Professional

Java^reg; for Web Applications

Nicholas S. Williams

The Birth of Enterprise Java

This brief history lesson might seem unnecessary — as an existing Java developer, you have likely heard most of this before. However, itrsquo;s important to include the context of the history of

the Java Platform, Standard Edition, because it is tightly woven into the birth and evolution of the Java Platform, Enterprise Edition. Sun was already aware of the need for more advanced tools for application development, particularly in the arena of the growing Internet and the popularity of web applications. In 1998, shortly before the release of J2SE 1.2, Sun announced it was working on a product called the Java Professional Edition, or JPE. Work had already begun on a technology known as Servlets, which are miniature applications capable of responding to HTTP requests. In 1997, Java Servlets 1.0 released alongside the Java Web Server with little fanfare because it lacked many features that the Java community wanted.

After several internal iterations of Servlets and the JPE, Sun released Java 2 Platform, Enterprise Edition (or J2EE) version 1.2 on December 12, 1999. The version number corresponded with the current Java and J2SE version at the time, and the specification included:

Servlets 2.2

JDBC Extension API 2.0

Java Naming and Directory Interface (JNDI) 1.0 JavaServer Pages (JSP) 1.2

Enterprise JavaBeans (EJB) 1.1

Java Message Service (JMS) 1.0 Java Transaction API (JTA) 1.0 JavaMail API 1.1

JavaBeans Activation Framework (JAF) 1.0.

Like J2SE, J2EE was a mere specification. Sun provided a reference implementation of the specificationrsquo;s components, but companies were free to create their own as well. Many implementations evolved, and you learn about some of them in the next chapter. These

implementations included and still include open source and commercial solutions. The J2EE quickly became a successful complement to the J2SE, and over the years some components were deemed so indispensable that they have migrated from J2EE to J2SE.

Java SE and Java EE Evolving Together

J2EE 1.3 released in September 2001, a little more than a year after Java and J2SE 1.3 and before Java/J2SE 1.4. Most of its components received minor upgrades, and new features were added into the fold. The following joined the J2EE specification, and the array of implementations expanded and upgraded:

Java API for XML Processing (JAXP) 1.1

JavaServer Pages Standard Tag Library (JSTL) 1.0 J2EE Connector Architecture 1.0

Java Authentication and Authorization Service (JAAS) 1.0

At this point the technology was maturing considerably, but it still had plenty of room for improvement.

J2EE 1.4 represented a major leap in the evolution of the Java Platform, Enterprise Edition. Released in November 2003 (approximately a year before Java/J2SE 5.0 and 2 years after Java/J2SE 1.4), it included Servlet 2.4 and JSP 2.0. It was in this version that the JDBC Extension API, JNDI, and JAAS specifications were removed because they had been deemed essential to Java and moved to Java/J2SE 1.4. This version also represented the point at which J2EE components were broken up into several higher-level categories:

Web Services Technologies: Included JAXP 1.2 and the new Web Services for J2EE 1.1, Java API for XML-based RPC (JAX-RPC) 1.1, and Java API for XML Registries (JAXR) 1.0

Web Application Technologies: Included the Servlet, JSP, and JSTL 1.1 components, as well as the new Java Server Faces (JSF) 1.1

Enterprise Application Technologies: Included EJB 2.1, Connector Architecture 1.5, JMS 1.1, JTA, JavaMail 1.3, and JAF

Management and Security Technologies: Included Java Authorization Service Provider Contract for Containers (JACC) 1.0, Java Management Extensions (JMX) 1.2, Enterprise Edition Management API 1.0, and Enterprise Edition Deployment API 1.1

UndersTAnding the BaSIC Web ApPlicATIon StRucTurE

A lot of components go into making a Java EE web application. First, you have your code and the third-party libraries it depends on. Then you have the deployment descriptor, which includes instructions for deploying and starting your application. You also have the ClassLoaders responsible for isolating your application from other web applications on the same server. Finally, you must package your application somehow, and for that you have WAR and EAR files.

