Introduction

by Jim Inscore and Nicholas Kassem

Since its introduction more than two years ago, the Java 2 Platform, Enterprise Edition (J2EE), has rapidly established a new model for developing distributed applications. This model is based on well-defined components that can automatically take advantage of sophisticated platform services. These components can be developed according to standard guidelines, combined into applications, deployed on a variety of compatible server products, and reused for maximum programmer productivity. This model is intended to both standardize and simplify the kind of distributed applications required for today's networked information economy. The success of the J2EE platform is in large part due to the success of this model.

Today, all leading application server and enterprise information system vendors have adopted the J2EE standard and introduced products based on the J2EE platform specification. Application architects and developers have come to rely on the J2EE standard to help them solve the various design challenges that face them day to day.

While the fundamentals of the J2EE platform are relatively easy to describe, mapping these features to architectural issues in the design of distributed applications requires deeper understanding and careful decision making. Although the J2EE standard offers a simplified programming model compared to previous alternatives, the platform isn't monolithic. Certain features require that architects and developers weigh their options before making design decisions and be prepared to re-think those decisions as they uncover new challenges. That, in turn, requires some understanding of the design motivations behind the platform and of the trade-offs involved in applying specific design features to a specific architectural problem.

Different implementations of the J2EE platform may provide distinguishing characteristics that improve their performance or development ease in particular areas. However, the level of abstraction provided by the J2EE standard enables common themes to be developed, explained, and explored and certain common design guidelines to be developed. That's what Java BluePrints is all about. It answers questions like:

• What's the best way to apply each type of J2EE component?
• Where does it make sense to use Java servlets and where to use JavaServer Pages?
• What's the best way to factor business logic between entity beans and session beans?
• How do you choose between container-managed and bean-managed persistence when using entity beans?
• What are the design and performance trade-offs between choosing a distributed architecture and one based on local interfaces?
• In this increasingly security-conscious world, how do you design distributed applications to be accessible to users who need them and secure from unwanted intrusion?

Before the remainder of this book takes you more deeply into these and other details of J2EE application architectures, this chapter gives you a look at some of the design motivations behind the J2EE platform. It describes the high-level benefits of the J2EE platform and discusses ways that using it as the underlying architecture for distributed applications makes sense for a variety of application requirements.