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<h1>CDI Events - Loose Coupling and Extensibility</h1>
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<p>CDI allows you to extend business code by the Notifier/Observer pattern.</p>
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<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>
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<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>
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of course you can add qualifiers to be more precise on your events.
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<h2 id="_example">Example</h2>
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<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>
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<p>This is our "business" code. It is a simple behavior (nothing).</p>
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<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>
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<p>The test itself (<code>EventTest</code>) simply verifies the dates were received.</p>
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<h2 id="_conclusion">Conclusion</h2>
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<p>CDI let&#8217;s you implement very easily plugins through this event mecanism.</p>
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<p>If you go further and look at CDI plugin API you&#8217;ll realize it is simply the same kind
of events. CDI events is really the basis of CDI.</p>
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