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Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]5
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]6 <title>Apache Felix - White Board Pattern Handler</title>
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28<table class="sectionMacro" border="0" cellpadding="5" cellspacing="0" width="100%"><tbody><tr>
29<td class="confluenceTd" valign="top" width="80%">
30<h1><a name="WhiteBoardPatternHandler-Thewhiteboardpatternhandler"></a>The white board pattern handler</h1>
31<p>The objective of this handler is to simplify the development of
32white-board architecture. This architecture-style is based is very
33close to the extender architecture style but use services instead of
34bundles.<br>
35A whiteboard is based on two different roles:</p>
36<ul>
37 <li>A consumer looking to special services or a services published with a special mark</li>
38 <li>Looked services</li>
39</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]40
41
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]42<p>More information on this pattern is available in this <span class="nobr"><a href="http://www.osgi.org/wiki/uploads/Links/whiteboard.pdf" title="Visit page outside Confluence" rel="nofollow">document<sup><img class="rendericon" src="white-board-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span><br>
43Implementing a white board pattern could be complex as the extender
44needs to track these services dynamically. Indeed looked services can
45be highly dynamic; they can arrive, leave or be modified at runtime.<br>
46Several services specified in the OSGi specification use white board pattern such as the Device Access Manager.</p>
47
48<p><b>UPDATE</b>: the 1.1.0-SNAPSHOT has a new namespace <tt>org.apache.felix.ipojo.whiteboard</tt> instead of <tt>org.apache.felix.ipojo.white-board-pattern</tt></p>
49
50<h2><a name="WhiteBoardPatternHandler-Usingthehandler"></a>Using the handler</h2>
51<p>First of all, you need to configure the component type to use the handler such as:</p>
52<div class="code"><div class="codeContent">
53<pre class="code-xml"><span class="code-tag">&lt;ipojo <span class="code-keyword">xmlns:wbp</span>=<span class="code-quote">"org.apache.felix.ipojo.whiteboard"</span>&gt;</span>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]54 &lt;component
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]55 className=<span class="code-quote">"org.apache.felix.ipojo.test.FooWhiteBoardPattern"</span>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]56 &gt;
57 &lt;wbp:wbp
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]58 filter=<span class="code-quote">"(my.property=1)"</span>
59 onArrival=<span class="code-quote">"onArrival"</span>
60 onDeparture=<span class="code-quote">"onDeparture"</span>
61 onModification=<span class="code-quote">"onModification"</span>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]62 /&gt;
63
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]64 <span class="code-tag">&lt;provides/&gt;</span>
65 <span class="code-tag">&lt;/component&gt;</span></pre>
66</div></div>
67<p>Notice that, this handler is an external handler. So, it uses the "org.apache.felix.ipojo.whiteboard" namespace.<br>
68Once described, you can implement your component. The methods specified
69methods will be called when a matching services arrives or leaves or
70are modified. The modification callback is optional. A matching service
71is detected by confronting the service reference against the specified
72filter.<br>
73The filter can target specific service interface (with the objectclass property) or property values.<br>
74In the previous example, these methods could be: </p>
75<div class="code"><div class="codeContent">
76<pre class="code-java"><span class="code-keyword">public</span> class FooWhiteBoardPattern <span class="code-keyword">implements</span> Observable {
77 List list = <span class="code-keyword">new</span> ArrayList();
78 <span class="code-object">int</span> modifications = 0;
79 <span class="code-keyword">public</span> <span class="code-keyword">synchronized</span> void onArrival(ServiceReference ref) {
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]80 list.add(ref);
81 }
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]82 <span class="code-keyword">public</span> <span class="code-keyword">synchronized</span> void onDeparture(ServiceReference ref) {
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]83 list.remove(ref);
84 }
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]85 <span class="code-keyword">public</span> <span class="code-keyword">synchronized</span> void onModification(ServiceReference ref) {
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]86 modifications = modifications + 1;
87 }
