Once, Run Anywhere TM philosophy of the Java family of technologies. Servlets run on any Web server, on any platform, and may access portable Java components or classes. Sun released the Java Servlet and JSP source code to the Apache and Java technology developer community, ensuring the availability of a free, open-source engine and supporting tight integration with the Apache Web Server. Most major Web and application servers support Java Servlet APIs as well. Performance Everyone hopes their Web site will grow in popularity, so it's best to start with scalability in mind.
Performance becomes an issue when the number of concurrent users accessing the Web page increases.
For high-volume sites, performance is the CGI application's fatal flaw. In a traditional CGI environment, the Web server spawns a new process every time a client requests a CGI application, loading and executing a Perl interpreter for each request. As the number of concurrent users grows, performance slows. Each program is compiled once, remaining in memory for subsequent requests. By supporting all of the Java language's benefits, Java Servlet programs make application development easier.