Java Servlet is the serverside Java programming language. We can say it as serverside applet. How applet is
used for writing the client side code, servlet is used for writing the serverside programming language. Servlet programming
is first created by Sun Microsystems in June 1997. The latest version is Servlet 2.5 which is released with JEE 5.0
specification. Servlet is a specification and it can be implemented by anyone who can fulfil the mandatory
requirements of the specification maintained by Sun.
The following are the servlet version released in the past:
- Servlet 3.0 – planned for next release
- Servlet 2.6 – September 2005
- Servlet 2.4 – November 2003
- Servlet 2.3 – August 2001
- Servlet 2.2 – August 1999
- Servlet 2.1 – November 1998
- Servlet 2.0 – 1997
- Servlet 1.0 – June 1997
Tomcat is the reference implementation for the servlet. Reference Implementation(RI) means Apache Tomcat implements
all the details in the servlet specification and creates a fully complaint servlet container. That can be used for
hosting and running the servlet application. Tomcat is maintained by the opensource foundation Apache. It is free and
anyone can use for their project without buying the license. A Servlet container is a specialized web server that supports Servlet execution. It combines the basic functionality of a web server with certain Java/Servlet specific optimizations and extensions – such as an integrated Java runtime environment, and the ability to automatically translate specific URLs into Servlet requests.
The following are the few popular webserver and application server vendors:
Servlets are not designed for a specific protocols. It is different thing that they are most commonly used with the HTTP protocols Servlets uses the classes in the java packages javax.servlet and javax.servlet.http.Servlets provides a way of creating the sophisticated server side extensions in a server as they follow the standard framework and use the highly portable java language.