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32<h1><a name="LaunchingandEmbeddingApacheFelix-LaunchingandEmbeddingApacheFelix"></a>Launching and Embedding Apache Felix</h1>
33
Richard S. Halld5860342008-01-30 15:08:32 +0000[diff] [blame]34<p><em>[This document is based on Felix 1.0.3.]</em></p>
Richard S. Hall5fcf4fa2008-01-27 18:03:10 +0000[diff] [blame]35
36<ul>
37 <li><a href="#LaunchingandEmbeddingApacheFelix-introduction" title="introduction on Launching and Embedding Apache Felix">Introduction</a></li>
38 <li><a href="#LaunchingandEmbeddingApacheFelix-overview" title="overview on Launching and Embedding Apache Felix">API Overview</a></li>
39 <li><a href="#LaunchingandEmbeddingApacheFelix-launching" title="launching on Launching and Embedding Apache Felix">Launching Felix</a>
40 <ul>
41 <li><a href="#LaunchingandEmbeddingApacheFelix-standardlauncher" title="standard-launcher on Launching and Embedding Apache Felix">Standard Felix Launcher</a></li>
42 <li><a href="#LaunchingandEmbeddingApacheFelix-customlauncher" title="custom-launcher on Launching and Embedding Apache Felix">Custom Felix Launcher</a></li>
43 </ul>
44 </li>
45 <li><a href="#LaunchingandEmbeddingApacheFelix-embedding" title="embedding on Launching and Embedding Apache Felix">Embedding Felix</a>
46 <ul>
47 <li><a href="#LaunchingandEmbeddingApacheFelix-configproperty" title="config-property on Launching and Embedding Apache Felix">Embedded Execution Configuration Property</a></li>
48 <li><a href="#LaunchingandEmbeddingApacheFelix-hostinteraction" title="host-interaction on Launching and Embedding Apache Felix">Host/Felix Interaction</a></li>
49 <li><a href="#LaunchingandEmbeddingApacheFelix-hostservices" title="host-services on Launching and Embedding Apache Felix">Providing Host Application Services</a></li>
50 <li><a href="#LaunchingandEmbeddingApacheFelix-hostserviceusage" title="host-service-usage on Launching and Embedding Apache Felix">Using Services Provided by Bundles</a>
51 <ul>
52 <li><a href="#LaunchingandEmbeddingApacheFelix-servicereflection" title="service-reflection on Launching and Embedding Apache Felix">Using Bundle Services via Reflection</a></li>
53 </ul>
54 </li>
55 </ul>
56 </li>
57 <li><a href="#LaunchingandEmbeddingApacheFelix-caveat" title="caveat on Launching and Embedding Apache Felix">Caveat</a></li>
58 <li><a href="#LaunchingandEmbeddingApacheFelix-feedback" title="feedback on Launching and Embedding Apache Felix">Feedback</a></li>
59</ul>
60
61
62<p><a name="LaunchingandEmbeddingApacheFelix-introduction"></a></p>
63
64<h1><a name="LaunchingandEmbeddingApacheFelix-Introduction"></a>Introduction</h1>
65
66<p>The Apache Felix OSGi framework is intended to be easily launchable
67and embeddable. For example, Felix avoids the use of system properties
68for configuration, since these are globals that can cause interference
69if multiple framework instances are created in the same VM. Felix is
70also implemented to multiplex singleton facilities, like the URL stream
71handler factory. The goal is to make it possible to use Felix in as
72many scenarios as possible; however, this is still just a goal. In
73other words, this is a work in progress and if any issues arise, it
74would be greatly appreciated if they are brought to the attention of
75the Felix community. The next section provides a Felix API overview,
76while the remainder of the document is divided into two sections, one
77focusing on how to launch Felix and one focusing on how to embed Felix
78into a host application.</p>
79
80<p><a name="LaunchingandEmbeddingApacheFelix-overview"></a></p>
81
82<h1><a name="LaunchingandEmbeddingApacheFelix-APIOverview"></a>API Overview</h1>
83
84<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>,
85that represents the framework at run time and appears like any other
86bundle in the list of installed bundles. To make this notion even more
87intuitive, the <tt>Felix</tt> class implements the <tt>org.osgi.framework.Bundle</tt> interface, which is reiterated here:</p>
88
89<div class="code"><div class="codeContent">
90<pre class="code-java"><span class="code-keyword">public</span> <span class="code-keyword">interface</span> Bundle
91{
92 <span class="code-keyword">public</span> BundleContext getBundleContext();
93 <span class="code-keyword">public</span> <span class="code-object">long</span> getBundleId();
94 <span class="code-keyword">public</span> URL getEntry(<span class="code-object">String</span> name);
95 <span class="code-keyword">public</span> Enumeration getEntryPaths(<span class="code-object">String</span> path);
96 <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);
97 <span class="code-keyword">public</span> Dictionary getHeaders();
98 <span class="code-keyword">public</span> Dictionary getHeaders(<span class="code-object">String</span> locale);
99 <span class="code-keyword">public</span> <span class="code-object">long</span> getLastModified();
100 <span class="code-keyword">public</span> <span class="code-object">String</span> getLocation();
101 <span class="code-keyword">public</span> URL getResource(<span class="code-object">String</span> name);
102 <span class="code-keyword">public</span> Enumeration getResources(<span class="code-object">String</span> name) <span class="code-keyword">throws</span> IOException;
103 <span class="code-keyword">public</span> ServiceReference[] getRegisteredServices();
104 <span class="code-keyword">public</span> ServiceReference[] getServicesInUse();
105 <span class="code-keyword">public</span> <span class="code-object">int</span> getState();
106 <span class="code-keyword">public</span> <span class="code-object">String</span> getSymbolicName();
107 <span class="code-keyword">public</span> <span class="code-object">boolean</span> hasPermission(<span class="code-object">Object</span> obj);
108 <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;
109 <span class="code-keyword">public</span> void start() <span class="code-keyword">throws</span> BundleException;
110 <span class="code-keyword">public</span> void stop() <span class="code-keyword">throws</span> BundleException;
