Java and the Web
To round off our discussion of Java, especially those aspects of special interest to Oracle developers using Java on the Web, we’ll take a look at servlets, JavaServer Pages, and servlet runners in the following sections.
Java Servlets
A Java servlet is nothing more than a Java program that sits on a web server delivering web content, doing much the same thing that a Perl CGI program might do. In fact, Java servlets are essentially just “Java CGI” programs. The name “servlet” itself is a sort of pun on “applet.” If it weren’t such a tongue-twister, applets might have been called “clientlets” (try saying that after a glass of Chardonnay).
Java servlets are becoming hugely important in the world of Oracle web applications, and in servlets Java has found itself a valuable niche, especially within the realm of the Apache JServ web server covered later in this chapter. Servlets have some advantages over traditional CGI scripting techniques, in particular:
- They are highly portable.
Java servlets written on your Windows NT machine can be transferred later to your Solaris or Linux machines without any code changes.
- They avoid the areas where Java is weak.
For example, they don’t require the AWT (Abstract Windowing Toolkit).
- They benefit from the strengths of the core Java APIs.
These strengths include JDBC, multi-threadability, networking, and so on.
- They are remarkably efficient.
Servlets usually remain as object instances in memory until the web server is shut down. If they ...