Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

1.3 JavaServer Pages

9

100 element array then write into the 999th  element,  which is really some

random part of program memory. So programmers who forget to do this

check themselves open their system up to deliberate or accidental buffer

overflow attacks. Servlets suffer from neither of these problems. Even if a

servlet executes a remote system call to invoke a program on the local oper 

ating system, it does not use a shell to do so. And of course array bounds

checking and other memory protection features are a central part of the

Java programming language.

Inexpensive

There are a number of free or very inexpensive Web servers available that are

good for  personal  use or low volume Web sites. However, with the major

exception of Apache, which is free, most commercial quality Web servers are

relatively expensive. Nevertheless, once you have a Web server, no matter its

cost, adding servlet support to it (if it doesn't come preconfigured to support

servlets) costs very little extra. This is in contrast to many of the other CGI

alternatives, which require a significant initial investment to purchase a pro 

prietary package.

1.3 JavaServer Pages

JavaServer Pages (JSP) technology enables you to mix regular, static HTML

with dynamically generated content from servlets. Many Web pages that

are built by CGI programs are primarily static, with the parts that change

limited to a few small locations. For example, the initial page at most

on line stores is the same for all visitors, except for a small welcome mes 

sage giving the visitor's name if it is known. But most CGI variations,

including servlets, make you generate the entire page via your program,

even though most of it is always the same. JSP lets you create the two parts

separately. Listing 1.1 gives an example. Most of the page consists of regu 

lar HTML, which is passed to the visitor unchanged. Parts that are gener 

ated dynamically are marked with special HTML like tags and mixed right

into the page. 

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.