111 <span class="code-keyword">public</span> void uninstall() <span class="code-keyword">throws</span> BundleException;
112 <span class="code-keyword">public</span> void update() <span class="code-keyword">throws</span> BundleException;
113 <span class="code-keyword">public</span> void update(InputStream is) <span class="code-keyword">throws</span> BundleException;
114}</pre>
115</div></div>
116
117<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 three additional public methods:</p>
118
119<div class="code"><div class="codeContent">
120<pre class="code-java"><span class="code-keyword">public</span> class Felix <span class="code-keyword">extends</span> FelixBundle
121{
122 <span class="code-keyword">public</span> Felix(Map configMutableMap, List activatorList);
123 <span class="code-keyword">public</span> Felix(Logger logger, Map configMutableMap, List activatorList)
124 <span class="code-keyword">public</span> void stopAndWait();
125}</pre>
126</div></div>
127
128<p>The first two methods are constructors used to instantiate framework
129instances; the important parameters of the constructors are the
130configuration properties and System Bundle activators, which are both
131described 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>
132
133<p><a name="LaunchingandEmbeddingApacheFelix-launching"></a></p>
134
135<h1><a name="LaunchingandEmbeddingApacheFelix-LaunchingFelix"></a>Launching Felix</h1>
136
137<p>Launching Felix is fairly simple and involves only three steps:</p>
138
139<ol>
140 <li>Defining some configuration properties.</li>
141 <li>Creating an instance of <tt>org.apache.felix.framework.Felix</tt> with the configuration properties.</li>
142 <li>Invoking the <tt>org.apache.felix.framework.Felix.start()</tt> method.</li>
143</ol>
144
145
146<p>The only configuration properties that are actually required to
147start Felix are ones that tell it where/how to locate the bundle cache
148profile directory where installed bundles will be cached. Felix' bundle
149cache implementation allows you to configure the location where bundles
150are cached using configuration properties. At a minimum, either a
151bundle cache profile name or directory must be specified; see the <a href="http://cwiki.apache.org/FELIX/apache-felix-bundle-cache.html" title="Apache Felix Bundle Cache">bundle cache document</a> for more detailed information on configuring the bundle cache.</p>
152
153<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>)
154on which all bundles depend. If you are creating a launcher for Felix,
155then often you want to automatically install and start bundles when you
156start the framework instance. The default Felix launcher defines
157reusable functionality to automatically install and/or start bundles
158upon framework startup; see the <a href="http://cwiki.apache.org/FELIX/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>
159
160<p>The remainder of this section describes how the standard Felix
161launcher works as well as how to create a custom launcher for Felix.</p>
162
163<p><a name="LaunchingandEmbeddingApacheFelix-standardlauncher"></a></p>
164
165<h2><a name="LaunchingandEmbeddingApacheFelix-StandardFelixLauncher"></a>Standard Felix Launcher</h2>
166
167<p>The standard Felix launcher is very simple and is not intended to
168solve every possible requirement; it is intended to work for most
169standard situations. Most special launching requirements should be
170resolved by creating a custom launcher. This section describes how the
171standard 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>
172
173<div class="code"><div class="codeContent">
174<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
175{
176 <span class="code-comment">// (1) Load system properties.
177</span> Main.loadSystemProperties();
178
179 <span class="code-comment">// (2) Read configuration properties.
180</span> Properties configProps = Main.loadConfigProperties();
181
182 <span class="code-comment">// (3) Copy framework properties from the system properties.
183</span> Main.copySystemProperties(configProps);
184
185 <span class="code-comment">// (4) See <span class="code-keyword">if</span> the profile name property was specified.
186</span> <span class="code-object">String</span> profileName = configProps.getProperty(BundleCache.CACHE_PROFILE_PROP);
187
188 <span class="code-comment">// (4) See <span class="code-keyword">if</span> the profile directory property was specified.
189</span> <span class="code-object">String</span> profileDirName = configProps.getProperty(BundleCache.CACHE_PROFILE_DIR_PROP);
190
191 <span class="code-comment">// Print welcome banner.
192</span> <span class="code-object">System</span>.out.println(<span class="code-quote">"\nWelcome to Felix."</span>);
193 <span class="code-object">System</span>.out.println(<span class="code-quote">"=================\n"</span>);
194
195 <span class="code-comment">// (5) If no profile or profile directory is specified in the
196</span> <span class="code-comment">// properties, then ask <span class="code-keyword">for</span> a profile name.
197</span> <span class="code-keyword">if</span> ((profileName == <span class="code-keyword">null</span>) &amp;&amp; (profileDirName == <span class="code-keyword">null</span>))
198 {
199 <span class="code-object">System</span>.out.print(<span class="code-quote">"Enter profile name: "</span>);
200 BufferedReader in = <span class="code-keyword">new</span> BufferedReader(<span class="code-keyword">new</span> InputStreamReader(<span class="code-object">System</span>.in));
201 <span class="code-keyword">try</span>
202 {
203 profileName = in.readLine();
204 }
205 <span class="code-keyword">catch</span> (IOException ex)
206 {
207 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not read input."</span>);
208 <span class="code-object">System</span>.exit(-1);
209 }
210 <span class="code-object">System</span>.out.println("");
211 <span class="code-keyword">if</span> (profileName.length() != 0)
212 {
213 configProps.setProperty(BundleCache.CACHE_PROFILE_PROP, profileName);
214 }
215 }
216
217 <span class="code-comment">// (6) A profile directory or name must be specified.
