 <span class="code-comment">// (6) A profile directory or name must be specified.
206</span> <span class="code-keyword">if</span> ((profileDirName == <span class="code-keyword">null</span>) &amp;&amp; (profileName.length() == 0))
207 {
208 <span class="code-object">System</span>.err.println(<span class="code-quote">"You must specify a profile name or directory."</span>);
209 <span class="code-object">System</span>.exit(-1);
210 }
211
212 <span class="code-keyword">try</span>
213 {
214 <span class="code-comment">// (7) Now create an instance of the framework.
215</span> m_felix = <span class="code-keyword">new</span> Felix(<span class="code-keyword">new</span> StringMap(configProps, <span class="code-keyword">false</span>), <span class="code-keyword">null</span>);
216 m_felix.start();
217 }
218 <span class="code-keyword">catch</span> (Exception ex)
219 {
220 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
221 ex.printStackTrace();
222 <span class="code-object">System</span>.exit(-1);
223 }
224}</pre>
225</div></div>
226
227<p>The general steps of the standard launcher are quite straightforward:</p>
228
229<ol>
230 <li>Load any system properties specified in the <tt>system.properties</tt> file; this file is typically located in the <tt>conf/</tt> directory of the Felix installation directory, but it can be specified directly using the <tt>felix.system.properties</tt>
231system property. This file is not needed to launch Felix and is
232provided merely for convenience when system properties must be
233specified. The file is a standard Java properties file, but it also
234supports property substitution using <tt>${&lt;property-name</tt>} syntax. Property substitution can be nested; only system properties will be used for substitution.</li>
235 <li>Load any configuration properties specified in the <tt>config.properties</tt> file; this file is typically located in the <tt>conf/</tt> directory of the Felix installation directory, but it can be specified directly using the <tt>felix.config.properties</tt>
236system property. This file is used to configure the Felix instance
237created by the launcher. The file is a standard Java properties file,
238but it also supports property substitution using "<tt>${&lt;property-name</tt>}"
239syntax. Property substitution can be nested; configuration and system
240properties will be used for substitution with configuration properties
241having precedence.</li>
242 <li>For convenience, any configuration
243properties that are set as system properties will be copied into the
244set of configuration properties to provide an easy way to add to or
245override configuration properties specified in the <tt>config.properties</tt> file.</li>
Karl Pauls7bca0de2007-09-16 20:38:10 +0000[diff] [blame]246 <li>Try to load the profile name or profile directory configuration properties. At least one of these must be specified so that the <a href="http://felix.apache.org/site/apache-felix-bundle-cache.html" title="Apache Felix Bundle Cache">bundle cache</a> knows where to save installed bundles.</li>
Richard S. Hall2cd5bed2007-07-16 20:32:41 +0000[diff] [blame]247 <li>If
248either the profile name or profile directory configuration property has
249not been specified, then ask the user to specify a profile name and add
250it to the current set of configuration properties.</li>
251 <li>Error if there is no profile name or profile directory.</li>
252 <li>Create the Felix instance passing in the configuration properties and then call <tt>start()</tt>.</li>
253</ol>
254
255
256<p>The framework is not active until the <tt>start()</tt> method is called. If no shell bundles are specified in the <tt>config.properties</tt>
257file or if there is difficulty locating the shell bundles that are
258specified, then it will appear as if the framework is hung, but it is
259actually running without any way to interact with it since the shell
260bundles provide the only means of interaction.</p>
261
262<p><a name="LaunchingandEmbeddingApacheFelix-customlauncher"></a></p>
263
264<h2><a name="LaunchingandEmbeddingApacheFelix-CustomFelixLauncher"></a>Custom Felix Launcher</h2>
265
266<p>This section creates a bare-bones launcher to demonstrate the
267minimum requirements for creating an interactive launcher for the Felix
268framework. This example uses the standard Felix shell bundles for
269interactivity, but any other bundles could be used instead. For
270example, the shell service and telnet bundles could be used to launch
271Felix and make it remotely accessible.</p>
272
273<p>This example launcher project has the following directory structure:</p>
274
275<div class="preformatted"><div class="preformattedContent">
276<pre>launcher/
277 lib/
278 org.apache.felix.framework-1.0.0.jar
279 bundle/
280 org.apache.felix.shell-1.0.0.jar
281 org.apache.felix.shell.tui-1.0.0.jar
282 src/
283 example/
284 Main.java
285</pre>
286</div></div>
287
288<p>The <tt>lib/</tt> directory contains the framework JAR file, which also contains the OSGi core interfaces. The <tt>bundle/</tt>
289directory contains the shell service and textual shell interface
290bundles that will be used for interacting with the framework instance.
