基于Apache Beehive的J2EE开发简化技术

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Apache Beehive 项目简介 Apache Beehive 项目是 Apache 软件基金会的一个开源项目，该项目的主要目的是简化 J2EE 开发，并使应用程序更加面向服务。Beehive 项目提供了一层基于 Java 1.5 中引入的注解（Annotation）技术的技术栈。 Beehive 项目的主要特点是使用注解来描述应用程序的配置和元数据，而不需要使用传统的部署描述符（Deployment Descriptor）。这种方式可以使开发者更方便地描述应用程序的配置和元数据，从而简化 J2EE 开发。 Beehive 项目的技术栈包括： * NetUI：一个基于 Java 服务器 faces（JSF）和 Struts 的 Web 应用程序框架。 * Page Flow：一个基于状态机的工作流引擎。 * Controls：一个基于 Java 服务器 faces（JSF）和 Struts 的组件库。 * Web Service Metadata（WSM）：一个基于 XML 的 Web 服务元数据描述语言。 Beehive 项目的这些技术栈可以帮助开发者更方便地构建面向服务的应用程序，并简化 J2EE 开发。在 Beehive 项目中，注解是核心技术之一。注解可以用来描述应用程序的配置和元数据，从而简化应用程序的开发和维护。Beehive 项目提供了许多有用的注解，例如 @pageFlow、@control 和 @wsdl 等，这些注解可以帮助开发者更方便地描述应用程序的配置和元数据。此外，Beehive 项目还提供了许多有用的工具和 API，可以帮助开发者更方便地构建和维护应用程序。例如，Beehive 项目提供了一个基于 Eclipse 的开发环境，可以帮助开发者更方便地构建和维护应用程序。 Apache Beehive 项目是一个功能强大且灵活的开源项目，可以帮助开发者更方便地构建面向服务的应用程序，并简化 J2EE 开发。

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CHAPTER 1

What’s Apache Beehive?

Welcome! You’ve obviously picked up this book because you’ve heard about Apache

Beehive and want to learn more. More than likely, you’re working on some sort of J2EE Web

application. You might even be an expert on BEA WebLogic Server and the technologies intro-

duced by WebLogic Workshop. If not, never mind—this book is not about BEA WebLogic, and

it’s not about BEA WebLogic Workshop. It’s about a set of technologies that are part of the

Apache Beehive project. Specifically, it’s about Service-Oriented Architecture (SOA)–based

development. It’s about using a technology such as Struts and using XML, Web Services, and

J2EE technologies to simplify SOA development.

This book is targeted at developers and architects who are interested in exploring several

new technologies that simplify SOA and Web application development.

In this chapter, you’ll briefly learn about the WebLogic Workshop IDE and how it’s inte-

grated into WebLogic Platform. With the release of WebLogic Workshop, BEA introduced

several underlying technologies. Recently these technologies were released to the Apache

Open Source Foundation. This book will cover all these technologies in detail and show you

how to use them with or without WebLogic Server. In fact, the primary platform for this book is

Apache Tomcat.

The book takes a hands-on approach to explaining the Apache Beehive technologies. In

other words, be prepared to get down and dirty with the code. We’ll introduce several concepts

and show you some code but then leave you with exercises or challenges. We’ll provide complete

solutions, but we definitely don’t recommend that you jump directly to them. We’ll point out

some tips and tricks, best practices, and so on, but at the end of the day, Apache Beehive is still

a nascent technology—so no one is really a master.

You’ll begin by learning about the challenges of enterprise application development and

about how WebLogic Workshop addresses some of those challenges. We’ll then introduce the

Apache Beehive project and XMLBeans. This will set the stage for learning all about SOA in

Chapter 2.

Enterprise Application Development:

The Challenges

The rise in IT spending that took place in the late 90s has definitely declined. Forrester Research

(http://www.forrester.com/) shows that IT spending increased about 20 percent in 2000. Since

then, it has fallen constantly every year. In 2003, Forrester Research did predict a slight rise, but

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CHAPTER 1

■ WHAT’S APACHE BEEHIVE?

the analysts don’t predict it to rise to the 2000 level until about 2005. So, these figures seem to

complicate the lives of CIOs. CIOs have the toughest challenges today when choosing technology,

products, and services while also ensuring productivity and security and providing new value-

added business features. In the following sections, we’ll describe some of the key challenges

that CIOs need to address, often with smaller budgets and more stringent software needs.

Delivering to the Customer

Time to market and productivity issues are key. End users are expecting software sooner rather

than later. Applications must be built correctly the first time, and they must continue to evolve

as the business requirements change and as management leads the business through new

evolution. The ever-changing needs of the business, the customers, the partners, the vendors,

and everyone else involved in this value chain must be quickly and accurately represented in

the applications that support these entities.

Therefore, enterprises today need business applications that accommodate increasing

functionality with constantly changing scope. A service-oriented approach promises to address

this problem through the implementation of granular services that can be shared and reused

across the enterprise. These services can be easily maintained, delivering greater agility and a

higher quality of service at lower costs.

Most CIOs are focusing on choosing widely adopted standards for software development.

This enables software development teams to concentrate on satisfying the business require-

ments quickly and with more predictable results. IT teams don’t have or can’t afford the luxury

to experiment with technologies. Programming models must evolve to support customers,

each requiring a different user interface. This will range from browser-based HTML, Java applet

clients, CGI-based Web pages, and dynamic ASP- or JSP-based sites to WAP- or WML-based

wireless devices such as PDAs.

