专家一对一J2EE开发：无EJB技术解析

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"Expert One-on-one J2EE Development Without EJB" 本书《Expert One-on-one J2EE Development Without EJB》由Rod Johnson和Juergen Hoeller合著，旨在探讨在不使用Enterprise JavaBeans (EJB)的情况下进行J2EE开发的方法。这本书版权归属2004年的Rod Johnson和Juergen Hoeller，由Wiley Publishing, Inc.在印第安纳波利斯出版，并同时在加拿大发行。尽管EJB在J2EE框架中通常被视为核心组件，用于实现企业级服务如事务管理、安全性以及持久化等，但该书提出了一个观点：EJB并非进行J2EE开发的唯一途径。作者们可能主张，通过其他轻量级框架和技术，开发者可以更高效、更灵活地构建应用程序，同时避免EJB的复杂性和额外开销。书中可能涵盖了替代EJB的技术和方法，如Spring框架（Spring Framework），这在当时是Rod Johnson的重要贡献，它简化了Java企业应用的开发，提供了依赖注入和面向切面编程等特性。Spring框架使得开发者能够不依赖EJB就能实现服务层和数据访问层的功能。此外，书中可能会讨论如何利用Servlet和JSP进行Web层的开发，以及如何使用轻量级持久化解决方案，如Hibernate或iBatis，来处理数据库交互。这些工具和框架降低了对大型EJB容器的依赖，使得开发过程更加敏捷，同时保持了应用的可扩展性和可维护性。可能还涉及的话题包括： 1. 事务管理：在没有EJB的情况下，如何使用JTA（Java Transaction API）或其他替代策略来管理分布式事务。 2. 安全性：如何通过Java Servlet API、JAAS（Java Authentication and Authorization Service）或其他第三方库实现安全控制。 3. 部署与集成：在非EJB环境中，如何有效地部署和集成应用到不同的服务器平台。 4. 测试与持续集成：如何利用JUnit和其他测试框架，以及持续集成工具（如Ant或Maven）来确保代码质量。《Expert One-on-one J2EE Development Without EJB》提供了一种实践性的指南，教导开发者如何在不使用EJB的情况下构建强大、灵活的J2EE应用程序，这对于希望降低成本、提高开发效率的团队来说，是一份宝贵的资源。

xiv

Contents

Chapter 13: Web Tier Design 363

Goals and Architectural Issues 364

Web Tier Design Goals 365

Ad hoc MVC via Servlets and JSPs 366

Integration into Overall Application Architecture 368

Request-driven Web MVC Frameworks 374

Struts 1.1 375

WebWork2 381

Web MVC with the Spring Framework 388

Appropriate View Technologies 401

Alternative Approaches to Web MVC 403

Portals and Portlets 403

Event-driven Web MVC Frameworks 404

A Word on ASP.NET 409

Summary 410

Chapter 14: Unit Testing and Testability 411

Why Testing Matters 412

Goals of Unit Testing 414

Ensuring Testability 415

Programming Style 415

How to Make Your Code Hard to Test 416

Standard Library Challenges 420

Techniques for Improving Testability 421

Inversion of Control 425

AOP 425

Unit Testing Techniques 425

Stubs 425

Mock Objects 426

Writing Effective Tests 430

Test-driven Development (TDD) 433

Benefits 433

Arguments against TDD 434

Practicing TDD 436

Learning TDD 436

Case Study: The Spring Experience 437

Testing Spring Applications 440

Testing POJOs 440

Benefiting from Spring Abstractions 440

When You Do Need to Depend on Spring APIs 441

Testing with an Alternate Configuration 442

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Introduction

This is a fairly short book, given its scope, because its subject is less complex than you’ve been led to

believe.

J2EE orthodoxy makes heavy work of many simple problems. Indeed it sometimes seems that the J2EE

industry is committed to the belief that there are no simple problems.

Many—probably most—J2EE applications are over-engineered, with unnecessarily complex architec-

tures. Over-engineering can be very costly. J2EE developers tend to assume that increased cost up front

will be more than balanced by reductions in future costs. Unfortunately, karma doesn’t apply to software

engineering, and this is often a fallacy. Greater complexity up front means more code to write and main-

tain, more potential for bugs, more delay in demonstrating functionality to users: ultimately, greater

chance of failure, and at greater cost.

