Using Annotations in Web Applications
Overview
The annotations specified by Java EE 5 simplify considerably the development process. They have two major benefits:
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They can replace the use of deployment descriptors.
Many of the tags in the deployment descriptors have their analogous annotations (such as <run-as>...</run-as> in the web.xml and the @RunAs annotation). You can configure the behavior of your application using annotations only or a combination between annotations and deployment descriptors.
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They can replace some of the complex pieces of source code (for example, the @Resource annotation can replace the code fragment for getting a resource from JNDI along with the corresponding tags in the web.xml ).
Annotations are processed during deploy time.
Annotations are not processed in the following cases:
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The Web application is compliant with J2EE 1.4 or lower
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The Web application is compliant with Java EE 5 and there is no web.xml
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The Web application is Java EE 5 and the metadata-complete attribute is set to true in the web.xml
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Annotation information is set outside the Web application (using references)
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Annotations information is not from classes placed in WEB-INF/classes or from JAR files placed in WEB-INF/lib
Annotations
More information: Annotations in Web Applications .
Web Components That Can Use Annotations
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Servlets
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Filters
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Listeners
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Taglib tag handlers
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JSF managed beans
Injecting EJB Resources into Web Applications
More information: Injecting EJB Resources into Web Applications .
Injecting Resources into Web Applications
More information: Injecting Resources into Web Applications .
Accessing Persistence in Web Applications
More information: Accessing Persistence in Web Applications .
Configuring Methods Using Annotations in Web Applications
More information: Configuring Methods Using Annotations in Web Applications .
Configuring Security Roles Using Annotations in Web Applications
More information: Configuring Security Roles Using Annotations in Web Applications .