Getting started with MVC(6)

MVC and CDI

In before posts, we have already use@Injectto inject bean into the Controller class. In fact, MVC embraced CDI internally.

RedirectScoped

There is a new CDI compatible scope namedRedirectScopedintroduced in MVC 1.0.

A bean annotated with@RedirectScopedannotation can be transfered between two requests, conceptly, it is similar with JSF Flash.

TheAlertMessageis an example.

1. Declare a bean with@RedirectScopedannotation.

   @RedirectScoped
   @Named("flashMessage")
   public class AlertMessage implements Serializable {}

2. Inject it into a Controller class.

   @Inject
   AlertMessage flashMessage;

3. Access the bean properties in the view via EL.

   <c:if test="${not empty flashMessage and not empty flashMessage.text}">
       <div class="alert alert-${flashMessage.type} alert-dismissible"
            role="alert">
           <button type="button" class="close" data-dismiss="alert"
                   aria-label="Close">
               <span aria-hidden="true"><![CDATA[&times;]]></span>
           </button>
           <p>${flashMessage.text}</p>
       </div>
   </c:if>

It is easy to understand the code snippets.

AlertMessageis aRedirectScopedbean, which means it is can be access in current request and the next request. It is named with CDI@Namedwhich indicates it can be accessed in view via EL by name flashMessage.

MVC Event

MVC defined a series of CDI compatible events, with which you can track the MVC request lifecycle.

MVC provides aMvcEventinterface as the base of all events in MVC, there are several specific event implementations.

• AfterControllerEvent
• AfterProcessViewEvent
• BeforeControllerEvent
• BeforeProcessViewEvent
• ControllerRedirectEvent

MVC itself will fire these events in the request processing progress, you can observe the events via CDI@Observes.

@ApplicationScoped
public class MvcEventListener {

    @Inject Logger LOGGER;

    private void onControllerMatched(@Observes BeforeControllerEvent event) {
        LOGGER.info(() -> "Controller matched for " + event.getUriInfo().getRequestUri());
    }

    private void onViewEngineSelected(@Observes BeforeProcessViewEvent event) {
        LOGGER.info(() -> "View engine: " + event.getEngine());
    }

    @PostConstruct
    private void init() {
        LOGGER.config(() -> this.getClass().getSimpleName() + " created");
    }
}

Source codes

1. Clone the codes from my github.com account.

   https://github.com/hantsy/ee8-sandbox/

2. Open the mvc project in NetBeans IDE.

3. Run it on Glassfish.
4. After it is deployed and runging on Glassfish application server, navigate http://localhost:8080/ee8-mvc/mvc/tasks in browser.