291Note: If you do not launch Felix with interactive bundles, it will
292appear as if the framework instance is hung, but it is actually just
293sitting there waiting for someone to tell it to do something. The <tt>src/example/</tt> directory contains the following <tt>Main.java</tt> file, which is a very simplistic Felix launcher.</p>
294
295<div class="code"><div class="codeContent">
296<pre class="code-java"><span class="code-keyword">package</span> example;
297
298<span class="code-keyword">import</span> java.util.Map;
299<span class="code-keyword">import</span> org.osgi.framework.Constants;
300<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
301<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
302<span class="code-keyword">import</span> org.apache.felix.framework.util.StringMap;
303<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
304
305<span class="code-keyword">public</span> class Main
306{
307 <span class="code-keyword">private</span> <span class="code-keyword">static</span> Felix m_felix = <span class="code-keyword">null</span>;
308
309 <span class="code-keyword">public</span> <span class="code-keyword">static</span> void main(<span class="code-object">String</span>[] argv) <span class="code-keyword">throws</span> Exception
310 {
311 <span class="code-comment">// Print welcome banner.
312</span> <span class="code-object">System</span>.out.println(<span class="code-quote">"\nWelcome to Felix."</span>);
313 <span class="code-object">System</span>.out.println(<span class="code-quote">"=================\n"</span>);
314
315 Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
316 configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
317 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
318 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
319 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
320 <span class="code-quote">"org.osgi.service.url; version=1.0.0"</span>);
321 configMap.put(FelixConstants.AUTO_START_PROP + <span class="code-quote">".1"</span>,
322 <span class="code-quote">"file:bundle/org.apache.felix.shell-1.0.0.jar "</span> +
323 <span class="code-quote">"file:bundle/org.apache.felix.shell.tui-1.0.0.jar"</span>);
324 configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
325
326 <span class="code-keyword">try</span>
327 {
328 <span class="code-comment">// Now create an instance of the framework.
329</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, <span class="code-keyword">null</span>);
330 m_felix.start();
331 }
332 <span class="code-keyword">catch</span> (Exception ex)
333 {
334 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
335 ex.printStackTrace();
336 <span class="code-object">System</span>.exit(-1);
337 }
338 }
339}</pre>
340</div></div>
341
342<p>This launcher has all information hard coded in it, unlike the
343default Felix launcher, which loads configuration properties from files
344and performs variable substitution. This simple launcher provides a
345good starting point if the features of the default launcher are not
346necessary. For example, if you want to create a launcher that
347automatically deletes the bundle cache directory each time it starts,
348then it is quite easy to figure out how to do that with this simple
349launcher.</p>
350
351<p>By breaking down the above source code into small chunks, it is quite easy to see what is going on.</p>
352
353<div class="code"><div class="codeContent">
354<pre class="code-java">Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);</pre>
355</div></div>
356
357<p>This simply creates a map to hold configuration properties where the keys are strings and lookups are case insensitive.</p>
358
359<div class="code"><div class="codeContent">
360<pre class="code-java">configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
361 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
362 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
363 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
364 <span class="code-quote">"org.osgi.service.url; version=1.0.0"</span>);</pre>
365</div></div>
366
367<p>This sets the <tt>Constants.FRAMEWORK_SYSTEMPACKAGES</tt> configuration property (string value "<tt>org.osgi.framework.system.packages</tt>"),
368which specifies the class path packages the system bundle should
369export; this is how classes on the class path are made available to
370bundles. This example only exports the core OSGi API packages, but
371other JRE packages could also be added, such as <tt>javax.swing</tt>.
372For example, the default Felix launcher defines properties for all
373packages in various JRE versions (e.g., 1.3.x, 1.4.x, 1.5.x) and
374appends them to this property using property substitution.</p>
375
376<div class="code"><div class="codeContent">
377<pre class="code-java">configMap.put(FelixConstants.AUTO_START_PROP + <span class="code-quote">".1"</span>,
378 <span class="code-quote">"file:bundle/org.apache.felix.shell-1.0.0.jar "</span> +
379 <span class="code-quote">"file:bundle/org.apache.felix.shell.tui-1.0.0.jar"</span>);</pre>
380</div></div>
381
382<p>This sets the <tt>FelixConstants.AUTO_START_PROP</tt> configuration property (string value "<tt>felix.auto.start</tt>"),
383which is a space-delimited list of bundle URLs that the framework will
384automatically install and start when the framework starts. However,
385this property key cannot be used as is; it must be appended with a "."
