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| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 186 | <h1><a name="ExtenderPatternHandler-Theextenderpatternhandler"></a>The extender pattern handler</h1> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 187 | <p><em>The objective of this handler is to simplify the development of |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 188 | extender-based architecture. This architecture-style is based on two |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 189 | different roles:</em></p> |
| 190 | <ul> |
| 191 | <li><em>The extender</em></li> |
| 192 | <li><em>The extensions</em></li> |
| 193 | </ul> |
| 194 | |
| 195 | |
| 196 | <div class="toc"> |
| 197 | <ul> |
| 198 | <li><a href="#ExtenderPatternHandler-TheExtenderpattern">The Extender pattern</a></li> |
| 199 | <li><a href="#ExtenderPatternHandler-Usingthehandler">Using the handler</a></li> |
| 200 | <li><a href="#ExtenderPatternHandler-Configuration">Configuration</a></li> |
| 201 | <li><a href="#ExtenderPatternHandler-Download">Download</a></li> |
| 202 | <li><a href="#ExtenderPatternHandler-Configuringthehandlerwithannotations">Configuring the handler with annotations</a></li> |
| 203 | <li><a href="#ExtenderPatternHandler-Amorerealisticexample">A more realistic example</a></li> |
| 204 | </ul></div> |
| 205 | |
| 206 | <h2><a name="ExtenderPatternHandler-TheExtenderpattern"></a>The Extender pattern</h2> |
| 207 | |
| 208 | <p>This architecture-style is based on two different roles:</p> |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 209 | <ul> |
| 210 | <li>The extender</li> |
| 211 | <li>The extension</li> |
| 212 | </ul> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 213 | |
| 214 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 215 | <p><img src="extender-pattern-handler_files/extender.png" border="0" align="absmiddle"></p> |
| 216 | |
| 217 | <p>The relation is basically a 1..n relation. The extender tracks |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 218 | extensions. The particularity of this architecture-style is that |
| 219 | extensions are packaged in different bundles. An extension is detected |
| 220 | by analyzing the bundle. Indeed these bundles can have a special mark |
| 221 | in their manifest of a special file...<br> |
| 222 | Implementing an extender pattern could be complex as the extender needs |
| 223 | to track these marks dynamically. When a bundle starts, it needs to |
| 224 | look at the mark. Then a bundle leave, the extender must release all |
| 225 | object created from this bundle.<br> |
| 226 | This handler tracks bundle for you based on the specified required |
| 227 | mark. At each time a matching bundle appears or disappears, a callback |
| 228 | is invoked. The mark is currently a header in the bundle manifest.<br> |
| 229 | Nowadays, a lot of frameworks use this pattern such as iPOJO it-self |
| 230 | (to find both bundles containing components and bundles adding a new |
| 231 | implementation type), Spring-DM ...</p> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 232 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 233 | <h2><a name="ExtenderPatternHandler-Usingthehandler"></a>Using the handler</h2> |
| 234 | <p>First of all, you need to configure the component type to use the handler such as:</p> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 235 | <div class="code"> |
| 236 | <div class="dp-highlighter"><table class="dp-xml" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td class="line1"><span></span><span class="tag"><</span><span>iPOJO xmlns:</span><span class="attribute">extender</span><span>=</span><span class="attribute-value">"org.apache.felix.ipojo.extender"</span><span>> </span></td></tr><tr><td class="line2"> <span class="tag"><</span><span>component </span></td></tr><tr><td class="line1"> <span class="attribute">classname</span><span>=</span><span class="attribute-value">"org.apache.felix.ipojo.extender.myextender"</span><span>> </span></td></tr><tr><td class="line2"> </td></tr><tr><td class="line1"> <span class="comments"><!