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| <h1><a name="ExtenderPatternHandler-Theextenderpatternhandler"></a>The extender pattern handler</h1> |
| <p>The objective of this handler is to simplify the development of |
| extender-based architecture. This architecture-style is based on two |
| different roles:</p> |
| <ul> |
| <li>The extender</li> |
| <li>The extension</li> |
| </ul> |
| |
| |
| <p><img src="extender-pattern-handler_files/extender.png" align="absmiddle" border="0"><br> |
| The relation is basically a 1..n relation. The extender tracks |
| extensions. The particularity of this architecture-style is that |
| extensions are packaged in different bundles. An extension is detected |
| by analyzing the bundle. Indeed these bundles can have a special mark |
| in their manifest of a special file...<br> |
| Implementing an extender pattern could be complex as the extender needs |
| to track these marks dynamically. When a bundle starts, it needs to |
| look at the mark. Then a bundle leave, the extender must release all |
| object created from this bundle.<br> |
| This handler tracks bundle for you based on the specified required |
| mark. At each time a matching bundle appears or disappears, a callback |
| is invoked. The mark is currently a header in the bundle manifest.<br> |
| Nowadays, a lot of frameworks use this pattern such as iPOJO it-self |
| (to find both bundles containing components and bundles adding a new |
| implementation type), Spring-DM ...</p> |
| |
| <h2><a name="ExtenderPatternHandler-Usingthehandler"></a>Using the handler</h2> |
| <p>First of all, you need to configure the component type to use the handler such as:</p> |
| <div class="code"><div class="codeContent"> |
| <pre class="code-xml"><span class="code-tag"><iPOJO <span class="code-keyword">xmlns:extender</span>=<span class="code-quote">"org.apache.felix.ipojo.extender"</span>></span> |
| <Component |
| className=<span class="code-quote">"org.apache.felix.ipojo.extender.myextender"</span>> |
| |
| <span class="code-tag"><!—Extender Pattern handler configuration --></span> |
| <extender:extender |
| extension=<span class="code-quote">"My-Extension"</span> |
| onArrival=<span class="code-quote">"onBundleArrival"</span> |
| onDeparture=<span class="code-quote">"onBundleDeparture"</span> |
| /> |
| |
| <span class="code-tag"><callback transition=<span class="code-quote">"invalidate"</span> method=<span class="code-quote">"stopping"</span> /></span> |
| <span class="code-tag"><callback transition=<span class="code-quote">"validate"</span> method=<span class="code-quote">"starting"</span> /></span> |
| <span class="code-tag"><provides /></span> |
| <span class="code-tag"></Component></span> |
| <span class="code-tag"></iPOJO></span></pre> |
| </div></div> |
| <p>Notice that, this handler is an external handler. So, it uses the "org.apache.felix.ipojo.extender" namespace.<br> |
| Once described, you can implement your component. The methods specified |
| methods will be called when a matching bundle arrives or leaves.<br> |
| In the previous example, these methods could be: </p> |
| <div class="code"><div class="codeContent"> |
| <pre class="code-java">void onBundleArrival(Bundle bundle, <span class="code-object">String</span> header) { |
| <span class="code-comment">// Do something |
| </span>} |
| |
| void onBundleDeparture(Bundle bundle) { |
| <span class="code-comment">// Do something |
| </span>}</pre> |
| </div></div> |
| <p>Notice the different signatures of the methods. The arrival method |
| is called with the arriving bundle and the matching header value (i.e. |
| the value of the My-Extension header of the bundle manifest). The |
| departure method just receives the leaving bundle.</p> |
| <h2><a name="ExtenderPatternHandler-Configuration"></a>Configuration</h2> |
| <p>The handler has only three mandatory attributes:</p> |
| <ul> |
| <li>Extension: declaring the looked manifest header.</li> |
| <li>onArrival: declaring the method to invoke when a matching bundle arrives</li> |
| <li>onDeparture: declaring the method to invoke when a matching bundle leaves</li> |
