Portlets

Ajax to JSR 168 Portlets

noreply@blogger.com (Unknown) — Sat, 30 Oct 2010 15:44:00 +0000

Good article on Best Practices for Applying AJAX to JSR 168 Portlets http://developers.sun.com/portalserver/reference/techart/ajax-portlets.html

JSR 286 Portlet filters

noreply@blogger.com (Unknown) — Fri, 29 Oct 2010 08:26:00 +0000

The new portlet filter functionality allows you to plug filters around any life-cycle call of the portlet. Following the common decorator pattern, filters can do pre- or post-processing, and they can modify or wrap the request and response objects that are passed to the portlet. Typical applications of portlet filters could include these:

Passing information from additional sources to the portlet as attributes or parameters

Output filtering for security enforcement or markup compliance

Collecting diagnostic information

Bridging between Web application frameworks, for example, uses a filter approach to augment the markup of portlets with additional semantic information for client-side click-to-action.

The portlet filter programming model is modeled on the servlet filter model:

Define the filters in the deployment descriptor. This definition is done using the element, where you also need to state the life-cycle call to which the filter should be applied.

Implement the corresponding Filter interface in your filter. You can also list multiple life-cycle entries and implement multiple Filter interfaces with your class.

Provide a filter-mapping element where you describe to which portlets your filter should be applied (you can also use an asterisk as a wildcard if it should be applied to all portlets in the application).

The order of the filter-mapping elements in the deployment descriptor also defines the order of the filters that are applied to the portlet.

Inter Portlet Coordination with JSR 286

noreply@blogger.com (Unknown) — Thu, 28 Oct 2010 15:58:00 +0000

Coordination between portlets is a very common requirement. An example of information sharing between portlets can be a weather portlet displaying the weather information of a city and a map portlet displaying the location of the city. Since, both the portlets would be using the same zip code for a user, there should be mechanism provided by the portlal containers to allow portlets to share the zip code.

Prior to JSR 286, the support for inter portlet communication was rather minimal and information sharing between different portlets was accompalished primarily using application scoped session objects or vendor specific APIs. Both of above methods were rather problematic as in the former maintaining the uniqueness of the session attribute over a complex aaplication was a concern and in the later portability of the portlet was hampered. In order to provide coordination between portlets the Java Portlet Specification v2.0 (JSR 286) introduces the following mechanisms:

public render parameters in order to share render state between portlets.
portlet events that a portlet can receive and send.

Let's have a look how to use the above features.

What is a Portlet?

noreply@blogger.com (Unknown) — Thu, 28 Oct 2010 15:01:00 +0000

A portlet is a Web based component that will process requests and generate dynamic content. The end-user would essentially see a portlet as being a specialized content area within a Web page that occupies a small window in the portal page. Depending on the content nature of the Web site providing the portlet you could use this area to receive different types of information such as news, travel information, or even local weather. The portlet provides users with the capability to customize the content, appearance and position of the portlet.

JSR-168 Portlet Specification

noreply@blogger.com (Unknown) — Thu, 28 Oct 2010 11:36:00 +0000

JSR 168 Portlet specification

http://jcp.org/aboutJava/communityprocess/final/jsr168/index.html

JSR-286 Portlet Specification (Portlet 2.0)

noreply@blogger.com (Unknown) — Thu, 28 Oct 2010 11:31:00 +0000

JSR 286 Specification (Portlet 2.0) is available to download from the JCP website. Here is the direct link - http://jcp.org/aboutJava/communityprocess/final/jsr286/index.html

JSR 168 Tutorial - part I

noreply@blogger.com (Unknown) — Thu, 28 Oct 2010 10:26:00 +0000

What is JSR 168?

•From the portletdevelopment point of view, it is really very simple:

–You write a java class that extends GenericPortlet.

–You override/implement several methods inherited from GenericPortlet.

–You use some supporting classes/interfaces

•Many are analogous to their servletequivalents

•Some (portletsession) actually seem to be trivial wrappers around servletequivalents in Pluto.

Some Terminology

Portlet: Java code that manages a piece of web content and which may invoke services.

PortletContainer: Manages the lifecycle of the portlets (inits, invokes,destroys).

Portal: Displays the portal content provided by the container. The portal is responsible for the actual layout.

Portlet Application: A webappcontaining a group of related portlets, content, supporting jars, etc.

The Big Picture

•As a portletdeveloper, the previous set of classes are all you normally touch.

•The portletcontainer (Pluto) is responsible for running your portlets.

–Init, invoke methods, destroy.

•Portletshave a very limited way of interacting with the container.

–It is a black box->black hole.

–The API is basically one-way.

Some Generic Portlet Methods

Init : Called when the portlet is created. Override if you need to set initial params.

doView : Controls what happens immediately before the portlet is displayed in view mode. Normally you override this.

doHelp, doEdit

Other portlet display modes

processAction : Place for handling any

html form actions before turning over to the display mode method (like doView). You should override this for web forms.

Some Supporting Classes/Interfaces

PortletContext

Similar to servlet context; get context info and the RequestDispatcher from here.

PortletSession

Stores attribute information for a single portlet application across multiple requests.

RenderRequest, RenderResponse

The request and response objects available to the doView() method. Similar to the normal servlet request

ActionRequest,ActionResponse

The request and response objects available to the processAction() method. Similar to the servlet request and response objects.

PortletURL

Use this to create URLs that reference the portal.

PortletRequestDispatcher

Use this to include/forward to a JSP or servlet in the same portlet app.

WindowState

See if you are in minimized, maximized, normal state.