386and then a number, where the number represents the start level for the
387bundle when it is installed. In this particular example, ".1" is
388appended to the property name, thus the two bundles will be installed
389into start level one. This example uses relative <tt>file:</tt> URLs, which will load the bundles from the <tt>bundle/</tt>
390directory assuming that the launcher is started from the root directory
391of the launcher project. It is also possible to specify absolute URLs
392or remote URLs.</p>
393
394<div class="code"><div class="codeContent">
395<pre class="code-java">configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);</pre>
396</div></div>
397
398<p>This sets the last configuration property, <tt>BundleCache.CACHE_PROFILE_DIR_PROP</tt> (string value "<tt>felix.cache.profiledir</tt>"),
399which is a string that specifies the precise directory to be used as
400the bundle cache profile directory; the Felix bundle cache supports
401other properties to configure its behavior, but those are not covered
402here. In this example, the bundle cache profile directory is specified
403as a relative directory called "<tt>cache</tt>". Assuming that the
404launcher is executed from the root directory of the launcher project,
405then the bundle cache profile directory will be created in the root
406directory of the project.</p>
407
408<div class="code"><div class="codeContent">
409<pre class="code-java">m_felix = <span class="code-keyword">new</span> Felix(configMap, <span class="code-keyword">null</span>);
410 m_felix.start();</pre>
411</div></div>
412
413<p>The last steps create the framework instance and start it. The configuration property map is passed into the <tt>Felix</tt> constructor.</p>
414
415<p>The following command compiles the launcher when run from the root directory of the launcher project:</p>
416
417<div class="preformatted"><div class="preformattedContent">
418<pre>javac -d . -classpath lib/org.apache.felix.framework-1.0.0.jar src/example/Main.java
419</pre>
420</div></div>
421
422<p>After executing this command, an <tt>example/</tt> directory is
423created in the current directory, which contains the generated class
424file. The following command executes the simple launcher when run from
425the root directory of the launcher project:</p>
426
427<div class="preformatted"><div class="preformattedContent">
428<pre>java -cp .:lib/org.apache.felix.framework-1.0.0.jar example.Main
429</pre>
430</div></div>
431
432<p>After executing this command, a <tt>cache/</tt> directory is created that contains the installed bundles, which were installed from the <tt>bundle/</tt> directory.</p>
433
434<p><a name="LaunchingandEmbeddingApacheFelix-embedding"></a></p>
435
436<h1><a name="LaunchingandEmbeddingApacheFelix-EmbeddingFelix"></a>Embedding Felix</h1>
437
438<p>Embedding Felix into a host application is a simple way to provide a
439sophisticated extensibility mechanism (i.e., plugin system) to the host
440application. Embedding Felix is very similar to launching Felix as
441described above, the main difference is that the host application
442typically wants to interact with the framework instance and/or
443installed bundles/services from the outside. This is fairly easy to
444achieve with Felix, but there are some subtle issues to understand.