If you think satisfying the business requirements is all CIOs need to do, you’ll definitely be

surprised. Users now not only want to see their data in a variety of formats but also want this

data to come from distinct, disparate, distributed data sources. This means you need to inte-

grate with other applications, not only within your own enterprise but many times across

enterprise boundaries. New business models and a more demanding business world demand

that executives have all sorts of information at their fingertips. You need to ensure security,

transactional integrity, auditing, logging, and monitoring across these systems. In addition,

you can’t forget about the integration of business processes. The data and the core business

services provided by one system need to be available to other systems to avoid redundancy in

building and maintaining the same functionality twice.

In addition, given evolving business requirements, it’s important that IT organizations

have the ability to make quick changes in technology decisions. Organizations need to be able

to mix and match products and technologies to provide the optimum configuration to solve

the business needs. This flexibility is required right from the hardware and operating system

level to the application deployment platforms and the tools used for application development.

These challenges clearly help motivate the need for standards in the programming model

and consistency between programming teams.

CHAPTER 1 ■ WHAT’S APACHE BEEHIVE?

Getting the Best Performance

One of the other key requirements for applications today is that they should support high

volumes of users and yet provide low response times. Typically, a user doesn’t want to wait for

more than a few seconds to see data. Systems also need to be available 24×7 and be highly fault

tolerant. Imagine that there’s a power failure at the Amazon.com server farm or, even worse,

the software had a bug and something went wrong, and you were in the process of placing an

order when something went wrong. You have no clue whether your order was processed. The

next day, you place your order again successfully. However, the first order actually had been

processed. So, you end up with two books and two charges on your credit card. Although you’ll

never know the actual cause of the problem, needless to say that you won’t be a happy camper

and probably won’t shop at that business again.

Imagine for a minute that the application is not a simple Amazon.com shopping cart that

you can easily repopulate. Instead, it’s some budgeting application or policy management

application, and you’ve spent the last hour filling in dozens of screens’ worth of form data. And

for some reason, you lose your connection for a few seconds and lose all your data. This could

be something such as a browser crash at your end or something more serious on the server

side. Now you’re really mad.

This brings up the requirements for features such as automatic load balancing, failover,

and user data replication across all layers of the architecture. Applications should be able to

handle the highest anticipated user volumes, always leaving room for the most unexpected

usage patterns, and should be able to switch configurations on the fly.

Securing Your Applications

Security is more of an issue than ever. It used to be sufficient to restrict the outside world from

accessing your data. However, since applications spanning enterprise boundaries now share

data, protecting sensitive data is more critical. You’re exchanging sensitive data with all your

suppliers, customers, and partners. You need to implement the levels of security and data

access policies carefully to ensure integrity of the data being shared.

On the flip side, the users don’t make this task any easier. They insist on a single sign-on

not only across all internal applications but also across these enterprise boundaries. Technologies

such as Microsoft Passport are fast gaining popularity. The security mechanisms need to support

this functionality while maintaining the highest levels of integrity.

Introduce wireless to this equation. Most executives do or soon will have some sort of

wireless connection to the Internet. This could be a cell phone, BlackBerry, or laptop. They will

soon start demanding the same reports and data that they can access on their desks from their

wireless devices. How do you maintain security configurations in these scenarios?

Integrating Your Applications

Large enterprises over the years have collected data in several different software systems. The

challenge today is how to reuse these systems and be able to extract data from them as needed

to serve your evolving business. To do this, IT departments need standards-based access to

these back-end systems and need to be able to ensure security, transactional control, resources,

and so on. You can use several technologies from Web Services to simple JDBC to address these

issues. Standard Enterprise Application Integration (EAI) techniques have evolved to provide

standardization on the integration problem.

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CHAPTER 1

■ WHAT’S APACHE BEEHIVE?

Having Freedom of Choice

IT departments need the flexibility to be able to mix and match solutions to form their optimal

architecture. They need to be able to choose in small chunks—right from the choice of an

application server to the development tools and frameworks they use. They also need the flex-

ibility to move from one configuration to another as business requirements change or better

technology becomes available. In addition, they need to be able to choose tools and solutions

that can help them deliver their business applications cheaper, faster, and better.

How Java Fits Into All of This

Now that I’ve covered some of the various challenges CIOs face, you may be wondering how

Java and J2EE address some of these issues. We’ll begin with a brief introduction to Java and

then talk about J2EE’s role.

The Growth of Java

Java today has become one of the leading languages for enterprise application development. Java

is a 100 percent object-oriented language. The syntax looks very much like C++ but without

some of the nightmares such as pointers and memory management. This makes it easier for

new programmers to come up to speed with the language and also provides relief for experi-

enced object-oriented programmers, who don’t have to spend hours debugging a typical C++

core dump. In addition, Java is a reliable software platform. Compile-time and then runtime

error checking teach programmers to have more reliable programming habits.

Java runs on all modern operating systems. Java code runs on top of a Java Virtual Machine

(JVM). A compiler takes the Java code and compiles it into bytecode. The JVM interprets this

bytecode at runtime. Sun and various other vendors ship platform-specific JVMs on which the

Java bytecode runs. This allows developers to write code on any platform and deploy on another

platform (see Figure 1-1). The JVM provides low-level support for operating system optimiza-

tions, shielding application developers from these issues.

Java is a free language. Anyone can download the latest version of the Java 2 Standard

Edition Development Kit (JDK) from Sun and start developing and deploying Java applications.

When you download the JDK, you get two items:

• Java API: This is a rich collection of classes that provides a programming framework

for programmers.

• JVM: This is what allows the Java code to run on different platforms. The JVM is

platform specific.

Figure 1-2 shows how a Java program sits on top of the APIs that eventually run using

the JVM.

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