J2EE over-engineering usually involves EJB. As I pointed out in Expert One-on-One J2EE Design and

Development, EJB is often used inappropriately. This is a real problem, because EJB can introduce more

complexity than it conceals. Some services provided by EJB are also overrated. For example, few experi-

enced developers or architects who have worked with entity EJBs to access relational data want to repeat

the experience—at least, given the alternatives of JDO, Hibernate, and other transparent persistence

technologies.

Critiques of EJB have become commonplace since late 2002. It’s easy enough to pick the flaws in an

imperfect existing technology, without suggesting alternatives. This book breaks new ground in describ-

ing and illustrating better approaches for the majority of J2EE applications that derive no benefit from

EJB. This book is no mere theoretical discussion, but a practical guide to designing and implementing

high-performance J2EE applications on time and budget. Our suggested architectures are backed up by

extensive experience, a realistic sample application, and comprehensive open source solutions that meet

typical infrastructure needs.

Despite the significant problems that have emerged with EJB, it continues to be adopted too often largely

because of fashion and fear. Fashion because even nontechnical managers have heard of EJB and because

many books on J2EE architecture barely mention alternatives to EJB for delivering enterprise services,

even where excellent alternatives exist. Fear that the alternatives are worse: for example, that without

EJB developers will be left to handle complex issues such as transaction management without the train-

ing wheels of the EJB container. This book aims to show that these fears are largely unfounded. Where

the potential complexity is real, it shows that there are alternatives that do a better job than EJB at

addressing the problems concerned.

This book demonstrates a much simpler approach to developing typical J2EE appli-

cations than the “classic” J2EE blueprints approach exemplified by the original Java

Pet Store. Our approach leads to reduced cost, shorter time to market, greater main-

tainability, and better performance.

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xviii

Introduction

The architectural approach described in this book is part of a growing movement towards simpler, more

rational J2EE architectures. It’s suitable for use with agile methodologies. It draws on recently developed

technologies such as Aspect Oriented Programming, and borrows where appropriate from alternative

platforms to J2EE such as .NET.

I aim to help you build the simplest possible applications that meet your requirements—and hence, also

the cheapest, most maintainable and testable.

The merits of EJB have become a surprisingly emotive issue in the J2EE community. There seems to be a

stark polarization between those would never use EJB unless compelled and those who believe that the

EJB skeptics are lazy, ignorant heretics, with little middle ground.

As you may suspect, I’m not a fan of EJB. However, I have developed many applications with EJB and

speak from experience and intimate knowledge of the EJB specification. I’ll also strive to justify my position

throughout this book. My goal is to help you develop effective applications, not to combat the use of EJB.

After reading this book, you should be able to assess the value proposition of EJB for each application. If,

with a strong understanding of EJB and the alternatives, you believe that your requirements are best

addressed by EJB, use EJB. The message of this book is not a black-and-white “don’t use EJB.”

Who This Book Is For

This book is for J2EE architects and developers who have a solid grasp of the technology and want to

use it more productively. It’s a book about the why and how of enterprise applications, rather than the

what. So you won’t find API listings here, and you won’t find yet another introduction to basic J2EE ser-

vices such as JNDI and JTA. There are many good books and articles that address these topics.

The material in this book is particularly relevant to those working on web applications. However, most

J2EE developers will find something of value. You may well read this book and decide that EJB is the

correct choice for your particular application; even in this case, by applying the criteria set out in this

book, you’ll know exactly why you are using EJB and what value it is providing.

Aims of This Book

This book aims to help you solve practical problems. It aims to demonstrate a simpler and more produc-

tive approach to J2EE development than the traditional J2EE approach exemplified in Sun blueprints

and based on the use of EJB to manage business logic.

You might end up having a lot more fun, as well.

What This Book Covers

This book covers:

❑

Problems with EJB and received wisdom in J2EE architecture

❑ Key values for successful J2EE projects

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