445This section presents the mechanisms for embedding Felix into a host
446application and the issues in doing so.</p>
447
448<p><a name="LaunchingandEmbeddingApacheFelix-configproperty"></a></p>
449
450<h2><a name="LaunchingandEmbeddingApacheFelix-EmbeddedExecutionConfigurationProperty"></a>Embedded Execution Configuration Property</h2>
451
452<p>When a Felix instance is embedded in a host application, the host
453application must inform the Felix instance that it is embedded. To do
454this, the host application sets the "<tt>felix.embedded.execution</tt>" configuration property to "<tt>true</tt>";
455this can be accomplished in the same way that all configuration
456properties are set, i.e., passing it into the Felix constructor via a
457map. This property specifically controls whether or not the Felix
458instance will shutdown the JVM (i.e., call <tt>System.exit()</tt> when
459the framework is shutdown. When embedding Felix it is generally not
460desirable for Felix to shutdown the JVM; therefore, by setting this
461property to "<tt>true</tt>" it can be avoided.</p>
462
463<p><a name="LaunchingandEmbeddingApacheFelix-hostinteraction"></a></p>
464
465<h2><a name="LaunchingandEmbeddingApacheFelix-Host/FelixInteraction"></a>Host/Felix Interaction</h2>
466
467<p>In the section on <a href="#LaunchingandEmbeddingApacheFelix-launching" title="launching on Launching and Embedding Apache Felix">launching</a> Felix above, the <tt>Felix</tt>
468constructor accepts two arguments, the first being the configuration
469properties for the framework, the second being a list of bundle
470activator instances. These bundle activator instances provide a
471convenient way for host applications to interact with the Felix
472framework.</p>
473
474<p>Each bundle activator instance passed into the constructor
475effectively becomes part of the System Bundle. This means that the
476start()/stop() method of each bundle activator instance in the passed
477in list gets invoked when the System Bundle's activator start()/stop()
478method gets invoked. Consequently, each bundle activator instance will
479be given the system bundle's <tt>BundleContext</tt> object so that they can interact with the framework externally. While it is possible to get the System Bundle's <tt>BundleContext</tt> object directly by calling <tt>Felix.getBundleContext()</tt>,
480this is generally not as convenient since it requires that you monitor
481when the System Bundle starts and/or stops. Consider following snippet
482of a bundle activator:</p>
483
484<div class="code"><div class="codeContent">
485<pre class="code-java"><span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
486{
487 <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
488
489 <span class="code-keyword">public</span> void start(BundleContext context)
490 {
491 m_context = context;
492 }
493
494 <span class="code-keyword">public</span> void stop(BundleContext context)
495 {
496 m_context = <span class="code-keyword">null</span>;
497 }
498
499 <span class="code-keyword">public</span> Bundle[] getBundles()
500 {
501 <span class="code-keyword">if</span> (m_context != <span class="code-keyword">null</span>)
502 {
503 <span class="code-keyword">return</span> m_context.getBundles();
504 }
505 <span class="code-keyword">return</span> <span class="code-keyword">null</span>;
506 }
507}</pre>
508</div></div>
509
510<p>Given the above bundle activator, it is now possible to embed Felix
511into a host application and interact with it as the following snippet
512illustrates:</p>
513
514<div class="code"><div class="codeContent">
515<pre class="code-java"><span class="code-keyword">public</span> class HostApplication
516{
517 <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
518 <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
519
520 <span class="code-keyword">public</span> HostApplication()
521 {
522 <span class="code-comment">// Create a <span class="code-keyword">case</span>-insensitive configuration property map.
523</span> Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
524 <span class="code-comment">// Configure the Felix instance to be embedded.
525</span> configMap.put(FelixConstants.EMBEDDED_EXECUTION_PROP, <span class="code-quote">"<span class="code-keyword">true</span>"</span>);
526 <span class="code-comment">// Add core OSGi packages to be exported from the class path
527</span> <span class="code-comment">// via the system bundle.
528</span> configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
529 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
530 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
531 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
532 <span class="code-quote">"org.osgi.service.url; version=1.0.0"</span>);
533 <span class="code-comment">// Explicitly specify the directory to use <span class="code-keyword">for</span> caching bundles.
534</span> configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
535
536 <span class="code-keyword">try</span>
537 {
538 <span class="code-comment">// Create host activator;
539</span> m_activator = <span class="code-keyword">new</span> HostActivator();
540 List list = <span class="code-keyword">new</span> ArrayList();
541 list.add(m_activator);
542
543 <span class="code-comment">// Now create an instance of the framework with
544</span> <span class="code-comment">// our configuration properties and activator.
545</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
546
547 <span class="code-comment">// Now start Felix instance.
548</span> m_felix.start();
549 }
550 <span class="code-keyword">catch</span> (Exception ex)
551 {
552 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
553 ex.printStackTrace();
554 }
555 }
556
557 <span class="code-keyword">public</span> Bundle[] getInstalledBundles()
558 {
559 <span class="code-comment">// Use the system bundle activator to gain external
560</span> <span class="code-comment">// access to the set of installed bundles.
561</span> <span class="code-keyword">return</span> m_activator.getBundles();
562 }
563
564 <span class="code-keyword">public</span> void shutdownApplication()
565 {
566 <span class="code-comment">// Shut down the felix framework when stopping the
567</span> <span class="code-comment">// host application.