218</span> <span class="code-keyword">if</span> ((profileDirName == <span class="code-keyword">null</span>) &amp;&amp; (profileName.length() == 0))
219 {
220 <span class="code-object">System</span>.err.println(<span class="code-quote">"You must specify a profile name or directory."</span>);
221 <span class="code-object">System</span>.exit(-1);
222 }
223
224 <span class="code-keyword">try</span>
225 {
226 <span class="code-comment">// (7) Create a list <span class="code-keyword">for</span> custom framework activators and
227</span> <span class="code-comment">// add an instance of the auto-activator it <span class="code-keyword">for</span> processing
228</span> <span class="code-comment">// auto-install and auto-start properties.
229</span> List list = <span class="code-keyword">new</span> ArrayList();
230 list.add(<span class="code-keyword">new</span> AutoActivator(configProps));
231 <span class="code-comment">// (8) Create a <span class="code-keyword">case</span>-insensitive property map.
232</span> Map configMap = <span class="code-keyword">new</span> StringMap(configProps, <span class="code-keyword">false</span>);
233 <span class="code-comment">// (9) Create an instance of the framework.
234</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
235 m_felix.start();
236 }
237 <span class="code-keyword">catch</span> (Exception ex)
238 {
239 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
240 ex.printStackTrace();
241 <span class="code-object">System</span>.exit(-1);
242 }
243}</pre>
244</div></div>
245
246<p>The general steps of the standard launcher are quite straightforward:</p>
247
248<ol>
249 <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>
250system property. This file is not needed to launch Felix and is
251provided merely for convenience when system properties must be
252specified. The file is a standard Java properties file, but it also
253supports property substitution using <tt>${&lt;property-name</tt>} syntax. Property substitution can be nested; only system properties will be used for substitution.</li>
254 <li>Load any configuration properties specified in the <tt>config.properties</tt> file; this file is typically located in the <tt>conf/</tt> directory of the Felix installation directory, but it can be specified directly using the <tt>felix.config.properties</tt>
255system property. This file is used to configure the Felix instance
256created by the launcher. The file is a standard Java properties file,
257but it also supports property substitution using "<tt>${&lt;property-name</tt>}"
258syntax. Property substitution can be nested; configuration and system
259properties will be used for substitution with configuration properties
260having precedence.</li>
261 <li>For convenience, any configuration
262properties that are set as system properties will be copied into the
263set of configuration properties to provide an easy way to add to or
264override configuration properties specified in the <tt>config.properties</tt> file.</li>
265 <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://cwiki.apache.org/FELIX/apache-felix-bundle-cache.html" title="Apache Felix Bundle Cache">bundle cache</a> knows where to save installed bundles.</li>
266 <li>If
267either the profile name or profile directory configuration property has
268not been specified, then ask the user to specify a profile name and add
269it to the current set of configuration properties.</li>
270 <li>Error if there is no profile name or profile directory.</li>
271 <li>Create a list to hold custom framework activators and add an instance of <tt>org.apache.felix.main.AutoActivator</tt>, which will process <tt>felix.auto.install</tt> and <tt>felix.auto.start</tt> configuration properties during framework startup to automatically install and/or start bundles; see the <a href="http://cwiki.apache.org/FELIX/apache-felix-usage-documentation.html#ApacheFelixUsageDocumentation-configuringfelix" title="configuring-felix on Apache Felix Usage Documentation">usage document</a> for more information configuration properties.</li>
272 <li>Create a case-insensitive map to hold our configuration properties.</li>
273 <li>Create the Felix instance passing in the configuration properties and custom framework activators, then call <tt>start()</tt>.</li>
274</ol>
275
276
277<p>The framework is not active until the <tt>start()</tt> method is
278called. If no shell bundles are installed and started or if there is
279difficulty locating the shell bundles specified in the auto-start
280property, then it will appear as if the framework is hung, but it is
281actually running without any way to interact with it since the shell
282bundles provide the only means of interaction.</p>
283
284<p><a name="LaunchingandEmbeddingApacheFelix-customlauncher"></a></p>
285
286<h2><a name="LaunchingandEmbeddingApacheFelix-CustomFelixLauncher"></a>Custom Felix Launcher</h2>
287
288<p>This section creates a bare-bones launcher to demonstrate the
289minimum requirements for creating an interactive launcher for the Felix
290framework. This example uses the standard Felix shell bundles for
291interactivity, but any other bundles could be used instead. For
292example, the shell service and telnet bundles could be used to launch
293Felix and make it remotely accessible.</p>
294
295<p>This example launcher project has the following directory structure:</p>
296
297<div class="preformatted"><div class="preformattedContent">
298<pre>launcher/
299 lib/
Richard S. Halld5860342008-01-30 15:08:32 +0000[diff] [blame]300 org.apache.felix.main-1.0.3.jar
Richard S. Hall5fcf4fa2008-01-27 18:03:10 +0000[diff] [blame]301 bundle/
302 org.apache.felix.shell-1.0.0.jar
303 org.apache.felix.shell.tui-1.0.0.jar
304 src/
305 example/
306 Main.java
307</pre>
308</div></div>
309
310<p>The <tt>lib/</tt> directory contains Felix' main JAR file, which
311also contains the OSGi core interfaces. The main JAR file is used so
312that we can reuse the default launcher's auto-install/auto-start
313configuration property handling; if these capabilities are needed, then
314it would be possible to use the framework JAR file. The <tt>bundle/</tt>
315directory contains the shell service and textual shell interface
316bundles that will be used for interacting with the framework instance.
317Note: If you do not launch Felix with interactive bundles, it will
318appear as if the framework instance is hung, but it is actually just
319sitting 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>
320
321<div class="code"><div class="codeContent">
322<pre class="code-java"><span class="code-keyword">package</span> example;
323
324<span class="code-keyword">import</span> java.util.Map;
325<span class="code-keyword">import</span> org.osgi.framework.Constants;
326<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
327<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
328<span class="code-keyword">import</span> org.apache.felix.framework.util.StringMap;
Richard S. Hall5fcf4fa2008-01-27 18:03:10 +0000[diff] [blame]329<span class="code-keyword">import</span> org.apache.felix.framework.main.AutoActivator;
330
331<span class="code-keyword">public</span> class Main
332{
333 <span class="code-keyword">private</span> <span class="code-keyword">static</span> Felix m_felix = <span class="code-keyword">null</span>;
334
335 <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
336 {
337 <span class="code-comment">// Print welcome banner.
