With the release of GateIn 3.6.0.Final we introduced some new CDI scopes to ease its use within a portlet.  This second blog on CDI scopes for GateIn, will cover @PortletRedisplayScoped. This scope can be used with GenericPortlets, Portlet Filters, or JSF Portlets.

This scope is retained beyond a single Portlet Request lifecycle to be retrieved for all subsequent Render Requests that don't involve an Action or Event. The Beans in this scope are destroyed subsequent Action or Event requests, enabling continual refreshing of the portlet by a user to repeatedly display the same exact content as the Bean data will not be re generated for each Render. The following table illustrates when the context for the scope is activated (A), destroyed (X), or when its already present (P):

An important distinction is that any Beans created within the scope context as part of a Portlet Action, Portlet Event or Portlet Render are not visible within a Portlet Resource call, and vice versa. Each ResourceRequest will receive a completely empty set of Beans that have been constructed, including calls to any @PostConstruct, but that have had no code executed against them.

There is one difference with how Resource Request Beans are handled as compared to @PortletLifecycleScoped, in that any Beans that are used during a Resource Request will be merged into the context of the main portlet lifecycle. What this means is that the values on a @PortletRedisplayScoped bean that was used during a Resource Request will replace the contents of the same Bean type for the next Render Request that is executed. In most cases that wouldn't be a problem, but it's a potential gotcha if you make lots of Ajax calls and suddenly wonder why the values in your Beans are all wrong the next time you Render the portlet.

To begin using the new scope, simply add the following dependency into your portlet project pom.xml:

        <dependency>
            <groupId>org.gatein.api</groupId>
            <artifactId>gatein-api</artifactId>
            <version>1.0.0.Final</version>
            <scope>provided</scope>
        </dependency>

We mark the dependency as provided since GateIn will automatically link our deployment to the latest API dependency at runtime.

With the above dependency we can then create a bean such as:

@PortletRedisplayScoped
public class LifecycleBean implements java.io.Serializable {
  ...
}

Note that we implement Serializable for our Bean, as the context is stored within the User Session, which can potentially be passivated by the container.

As far as CDI is concerned, @PortletRedisplayScoped is a bean scope like all those that it provides. This enables us to inject @RequestScoped, @ConversationScoped, @SessionScoped or @ApplicationScoped beans into a @PortletRedisplayScoped bean, or vice versa.

Hope this and the scope we covered in the previous blog will make developing CDI portlets with GateIn that much easier!

With the release of GateIn 3.6.0.Final we now have the ability to inject CDI beans directly into our portlet classes, whether they extend GenericPortlet or implement the Portlet interface, and any class that implements a Portlet Filter interface.

The injection works just the same as with any other CDI injection, with one small caveat. When deciding which Beans to inject into our portlet or filter, keep in mind that injecting a normal scoped bean, such as @SessionScoped, is fine even though there is no User Session present, because the container will simply inject a client proxy for us, but it's not possible to inject a Bean that is being produced by another Bean that doesn't have a valid context.

To explain this with an example, if we take the following portlet class:

public class BadPortlet extends GenericPortlet {
  @Inject
  private Greeting myGreeting;
}

and create a producer for it such as:

@SessionScoped
public class GreetingProducer implements Serializable {
  @Produces
  public Greeting produceGreeting(InjectionPoint point) {
    ...
  }
}

We receive a ContextNotActiveException because we're trying to produce one Bean from another Bean that is not yet, as there is no User Session during Portlet Container initialization.

When wanting to inject a produced Bean into a portlet class or filter, they need to be produced by @ApplicationScoped or @Dependent scoped Beans.

Here's an example portlet showing how we can use CDI injection:

public class MyPortlet extends GenericPortlet {
  @Inject
  MyBean bean;

  public void doView(RenderRequest request, RenderResponse response) throws PortletException, IOException {
    PortletRequestDispatcher dispatcher = getPortletContext().getRequestDispatcher("/myPage.jsp");
    request.setAttribute("myBean", bean);
    dispatcher.include(request, response);
  }
}

In our JSP we can then access the bean with ${myBean}.

I hope that this introduction into creating CDI enabled portlets and portlet filters will make your next portlet a bit easier to use with CDI!