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]88 <span class="code-keyword">public</span> <span class="code-keyword">synchronized</span> Map getObservations() {
89 Map map = <span class="code-keyword">new</span> HashMap();
90 map.put(<span class="code-quote">"list"</span>, list);
91 map.put(<span class="code-quote">"modifications"</span>, <span class="code-keyword">new</span> <span class="code-object">Integer</span>(modifications));
92 <span class="code-keyword">return</span> map;
93 }</pre>
94</div></div>
95<p>All method received the arriving, leaving or modified service reference.</p>
96<h2><a name="WhiteBoardPatternHandler-Configuration"></a>Configuration</h2>
97<p>The handler has only three mandatory attributes:</p>
98<ul>
99 <li>Filter: filter use to discover matching filter.</li>
100 <li>onArrival: declaring the method to invoke when a matching service arrives</li>
101 <li>onDeparture: declaring the method to invoke when a matching service leaves</li>
102</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]103
104
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]105<p>The onModification attribute is optional. This method is called when
106an injected service reference is modified but stills valid against the
107filter.</p>
108<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="white-board-pattern-handler_files/warning.gif" alt="" align="absmiddle" border="0" width="16" height="16"></td><td>
109<p>The implementation will be notified of arrivals, modifications and
110departures, despite the instance is invalid. Indeed, the implementation
111must release all objects created from another bundle as soon it leaves.</p></td></tr></tbody></table>
112<h2><a name="WhiteBoardPatternHandler-Configuringthehandlerwithannotations\Newin1.1.0SNAPSHOT\"></a>Configuring the handler with annotations [New in 1.1.0-SNAPSHOT]</h2>
113
114<p>It is possible to configure the handler with a simple annotation
115available in the annotation pack ('annotation' project in the iPOJO
116trunk). Here is an example of usage:</p>
117<div class="code"><div class="codeContent">
118<pre class="code-java"><span class="code-keyword">import</span> org.apache.felix.ipojo.annotations.Component;
119<span class="code-keyword">import</span> org.osgi.framework.ServiceReference;
120
121@Component
122@org.apache.felix.ipojo.whiteboard.Wbp(filter=<span class="code-quote">"(foo=<span class="code-keyword">true</span>)"</span>,
123 onArrival=<span class="code-quote">"onArrival"</span>,
124 onDeparture=<span class="code-quote">"onDeparture"</span>,
125 onModification=<span class="code-quote">"onModification"</span>)
126<span class="code-keyword">public</span> class WhiteBoardExemple {
127
128 <span class="code-keyword">public</span> void onArrival(ServiceReference ref) {
129 <span class="code-comment">// <span class="code-keyword">do</span> something
130</span> }
131
132 <span class="code-keyword">public</span> void onDeparture(ServiceReference ref) {
133 <span class="code-comment">// <span class="code-keyword">do</span> something
134</span> }
135
136 <span class="code-keyword">public</span> void onModification(ServiceReference ref) {
137 <span class="code-comment">// <span class="code-keyword">do</span> something
138</span> }
139
140}</pre>
141</div></div>
142
143<p>The <tt>onModification</tt> attribute is optional.The <tt>filter</tt> attribute allows setting the service filter.</p>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]144
145
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]146<h2><a name="WhiteBoardPatternHandler-Download"></a>Download</h2>
147<p>The handler is available on the <a href="http://felix.apache.org/site/download.html" title="Download">download</a> page.<br>
148Sources 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/whiteboard" title="Visit page outside Confluence" rel="nofollow">http://svn.apache.org/repos/asf/felix/trunk/ipojo/handler/whiteboard<sup><img class="rendericon" src="white-board-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></p></td>
149<td class="confluenceTd" valign="top" width="20%">
150<h6><a name="WhiteBoardPatternHandler-Overview"></a><b>Overview</b></h6>
151<ul>
152 <li><a href="http://felix.apache.org/site/apache-felix-ipojo.html" title="Apache Felix iPOJO">Home Page</a></li>
153 <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>
154 <li><a href="http://felix.apache.org/site/download.html" title="Download">Download &amp; Install </a></li>
155</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]156
157
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]158<h6><a name="WhiteBoardPatternHandler-GettingStarted"></a><b>Getting Started</b></h6>
159<ul>
160 <li><a href="http://felix.apache.org/site/ipojo-in-10-minutes.html" title="iPOJO in 10 minutes">iPOJO in 10 minutes</a></li>
161 <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>
162 <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>
