8.6 Summary

I've chosen the jPetStore application for a variety of reasons. The biggest is that you can quickly see the difference between a simple, fast, light application and the alternative. If you are not yet a believer, I challenge you to look up the EJB version of Pet Store. If you've never seen it, you'll be blown away by the difference. Our version is transparent and independent; the EJB example is invasive and dependent on the container. Ours is easy to understand, whereas the J2EE counterpart was buried under the complexity of EJB best practices.

I haven't always been a believer. In fact, I didn't know who Rod Johnson was before we were introduced in Boston at a conference. I've since come to appreciate this simple framework as elegant and important. If you're new to Spring, you've seen only a single application. I hope that through it, you can see how it embraces the principles in this book:

Keep it simple

Spring's easy to use and understand. In a single chapter, our example covers an application with transactions, persistence, a full web frontend, and a completely modular configuration engine.

Do one thing, and do it well

Spring's framework has many different aspects and subframeworks. However, it separates each concept nicely. The fundamental value of Spring is the bean factory and configuration service, which let you manage dependencies without coupling your code. Each additional layer of Spring is cleanly decoupled and independent.

Strive for transparency

Spring applications don't need to rely on the basic container at all. In fact, they can easily exist outside of the container. You need only create and configure them manually. This ability makes Spring applications a joy to test.

You are what you eat

Spring makes smart choices in the frameworks that it includes. The respected Apache projects for data sources and logging form a good foundation. Spring allows many configurable choices, letting you choose the best frameworks for a given solution.

Allow for extension

Spring may be the most open, extensible container in existence today. It allows effective and rapid extension with common configuration services and clean abstractions.

I haven't covered Spring in its entirety. My goal is only to show you that it's possible to build real-world applications that embrace the concepts set out in the first six chapters of this book. If you decide that you'd like to see more, make sure that you look into Spring's advanced features:

• Integration with Hibernate and JDO

• AOP concepts

• Transactional templates with JTA support

In the chapters to come, we continue to explore practical examples of the principles in this book. You'll see an implementation of a service called Simple Spider, and see that service integrated into Spring. Then, you'll be able to see the benefits of improved maintenance of a framework like this going forward.