338</span> <span class="code-object">System</span>.out.println(<span class="code-quote">"\nWelcome to Felix."</span>);
339 <span class="code-object">System</span>.out.println(<span class="code-quote">"=================\n"</span>);
340
341 Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
342 configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
343 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
344 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
345 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
346 <span class="code-quote">"org.osgi.service.url; version=1.0.0"</span>);
Richard S. Halld5860342008-01-30 15:08:32 +0000[diff] [blame]347 configMap.put(AutoActivator.AUTO_START_PROP + <span class="code-quote">".1"</span>,
Richard S. Hall5fcf4fa2008-01-27 18:03:10 +0000[diff] [blame]348 <span class="code-quote">"file:bundle/org.apache.felix.shell-1.0.0.jar "</span> +
349 <span class="code-quote">"file:bundle/org.apache.felix.shell.tui-1.0.0.jar"</span>);
350 configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
351
352 <span class="code-keyword">try</span>
353 {
354 List list = <span class="code-keyword">new</span> ArrayList();
355 list.add(<span class="code-keyword">new</span> AutoActivator(configProps));
356 Map configMap = <span class="code-keyword">new</span> StringMap(configProps, <span class="code-keyword">false</span>);
357 m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
358 m_felix.start();
359 }
360 <span class="code-keyword">catch</span> (Exception ex)
361 {
362 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
363 ex.printStackTrace();
364 <span class="code-object">System</span>.exit(-1);
365 }
366 }
367}</pre>
368</div></div>
369
370<p>This launcher has all information hard coded in it, unlike the
371default Felix launcher, which loads configuration properties from files
372and performs variable substitution. This simple launcher provides a
373good starting point if the features of the default launcher are not
374necessary. For example, if you want to create a launcher that
375automatically deletes the bundle cache directory each time it starts,
376then it is quite easy to figure out how to do that with this simple
377launcher.</p>
378
379<p>By breaking down the above source code into small chunks, it is quite easy to see what is going on.</p>
380
381<div class="code"><div class="codeContent">
382<pre class="code-java">Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);</pre>
383</div></div>
384
385<p>This simply creates a map to hold configuration properties where the keys are strings and lookups are case insensitive.</p>
386
387<div class="code"><div class="codeContent">
388<pre class="code-java">configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
389 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
390 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
391 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
392 <span class="code-quote">"org.osgi.service.url; version=1.0.0"</span>);</pre>
393</div></div>
394
395<p>This sets the <tt>Constants.FRAMEWORK_SYSTEMPACKAGES</tt> configuration property (string value "<tt>org.osgi.framework.system.packages</tt>"),
396which specifies the class path packages the system bundle should
397export; this is how classes on the class path are made available to
398bundles. This example only exports the core OSGi API packages, but
399other JRE packages could also be added, such as <tt>javax.swing</tt>.
400For example, the default Felix launcher defines properties for all
401packages in various JRE versions (e.g., 1.3.x, 1.4.x, 1.5.x) and
402appends them to this property using property substitution.</p>
403
404<div class="code"><div class="codeContent">
Richard S. Halld5860342008-01-30 15:08:32 +0000[diff] [blame]405<pre class="code-java">configMap.put(AutoActivator.AUTO_START_PROP + <span class="code-quote">".1"</span>,
Richard S. Hall5fcf4fa2008-01-27 18:03:10 +0000[diff] [blame]406 <span class="code-quote">"file:bundle/org.apache.felix.shell-1.0.0.jar "</span> +
407 <span class="code-quote">"file:bundle/org.apache.felix.shell.tui-1.0.0.jar"</span>);</pre>
408</div></div>
409
Richard S. Halld5860342008-01-30 15:08:32 +0000[diff] [blame]410<p>This sets the <tt>AutoActivator.AUTO_START_PROP</tt> configuration property (string value "<tt>felix.auto.start</tt>"),
Richard S. Hall5fcf4fa2008-01-27 18:03:10 +0000[diff] [blame]411which is a space-delimited list of bundle URLs that the framework will
412automatically install and start when the framework starts. However,
413this property key cannot be used as is; it must be appended with a "."