Servlets, Filters, Listeners, and JSPs

Servlets are a key component of any Java EE web application. Servlets, which you learn about in Chapter 3, are Java classes responsible for accepting and responding to HTTP requests. Nearly every request to your application goes through a Servlet of some type, except those requests that are erroneous or intercepted by some other component. A filter is one such component that can intercept requests to your Servlets. You can use filters to meet a variety of needs, from data formatting, to response compression, to authentication and authorization.

As with many other different types of applications, web applications have a life cycle. There are both startup and shutdown processes, and many different things happen during these stages. Java EE web applications support various types of listeners, which you learn about throughout Parts I and II. These listeners can notify your code of multiple events, such as application startup, application shutdown, HTTP session creation, and session destruction.

Perhaps one of the most powerful Java EE tools at your disposal is the JavaServer Pages technology, or JSP. JSPs provide you with the means to easily create dynamic, HTML-based graphical user interfaces for your web applications without having to

Professional 专业的Java ^reg; for Web Applications^reg;Java的 Web应用程序

Nicholas S. Williams 尼古拉斯·威廉姆斯

The Birth of Enterprise Java企业Java的诞生

讲述T his brief history lesson might seem unnecessary — as an existing Java developer, you have likely heard most of this before.他短暂的历史似乎是不必要的-因为现有的Java开发者，你可能已经听说过这个最新的历史。 However, it#39;s important to include the context of the history of 但是，重要的是要包括历史的背景

the Java Platform, Standard Edition, because it is tightly woven into the birth and evolution of the Java Platform, Enterprise Edition. Java平台标准版，因为它紧密地融入了Java平台企业版的诞生和发展。 Sun was already aware of the need for more advanced tools for application development, particularly in the arena of the growing Internet and the popularity of web applications. Sun已经意识到需要更高级的应用程序开发工具，特别是在不断发展的Internet领域以及Web应用程序的普及。 In 1998, shortly before the release of J2SE 1.2, Sun announced it was working on a product called the Java Professional Edition, or JPE. 1998年，在J2SE 1.2发布前不久，Sun宣布它正在开发一种名为Java Professional Edition或JPE的产品。 Work had already begun on a technology known as Servlets, which are miniature applications capable of responding to HTTP requests. 已经开始研究一种名为Servlets的技术，这种技术是能够响应HTTP请求的微型应用程序。 In 1997, Java Servlets 1.0 released alongside the Java Web Server with little fanfare because it lacked many features that the Java community wanted. 1997年，Java Servlets 1.0与Java Web Server一起发布，并没有大张旗鼓，因为它缺少Java社区所需的许多功能。

After several internal iterations of Servlets and the JPE, Sun released Java 2 Platform, Enterprise Edition (or J2EE) version 1.2 on December 12, 1999. The version number corresponded with the current Java and J2SE version at the time, and the specification included: 经过几次Servlet和JPE的内部迭代后，Sun于1999年12月12日发布了Java 2平台企业版（或J2EE）1.2版。版本号与当时的Java和J2SE版本相对应，规范包括：

Servlets 2.2 Servlets 2.2

JDBC Extension API 2.0 JDBC Extension API 2.0

Java Naming and Directory Interface (JNDI) 1.0 JavaServer Pages (JSP) 1.2 Java命名和目录接口（JNDI）1.0 JavaServer Pages（JSP）1.2

Enterprise JavaBeans (EJB) 1.1 Enterprise JavaBeans（EJB）1.1

Java Message Service (JMS) 1.0 Java Transaction API (JTA) 1.0 JavaMail API 1.1 Java消息服务（JMS）1.0 Java事务API（JTA）1.0 JavaMail API 1.1

JavaBeans Activation Framework (JAF) 1.0. JavaBeans Activation Framework（JAF）1.0。