568</span> m_felix.shutdown();
569 }
570}</pre>
571</div></div>
572
573<p>Notice how the <tt>HostApplication.getInstalledBundles()</tt> method
574uses its activator instance to get access to the System Bundle's
575context in order to interact with the embedded Felix framework
576instance. This approach provides the foundation for all interaction
577between the host application and the embedded framework instance.</p>
578
579<p><a name="LaunchingandEmbeddingApacheFelix-hostservices"></a></p>
580
581<h2><a name="LaunchingandEmbeddingApacheFelix-ProvidingHostApplicationServices"></a>Providing Host Application Services</h2>
582
583<p>Providing services from the host application to bundles inside the
584embedded Felix framework instance follows the basic approach laid out
585in <a href="#LaunchingandEmbeddingApacheFelix-hostinteraction" title="host-interaction on Launching and Embedding Apache Felix">above</a>.
586The main complication for providing a host application service to
587bundles is the fact that both the host application and the bundles must
588be using the same class definitions for the service interface classes.
589Since the host application cannot import classes from a bundle, this
590means that the service interface classes <b>must</b> be accessible on
591the class path, typically as part of the host application itself. The
592host application then must export the service interface package via the
593system bundle so that bundles installed into the embedded framework
594instance can import it. This is achieved using the <tt>org.osgi.framework.system.packages</tt> configuration property previously presented.</p>
595
596<p>Consider the follow simple property lookup service:</p>
597
598<div class="code"><div class="codeContent">
599<pre class="code-java"><span class="code-keyword">package</span> host.service.lookup;
600
601<span class="code-keyword">public</span> class Lookup
602{
603 <span class="code-keyword">public</span> <span class="code-object">Object</span> lookup(<span class="code-object">String</span> name);
604}</pre>
605</div></div>
606
607<p>This package is simply part of the host application, which is potentially packaged into a JAR file and started with the "<tt>java -jar</tt>"
608command. Now consider the following host application bundle activator,
609which will be used to register/unregister the property lookup service
610when the embedded framework instance starts/stops:</p>
611
612<div class="code"><div class="codeContent">
613<pre class="code-java"><span class="code-keyword">package</span> host.core;
614
615<span class="code-keyword">import</span> java.util.Map;
616<span class="code-keyword">import</span> org.osgi.framework.BundleActivator;
617<span class="code-keyword">import</span> org.osgi.framework.BundleContext;
618<span class="code-keyword">import</span> org.osgi.framework.ServiceRegistration;
619<span class="code-keyword">import</span> host.service.lookup;
620
621<span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
622{
623 <span class="code-keyword">private</span> Map m_lookupMap = <span class="code-keyword">null</span>;
624 <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
625 <span class="code-keyword">private</span> ServiceRegistration m_registration = <span class="code-keyword">null</span>;
626
627 <span class="code-keyword">public</span> HostActivator(Map lookupMap)
628 {
629 <span class="code-comment">// Save a reference to the service's backing store.
630</span> m_lookupMap = lookupMap;
631 }
632
633 <span class="code-keyword">public</span> void start(BundleContext context)
634 {
635 <span class="code-comment">// Save a reference to the bundle context.
636</span> m_context = context;
637 <span class="code-comment">// Create a property lookup service implementation.
638</span> Lookup lookup = <span class="code-keyword">new</span> Lookup() {
639 <span class="code-keyword">public</span> <span class="code-object">Object</span> lookup(<span class="code-object">String</span> name)
640 {
641 <span class="code-keyword">return</span> m_lookupMap.get(name);
642 }
643 };
644 <span class="code-comment">// Register the property lookup service and save
645</span> <span class="code-comment">// the service registration.
646</span> m_registration = m_context.registerService(
647 Lookup.class.getName(), lookup, <span class="code-keyword">null</span>);
648 }
649
650 <span class="code-keyword">public</span> void stop(BundleContext context)
651 {
652 <span class="code-comment">// Unregister the property lookup service.
