Chapter 1: J2EE Architectures 第一章 J2EE框架 【概述】

Chapter 1: J2EE Architectures

Overview

J2EE provides many architectural choices. J2EE also offers many component types (such as servlets, EJBs, JSP pages, and servlet filters), and J2EE application servers provide many additional services. While this array of options enables us to design the best solution for each problem, it also poses dangers. J2EE developers can be overwhelmed by the choices on offer, or can be tempted to use infrastructure inappropriate to the problem in hand, simply because it's available.

J2EE提供了许多可供选择的框架。J2EE也支持许多类型的部件（例如：servlets，EJBs，JSP pages和servlet过滤器），并且J2EE应用服务器也提供了许多额外的服务。而这些不同的选择能够使我们对于不同的问题设计出最好的解决方案，但同时也会有一定的危险。J2EE开发人员可以选择一些提供的，或者是使用基础架构来规避手上的一些问题，因为它是可用的。

In this book I aim to help professional J2EE developers and architects make the appropriate choices to deliver high-quality solutions on time and within budget. I'll focus on those features of J2EE that have proven most useful for solving the commonest problems in enterprise software development.

在这本书里我的目标是帮助J2EE职业开发人员和工程师在预算之内做出适当的选择，提供高质量的解决方案。我将专注于那些被证明可以有效解决大多数企业软件开发问题的J2EE特性。

In this chapter, we discuss the high-level choices in developing a J2EE architecture, and how to decide which parts of J2EE to use to solve real problems. We'll look at:

在这个章节里，我们讨论在开发中可以选择的J2EE框架，并且决定如何使用一种来解决实际的问题。我们将会看到：

• Distributed and non-distributed applications, and how to choose which model is appropriate

• 分布式和非分布式的应用 ， 如何去选择一种适当的模式。

• The implications for J2EE design of changes in the EJB 2.0 specification and the emergence of web services

• J2EE中EJB2.0规范和新的WEB服务

• When to use EJB

• 如何使用EJB

• Data access strategies for J2EE applications

• J2EE应用程序中数据访问的策略

• Four J2EE architectures, and how to choose between them

• 四种J2EE框架和如何在他们当中进行选择

• Web tier design

• Web层设计

• Portability issues 

• 移植问题

This book reflects my experience and discussions with other enterprise architects. I will attempt to justify the claims made in this chapter in the remainder of the book. However, there are, necessarily, many matters of opinion.

这本书是我和其它企业的架构师的共同的经验与讨论的产物。我将在这本书中剩下的部分去说明这些。无论如何，这些意见都将是非常重要的。