Java Servlet编程深度探索与实践指南

需积分: 9 141 浏览量更新于2024-07-26 1 收藏 4.32MB PDF 举报

《O'Reilly Java Servlet Programming》是一本深入探讨Java Servlet编程的专业指南，适合那些希望在Web应用程序开发领域中熟练掌握这一技术的开发者。本书由Jason Hunter与William Crawford合著，它涵盖了Java Servlet技术的核心内容以及其在Java网络编程中的应用，包括但不限于： 1. **历史回顾与背景**：章节一开始，作者介绍了Web应用程序的历史发展，阐述了Java Servlet在早期Web技术演进中的地位和作用，强调了其在支持动态内容和服务请求处理方面的关键性。 2. **Servlet支持**：这部分详细介绍了Servlet的架构和支持，包括Java虚拟机（Java Virtual Machine, JVM）如何在服务器端执行Servlet，以及Servlet API的基础结构，如Servlet生命周期、请求和响应管理等。 3. **Servlet的强大之处**：书中深入解析了Servlet的威力，如其灵活性、可扩展性和模块化设计，展示了如何利用Servlet构建高效、可维护的Web应用。 4. **HTTP基础与基本操作**：这部分介绍了HTTP协议的基础知识，帮助读者理解如何通过Servlet处理HTTP请求和响应，包括页面生成、动态内容的生成等。 5. **服务器端包含（Server-Side Includes,SSI）**：讲解了如何利用SSI技术在Servlet中嵌入动态内容，提高开发效率。 6. **Servlet链与过滤器（Servlet Chaining and Filters）**：讨论了如何通过Servlet链来组织多个Servlet处理请求，并介绍过滤器（Filters）在控制请求流程中的作用。 7. **JavaServer Pages (JSP)**：作为Servlet的重要补充，JSP是将服务器端代码嵌入HTML的一种方式，作者会解释JSP的工作原理和如何与Servlet协同工作。 8. **进一步学习与实践**：书的后半部分可能包含了对其他Java技术的链接，如线程处理、数据库编程（JDBC）、分布式计算、JavaBean开发、安全性、加密、图形用户界面（AWT/Swing）等内容，让读者在Servlet基础上拓宽知识面。此外，该书还提到了与之相关的其他O'Reilly出版物，如《Java in a Nutshell》系列，这些书籍为读者提供了丰富的学习资源和实例，有助于深入理解和实践Java技术。《O'Reilly Java Servlet Programming》是一本全面而实用的指南，不仅介绍了核心概念和技术，还为读者提供了探索更广阔Java编程世界的桥梁，对于想要在Web开发领域深化技能的程序员来说，是一本不可多得的参考资料。

xvi PREFACE

Java™ Servlet Programming, eMatter Edition

(who looks the spitting image of James Gosling), Jim Driscoll, Rob Clark, and Dave

Brownell.

Thanks also to the members of the jserv-interest mailing list, whose questions and

answers have shaped the content of this book; Will Ramey, an old friend who

didn’t let friendship blind his critical eye; Mike Engber, the man to whom I turned

when I had run out of elegant workarounds and was ready to accept the crazy

things he comes up with; Dave Vandegrift, the first person to read many of the

chapters; Bill Day, author of Java Media Players, who helped intangibly by going

through the book writing process in parallel with me; Michael O’Connell and Jill

Steinberg, editors at JavaWorld, where I did my first professional writing; Doug

Young, who shared with me the tricks he learned writing seven technical books of

his own; and Shoji Kuwabara, Mieko Aono, Song Yung, Matthew Kim, and Alex-

andr Pashintsev for their help translating “Hello World” for Chapter 12.

Finally, thanks to Mom and Dad, for their love and support and for the time they

spent long ago teaching me the basics of writing. And a special thanks to my girl-

friend, Kristi Taylor, who made the small time away from work a pleasure.

And Grandpa, I wish you could have seen this.

Jason Hunter

July 1998

William Crawford

First and foremost, thanks to Shelley Norton, Dr. Isaac Kohane, Dr. James Fackler,

and Dr. Richard Kitz (plus a supporting cast whose contributions were invalu-

able), whose assistance and early support have made everything since possible.

Also, to Martin Streeter of Invantage, Inc., for his support during this project.

Without Rob Leith, Roger Stacey, and Fred Strebeigh, I would probably still be

stuck in the passive voice. Dale Dougherty offered me money in exchange for

words, a twist of events that I still haven’t gotten over. Andy Kwak, Joel Pomerantz,

and Matthew Proto, brave souls all, were willing to read drafts and listen to

complaints at one o’clock in the morning.

And, of course, to Mom and Dad for their years of support, and to my sister Faith

for (usually) letting me get away with being a nerd.

William Crawford

July 1998

Java™ Servlet Programming, eMatter Edition

Chapter 1

In this chapter:

• History of Web

Applications

• Support for Servlets

• The Power of Servlets

1. Introduction 1:

The rise of server-side Java applications is one of the latest and most exciting

trends in Java programming. The Java language was originally intended for use in

small, embedded devices. It was first hyped as a language for developing elaborate

client-side web content in the form of applets. Until recently, Java’s potential as a

server-side development platform had been sadly overlooked. Now, Java is coming

into its own as a language ideally suited for server-side development.

Businesses in particular have been quick to recognize Java’s potential on the

server—Java is inherently suited for large client/server applications. The cross-

platform nature of Java is extremely useful for organizations that have a heteroge-

neous collection of servers running various flavors of the Unix and Windows

operating systems. Java’s modern, object-oriented, memory-protected design

allows developers to cut development cycles and increase reliability. In addition,

Java’s built-in support for networking and enterprise APIs provides access to legacy

data, easing the transition from older client/server systems.