653</span> m_registration.unregister();
654 m_context = <span class="code-keyword">null</span>;
655 }
656}</pre>
657</div></div>
658
659<p>Given the above host application bundle activator, the following
660code snippet shows how the host application could create an embedded
661version of the Felix framework and provide the property lookup service
662to installed bundles:</p>
663
664<div class="code"><div class="codeContent">
665<pre class="code-java"><span class="code-keyword">package</span> host.core;
666
667<span class="code-keyword">import</span> java.util.List;
668<span class="code-keyword">import</span> java.util.ArrayList;
669<span class="code-keyword">import</span> java.util.Map;
670<span class="code-keyword">import</span> java.util.HashMap;
671<span class="code-keyword">import</span> host.service.lookup.Lookup;
672<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
673<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
674<span class="code-keyword">import</span> org.apache.felix.framework.util.StringMap;
675<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
676
677<span class="code-keyword">public</span> class HostApplication
678{
679 <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
680 <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
681 <span class="code-keyword">private</span> Map m_lookupMap = <span class="code-keyword">new</span> HashMap();
682
683 <span class="code-keyword">public</span> HostApplication()
684 {
685 <span class="code-comment">// Initialize the map <span class="code-keyword">for</span> the property lookup service.
686</span> m_lookupMap.put(<span class="code-quote">"name1"</span>, <span class="code-quote">"value1"</span>);
687 m_lookupMap.put(<span class="code-quote">"name2"</span>, <span class="code-quote">"value2"</span>);
688 m_lookupMap.put(<span class="code-quote">"name3"</span>, <span class="code-quote">"value3"</span>);
689 m_lookupMap.put(<span class="code-quote">"name4"</span>, <span class="code-quote">"value4"</span>);
690
691 <span class="code-comment">// Create a <span class="code-keyword">case</span>-insensitive configuration property map.
692</span> Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
693 <span class="code-comment">// Configure the Felix instance to be embedded.
694</span> configMap.put(FelixConstants.EMBEDDED_EXECUTION_PROP, <span class="code-quote">"<span class="code-keyword">true</span>"</span>);
695 <span class="code-comment">// Add the host provided service <span class="code-keyword">interface</span> <span class="code-keyword">package</span> and the core OSGi
696</span> <span class="code-comment">// packages to be exported from the class path via the system bundle.
697</span> configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
698 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
699 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
700 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
701 <span class="code-quote">"org.osgi.service.url; version=1.0.0,"</span> +
702 <span class="code-quote">"host.service.lookup; version=1.0.0"</span>);
703 <span class="code-comment">// Explicitly specify the directory to use <span class="code-keyword">for</span> caching bundles.
704</span> configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
705
706 <span class="code-keyword">try</span>
707 {
708 <span class="code-comment">// Create host activator;
709</span> m_activator = <span class="code-keyword">new</span> HostActivator(m_lookupMap);
710 List list = <span class="code-keyword">new</span> ArrayList();
711 list.add(m_activator);
712
713 <span class="code-comment">// Now create an instance of the framework with
714</span> <span class="code-comment">// our configuration properties and activator.
715</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
716
717 <span class="code-comment">// Now start Felix instance.
718</span> m_felix.start();
719 }
720 <span class="code-keyword">catch</span> (Exception ex)
721 {
722 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
723 ex.printStackTrace();
724 }
725 }
726
727 <span class="code-keyword">public</span> void shutdownApplication()
728 {
729 <span class="code-comment">// Shut down the felix framework when stopping the
730</span> <span class="code-comment">// host application.
731</span> m_felix.shutdown();
732 }
733}</pre>
734</div></div>
735
736<p>Rather than having the host application bundle activator register
737the service, it is also possible for the the host application to simply
738get the bundle context from the bundle activator and register the
739service directly, but the presented approach is perhaps a little
740cleaner since it allows the host application to register/unregister the
741service when the system bundle starts/stops.</p>
742
743<p><a name="LaunchingandEmbeddingApacheFelix-hostserviceusage"></a></p>
744
745<h2><a name="LaunchingandEmbeddingApacheFelix-UsingServicesProvidedbyBundles"></a>Using Services Provided by Bundles</h2>
746
747<p>Using services provided by bundles follows the same general approach
748of using a host application bundle activator. The main complication for
749the host application using a service from a bundle is the fact that
750both the host application and the bundle must be using the same class
751definitions for the service interface classes. Since the host
752application cannot import classes from a bundle, this means that the
753service interface classes <b>must</b> be accessible on the class path,
754typically as part of the host application itself. The host application
755then must export the service interface package via the system bundle so
756that bundles installed into the embedded framework instance can import
757it. This is achieved using the <tt>org.osgi.framework.system.packages</tt> configuration property previously presented.</p>
758
759<p>Consider the following simple command service interface for which