| </ul> |
| |
| |
| <table class="noteMacro" align="center" border="0" cellpadding="5" cellspacing="8" width="85%"><colgroup><col width="24"><col></colgroup><tbody><tr><td valign="top"><img src="extender-pattern-handler_files/warning.gif" alt="" align="absmiddle" border="0" width="16" height="16"></td><td> |
| <p>The implementation will be notified of arrivals and departures |
| despite the instance is invalid. Indeed, the implementation must |
| release all objects created from another bundle as soon it leaves.</p></td></tr></tbody></table> |
| |
| <h2><a name="ExtenderPatternHandler-Download"></a>Download</h2> |
| <p>The handler is available on the <a href="http://felix.apache.org/site/download.html" title="Download">download</a> page.<br> |
| Sources are available on the Felix trunk at the following location: <span class="nobr"><a href="http://svn.apache.org/repos/asf/felix/trunk/ipojo/handler/extender/" title="Visit page outside Confluence" rel="nofollow">http://svn.apache.org/repos/asf/felix/trunk/ipojo/handler/extender/<sup><img class="rendericon" src="extender-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></p> |
| |
| <h2><a name="ExtenderPatternHandler-Configuringthehandlerwithannotations\Newin1.1.0SNAPSHOT\"></a>Configuring the handler with annotations [New in 1.1.0-SNAPSHOT]</h2> |
| |
| <p>It is possible to configure the handler with a simple annotation |
| available in the annotation pack ('annotation' project in the iPOJO |
| trunk). Here is an example of usage:</p> |
| <div class="code"><div class="codeContent"> |
| <pre class="code-java"><span class="code-keyword">import</span> org.apache.felix.ipojo.annotations.Component; |
| <span class="code-keyword">import</span> org.osgi.framework.Bundle; |
| |
| @Component |
| @org.apache.felix.ipojo.extender.Extender(extension=<span class="code-quote">"foo"</span>, onArrival=<span class="code-quote">"onArrival"</span>, onDeparture=<span class="code-quote">"onDeparture"</span>) |
| <span class="code-keyword">public</span> class Extender { |
| |
| <span class="code-keyword">public</span> void onArrival(Bundle bundle, <span class="code-object">String</span> foo) { |
| <span class="code-comment">// <span class="code-keyword">do</span> something |
| </span> } |
| |
| <span class="code-keyword">public</span> void onDeparture(Bundle bundle) { |
| <span class="code-comment">// <span class="code-keyword">do</span> something |
| </span> } |
| }</pre> |
| </div></div> |
| |
| <p>The <tt>extension</tt> attribute allows setting the bundle filter.</p> |
| |
| |
| <h2><a name="ExtenderPatternHandler-Amorerealisticexample"></a>A more realistic example</h2> |
| <p>The Junit4OSGi framework, available <span class="nobr"><a href="https://svn.apache.org/repos/asf/felix/trunk/ipojo/examples/junit4osgi" title="Visit page outside Confluence" rel="nofollow">here<sup><img class="rendericon" src="extender-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span> |
| , uses this handler to track Junit Test Suite offered by the installed |
| bundles. The Junit4Osgi bundle has a component using this handler to be |
| notified when a bundle with the "Test-Suite" header appears or leaves.</p> |
| </td> |
| <td class="confluenceTd" valign="top" width="20%"> |
| <h6><a name="ExtenderPatternHandler-Overview"></a><b>Overview</b></h6> |
| <ul> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo.html" title="Apache Felix iPOJO">Home Page</a></li> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo-feature-overview.html" title="Apache Felix iPOJO Feature Overview">iPOJO Feature Overview</a></li> |
| <li><a href="http://felix.apache.org/site/download.html" title="Download">Download & Install </a></li> |
| </ul> |
| |
| |
| <h6><a name="ExtenderPatternHandler-GettingStarted"></a><b>Getting Started</b></h6> |
| <ul> |
| <li><a href="http://felix.apache.org/site/ipojo-in-10-minutes.html" title="iPOJO in 10 minutes">iPOJO in 10 minutes</a></li> |
