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According to the Web Beans specification:
In many systems, use of architectural patterns produces a set of recurring Web Bean roles. A stereotype allows a framework developer to identify such a role and declare some common metadata for Web Beans with that role in a central place.
A stereotype encapsulates any combination of:
a default deployment type,
a default scope type,
a restriction upon the Web Bean scope,
a requirement that the Web Bean implement or extend a certain type, and
a set of interceptor binding annotations.
A stereotype may also specify that all Web Beans with the stereotype have defaulted Web Bean names.
A Web Bean may declare zero, one or multiple stereotypes.
A stereotype is a Java annotation type. This stereotype identifies action classes in some MVC framework:
@Retention(RUNTIME)
@Target(TYPE)
@Stereotype
public @interface Action {}
We use the stereotype by applying the annotation to a Web Bean.
@Action
public class LoginAction { ... }
A stereotype may specify a default scope and/or default deployment
type for Web Beans with that stereotype. For example, if the deployment
type @WebTier identifies Web Beans that should only
be deployed when the system executes as a web application, we might
specify the following defaults for action classes:
@Retention(RUNTIME)
@Target(TYPE)
@RequestScoped
@WebTier
@Stereotype
public @interface Action {}
Of course, a particular action may still override these defaults if necessary:
@Dependent @Mock @Action
public class MockLoginAction { ... }
If we want to force all actions to a particular scope, we can do that too.
Suppose that we wish to prevent actions from declaring certain scopes. Web Beans lets us explicitly specify the set of allowed scopes for Web Beans with a certain stereotype. For example:
@Retention(RUNTIME)
@Target(TYPE)
@RequestScoped
@WebTier
@Stereotype(supportedScopes=RequestScoped.class)
public @interface Action {}
If a particular action class attempts to specify a scope other than the Web Beans request scope, an exception will be thrown by the Web Bean manager at initialization time.
We can also force all Web Bean with a certain stereotype to implement an interface or extend a class:
@Retention(RUNTIME)
@Target(TYPE)
@RequestScoped
@WebTier
@Stereotype(requiredTypes=AbstractAction.class)
public @interface Action {}
If a particular action class does not extend the class
AbstractAction, an exception will be thrown by the
Web Bean manager at initialization time.
A stereotype may specify a set of interceptor bindings to be inherited by all Web Beans with that stereotype.
@Retention(RUNTIME)
@Target(TYPE)
@RequestScoped
@Transactional(requiresNew=true)
@Secure
@WebTier
@Stereotype
public @interface Action {}
This helps us get technical concerns even further away from the business code!
Finally, we can specify that all Web Beans with a certain stereotype
have a Web Bean name, defaulted by the Web Bean manager. Actions are often
referenced in JSP pages, so they're a perfect use case for this feature.
All we need to do is add an empty @Named annotation:
@Retention(RUNTIME)
@Target(TYPE)
@RequestScoped
@Transactional(requiresNew=true)
@Secure
@Named
@WebTier
@Stereotype
public @interface Action {}
Now, LoginAction will have the name
loginAction.
We've already met two standard stereotypes defined by the Web Beans
specification: @Interceptor and @Decorator.
Web Beans defines one further standard stereotype:
@Named
@RequestScoped
@Stereotype
@Target({TYPE, METHOD})
@Retention(RUNTIME)
public @interface Model {}
This stereotype is intended for use with JSF. Instead of using JSF
managed beans, just annotate a Web Bean @Model, and
use it directly in your JSF page.