-- Extender Pattern handler configuration --></span><span> </span></td></tr><tr><td class="line2"> <span class="tag"><</span><span>extender:extender </span></td></tr><tr><td class="line1"> <span class="attribute">extension</span><span>=</span><span class="attribute-value">"My-Extension"</span><span> </span></td></tr><tr><td class="line2"> <span class="attribute">onArrival</span><span>=</span><span class="attribute-value">"onBundleArrival"</span><span> </span></td></tr><tr><td class="line1"> <span class="attribute">onDeparture</span><span>=</span><span class="attribute-value">"onBundleDeparture"</span><span> </span></td></tr><tr><td class="line2"> <span class="tag">/></span><span> </span></td></tr><tr><td class="line1"> </td></tr><tr><td class="line2"> <span class="tag"><</span><span>callback </span><span class="attribute">transition</span><span>=</span><span class="attribute-value">"invalidate"</span><span> </span><span class="attribute">method</span><span>=</span><span class="attribute-value">"stopping"</span><span> </span><span class="tag">/></span><span> </span></td></tr><tr><td class="line1"> <span class="tag"><</span><span>callback </span><span class="attribute">transition</span><span>=</span><span class="attribute-value">"validate"</span><span> </span><span class="attribute">method</span><span>=</span><span class="attribute-value">"starting"</span><span> </span><span class="tag">/></span><span> </span></td></tr><tr><td class="line2"> <span class="tag"><</span><span>provides </span><span class="tag">/></span><span> </span></td></tr><tr><td class="line1"> <span class="tag"></</span><span>component</span><span class="tag">></span><span> </span></td></tr><tr><td class="line2"><span class="tag"></</span><span>iPOJO</span><span class="tag">></span><span> </span></td></tr></tbody></table></div><textarea style="display: none;" name="newcodemacro" class="xml:nocontrols:nogutter" rows="10" readonly="readonly"><iPOJO xmlns:extender="org.apache.felix.ipojo.extender"> |
| 237 | <component |
| 238 | classname="org.apache.felix.ipojo.extender.myextender"> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 239 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 240 | <!-- Extender Pattern handler configuration --> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 241 | <extender:extender |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 242 | extension="My-Extension" |
| 243 | onArrival="onBundleArrival" |
| 244 | onDeparture="onBundleDeparture" |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 245 | /> |
| 246 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 247 | <callback transition="invalidate" method="stopping" /> |
| 248 | <callback transition="validate" method="starting" /> |
| 249 | <provides /> |
| 250 | </component> |
| 251 | </iPOJO></textarea> |
| 252 | <script class="javascript"> |
| 253 | if(!window.newcodemacro_initialised) |
| 254 | { |
| 255 | window.newcodemacro_initialised = true; |
| 256 | window.oldonloadmethod = window.onload; |
| 257 | window.onload = function(){ |
| 258 | dp.SyntaxHighlighter.HighlightAll('newcodemacro'); |
| 259 | if(window.oldonloadmethod) |
| 260 | { |
| 261 | window.oldonloadmethod(); |
| 262 | } |
| 263 | } |
| 264 | } |
| 265 | |
| 266 | </script> |
| 267 | </div> |
| 268 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 269 | <p>Notice that, this handler is an external handler. So, it uses the "org.apache.felix.ipojo.extender" namespace.<br> |
| 270 | Once described, you can implement your component. The methods specified |
| 271 | methods will be called when a matching bundle arrives or leaves.<br> |
| 272 | In the previous example, these methods could be: </p> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 273 | <div class="code"> |
| 274 | <div class="dp-highlighter"><table class="dp-c" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td class="line1"><span></span><span class="keyword">void</span><span> onBundleArrival(Bundle bundle, String header) { </span></td></tr><tr><td class="line2"> <span class="comment">// Do something</span><span> </span></td></tr><tr><td class="line1">} </td></tr><tr><td class="line2"> </td></tr><tr><td class="line1"><span class="keyword">void</span><span> onBundleDeparture(Bundle bundle) { </span></td></tr><tr><td class="line2"> <span class="comment">// Do something</span><span> </span></td></tr><tr><td class="line1">} </td></tr></tbody></table></div><textarea style="display: none;" name="newcodemacro" class="java:nocontrols:nogutter" rows="10" readonly="readonly">void onBundleArrival(Bundle bundle, String header) { |