Like J2SE, J2EE was a mere specification. 与J2SE一样，J2EE仅仅是一个规范。 Sun provided a reference implementation of the specification#39;s components, but companies were free to create their own as well. Sun提供了 规范组件 的 参考实现 ，但公司也可以自由创建自己的组件。 Many implementations evolved, and you learn about some of them in the next chapter. 许多实现都在不断发展，您将在下一章中了解其中的一些实现。 These 这些

implementations included and still include open source and commercial solutions. 实施包括但仍包括开源和商业解决方案。 The J2EE quickly became a successful complement to the J2SE, and over the years some components were deemed so indispensable that they have migrated from J2EE to J2SE. J2EE很快成为J2SE的成功补充，多年来，一些组件被认为是不可或缺的，他们已经从J2EE迁移到J2SE。

Java SE and Java EE Evolving Together Java SE和Java EE共同发展

J2EE 1.3 released in September 2001, a little more than a year after Java and J2SE 1.3 and before Java/J2SE 1.4. J2EE 1.3于2001年9月发布，比Java和J2SE 1.3以及Java / J2SE 1.4之前的一年多一点。 Most of its components received minor upgrades, and new features were added into the fold. 它的大多数组件都经过了小幅升级，并且新功能也被添加到了折叠中。 The following joined the J2EE specification, and the array of implementations expanded and upgraded: 以下内容加入了J2EE规范，并扩展和升级了实现数组：

Java API for XML Processing (JAXP) 1.1 用于XML处理的Java API（JAXP）1.1

JavaServer Pages Standard Tag Library (JSTL) 1.0 J2EE Connector Architecture 1.0 JavaServer Pages标准标记库（JSTL）1.0 J2EE连接器体系结构1.0

Java Authentication and Authorization Service (JAAS) 1.0 Java身份验证和授权服务（JAAS）1.0

At this point the technology was maturing considerably, but it still had plenty of room for improvement. 在这一点上，该技术已经相当成熟，但它仍有很大的改进空间。

J2EE 1.4 represented a major leap in the evolution of the Java Platform, Enterprise Edition. J2EE 1.4代表了Java平台企业版发展的一次重大飞跃。 Released in November 2003 (approximately a year before Java/J2SE 5.0 and 2 years after Java/J2SE 1.4), it included Servlet 2.4 and JSP 2.0. 2003年11月发布（大约在Java / J2SE 5.0之前一年和Java / J2SE 1.4之后两年），它包括Servlet 2.4和JSP 2.0。 It was in this version that the JDBC Extension API, JNDI, and JAAS specifications were removed because they had been deemed essential to Java and moved to Java/J2SE 1.4. 在这个版本中，JDBC Extension API，JNDI和JAAS规范被删除了，因为它们被认为是Java必不可少的，并且已经转移到Java / J2SE 1.4。 This version also represented the point at which J2EE components were broken up into several higher-level categories: 此版本还表示J2EE组件分为几个更高级别的类别：

Web Services Technologies: Included JAXP 1.2 and the new Web Services for J2EE 1.1, Java Web服务技术： 包括JAXP 1.2和新的Web Services for J2EE 1.1，Java API for XML-based RPC (JAX-RPC) 1.1, and Java API for XML Registries (JAXR) 1.0 基于XML的RPC（JAX-RPC）1.1的API和用于XML注册表的Java API（JAXR）1.0

Web Application Technologies: Included the Servlet, JSP, and JSTL 1.1 components, as well Web应用程序技术：还 包括Servlet，JSP和JSTL 1.1组件 as the new Java Server Faces (JSF) 1.1 作为新的Java Server Faces（JSF）1.1

Enterprise Application Technologies: Included EJB 2.1, Connector Architecture 1.5, JMS 企业应用技术： 包括EJB 2.1，Connector Architecture 1.5，JMS 1.1, JTA, JavaMail 1.3, and JAF 1.1，JTA，JavaMail 1.3和JAF

Management and Security Technologies: Included Java Authorization Service Provider 管理和安全技术： 包含Java授权服务提供商 Contract for Containers (JACC) 1.0, Java Management Extensions (JMX) 1.2, Enterprise Edition Management API 1.0, and Enterprise Edition Deployment API 1.1 容器合同（JACC）1.0，Java管理扩展（JMX）1.2，企业版管理API 1.0和企业

资料编号：[5695]