414and then a number, where the number represents the start level for the
415bundle when it is installed. In this particular example, ".1" is
416appended to the property name, thus the two bundles will be installed
417into start level one. This example uses relative <tt>file:</tt> URLs, which will load the bundles from the <tt>bundle/</tt>
418directory assuming that the launcher is started from the root directory
419of the launcher project. It is also possible to specify absolute URLs
420or remote URLs.</p>
421
422<div class="code"><div class="codeContent">
423<pre class="code-java">configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);</pre>
424</div></div>
425
426<p>This sets the last configuration property, <tt>BundleCache.CACHE_PROFILE_DIR_PROP</tt> (string value "<tt>felix.cache.profiledir</tt>"),
427which is a string that specifies the precise directory to be used as
428the bundle cache profile directory; the Felix bundle cache supports
429other properties to configure its behavior, but those are not covered
430here. In this example, the bundle cache profile directory is specified
431as a relative directory called "<tt>cache</tt>". Assuming that the
432launcher is executed from the root directory of the launcher project,
433then the bundle cache profile directory will be created in the root
434directory of the project.</p>
435
436<div class="code"><div class="codeContent">
437<pre class="code-java">List list = <span class="code-keyword">new</span> ArrayList();
438 list.add(<span class="code-keyword">new</span> AutoActivator(configProps));</pre>
439</div></div>
440
441<p>This above creates a list to hold custom framework activators and adds an instance of <tt>org.apache.felix.main.AutoActivator</tt> to it, which will process the auto-install and auto-start configuration properties during framework startup.</p>
442
443<div class="code"><div class="codeContent">
444<pre class="code-java">Map configMap = <span class="code-keyword">new</span> StringMap(configProps, <span class="code-keyword">false</span>);</pre>
445</div></div>
446
447<p>This above creates a case-insensitive map from the configuration
448properties, since the OSGi specification says that properties are not
449case sensitive.</p>
450
451<div class="code"><div class="codeContent">
452<pre class="code-java">m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
453 m_felix.start();</pre>
454</div></div>
455
456<p>These last steps create the framework instance and start it. The
457configuration property map and custom framework activator list are
458passed into the <tt>Felix</tt> constructor.</p>
459
460<p>The following command compiles the launcher when run from the root directory of the launcher project:</p>
461
462<div class="preformatted"><div class="preformattedContent">
463<pre>javac -d . -classpath lib/org.apache.felix.main-1.0.2.jar src/example/Main.java
464</pre>
465</div></div>
466
467<p>After executing this command, an <tt>example/</tt> directory is
468created in the current directory, which contains the generated class
469file. The following command executes the simple launcher when run from
470the root directory of the launcher project:</p>
471
472<div class="preformatted"><div class="preformattedContent">
473<pre>java -cp .:lib/org.apache.felix.main-1.0.2.jar example.Main
474</pre>
475</div></div>
476
477<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>
478
479<p><a name="LaunchingandEmbeddingApacheFelix-embedding"></a></p>
480
481<h1><a name="LaunchingandEmbeddingApacheFelix-EmbeddingFelix"></a>Embedding Felix</h1>
482
483<p>Embedding Felix into a host application is a simple way to provide a
484sophisticated extensibility mechanism (i.e., plugin system) to the host
485application. Embedding Felix is very similar to launching Felix as
486described above, the main difference is that the host application
487typically wants to interact with the framework instance and/or
488installed bundles/services from the outside. This is fairly easy to
489achieve with Felix, but there are some subtle issues to understand.
490This section presents the mechanisms for embedding Felix into a host
491application and the issues in doing so.</p>
492
493<p><a name="LaunchingandEmbeddingApacheFelix-configproperty"></a></p>
494
495<h2><a name="LaunchingandEmbeddingApacheFelix-EmbeddedExecutionConfigurationProperty"></a>Embedded Execution Configuration Property</h2>
496
497<p>When a Felix instance is embedded in a host application, the host
498application must inform the Felix instance that it is embedded. To do
499this, the host application sets the "<tt>felix.embedded.execution</tt>" configuration property to "<tt>true</tt>";
500this can be accomplished in the same way that all configuration
501properties are set, i.e., passing it into the Felix constructor via a
502map. This property specifically controls whether or not the Felix
503instance will shutdown the JVM (i.e., call <tt>System.exit()</tt>)
504when the framework is shutdown. When embedding Felix it is generally
505not desirable for Felix to shutdown the JVM; therefore, by setting this
506property to "<tt>true</tt>" it can be avoided.</p>
507
508<p><a name="LaunchingandEmbeddingApacheFelix-hostinteraction"></a></p>
509
510<h2><a name="LaunchingandEmbeddingApacheFelix-Host/FelixInteraction"></a>Host/Felix Interaction</h2>
511
512<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>
513constructor accepts two arguments, the first being the configuration
514properties for the framework, the second being a list of bundle
515activator instances. These bundle activator instances provide a
516convenient way for host applications to interact with the Felix
517framework.</p>
518
519<p>Each bundle activator instance passed into the constructor
520effectively becomes part of the System Bundle. This means that the
521start()/stop() method of each bundle activator instance in the passed
522in list gets invoked when the System Bundle's activator start()/stop()
523method gets invoked. Consequently, each bundle activator instance will
524be 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>,
525this is generally not as convenient since it requires that you monitor
526when the System Bundle starts and/or stops. Consider following snippet
527of a bundle activator:</p>
528
529<div class="code"><div class="codeContent">
530<pre class="code-java"><span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
531{
532 <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
533
534 <span class="code-keyword">public</span> void start(BundleContext context)
535 {
536 m_context = context;
537 }
538
539 <span class="code-keyword">public</span> void stop(BundleContext context)
540 {
541 m_context = <span class="code-keyword">null</span>;
542 }
543
544 <span class="code-keyword">public</span> Bundle[] getBundles()
545 {
546 <span class="code-keyword">if</span> (m_context != <span class="code-keyword">null</span>)
547 {
548 <span class="code-keyword">return</span> m_context.getBundles();
549 }
550 <span class="code-keyword">return</span> <span class="code-keyword">null</span>;
551 }
552}</pre>
553</div></div>
554
555<p>Given the above bundle activator, it is now possible to embed Felix
556into a host application and interact with it as the following snippet
557illustrates:</p>
558
559<div class="code"><div class="codeContent">
560<pre class="code-java"><span class="code-keyword">public</span> class HostApplication
561{
562 <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
563 <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
564
565 <span class="code-keyword">public</span> HostApplication()
566 {
567 <span class="code-comment">// Create a <span class="code-keyword">case</span>-insensitive configuration property map.
568</span> Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
569 <span class="code-comment">// Configure the Felix instance to be embedded.
570</span> configMap.put(FelixConstants.EMBEDDED_EXECUTION_PROP, <span class="code-quote">"<span class="code-keyword">true</span>"</span>);
571 <span class="code-comment">// Add core OSGi packages to be exported from the class path
572</span> <span class="code-comment">// via the system bundle.
573</span> configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
574 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
575 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
576 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
577 <span class="code-quote">"org.osgi.service.url; version=1.0.0"</span>);
578 <span class="code-comment">// Explicitly specify the directory to use <span class="code-keyword">for</span> caching bundles.