| 275 | // Do something |
| 276 | } |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 277 | |
| 278 | void onBundleDeparture(Bundle bundle) { |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 279 | // Do something |
| 280 | }</textarea> |
| 281 | <script class="javascript"> |
| 282 | if(!window.newcodemacro_initialised) |
| 283 | { |
| 284 | window.newcodemacro_initialised = true; |
| 285 | window.oldonloadmethod = window.onload; |
| 286 | window.onload = function(){ |
| 287 | dp.SyntaxHighlighter.HighlightAll('newcodemacro'); |
| 288 | if(window.oldonloadmethod) |
| 289 | { |
| 290 | window.oldonloadmethod(); |
| 291 | } |
| 292 | } |
| 293 | } |
| 294 | |
| 295 | </script> |
| 296 | </div> |
| 297 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 298 | <p>Notice the different signatures of the methods. The arrival method |
| 299 | is called with the arriving bundle and the matching header value (i.e. |
| 300 | the value of the My-Extension header of the bundle manifest). The |
| 301 | departure method just receives the leaving bundle.</p> |
| 302 | <h2><a name="ExtenderPatternHandler-Configuration"></a>Configuration</h2> |
| 303 | <p>The handler has only three mandatory attributes:</p> |
| 304 | <ul> |
| 305 | <li>Extension: declaring the looked manifest header.</li> |
| 306 | <li>onArrival: declaring the method to invoke when a matching bundle arrives</li> |
| 307 | <li>onDeparture: declaring the method to invoke when a matching bundle leaves</li> |
| 308 | </ul> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 309 | |
| 310 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 311 | |
| 312 | |
| 313 | <div class="box"> |
| 314 | <div class="box-yellow-header"> |
| 315 | <div class="box-yellow-title"> |
| 316 | <img src="extender-pattern-handler_files/warning.gif"> <b>Called despite being invalid</b> |
| 317 | </div> |
| 318 | </div> |
| 319 | <div class="box-yellow-content"> |
| 320 | The implementation will be notified of arrivals and departures despite |
| 321 | the instance is invalid. Indeed, the implementation must release all |
| 322 | objects created from another bundle as soon it leaves. </div> |
| 323 | <div class="box-yellow-footer"></div> |
| 324 | </div> |
| 325 | |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 326 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 327 | <h2><a name="ExtenderPatternHandler-Download"></a>Download</h2> |
| 328 | <p>The handler is available on the <a href="http://felix.apache.org/site/download.html" title="Download">download</a> page.<br> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 329 | Sources are available on the Felix trunk at the following location: <a href="http://svn.apache.org/repos/asf/felix/trunk/ipojo/handler/extender/" rel="nofollow">http://svn.apache.org/repos/asf/felix/trunk/ipojo/handler/extender/</a></p> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 330 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 331 | <h2><a name="ExtenderPatternHandler-Configuringthehandlerwithannotations"></a>Configuring the handler with annotations</h2> |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 332 | |
| 333 | <p>It is possible to configure the handler with a simple annotation |
| 334 | available in the annotation pack ('annotation' project in the iPOJO |
| 335 | trunk). Here is an example of usage:</p> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 336 | <div class="code"> |
| 337 | <div class="dp-highlighter"><table class="dp-c" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td class="line1"><span></span><span class="keyword">import</span><span> org.apache.felix.ipojo.annotations.Component; </span></td></tr><tr><td class="line2"><span class="keyword">import</span><span> org.osgi.framework.Bundle; </span></td></tr><tr><td class="line1"><span class="preprocessor"></span></td></tr><tr><td class="line2"><span class="preprocessor">@Component</span><span> </span></td></tr><tr><td class="line1"><span class="preprocessor">@org.apache.felix.ipojo.extender.Extender(extension="foo", onArrival="onArrival", onDeparture="onDeparture")</span><span> </span></td></tr><tr><td class="line2"><span class="keyword">public</span><span> </span><span class="keyword">class</span><span> Extender { </span></td></tr><tr><td class="line1"> </td></tr><tr><td class="line2"> <span class="keyword">public</span><span> </span><span class="keyword">void</span><span> onArrival(Bundle bundle, String foo) { </span></td></tr><tr><td class="line1"> <span class="comment">// do something</span><span> </span></td></tr><tr><td class="line2"> } </td></tr><tr><td class="line1"> </td></tr><tr><td class="line2"> <span class="keyword">public</span><span> </span><span class="keyword">void</span><span> onDeparture(Bundle bundle) { </span></td></tr><tr><td class="line1"> <span class="comment">// do something</span><span> </span></td></tr><tr><td class="line2"> } </td></tr><tr><td class="line1">} </td></tr></tbody></table></div><textarea style="display: none;" name="newcodemacro" class="java:nocontrols:nogutter" rows="10" readonly="readonly">import org.apache.felix.ipojo.annotations.Component; |
| 338 | import org.osgi.framework.Bundle; |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 339 | |
| 340 | @Component |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 341 | @org.apache.felix.ipojo.extender.Extender(extension="foo", onArrival="onArrival", onDeparture="onDeparture") |
| 342 | public class Extender { |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 343 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 344 | public void onArrival(Bundle bundle, String foo) { |
| 345 | // do something |
| 346 | } |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 347 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 348 | public void onDeparture(Bundle bundle) { |
| 349 | // do something |
| 350 | } |
| 351 | }</textarea> |
| 352 | <script class="javascript"> |
| 353 | if(!window.newcodemacro_initialised) |
| 354 | { |
| 355 | window.newcodemacro_initialised = true; |
| 356 | window.oldonloadmethod = window.onload; |
| 357 | window.onload = function(){ |
| 358 | dp.SyntaxHighlighter.HighlightAll('newcodemacro'); |
| 359 | if(window.oldonloadmethod) |
| 360 | { |
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| 363 | } |
| 364 | } |
| 365 | |
| 366 | </script> |
| 367 | </div> |
| 368 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 369 | |
| 370 | <p>The <tt>extension</tt> attribute allows setting the bundle filter.</p> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 371 | |
| 372 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 373 | <h2><a name="ExtenderPatternHandler-Amorerealisticexample"></a>A more realistic example</h2> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 374 | <p>The Junit4OSGi framework, available <a href="https://svn.apache.org/repos/asf/felix/trunk/ipojo/examples/junit4osgi" rel="nofollow">here</a> |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 375 | , uses this handler to track Junit Test Suite offered by the installed |
| 376 | bundles. The Junit4Osgi bundle has a component using this handler to be |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 377 | notified when a bundle with the <tt>Test-Suite</tt> header appears or leaves. |
| 378 | <br clear="all"> |
| 379 | <br clear="all"></p> |
| Clement Escoffier | 8350751 | 2008-10-13 07:33:03 +0000 | [diff] [blame] | 380 | |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 381 | </div> |
| 382 | <img src="extender-pattern-handler_files/footer.png" class="footer"> |
| 383 | </div> |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 384 | |
| 385 | <script type="text/javascript"> |
| 386 | var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); |
| 387 | document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); |
| 388 | </script><script src="extender-pattern-handler_files/ga.js" type="text/javascript"></script> |
| 389 | <script type="text/javascript"> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 390 | try{ |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 391 | var pageTracker = _gat._getTracker("UA-1518442-4"); |
| 392 | pageTracker._trackPageview(); |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 393 | } catch(err) {} |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 394 | </script> |
| Clement Escoffier | 373a57d | 2009-07-21 12:06:46 +0000 | [diff] [blame] | 395 | |
| Clement Escoffier | 8251f60 | 2009-01-15 15:35:17 +0000 | [diff] [blame] | 396 | </div> |
| 397 | </body></html> |