760bundles provide implementations, such as might be used to create an
761extensible interactive shell:</p>
762
763<div class="code"><div class="codeContent">
764<pre class="code-java"><span class="code-keyword">package</span> host.service.command;
765
766<span class="code-keyword">public</span> class Command
767{
768 <span class="code-keyword">public</span> <span class="code-object">String</span> getName();
769 <span class="code-keyword">public</span> <span class="code-object">String</span> getDescription();
770 <span class="code-keyword">public</span> <span class="code-object">boolean</span> execute(<span class="code-object">String</span> commandline);
771}</pre>
772</div></div>
773
774<p>This package is simply part of the host application, which is potentially packaged into a JAR file and started with the "<tt>java -jar</tt>"
775command. Now consider the previously introduced host application bundle
776activator below, which simply provides access to the system bundle
777context:</p>
778
779<div class="code"><div class="codeContent">
780<pre class="code-java"><span class="code-keyword">package</span> host.core;
781
782<span class="code-keyword">import</span> org.osgi.framework.BundleActivator;
783<span class="code-keyword">import</span> org.osgi.framework.BundleContext;
784
785<span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
786{
787 <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
788
789 <span class="code-keyword">public</span> void start(BundleContext context)
790 {
791 m_context = context;
792 }
793
794 <span class="code-keyword">public</span> void stop(BundleContext context)
795 {
796 m_context = <span class="code-keyword">null</span>;
797 }
798
799 <span class="code-keyword">public</span> BundleContext getContext()
800 {
801 <span class="code-keyword">return</span> m_context;
802 }
803}</pre>
804</div></div>
805
806<p>With this bundle activator, the host application can command
807services provided by bundles installed inside its embedded Felix
808framework instance. The following code snippet illustrates one possible
809approach:</p>
810
811<div class="code"><div class="codeContent">
812<pre class="code-java"><span class="code-keyword">package</span> host.core;
813
814<span class="code-keyword">import</span> java.util.List;
815<span class="code-keyword">import</span> java.util.ArrayList;
816<span class="code-keyword">import</span> java.util.Map;
817<span class="code-keyword">import</span> host.service.command.Command;
818<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
819<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
820<span class="code-keyword">import</span> org.apache.felix.framework.util.StringMap;
821<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
822<span class="code-keyword">import</span> org.osgi.util.tracker.ServiceTracker;
823
824<span class="code-keyword">public</span> class HostApplication
825{
826 <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
827 <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
828 <span class="code-keyword">private</span> ServiceTracker m_tracker = <span class="code-keyword">null</span>;
829
830 <span class="code-keyword">public</span> HostApplication()
831 {
832 <span class="code-comment">// Create a <span class="code-keyword">case</span>-insensitive configuration property map.
833</span> Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
834 <span class="code-comment">// Configure the Felix instance to be embedded.
835</span> configMap.put(FelixConstants.EMBEDDED_EXECUTION_PROP, <span class="code-quote">"<span class="code-keyword">true</span>"</span>);
836 <span class="code-comment">// Add the bundle provided service <span class="code-keyword">interface</span> <span class="code-keyword">package</span> and the core OSGi
837</span> <span class="code-comment">// packages to be exported from the class path via the system bundle.
838</span> configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
839 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
840 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
841 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
842 <span class="code-quote">"org.osgi.service.url; version=1.0.0,"</span> +
843 <span class="code-quote">"host.service.command; version=1.0.0"</span>);
844 <span class="code-comment">// Explicitly specify the directory to use <span class="code-keyword">for</span> caching bundles.
845</span> configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
846
847 <span class="code-keyword">try</span>
848 {
849 <span class="code-comment">// Create host activator;
850</span> m_activator = <span class="code-keyword">new</span> HostActivator(m_lookupMap);
851 List list = <span class="code-keyword">new</span> ArrayList();
852 list.add(m_activator);
853
854 <span class="code-comment">// Now create an instance of the framework with
855</span> <span class="code-comment">// our configuration properties and activator.
856</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
857
858 <span class="code-comment">// Now start Felix instance.
859</span> m_felix.start();
860 }
861 <span class="code-keyword">catch</span> (Exception ex)
862 {
863 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
864 ex.printStackTrace();
865 }
866
867 m_tracker = <span class="code-keyword">new</span> ServiceTracker(
868 m_activator.getContext(), Command.class.getName(), <span class="code-keyword">null</span>);
869 m_tracker.open();
870 }
871
872 <span class="code-keyword">public</span> <span class="code-object">boolean</span> execute(<span class="code-object">String</span> name, <span class="code-object">String</span> commandline)
873 {
874 <span class="code-comment">// See <span class="code-keyword">if</span> any of the currently tracked command services
875</span> <span class="code-comment">// match the specified command name, <span class="code-keyword">if</span> so then execute it.
