A Spring Jump Start, Part 2
WebWork is another MVC framework. Like Struts and Spring, it supports multiple view technologies. One of the biggest differentiators for WebWork is that it adds another layer of abstraction for handling web requests. The core interface for handling requests is the Action interface, which has one method: execute(). Notice that this interface is not tied to the web layer in any way. The WebWork designers went out of their way to make the Action interface unaware that it could be used in a web context. This is good or bad, depending on your perspective. Most of the time it will be used in a web application, so hiding this fact through abstraction does not buy you much.
A feature that WebWork provides that Spring does not (at least, not explicitly) is action chaining. This allows you to map a logical request to a series of Actions. This means you can create several Action objects that all perform discrete tasks and chain them together to execute a single web request.
The idea behind Tapestry is to relieve the developer from thinking about Session attributes and URLs, and instead think of web applications in terms of components and methods. Tapestry takes on the other responsibilities, such as managing user state and mapping URLs to methods and objects.
Tapestry provides a view mechanism as well. That is, Tapestry is not a framework for using JSPs—it is an alternative to JSPs. Much of Tapestry's power lies in its custom tags that are embedded with HTML documents and used by the Tapestry framework. Needless to say, Tapestry provides a unique web application framework. To learn more about Tapestry, take a look at Tapestry in Action (Manning, 2004).
1.6.4 Persistence frameworks
There really isn't a direct comparison between Spring and any persistence framework. As mentioned earlier, Spring does not contain any built-in persistence framework. Instead, Spring's developers recognized there were already several good frameworks for this and felt no need to reinvent the wheel. They created an ORM module that integrates these frameworks with rest of Spring. Spring provides integration points for Hibernate, JDO, OJB, and iBATIS.
Spring also provides a very rich framework for writing JDBC. JDBC requires a lot of boilerplate code (getting resources, executing statements, iterating though query results, exception handling, cleaning up resources). Spring's JDBC module handles this boilerplate, allowing you to focus on writing queries and handling the results.
Spring's JDBC and ORM frameworks work within Spring's transaction management framework. This means you can use declarative transactions with just about any persistence framework you choose.
You should now have a pretty good idea of what Spring brings to the table. Spring aims to make J2EE development easier, and central to this is its inversion of control. This enables you to develop enterprise applications using simple Java objects that collaborate with each other through interfaces. These beans will be wired together at runtime by the Spring container. It lets you maintain loosely coupled code with minimal cost.
On top of Spring's inversion control, Spring's container also offers AOP. This allows you place code that would otherwise be scattered throughout you application in one place—an aspect. When your beans are wired together, these aspects can be woven in at runtime, giving these beans new behavior.
Staying true to aiding enterprise development, Spring offers integration to several persistence technologies. Whether you persist data using JDBC, Hibernate, or JDO, Spring's DAO frameworks ease your development by providing a consistent model for error handling and resource management for each of these persistence frameworks.
Complementing the persistence integration is Spring's transaction support. Through AOP, you can add declarative transaction support to your application without EJB. Spring also supports a variety of transaction scenarios, including integration with JTA transactions for distributed transactions.
Filling out its support for the middle tier, Spring offers integration with other various J2EE services, such as mail, EJBs, web services, and JNDI. With its inversion of control, Spring can easily configure these services and provide your application objects with simpler interfaces.
To help with the presentation tier, Spring supports multiple view technologies. This includes web presentation technologies like Velocity and JSP as well as support for creating Microsoft Excel spreadsheets and Adobe Acrobat Portable Document Format (PDF) files. And on top of the presentation, Spring comes with a built-in MVC framework. This offers an alternative to other web frameworks like Struts and WebWork and more easily integrates with all of the Spring services.
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About the Authors
Craig Walls is a software developer with over 10 years' experience and co-author of XDoclet in Action. He has sucessfully implemented a number of Spring applications. Craig lives in Denton, Texas.
An avid supporter of open source Java technologies, Ryan Breidenbach has been developing Java web applications for the past five years. He lives in Coppell, Texas.
About the Book
Spring in Action by Craig Walls and Ryan Breidenbach
Published February 2005, Softbound, 472 pages
Published by Manning Publications Co.
Retail price: $44.95
Ebook price: $22.50. To purchase the ebook go to http://www.manning.com/walls2.
This material is from Chapter 1 of the book.
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