579</span> configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
580
581 <span class="code-keyword">try</span>
582 {
583 <span class="code-comment">// Create host activator;
584</span> m_activator = <span class="code-keyword">new</span> HostActivator();
585 List list = <span class="code-keyword">new</span> ArrayList();
586 list.add(m_activator);
587
588 <span class="code-comment">// Now create an instance of the framework with
589</span> <span class="code-comment">// our configuration properties and activator.
590</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
591
592 <span class="code-comment">// Now start Felix instance.
593</span> m_felix.start();
594 }
595 <span class="code-keyword">catch</span> (Exception ex)
596 {
597 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
598 ex.printStackTrace();
599 }
600 }
601
602 <span class="code-keyword">public</span> Bundle[] getInstalledBundles()
603 {
604 <span class="code-comment">// Use the system bundle activator to gain external
605</span> <span class="code-comment">// access to the set of installed bundles.
606</span> <span class="code-keyword">return</span> m_activator.getBundles();
607 }
608
609 <span class="code-keyword">public</span> void shutdownApplication()
610 {
611 <span class="code-comment">// Shut down the felix framework when stopping the
612</span> <span class="code-comment">// host application.
613</span> m_felix.shutdown();
614 }
615}</pre>
616</div></div>
617
618<p>Notice how the <tt>HostApplication.getInstalledBundles()</tt> method
619uses its activator instance to get access to the System Bundle's
620context in order to interact with the embedded Felix framework
621instance. This approach provides the foundation for all interaction
622between the host application and the embedded framework instance.</p>
623
624<p><a name="LaunchingandEmbeddingApacheFelix-hostservices"></a></p>
625
626<h2><a name="LaunchingandEmbeddingApacheFelix-ProvidingHostApplicationServices"></a>Providing Host Application Services</h2>
627
628<p>Providing services from the host application to bundles inside the
629embedded Felix framework instance follows the basic approach laid out
630in <a href="#LaunchingandEmbeddingApacheFelix-hostinteraction" title="host-interaction on Launching and Embedding Apache Felix">above</a>.
631The main complication for providing a host application service to
632bundles is the fact that both the host application and the bundles must
633be using the same class definitions for the service interface classes.
634Since the host application cannot import classes from a bundle, this
635means that the service interface classes <b>must</b> be accessible on
636the class path, typically as part of the host application itself. The
637host application then must export the service interface package via the
638system bundle so that bundles installed into the embedded framework
639instance can import it. This is achieved using the <tt>org.osgi.framework.system.packages</tt> configuration property previously presented.</p>
640
641<p>Consider the follow simple property lookup service:</p>
642
643<div class="code"><div class="codeContent">
644<pre class="code-java"><span class="code-keyword">package</span> host.service.lookup;
645
646<span class="code-keyword">public</span> class Lookup
647{
648 <span class="code-keyword">public</span> <span class="code-object">Object</span> lookup(<span class="code-object">String</span> name);
649}</pre>
650</div></div>
651
652<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>"
653command. Now consider the following host application bundle activator,
654which will be used to register/unregister the property lookup service
655when the embedded framework instance starts/stops:</p>
656
657<div class="code"><div class="codeContent">
658<pre class="code-java"><span class="code-keyword">package</span> host.core;
659
660<span class="code-keyword">import</span> java.util.Map;
661<span class="code-keyword">import</span> org.osgi.framework.BundleActivator;
662<span class="code-keyword">import</span> org.osgi.framework.BundleContext;
663<span class="code-keyword">import</span> org.osgi.framework.ServiceRegistration;
664<span class="code-keyword">import</span> host.service.lookup;
665
666<span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
667{
668 <span class="code-keyword">private</span> Map m_lookupMap = <span class="code-keyword">null</span>;
669 <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
670 <span class="code-keyword">private</span> ServiceRegistration m_registration = <span class="code-keyword">null</span>;
671
672 <span class="code-keyword">public</span> HostActivator(Map lookupMap)
673 {
674 <span class="code-comment">// Save a reference to the service's backing store.
675</span> m_lookupMap = lookupMap;
676 }
677
678 <span class="code-keyword">public</span> void start(BundleContext context)
679 {
680 <span class="code-comment">// Save a reference to the bundle context.
681</span> m_context = context;
682 <span class="code-comment">// Create a property lookup service implementation.
683</span> Lookup lookup = <span class="code-keyword">new</span> Lookup() {
684 <span class="code-keyword">public</span> <span class="code-object">Object</span> lookup(<span class="code-object">String</span> name)
685 {
686 <span class="code-keyword">return</span> m_lookupMap.get(name);
687 }
688 };
689 <span class="code-comment">// Register the property lookup service and save
690</span> <span class="code-comment">// the service registration.
691</span> m_registration = m_context.registerService(
692 Lookup.class.getName(), lookup, <span class="code-keyword">null</span>);
693 }
694
695 <span class="code-keyword">public</span> void stop(BundleContext context)
696 {
697 <span class="code-comment">// Unregister the property lookup service.
698</span> m_registration.unregister();
699 m_context = <span class="code-keyword">null</span>;
700 }
701}</pre>
702</div></div>
703
704<p>Given the above host application bundle activator, the following
705code snippet shows how the host application could create an embedded
706version of the Felix framework and provide the property lookup service
707to installed bundles:</p>
708
709<div class="code"><div class="codeContent">
710<pre class="code-java"><span class="code-keyword">package</span> host.core;
711
712<span class="code-keyword">import</span> java.util.List;
713<span class="code-keyword">import</span> java.util.ArrayList;
714<span class="code-keyword">import</span> java.util.Map;
715<span class="code-keyword">import</span> java.util.HashMap;
716<span class="code-keyword">import</span> host.service.lookup.Lookup;
717<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
718<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
719<span class="code-keyword">import</span> org.apache.felix.framework.util.StringMap;
720<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
721
722<span class="code-keyword">public</span> class HostApplication
723{
724 <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
725 <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
726 <span class="code-keyword">private</span> Map m_lookupMap = <span class="code-keyword">new</span> HashMap();
727
728 <span class="code-keyword">public</span> HostApplication()
729 {
730 <span class="code-comment">// Initialize the map <span class="code-keyword">for</span> the property lookup service.
