Using Annotations in Web Applications (SAP Library - Developing Java EE 5 Applications)

Using Annotations in Web Applications

Use

Overview

The annotations specified by Java EE 5 simplify considerably the development process. They have two major benefits:

● 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.

· 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.

Note

Annotations are not processed in the following cases:

■ The Web application is compliant with J2EE 1.4 or lower

■ The Web application is compliant with Java EE 5 and there is no web.xml

■ The Web application is Java EE 5 and the metadata-complete attribute is set to true in the web.xml

■ Annotation information is set outside the Web application (using references)

■ 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

· Servlets

· Filters

· Listeners

· Taglib tag handlers

· JSF managed beans

Procedure