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<small><a href="./../../index.html">Home</a>&nbsp;&raquo&nbsp;<a href="./../../examples-trunk/">Examples Trunk</a>&nbsp;&raquo&nbsp;<a href="./../../examples-trunk/cdi-events/">Cdi Events</a></small><br>
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<h1>CDI events: loose coupling and extensibility</h1>
<p>CDI allows you to extend business code by the Notifier/Observer pattern.</p>
<p>To do it you simply inject a field <code>Event</code> in the notifier class. This class is a template
and the parameter type is the object type to fire. Then when you want to notify observers
you simply call the method fire of the event object passing as a parameter the event itself
(your own class!).</p>
<p>On the other side you annotated a method parameter <code>@Observes</code> and the parameter type is the sent type
by the notifier.</p>
<p>Note: of course you can add qualifiers to be more precise on your events.</p>
<h1>The example</h1>
<p>The example is pretty simple: an ejb uses the <code>@Schedule</code> annotation to get a notification each second.
The each second this EJB will send the current date through CDI events.</p>
<p>This is our "business" code. It is a simple behavior (nothing).</p>
<p>In our test (which is considered as an extension) we created an observer (<code>Observer</code> class)
which simply store and log each received date.</p>
<p>The test itself (<code>EventTest</code>) simply verifies the dates were received.</p>
<h1>Conclusion</h1>
<p>CDI let's implement very easily plugins through this event mecanism.</p>
<p>If you go further and look at CDI plugin API you'll realize it is simply the same kind
of events. CDI events is really the basis of CDI.</p>
<div class="page-header">&nbsp;</div>
<h4>APIs Used</h4>
<ul><li><a href="http://docs.oracle.com/javaee/6/api/javax/ejb/Schedule.html">javax.ejb.Schedule</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/ejb/Singleton.html">javax.ejb.Singleton</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/ejb/embeddable/EJBContainer.html">javax.ejb.embeddable.EJBContainer</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/enterprise/event/Event.html">javax.enterprise.event.Event</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/enterprise/event/Observes.html">javax.enterprise.event.Observes</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/inject/Inject.html">javax.inject.Inject</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/inject/Singleton.html">javax.inject.Singleton</a></li>
<li><a href="http://docs.oracle.com/javaee/6/api/javax/naming/NamingException.html">javax.naming.NamingException</a></li>
</ul>
<h3>Source</h3>
<ul>
<li>Apache <a href="http://svn.apache.org/repos/asf/tomee/tomee/trunk/examples/cdi-events">cdi-events</a></li>
<li>Github <a href="https://github.com/apache/tomee/tree/trunk/examples/cdi-events">cdi-events</a></li>
</ul>
<pre>
svn co http://svn.apache.org/repos/asf/tomee/tomee/trunk/examples/cdi-events
cd cdi-events
mvn clean install
</pre>
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