731</span> m_lookupMap.put(<span class="code-quote">"name1"</span>, <span class="code-quote">"value1"</span>);
732 m_lookupMap.put(<span class="code-quote">"name2"</span>, <span class="code-quote">"value2"</span>);
733 m_lookupMap.put(<span class="code-quote">"name3"</span>, <span class="code-quote">"value3"</span>);
734 m_lookupMap.put(<span class="code-quote">"name4"</span>, <span class="code-quote">"value4"</span>);
735
736 <span class="code-comment">// Create a <span class="code-keyword">case</span>-insensitive configuration property map.
737</span> Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
738 <span class="code-comment">// Configure the Felix instance to be embedded.
739</span> configMap.put(FelixConstants.EMBEDDED_EXECUTION_PROP, <span class="code-quote">"<span class="code-keyword">true</span>"</span>);
740 <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
741</span> <span class="code-comment">// packages to be exported from the class path via the system bundle.
742</span> configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
743 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
744 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
745 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
746 <span class="code-quote">"org.osgi.service.url; version=1.0.0,"</span> +
747 <span class="code-quote">"host.service.lookup; version=1.0.0"</span>);
748 <span class="code-comment">// Explicitly specify the directory to use <span class="code-keyword">for</span> caching bundles.
749</span> configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
750
751 <span class="code-keyword">try</span>
752 {
753 <span class="code-comment">// Create host activator;
754</span> m_activator = <span class="code-keyword">new</span> HostActivator(m_lookupMap);
755 List list = <span class="code-keyword">new</span> ArrayList();
756 list.add(m_activator);
757
758 <span class="code-comment">// Now create an instance of the framework with
759</span> <span class="code-comment">// our configuration properties and activator.
760</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
761
762 <span class="code-comment">// Now start Felix instance.
763</span> m_felix.start();
764 }
765 <span class="code-keyword">catch</span> (Exception ex)
766 {
767 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
768 ex.printStackTrace();
769 }
770 }
771
772 <span class="code-keyword">public</span> void shutdownApplication()
773 {
774 <span class="code-comment">// Shut down the felix framework when stopping the
775</span> <span class="code-comment">// host application.
776</span> m_felix.shutdown();
777 }
778}</pre>
779</div></div>
780
781<p>Rather than having the host application bundle activator register
782the service, it is also possible for the the host application to simply
783get the bundle context from the bundle activator and register the
784service directly, but the presented approach is perhaps a little
785cleaner since it allows the host application to register/unregister the
786service when the system bundle starts/stops.</p>
787
788<p><a name="LaunchingandEmbeddingApacheFelix-hostserviceusage"></a></p>
789
790<h2><a name="LaunchingandEmbeddingApacheFelix-UsingServicesProvidedbyBundles"></a>Using Services Provided by Bundles</h2>
791
792<p>Using services provided by bundles follows the same general approach
793of using a host application bundle activator. The main complication for
794the host application using a service from a bundle is the fact that
795both the host application and the bundle must be using the same class
796definitions for the service interface classes. Since the host
797application cannot import classes from a bundle, this means that the
798service interface classes <b>must</b> be accessible on the class path,
799typically as part of the host application itself. The host application
800then must export the service interface package via the system bundle so
801that bundles installed into the embedded framework instance can import
802it. This is achieved using the <tt>org.osgi.framework.system.packages</tt> configuration property previously presented.</p>
803
804<p>Consider the following simple command service interface for which
805bundles provide implementations, such as might be used to create an
806extensible interactive shell:</p>
807
808<div class="code"><div class="codeContent">
809<pre class="code-java"><span class="code-keyword">package</span> host.service.command;
810
811<span class="code-keyword">public</span> class Command
812{
813 <span class="code-keyword">public</span> <span class="code-object">String</span> getName();
814 <span class="code-keyword">public</span> <span class="code-object">String</span> getDescription();
815 <span class="code-keyword">public</span> <span class="code-object">boolean</span> execute(<span class="code-object">String</span> commandline);
816}</pre>
817</div></div>
818
819<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>"
820command. Now consider the previously introduced host application bundle
821activator below, which simply provides access to the system bundle
822context:</p>
823
824<div class="code"><div class="codeContent">
825<pre class="code-java"><span class="code-keyword">package</span> host.core;
826
827<span class="code-keyword">import</span> org.osgi.framework.BundleActivator;
828<span class="code-keyword">import</span> org.osgi.framework.BundleContext;
829
830<span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
831{
832 <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
833
834 <span class="code-keyword">public</span> void start(BundleContext context)
835 {
836 m_context = context;
837 }
838
839 <span class="code-keyword">public</span> void stop(BundleContext context)
840 {
841 m_context = <span class="code-keyword">null</span>;
842 }
843
844 <span class="code-keyword">public</span> BundleContext getContext()
845 {
846 <span class="code-keyword">return</span> m_context;
847 }
848}</pre>
849</div></div>
850
851<p>With this bundle activator, the host application can command
852services provided by bundles installed inside its embedded Felix
853framework instance. The following code snippet illustrates one possible
854approach:</p>
855
856<div class="code"><div class="codeContent">
857<pre class="code-java"><span class="code-keyword">package</span> host.core;
858
859<span class="code-keyword">import</span> java.util.List;
860<span class="code-keyword">import</span> java.util.ArrayList;
861<span class="code-keyword">import</span> java.util.Map;
862<span class="code-keyword">import</span> host.service.command.Command;
863<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
864<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
865<span class="code-keyword">import</span> org.apache.felix.framework.util.StringMap;
866<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
867<span class="code-keyword">import</span> org.osgi.util.tracker.ServiceTracker;
868
869<span class="code-keyword">public</span> class HostApplication
870{
871 <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
872 <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
873 <span class="code-keyword">private</span> ServiceTracker m_tracker = <span class="code-keyword">null</span>;
874
875 <span class="code-keyword">public</span> HostApplication()
876 {
877 <span class="code-comment">// Create a <span class="code-keyword">case</span>-insensitive configuration property map.
