25.8 Using Stereotypes in CDI Applications

A stereotype is a kind of annotation, applied to a bean, that incorporates other annotations. Stereotypes can be particularly useful in large applications in which you have a number of beans that perform similar functions. A stereotype is a kind of annotation that specifies the following:

• A default scope

• Zero or more interceptor bindings

• Optionally, a @Named annotation, guaranteeing default EL naming

• Optionally, an @Alternative annotation, specifying that all beans with this stereotype are alternatives

A bean annotated with a particular stereotype will always use the specified annotations, so you do not have to apply the same annotations to many beans.

For example, you might create a stereotype named Action, using the javax.enterprise.inject.Stereotype annotation:

@RequestScoped
@Secure
@Transactional
@Named
@Stereotype
@Target(TYPE)
@Retention(RUNTIME)
public @interface Action {}

All beans annotated @Action will have request scope, use default EL naming, and have the interceptor bindings @Transactional and @Secure.

You could also create a stereotype named Mock:

@Alternative
@Stereotype
@Target(TYPE)
@Retention(RUNTIME)
public @interface Mock {}

All beans with this annotation are alternatives.

It is possible to apply multiple stereotypes to the same bean, so you can annotate a bean as follows:

@Action
@Mock
public class MockLoginAction extends LoginAction { ... }

It is also possible to override the scope specified by a stereotype, simply by specifying a different scope for the bean. The following declaration gives the MockLoginAction bean session scope instead of request scope:

@SessionScoped
@Action
@Mock
public class MockLoginAction extends LoginAction { ... }

CDI makes available a built-in stereotype called Model, which is intended for use with beans that define the model layer of a model-view-controller application architecture. This stereotype specifies that a bean is both @Named and @RequestScoped:

@Named
@RequestScoped
@Stereotype
@Target({TYPE, METHOD, FIELD})
@Retention(RUNTIME)
public @interface Model {}