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<p>This page provides a quick run-through of what the <code>stored_override</code> example does.  For more details, you should refer to the source, which you will find in the download kit under:</p>

<table class="wysiwyg-macro" data-macro-name="noformat" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e25vZm9ybWF0fQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
  examples/stored_override
</pre></td></tr></table>

<p>You can build and run the example by simply <code>cd</code>'ing into that directory and typing <code>ant</code>. </p>

<h3>Example Scenario</h3>

<p>Suppose that we have a simple JSR175 annotation type called <code>DeploymentInfo</code> which specifies a 'cacheSize' attribute for some kind of deployment unit:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid|title=DeploymentInfo.java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR8dGl0bGU9RGVwbG95bWVudEluZm8uamF2YX0&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@AnnogenInfo(
  annoBeanClass = "org.codehaus.annogen.examples.stored_override.DeploymentInfoAnnoBean"
)
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)

public @interface DeploymentInfo {
  public int cacheSize();

}
</pre></td></tr></table>

<p>Suppose that we also have an deployment unit called <code>TinyCacheEJB</code> which has a <code>DeploymentInfo</code> annotation:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid|title=TinyCacheEJB.java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR8dGl0bGU9VGlueUNhY2hlRUpCLmphdmF9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@DeploymentInfo(cacheSize = 3)
public class TinyCacheEJB {
  //...
}
</pre></td></tr></table>

<p>This example demonstrates a very simple way in which we might use Annogen to allow for the value of <code>cacheSize</code> to be overridden.  </p>

<h3>Generate Phase</h3>

<p>The first thing we have to do is generate an <code>AnnoBean</code> that will act as a proxy to instances of <code>DeploymentInfo</code>.  To do this, we simply run Annogen's compilation task on <code>DeploymentInfo</code>:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid|title=build.xml" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR8dGl0bGU9YnVpbGQueG1sfQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
&lt;annogen outputdir='${codegen_dir}'
         classpathref='classpath'
         srcdir='src'
         includes='org/codehaus/annogen/examples/stored_override/DeploymentInfo.java'
         implementAnnotationTypes='true'/>
</pre></td></tr></table>

<p>This generates a <code>DeploymentInfoAnnoBean</code> that implements <code>DeploymentInfo</code>:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid|title=DeploymentInfoAnnoBean.java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR8dGl0bGU9RGVwbG95bWVudEluZm9Bbm5vQmVhbi5qYXZhfQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
public class DeploymentInfoAnnoBean extends AnnoBeanBase implements DeploymentInfo {

private int cacheSize;

public int cacheSize() {
    return this.cacheSize;
  }

public void set_cacheSize(int in) {
    this.cacheSize = in;
  }
}
</pre></td></tr></table>