878</span> Map configMap = <span class="code-keyword">new</span> StringMap(<span class="code-keyword">false</span>);
879 <span class="code-comment">// Configure the Felix instance to be embedded.
880</span> configMap.put(FelixConstants.EMBEDDED_EXECUTION_PROP, <span class="code-quote">"<span class="code-keyword">true</span>"</span>);
881 <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
882</span> <span class="code-comment">// packages to be exported from the class path via the system bundle.
883</span> configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES,
884 <span class="code-quote">"org.osgi.framework; version=1.3.0,"</span> +
885 <span class="code-quote">"org.osgi.service.packageadmin; version=1.2.0,"</span> +
886 <span class="code-quote">"org.osgi.service.startlevel; version=1.0.0,"</span> +
887 <span class="code-quote">"org.osgi.service.url; version=1.0.0,"</span> +
888 <span class="code-quote">"host.service.command; version=1.0.0"</span>);
889 <span class="code-comment">// Explicitly specify the directory to use <span class="code-keyword">for</span> caching bundles.
890</span> configMap.put(BundleCache.CACHE_PROFILE_DIR_PROP, <span class="code-quote">"cache"</span>);
891
892 <span class="code-keyword">try</span>
893 {
894 <span class="code-comment">// Create host activator;
895</span> m_activator = <span class="code-keyword">new</span> HostActivator(m_lookupMap);
896 List list = <span class="code-keyword">new</span> ArrayList();
897 list.add(m_activator);
898
899 <span class="code-comment">// Now create an instance of the framework with
900</span> <span class="code-comment">// our configuration properties and activator.
901</span> m_felix = <span class="code-keyword">new</span> Felix(configMap, list);
902
903 <span class="code-comment">// Now start Felix instance.
904</span> m_felix.start();
905 }
906 <span class="code-keyword">catch</span> (Exception ex)
907 {
908 <span class="code-object">System</span>.err.println(<span class="code-quote">"Could not create framework: "</span> + ex);
909 ex.printStackTrace();
910 }
911
912 m_tracker = <span class="code-keyword">new</span> ServiceTracker(
913 m_activator.getContext(), Command.class.getName(), <span class="code-keyword">null</span>);
914 m_tracker.open();
915 }
916
917 <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)
918 {
919 <span class="code-comment">// See <span class="code-keyword">if</span> any of the currently tracked command services
920</span> <span class="code-comment">// match the specified command name, <span class="code-keyword">if</span> so then execute it.
921</span> <span class="code-object">Object</span>[] services = m_tracker.getServices();
922 <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++)
923 {
924 <span class="code-keyword">try</span>
925 {
926 <span class="code-keyword">if</span> (((Command) services[i]).getName().equals(name))
927 {
928 <span class="code-keyword">return</span> ((Command) services[i]).execute(commandline);
929 }
930 }
931 <span class="code-keyword">catch</span> (Exception ex)
932 {
933 <span class="code-comment">// Since the services returned by the tracker could become
934</span> <span class="code-comment">// invalid at any moment, we will <span class="code-keyword">catch</span> all exceptions, log
935</span> <span class="code-comment">// a message, and then ignore faulty services.
936</span> <span class="code-object">System</span>.err.println(ex);
937 }
938 }
939 <span class="code-keyword">return</span> <span class="code-keyword">false</span>;
940 }
941
942 <span class="code-keyword">public</span> void shutdownApplication()
943 {
944 <span class="code-comment">// Shut down the felix framework when stopping the
945</span> <span class="code-comment">// host application.
946</span> m_felix.shutdown();
947 }
948}</pre>
949</div></div>
950
951<p>The above example is overly simplistic with respect to concurrency
952issues and error conditions, but it demonstrates the overall approach
953for using bundle-provided services from the host application. Note, to
954compile the above code you will need to compile against the Felix
955framework 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>
956
957<p><a name="LaunchingandEmbeddingApacheFelix-servicereflection"></a></p>
958
959<h3><a name="LaunchingandEmbeddingApacheFelix-UsingBundleServicesviaReflection"></a>Using Bundle Services via Reflection</h3>
960
961<p>It possible for the host application to use services provided by
962bundles without having access to the service interface classes and thus
963not needing to put the service interface classes on the class path. To
964do this, the host application uses the same general approach to acquire
965the system bundle context object, which it can use to look up service
966objects. Using either an LDAP filter or the service interface class
967name, the host application can retrieve the service object and then use
968standard Java reflection to invoke methods on the service object.</p>
969
970<p><a name="LaunchingandEmbeddingApacheFelix-caveat"></a></p>
971
972<h1><a name="LaunchingandEmbeddingApacheFelix-Caveat"></a>Caveat</h1>
973
974<p>The code in this document has not been thoroughly tested or even
975compiled and may be out of date with respect to the current Felix
976source code. If you find errors please report them so the that they can
977be corrected.</p>
978
979<p><a name="LaunchingandEmbeddingApacheFelix-feedback"></a></p>
980
981<h2><a name="LaunchingandEmbeddingApacheFelix-Feedback"></a>Feedback</h2>
982
983<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>
984 </div>
Richard S. Halld5860342008-01-30 15:08:32 +0000[diff] [blame]985 </body></html>