876</span> <span class="code-object">Object</span>[] services = m_tracker.getServices();
877 <span class="code-keyword">for</span> (<span class="code-object">int</span> i = 0; (services != <span class="code-keyword">null</span>) &amp;&amp; (i &lt; services.length); i++)
878 {
879 <span class="code-keyword">try</span>
880 {
881 <span class="code-keyword">if</span> (((Command) services[i]).getName().equals(name))
882 {
883 <span class="code-keyword">return</span> ((Command) services[i]).execute(commandline);
884 }
885 }
886 <span class="code-keyword">catch</span> (Exception ex)
887 {
888 <span class="code-comment">// Since the services returned by the tracker could become
889</span> <span class="code-comment">// invalid at any moment, we will <span class="code-keyword">catch</span> all exceptions, log
890</span> <span class="code-comment">// a message, and then ignore faulty services.
891</span> <span class="code-object">System</span>.err.println(ex);
892 }
893 }
894 <span class="code-keyword">return</span> <span class="code-keyword">false</span>;
895 }
896
897 <span class="code-keyword">public</span> void shutdownApplication()
898 {
899 <span class="code-comment">// Shut down the felix framework when stopping the
900</span> <span class="code-comment">// host application.
901</span> m_felix.shutdown();
902 }
903}</pre>
904</div></div>
905
906<p>The above example is overly simplistic with respect to concurrency
907issues and error conditions, but it demonstrates the overall approach
908for using bundle-provided services from the host application. Note, to
909compile the above code you will need to compile against the Felix
910framework and Felix OSGi compendium JAR files, since the <tt>ServiceTracker</tt> classes are included in the compendium JAR file, not the framework JAR file.</p>
911
912<p><a name="LaunchingandEmbeddingApacheFelix-servicereflection"></a></p>
913
914<h3><a name="LaunchingandEmbeddingApacheFelix-UsingBundleServicesviaReflection"></a>Using Bundle Services via Reflection</h3>
915
916<p>It possible for the host application to use services provided by
917bundles without having access to the service interface classes and thus
918not needing to put the service interface classes on the class path. To
919do this, the host application uses the same general approach to acquire
920the system bundle context object, which it can use to look up service
921objects. Using either an LDAP filter or the service interface class
922name, the host application can retrieve the service object and then use
923standard Java reflection to invoke methods on the service object.</p>
924
925<p><a name="LaunchingandEmbeddingApacheFelix-caveat"></a></p>
926
927<h1><a name="LaunchingandEmbeddingApacheFelix-Caveat"></a>Caveat</h1>
928
929<p>The code in this document has not been thoroughly tested or even
930compiled and may be out of date with respect to the current Felix
931source code. If you find errors please report them so the that they can
932be corrected.</p>
Karl Pauls7bca0de2007-09-16 20:38:10 +0000[diff] [blame]933
934<p><a name="LaunchingandEmbeddingApacheFelix-feedback"></a></p>
935
936<h2><a name="LaunchingandEmbeddingApacheFelix-Feedback"></a>Feedback</h2>
937
938<p>Subscribe to the Felix users mailing list by sending a message to <span class="nobr"><a href="mailto:users-subscribe@felix.apache.org" title="Send mail to users-subscribe@felix.apache.org" rel="nofollow">users-subscribe@felix.apache.org<sup><img class="rendericon" src="launching-and-embedding-apache-felix_files/mail_small.gif" alt="" align="absmiddle" border="0" height="12" width="13"></sup></a></span>; after subscribing, email questions or feedback to <span class="nobr"><a href="mailto:users@felix.apache.org" title="Send mail to users@felix.apache.org" rel="nofollow">users@felix.apache.org<sup><img class="rendericon" src="launching-and-embedding-apache-felix_files/mail_small.gif" alt="" align="absmiddle" border="0" height="12" width="13"></sup></a></span>.</p>
Richard S. Hall2cd5bed2007-07-16 20:32:41 +0000[diff] [blame]939 </div>
Karl Pauls7bca0de2007-09-16 20:38:10 +0000[diff] [blame]940
941</body></html>