Portlet Window
The portlet window provides the face of a Web application in the portlet container. On portlet instantiation after downloading the portlet module from the container server, this window connects to the Web server, which the portlet depends on for data, and then shows the portlet UI populated with data from the server. This window has common icon buttons: setting, help, minimize, maximize, and restore. The portlet window and its views are shown in Figure 5.

The settings button has a simple menu to configure and print the portlet. On clicking “Configure,” the portlet window changes its state and shows the configuration screen for the portlet as shown in Figure 5. The view can be set back to “Data View” by again clicking “Configure” and choosing “Data View” from the menu choices.

The portlet window contains the portlet and draws different states of the portlet. To provide the basic content of the portlet rendered inside the portlet window, the portlet needs to implement the IPortlet interface. A simple IPortlet definition is shown below:

public interface IPortlet
           {
                       function get shortTitle():String;
                       function get isFlipping():Boolean;
                       function doFlip():void;
                       function getPrintView():Container;
                       function isPortletAccessible(IPortalUser user):void;
            }

Deploying Portlets to a Portal Container
Portlets are deployed to portal container as Flex modules. The module contains the Flex UI of the portlet in a IPortlet implementation. The main module inside the portlet also needs to implement the IPortletModule interface so that the actual IPortlet implementation present in the portlet module can be easily loaded. 

            public interface IPortletModule
            {
                        function getPortlet():IPortlet;
            }

To make the module smaller in size, the link report of the container may be referred during compilation. To deploy the portlet module in the container, the portlet module needs to be uploaded to the deploy folder of the container with the configuration details provided in an XML file. Depending on the server-side implementation, hot-deploy also may be done.

Cross-Platform Portlet Support
The Flex container discussed here can host portlets running on any back-end data. The only requirement is the crossdomain.xml file that needs to be present in the server from where the portlet is getting data, with an entry exposing the container root URL. Flex portlets written on J2EE, .NET, Web services, or any other custom back end can readily be hosted in the Flex container.

A Simple Implementation
In this section I explain a simple implementation with the features described in the previous section. For brevity I won’t discuss every detail here, but just try to clarify the basic infrastructure and concepts. Refer to Figure 6 for more details

In Figure 6, the bottom section shows the detailed view of the portlet container with real Flex classes that may be used to build the container functionality. In the top section the service interfaces, which need to be implemented to complete the portal container functionality, are shown. The persistence and authentication requirements for the Flex portal container are based on interfaces so that any type of server implementation (HTTP/SOAP) is possible. The source code for the interfaces can be found in the annexure-1.

Conclusion
This article provides just a cursory look at the Flex portal container. The detailed implementation and architecture details can not be covered in one article. I have already done a basic implementation of the Flex portal container; please refer to reference section for more details. Depending on the response to this article, I can start an open source project sharing my code and, with active participation from the community, build a full-fledged Flex portal container. The only flip side to this approach is that the Web application needs to be written in Flex to get any benefit from this portal container. The non-Flex JSP/ASP-based Web application won’t benefit without a Flex-based rewrite of the application.

This Flex-based portlet technology will definitely provide the infrastructure to host Flex-based content from different applications in a common container. It will enable maximum code reuse and easy deployment. For Web services, a Flex-based portal container can provide reusable UI for easy deployment in any Flex portal container. It can definitely solve the issue faced in contemporary enterprises whether to host portlets from cross-platform portal implementations.

References
Introducing Java Portlet Specifications: JSR 168 and JSR 286
http://developers.sun.com/portalserver/reference/techart/jsr168/

JSR 286: Portlet Specification 2.0
www.jcp.org/en/jsr/detail?id=286

JSR 301: Portlet Bridge Specification for JavaServer Faces
www.jcp.org/en/jsr/detail?id=301

Using Flex in a Portal
http://www.adobe.com/devnet/flex/articles/flex_portals_04.html

Open Portal, Portal Container Project
https://portlet-container.dev.java.net/