Blogging Roller

For a number of reasons, I'm trying to come up to speed on Portal technology and the status of the Java Portlet API specification. I've done a little research and this is what I have gathered so far. Your comments and corrections are welcome.

What is a Portal?

A Portal is a web site that provies a starting point for access to information and applications. Registered users of a Portal are able to create their own personal views of the Portal and are able to customize both the content and layout of these views. A Portal Server provides the infrastructure for building a Portal. A Portlet is a component that plugs into a Portal Server and may then be included in a users personal views.

The Porlet API specification

The Java community has been working to standardize Portal technology for years now. So far there have been three JSR's for a Portlet API spec, JSR-162 which was withdrawn, JSR-167 which was withdrawn, and now JSR-168 which has been cooking for over a year now. JSR-168 is still private, but a public draft is expected any day now.

The Portlet API specification will make Portlets the fundamental unit of execution in a Portal Server just as the Serlvet API made Servlets the fundamental unit of execution in a Web Application Server. If you write your Portlet using the Portlet API, you'll be able to deploy it without code changes to any standard Java Portal Server just as you can deploy a Servlet to any Java Web Application Server.

Portal Servers and the Reference Implementation

The abscence of a Portal Server standard has not stopped the big J2EE players from pushing ahead with Portal Server products. Here is a quick summary of the offerings from the big players:

• Jakarta: Jetspeed - Based on the Turbine Framework. Javadocs.
• IBM: Websphere Portal - based on Jetspeed. Has it's own Portlet interface. Javadocs.
• BEA: Weblogic Portal - has it's own Portlet interface. Javadocs.
• Sun: Sun One Portal Server - doesn't define a Porlet interface. Javadocs.

Every Java spec is accompanied by a Reference Implementation (RI) and often the RI is released as an open source product.  Stefan Hepper of IBM, who is the Specification Lead for the Portlet API has proposed a new Jakarta sub-project called Pluto to develop an RI for the Portlet API. Pluto will be implemented using technology from the existing Jakarta Jetspeed product. Jetspeed committer Andy Oliver has done a nice job of summarizing the various mailing lists discussions concerning Pluto on the Pluto Talk Page.

Speculation

The Portlet API is still a secret guarded by the Java Community Process, but it is likely that the final API will look a lot like the Websphere Portal's API. After all, the specification lead works for IBM, Jetspeed is favored for the RI, and the Websphere Portal is based on Jetspeed. Based on this speculation, the best source for information on Portlet development is probably IBM's Websphere Portal Zone.  There you will find a recent interview with the lead architect of the Websphere Portal team, a very recently revised Portlet Development Guide, and an article on Developing a Struts Application for Websphere Portal 4.2.

Update: Floyd Marinescu wrote in to recommend a ServerSide article Portal Standards by Thomas Schaeck and Portlet API spec lead Steffan Hepper.