| <li><a href="http://felix.apache.org/site/how-to-use-ipojo-annotations.html" title="How to use iPOJO Annotations">How to use iPOJO Annotations</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-hello-word-maven-based-tutorial.html" title="iPOJO Hello Word (Maven-Based) tutorial">iPOJO Hello Word (Maven-Based) tutorial</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-advanced-tutorial.html" title="iPOJO Advanced Tutorial">iPOJO Advanced Tutorial</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-composition-tutorial.html" title="iPOJO Composition Tutorial">iPOJO Composition Tutorial</a></li> |
| </ul> |
| |
| |
| <h6><a name="ExtenderPatternHandler-UserGuide"></a><b>User Guide</b></h6> |
| <ul> |
| <li><a href="http://felix.apache.org/site/describing-components.html" title="Describing components">Describing components (handler list) </a></li> |
| <li><a href="http://felix.apache.org/site/using-xml-schemas.html" title="Using XML Schemas">Using XML Schemas</a></li> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo-testing-components.html" title="apache-felix-ipojo-testing-components">Testing components</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-advanced-topics.html" title="iPOJO Advanced Topics">Advanced Topics</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-faq.html" title="iPOJO FAQ">FAQ</a></li> |
| </ul> |
| |
| |
| <h6><a name="ExtenderPatternHandler-Tools"></a><b>Tools</b></h6> |
| <ul> |
| <li><a href="http://felix.apache.org/site/ipojo-eclipse-plug-in.html" title="iPOJO Eclipse Plug-in">iPOJO Eclipse Plug-in</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-ant-task.html" title="iPOJO Ant Task">iPOJO Ant Task</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-maven-plug-in.html" title="iPOJO Maven Plug-in">iPOJO Maven Plug-in</a></li> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo-junit4osgi.html" title="apache-felix-ipojo-junit4osgi">Junit4OSGi</a></li> |
| <li><a href="http://felix.apache.org/site/ipojo-concepts-overview.html" title="iPOJO Concepts Overview">iPOJO concepts overview</a></li> |
| </ul> |
| |
| |
| <h6><a name="ExtenderPatternHandler-DeveloperGuide"></a><b>Developer Guide</b></h6> |
| <ul> |
| <li>API: <span class="nobr"><a href="http://people.apache.org/%7Eclement/ipojo/api/1.0/" title="Visit page outside Confluence" rel="nofollow">1.0<sup><img class="rendericon" src="extender-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></li> |
| <li><a href="http://felix.apache.org/site/how-to-write-your-own-handler.html" title="How to write your own handler">How to write your own handler</a></li> |
| <li><a href="http://felix.apache.org/site/how-to-use-ipojo-manipulation-metadata.html" title="How to use iPOJO Manipulation Metadata">How to use iPOJO Manipulation Metadata</a></li> |
| <li><a href="http://felix.apache.org/site/dive-into-the-ipojo-manipulation-depths.html" title="Dive into the iPOJO Manipulation depths">Dive into the iPOJO Manipulation depths</a></li> |
| </ul> |
| |
| |
| <h6><a name="ExtenderPatternHandler-Misc&Contact"></a><b>Misc & Contact</b></h6> |
| <ul> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo-issuestracker.html" title="apache-felix-ipojo-issuestracker">Issues Tracker</a></li> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo-supportedvms.html" title="apache-felix-ipojo-supportedVMs">Supported JVMs</a></li> |
| <li><a href="http://felix.apache.org/site/apache-felix-ipojo-supportedosgi.html" title="apache-felix-ipojo-supportedOSGi">Supported OSGi Implementations</a></li> |
| <li><span class="nobr"><a href="http://ipojo-dark-side.blogspot.com/" title="Visit page outside Confluence" rel="nofollow">iPOJO's Dark Side Blog<sup><img class="rendericon" src="extender-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></li> |
| <li><a href="http://felix.apache.org/site/future-ideas.html" title="Future Ideas">Future Ideas</a></li> |
| <li><a href="http://felix.apache.org/site/contact.html" title="Contact">Contact</a></li> |
| <li><a href="http://felix.apache.org/site/related-works.html" title="Related Works">Related Works</a></li> |
| <li><a href="http://felix.apache.org/site/article-presentations.html" title="Article & Presentations">Article & Presentations</a></li> |
| </ul> |
| |
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