A Word About Spring Web Flow and Portlet API

Two additional user-interface Spring technologies might be of interest to you, if you have the need for features they provide.

Spring Web Flow

Spring Web Flow, based on similar concepts as Spring Web MVC Framework, essentially provides wizardlike screen functionality to implement a business process. Good examples of such applications include an online shopping site such as amazon.com, which requires you to go through several screens before the transaction is considered complete. This type of functionality requires session/state management, which provides the capability to go back and forth through the screens without losing the information you have already entered. This is precisely the type of functionality Web Flow eases. However, our application, Time Expression, does not require such a feature and would not be a good example for the Spring's Web Flow.

Even though Web Flow is not covered in this book, given the scope of this book, I highly recommend that you give this technology a serious look if your requirements call for this type of functionality.

Spring Portlet API

The Spring Portlet API is a new addition to Spring 2.0. It essentially implements the JSR-168 Portlet Specification defined on the Java Community Process (JCP) website (http://www.jcp.org/en/jsr/detail?id=168). According to this, the Portlet API can be used for "Portal computing addressing the areas of aggregation, personalization, presentation and security." Another way to look at this is that portlets are part of a portal website, which might contain several portlets. Portlets are different from servlets in that they do not redirect or forward any requests from or to the browser; instead, they are managed by a portlet container.

If you are interested in this API, you should check out the JCP website. Also, you might want to check out Apache's Pluto, a reference implementation for the Portlet API.