<h3>Override Phase</h3>

<p>Notice that the generated <code>DeploymentInfoAnnoBean</code> class has a setter for <code>cacheSize</code>.  We're now going to create an <table class="wysiwyg-macro" data-macro-name="unmigrated-inline-wiki-markup" data-macro-parameters="atlassian-macro-output-type=BLOCK" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e3VubWlncmF0ZWQtaW5saW5lLXdpa2ktbWFya3VwOmF0bGFzc2lhbi1tYWNyby1vdXRwdXQtdHlwZT1CTE9DS30&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>{link:AnnoOverrider|http://annogen.codehaus.org/annogen-api/org/codehaus/annogen/override/AnnoOverrider.html}{link}</pre></td></tr></table> which uses that setter to effectively change the size of the cache on <code>TinyCacheEJB</code>.  We create an instance of <table class="wysiwyg-macro" data-macro-name="unmigrated-inline-wiki-markup" data-macro-parameters="atlassian-macro-output-type=BLOCK" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e3VubWlncmF0ZWQtaW5saW5lLXdpa2ktbWFya3VwOmF0bGFzc2lhbi1tYWNyby1vdXRwdXQtdHlwZT1CTE9DS30&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>{link:StoredAnnoOverrider|http://annogen.codehaus.org/annogen-api/org/codehaus/annogen/override/StoredAnnoOverrider.html}{link}</pre></td></tr></table>, which is a helper class Annogen provides for building simple <code>AnnoOverriders</code>.</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid|title=User.java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR8dGl0bGU9VXNlci5qYXZhfQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
StoredAnnoOverrider storedOverrides = StoredAnnoOverrider.Factory.create();
</pre></td></tr></table>
<p><br class="atl-forced-newline" />
<code>StoredAnnoOverrider</code> requires us to make an <table class="wysiwyg-macro" data-macro-name="unmigrated-inline-wiki-markup" data-macro-parameters="atlassian-macro-output-type=BLOCK" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e3VubWlncmF0ZWQtaW5saW5lLXdpa2ktbWFya3VwOmF0bGFzc2lhbi1tYWNyby1vdXRwdXQtdHlwZT1CTE9DS30&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>{link:ElementId|http://annogen.codehaus.org/annogen-api/org/codehaus/annogen/override/ElementId.html}{link}</pre></td></tr></table> for the <code>TinyCacheEJB</code> class:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
ReflectElementIdPool elementPool =  ReflectElementIdPool.Factory.create();
ElementId tinyCacheEJBClassId = elementPool.getIdFor(TinyCacheEJB.class);
</pre></td></tr></table>
<p><br class="atl-forced-newline" />
...which we will use to get an instance of the <code>DeploymentInfoAnnoBean</code> which applies to <code>TinyCacheEJB</code>.</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
AnnoBeanSet annos = storedOverrides.findOrCreateStoredAnnoSetFor(tinyCacheEJBClassId);
DeploymentInfoAnnoBean annoBean = (DeploymentInfoAnnoBean)
  annos.findOrCreateBeanFor(DeploymentInfo.class);
</pre></td></tr></table>
<p><br class="atl-forced-newline" />
The <code>StoredAnnoOverrider</code> will provide this <code>DeplyomentInfoAnnoBean</code> as a replacement for the <code>DeploymentInfo</code> annotation on <code>TinyCacheEJB</code>.  So, if we change the value of cacheSize on it:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
annoBean.set_cacheSize(newCacheSize);
</pre></td></tr></table>
<p><br class="atl-forced-newline" />
We have changed the value of cache size for <code>TinyCacheEJB</code> as it will appear when our framework code views its <code>DeploymentInfo</code> annotation.</p>

<h3>View Phase</h3>

<p>Compared to the Override phase, the View phase is very simple.  All we have to do is create a <table class="wysiwyg-macro" data-macro-name="unmigrated-inline-wiki-markup" data-macro-parameters="atlassian-macro-output-type=BLOCK" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e3VubWlncmF0ZWQtaW5saW5lLXdpa2ktbWFya3VwOmF0bGFzc2lhbi1tYWNyby1vdXRwdXQtdHlwZT1CTE9DS30&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>{link:ReflectAnnoViewer|http://annogen.codehaus.org/annogen-api/org/codehaus/annogen/view/ReflectAnnoViewer.html}{link}</pre></td></tr></table> which knows about the <code>AnnoOverrider</code> we created above:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid|title=DeployerTool.java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR8dGl0bGU9RGVwbG95ZXJUb29sLmphdmF9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
annoViewer = ReflectAnnoViewer.Factory.create(myAnnoOverrider);
</pre></td></tr></table>
<p><br class="atl-forced-newline" />
This <code>annoViewer</code> can now tell us about any annotations we want to know about, and it will take our overrides into account.  So, if we get the <code>DeploymentInfo</code> for <code>TinyCacheEJB</code>:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="borderStyle=solid" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6Ym9yZGVyU3R5bGU9c29saWR9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
    DeploymentInfo deploymentInfo = (DeploymentInfo)
      annoViewer.getAnnotation(DeploymentInfo.class, TinyCacheEJB.class);
</pre></td></tr></table>
<p><br class="atl-forced-newline" />
we will get back a DeploymentInfo annotation object which reflects our cacheSize override.  </p>

<p>In reality, <code>deploymentInfo</code> is an instance of <code>DeploymentInfoAnnoBean</code>, but one nice thing here is that it is an instance of our regular 175 annotation type, <code>DeploymentInfo</code>.  We can look at the <code>cacheSize</code> value on the TinyCacheEJB and just go deploy it without a bunch of extra messy logic to check whether the value was overridden.</p>

<p>This illustrates one of the key advantages that Annogen provides: the logic for overriding annotations is cleanly paritioned away from the code which is trying to do something with those annotations.  </p>