163 <li><a href="http://felix.apache.org/site/ipojo-advanced-tutorial.html" title="iPOJO Advanced Tutorial">iPOJO Advanced Tutorial</a></li>
164 <li><a href="http://felix.apache.org/site/ipojo-composition-tutorial.html" title="iPOJO Composition Tutorial">iPOJO Composition Tutorial</a></li>
165</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]166
167
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]168<h6><a name="WhiteBoardPatternHandler-UserGuide"></a><b>User Guide</b></h6>
169<ul>
170 <li><a href="http://felix.apache.org/site/describing-components.html" title="Describing components">Describing components (handler list) </a></li>
171 <li><a href="http://felix.apache.org/site/using-xml-schemas.html" title="Using XML Schemas">Using XML Schemas</a></li>
172 <li><a href="http://felix.apache.org/site/apache-felix-ipojo-testing-components.html" title="apache-felix-ipojo-testing-components">Testing components</a></li>
173 <li><a href="http://felix.apache.org/site/ipojo-advanced-topics.html" title="iPOJO Advanced Topics">Advanced Topics</a></li>
174 <li><a href="http://felix.apache.org/site/ipojo-faq.html" title="iPOJO FAQ">FAQ</a></li>
175 <li><a href="http://felix.apache.org/site/ipojo-reference-card.html" title="iPOJO-Reference-Card">iPOJO Reference Card</a></li>
176</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]177
178
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]179<h6><a name="WhiteBoardPatternHandler-Tools"></a><b>Tools</b></h6>
180<ul>
181 <li><a href="http://felix.apache.org/site/ipojo-eclipse-plug-in.html" title="iPOJO Eclipse Plug-in">iPOJO Eclipse Plug-in</a></li>
182 <li><a href="http://felix.apache.org/site/ipojo-ant-task.html" title="iPOJO Ant Task">iPOJO Ant Task</a></li>
183 <li><a href="http://felix.apache.org/site/ipojo-maven-plug-in.html" title="iPOJO Maven Plug-in">iPOJO Maven Plug-in</a></li>
184 <li><a href="http://felix.apache.org/site/ipojo-arch-command.html" title="iPOJO-Arch-Command">iPOJO Arch Command</a></li>
185 <li><a href="http://felix.apache.org/site/apache-felix-ipojo-junit4osgi.html" title="apache-felix-ipojo-junit4osgi">Junit4OSGi</a></li>
186 <li><a href="http://felix.apache.org/site/ipojo-concepts-overview.html" title="iPOJO Concepts Overview">iPOJO concepts overview</a></li>
187</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]188
189
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]190<h6><a name="WhiteBoardPatternHandler-DeveloperGuide"></a><b>Developer Guide</b></h6>
191<ul>
192 <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="white-board-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></li>
193 <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>
194 <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>
195 <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>
196</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]197
198
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]199<h6><a name="WhiteBoardPatternHandler-Misc&amp;Contact"></a><b>Misc &amp; Contact</b></h6>
200<ul>
201 <li><a href="http://felix.apache.org/site/apache-felix-ipojo-issuestracker.html" title="apache-felix-ipojo-issuestracker">Issues Tracker</a></li>
202 <li><a href="http://felix.apache.org/site/apache-felix-ipojo-supportedvms.html" title="apache-felix-ipojo-supportedVMs">Supported JVMs</a></li>
203 <li><a href="http://felix.apache.org/site/apache-felix-ipojo-supportedosgi.html" title="apache-felix-ipojo-supportedOSGi">Supported OSGi Implementations</a></li>
204 <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="white-board-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></li>
205 <li><a href="http://felix.apache.org/site/future-ideas.html" title="Future Ideas">Future Ideas</a></li>
206 <li><a href="http://felix.apache.org/site/contact.html" title="Contact">Contact</a></li>
207 <li><a href="http://felix.apache.org/site/related-works.html" title="Related Works">Related Works</a></li>
208 <li><a href="http://felix.apache.org/site/article-presentations.html" title="Article &amp; Presentations">Article &amp; Presentations</a></li>
209</ul>
Clement Escoffier83507512008-10-13 07:33:03 +0000[diff] [blame]210
Clement Escoffier8251f602009-01-15 15:35:17 +0000[diff] [blame]211
212<hr>
213<div class="" align="center">
214<p><span class="nobr"><a href="http://cwiki.apache.org/confluence/createrssfeed.action?types=blogpost&amp;statuses=created&amp;statuses=modified&amp;spaces=FELIX&amp;labelString=iPOJO&amp;rssType=atom&amp;maxResults=10&amp;timeSpan=5&amp;publicFeed=true&amp;title=iPOJO%20Atom%20Feed" title="Stay tuned!" rel="nofollow"><img src="white-board-pattern-handler_files/feed-icon-32x32.png" align="absmiddle" border="0"><sup><img class="rendericon" src="white-board-pattern-handler_files/linkext7.gif" alt="" align="absmiddle" border="0" width="7" height="7"></sup></a></span></p></div>
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