Java servlets are a key component of server-side Java development. A servlet is a

small, pluggable extension to a server that enhances the server’s functionality.

Servlets allow developers to extend and customize any Java-enabled server—a web

server, a mail server, an application server, or any custom server—with a hitherto

unknown degree of portability, flexibility, and ease. But before we go into any

more detail, let’s put things into perspective.

History of Web Applications

While servlets can be used to extend the functionality of any Java-enabled server,

today they are most often used to extend web servers, providing a powerful, effi-

cient replacement for CGI scripts. When you use a servlet to create dynamic

2CHAPTER 1: INTRODUCTION

Java™ Servlet Programming, eMatter Edition

content for a web page or otherwise extend the functionality of a web server, you

are in effect creating a web application. While a web page merely displays static

content and lets the user navigate through that content, a web application

provides a more interactive experience. A web application can be as simple as a

keyword search on a document archive or as complex as an electronic storefront.

Web applications are being deployed on the Internet and on corporate intranets

and extranets, where they have the potential to increase productivity and change

the way that companies, large and small, do business.

To understand the power of servlets, we need to step back and look at some of the

other approaches that can be used to create web applications.

Common Gateway Interface

The Common Gateway Interface, normally referred to as CGI, was one of the first

practical techniques for creating dynamic content. With CGI, a web server passes

certain requests to an external program. The output of this program is then sent

to the client in place of a static file. The advent of CGI made it possible to imple-

ment all sorts of new functionality in web pages, and CGI quickly became a de

facto standard, implemented on dozens of web servers.

It’s interesting to note that the ability of CGI programs to create dynamic web

pages is a side effect of its intended purpose: to define a standard method for an

information server to talk with external applications. This origin explains why CGI

has perhaps the worst life cycle imaginable. When a server receives a request that

accesses a CGI program, it must create a new process to run the CGI program and

then pass to it, via environment variables and standard input, every bit of informa-

tion that might be necessary to generate a response. Creating a process for every

such request requires time and significant server resources, which limits the

number of requests a server can handle concurrently. Figure 1-1 shows the CGI

life cycle.

Figure 1-1. The CGI life cycle

CGI-based Web Server

Main Process

Request for CGI1

Request for CGI2

Request for CGI1

Child Process for CGI1

Child Process for CGI2

Child Process for CGI1

HISTORY OF WEB APPLICATIONS 3

Java™ Servlet Programming, eMatter Edition

Even though a CGI program can be written in almost any language, the Perl

programming language has become the predominant choice. Its advanced text-

processing capabilities are a big help in managing the details of the CGI interface.

Writing a CGI script in Perl gives it a semblance of platform independence, but it

also requires that each request start a separate Perl interpreter, which takes even

more time and requires extra resources.

Another often-overlooked problem with CGI is that a CGI program cannot

interact with the web server or take advantage of the server’s abilities once it

begins execution because it is running in a separate process. For example, a CGI

script cannot write to the server’s log file.

For more information on CGI programming, see CGI Programming on the World

Wide Web by Shishir Gundavaram (O’Reilly).

FastCGI

A company named Open Market developed an alternative to standard CGI named

FastCGI. In many ways, FastCGI works just like CGI—the important difference is

that FastCGI creates a single persistent process for each FastCGI program, as

shown in Figure 1-2. This eliminates the need to create a new process for each

request.

Although FastCGI is a step in the right direction, it still has a problem with process

proliferation: there is at least one process for each FastCGI program. If a FastCGI

program is to handle concurrent requests, it needs a pool of processes, one per

request. Considering that each process may be executing a Perl interpreter, this

approach does not scale as well as you might hope. (Although, to its credit, FastCGI

can distribute its processes across multiple servers.) Another problem with FastCGI

is that it does nothing to help the FastCGI program more closely interact with the

server. As of this writing, the FastCGI approach has not been implemented by some

Figure 1-2. The FastCGI life cycle

Main Process

Request for CGI1

Request for CGI2

Request for CGI1

Single Child Process for CGI1

Single Child Process for CGI2

FastCGI-based Web Server

4CHAPTER 1: INTRODUCTION

Java™ Servlet Programming, eMatter Edition

of the more popular servers, including Microsoft’s Internet Information Server.

Finally, FastCGI programs are only as portable as the language in which they’re

written.

For more information on FastCGI, see http://www.fastcgi.com/.

mod_perl

If you are using the Apache web server, another option for improving CGI perfor-

mance is using mod_perl. mod_perl is a module for the Apache server that embeds a

copy of the Perl interpreter into the Apache httpd executable, providing complete

access to Perl functionality within Apache. The effect is that your CGI scripts are

precompiled by the server and executed without forking, thus running much

more quickly and efficiently. For more information on mod_perl, see http://perl.

apache.org/.

PerlEx

PerlEx, developed by ActiveState, improves the performance of CGI scripts written

in Perl that run on Windows NT web servers (Microsoft’s Internet Information

Server, O’Reilly’s WebSite Professional, and Netscape’s FastTrack Server and

Enterprise Server). PerlEx uses the web server’s native API to achieve its perfor-

mance gains. For more information, see http://www.activestate.com/plex/.

Java Servlet编程深度探索与实践指南

Java Servlet Programming

Java Programming with Oracle JDBC

Java学习书目（各学习阶段都有推荐）

javaXP极限编程

学java该看的一些书~

深入探索Java Servlet编程

深入学习Java Servlet编程

Java Servlet编程入门指南

Java Servlet编程入门与核心知识点

全面指南：Java Servlet编程实战与核心技术

最新资源