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[Andromdaplugins-cvs] CVS update: cartridges/andromda-ejb3/src/site/xdoc howto13.xml
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From: Vance K. <va...@us...> - 2006-03-09 05:45:30
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User: vancek
Date: 06/03/08 21:45:29
Added: andromda-ejb3/src/site/xdoc howto13.xml
Log:
initial revision
Revision Changes Path
1.1 cartridges/andromda-ejb3/src/site/xdoc/howto13.xml
Index: howto13.xml
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<?xml version="1.0" encoding="iso-8859-1"?>
<document>
<properties>
<author email="va...@us...">Vance Karimi</author>
<title>AndroMDA - EJB3 - Interceptors</title>
</properties>
<body>
<section name="Interceptor">
<p>
Adding custom written interceptors is very easy using the EJB3 cartridge. The following sections
will provide you with enough detail to add your custom made interceptors to session and
message-driven beans. It discusses default, class and method interceptors.
</p>
<p>
All interceptors are configured through the ejb-jar deployment descriptor. The EJB3 cartridges
does NOT use annotations to define interceptors and it's exclusions.
</p>
<a name="Default_Interceptors"/>
<subsection name="Default Interceptor">
<p>
A default interceptor is invoked any time a business method of any bean within that
deployment is invoked, unless default interceptors have been excluded on beans or
business methods of beans.
</p>
<p>
To define a default interceptor for your deployment, model the
<![CDATA[<<DefaultInterceptor>>]]> stereotype on a class. Since this interceptor is invoked
for all business methods of all beans, you do not need to model any dependencies on it.
The cartridge will generate the class with the necessary interceptor operation and
corresponding annotations within the interceptor class. It will also add the
<code>interceptor-binding</code> attribute to the <code>assembly-descriptor</code> element
of the ejb-jar deployment descriptor.
</p>
<p>
You can model as many default interceptor as you require, but at this stage, the ordering
of default interceptors is not guaranteed.
</p>
</subsection>
<a name="Class_Level_Interceptor"/>
<subsection name="Class Level Interceptor">
<p>
Class level interceptors are invoked when business methods of the modelled class are invoked,
unless class level interceptors have been excluded on business methods.
</p>
<p>
To define a class level interceptor, model the <![CDATA[<<Interceptor>>]]> stereotype on
a class. You must model a dependency from a source bean to this target class level interceptor
so that the cartridge knows to configure this interceptor at the class level in the ejb-jar
deployment descriptor.
</p>
<p>
If you would like to define multiple class level interceptors, then to guarantee the ordering
in which these interceptors are invoked, you must draw a dependency from the first interceptor
to the second interceptor and so forth. This will chain the interceptors and allow the
cartridge to configure them correctly in the ejb-jar deployment descriptor.
</p>
</subsection>
<a name="Method_Level_Interceptor"/>
<subsection name="Method Level Interceptor">
<p>
Method level interceptors are very much similar to class level interceptors, but they are
bound to a specific business method within a bean. This means that they are only invoked
when the modelled business method of a bean are invoked.
</p>
<p>
To define a method level interceptor, model the <![CDATA[<<Interceptor>>]]> stereotype on
a class. You must model a dependency from a bean method to this target method level interceptor
so that the cartridge knows to configure this interceptor at the method level in the ejb-jar
deployment descriptor.
</p>
<p>
Chaining method level interceptors is exactly the same process as for class level interceptors.
</p>
</subsection>
<a name="Interceptor_Ordering"/>
<subsection name="Interceptor Ordering">
<p>
The following shows the ordering of default, class and method level interceptors.
</p>
<p>
<ul>
<li>Default Interceptors - Invoked before all other interceptors</li>
<li>
Class Level Interceptors - Invoked in the chain after default interceptors and before
method level interceptors.
</li>
<li>
Method Level Interceptors - Invoked in the chain after all class level interceptors.
</li>
</ul>
</p>
<p>
The above are the ordering for externally defined interceptors. If you define
class interceptor methods within your bean, then these are the last interceptors
to be invoked.
</p>
</subsection>
<a name="Interceptor_Exclusion"/>
<subsection name="Interceptor Exclusions">
<p>
The EJB3 cartridge allows you to exclude default interceptors for beans and bean methods.
It also allows you to exclude class level interceptors for bean methods.
</p>
<p>
To exclude the default interceptors, model the
<code>@andromda.service.interceptor.excludeDefault</code> tagged value. If this is applied to
a bean class, then the interceptor will be ignored for all methods of the bean class. If
it is modelled on a business method of a bean, then invocation of that business method
will NOT trigger invocation of the defined default interceptors.
</p>
<p>
To exclude class level interceptors, model the
<code>@andromda.service.interceptor.excludeClass</code> tagged value on business method
of beans. This will prevent the container from invoking the defined class level interceptor
when the associated bean method is invoked.
</p>
</subsection>
<a name="Interceptor_Tips"/>
<subsection name="Interceptor Tips">
<p>
In situations where you have an inheritance hierarchy, interceptor methods from the super
class are always invoked first. The exception to this rule is the case where the interceptor
has been overridden, regardless of whether the overriding method is defined as an
interceptor.
</p>
<p>
Once the interceptors have been generated, they will never be overwritten. This way, you
can add your implementation for the interceptor and call <code>InvocationContext.proceed()</code>
to continue to call the next interceptors.
</p>
<p>
Similar to bean classes, bean classes enjoy the benefits of dependency injection in much the same
way. You can inject resources using the <code>@Resource</code> annotation or an
entity manager using the <code>@PersistenceContext</code> annotation.
</p>
</subsection>
</section>
<section name="Next">
<p>
For usage of lifecycle callbacks in entity, session and message-driven beans
click <a href="howto14.html">here</a>.
</p>
</section>
</body>
</document>
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