Java Servlets - Downloading and Installation
Servlets are server side components that provides a powerful mechanism
for developing server side of web application. Earlier CGI was developed
to provide server side capabilities to the web applications. Although
CGI played a major role in the explosion of the Internet, its
performance, scalability and reusability issues make it less than
optimal solutions. Java Servlets changes all that. Built from ground up
using Sun's write once run anywhere technology java servlets provide
excellent framework for server side processing.
Java servlets web developers can create fast and efficient server side
application and can run it on any Servlet enabled web
server. Servlets runs entirely inside the Java Virtual Machine. Because
the Servlet is running on the server side, it does not depend on browser
compatibility. I just send the result in html formats.
Servlets have a number of advantages over CGI and other API's. They are:
- Platform Independence
Java Servlets are 100% pure Java, so it is platform independent. It
can run on any Servlet enabled web server. For example if you
develop an web application in windows machine running Java web
server. You can easily run the same on apache web server (if Apache
Serve is installed) without modification or compilation of code.
Platform independency of servlets provides a great advantage over
alternatives of servlets.
Due to interpreted nature of java, programs written in java are
slow. But the java servlets runs very fast. These are due to the way
servlets run on web server. For any program initialization takes
significant amount of time. But in case of servlets initialization
takes place very first time it receives a request and remains in
memory till times out or server shut downs. After servlet is loaded,
to handle a new request it simply creates a new thread and runs
service method of servlet. In comparison to traditional CGI scripts
which creates a new process to serve the request. This intuitive
method of servlets could be use to develop high speed data driven
Java Servlets are developed in java which is robust, well-designed
and object oriented language which can be extended or polymorphed
into new objects. So the java servlets takes all these advantages
and can be extended from existing class the provide the ideal
Java provides a very good safety features like memory management,
exception handling etc. Servlets inherits all these features and
emerged as a very powerful web server extension.
Servlets are server side components, so it inherits the security
provided by the web server. Servlets are also benefited with Java
Java Servlet API
Java Servlet API contains two core packages:
Servlets implement the javax.servlet.Servlet
interface. The javax.servlet package contains the generic
interfaces and classes that are implemented and extended by all servlets.
While the javax.servlet.http package contains the classes that
are used when developing HTTP - specific servlets. The HttpServlet
is extended from GenericServlet base class and it implements
the Servlet interface. HttpServlet class provides a framework
for handling the HTTP requests.
The javax.servlet.Servlet defines five methods:
- service() metho called by servlet to handle the client
request in a new thead. service() methos accepts ServletRequest
and a ServletResponse ohjects as parameters. ServletRequest
object represents the client request. It contains the data sent
in name/value pairs. ServletResponse object is used to send
the response to the client.
- init() is called once when servlet is loaded. It is a
good place to initialize global variables. This methos accepts ServletConfig
as parameter which provides initialization arguments for the servlet.
- getServletConfig() returns the ServletConfig
object passed to init().
- destory() is called when wervlet is unloaded from memory.
This is a good place to clean up any resources(such as open files or
- getServletInfo() returns a string with version, copyright
The servlet run inside a Web Server program. After
it has been compiled, it must be installed onto Web Server in order to
test it. Thus we have to follow the following steps:
- Install the servlet in a hosting server
- Request the servlet through web browser.
Java servlets are supported by a number of web servers. Java Web
Server from JavaSoft was first servlet enabled web server. Now a days a
number of web server supports java servlets. In this article we will use
Java Web Server, whose evaluation copy can be downloaded from http://jserv.javasoft.com
. In order to compile your servlet you also need Java Servlet
Development Kit (JSDK) which is available at same place.
Installing on Windows95 and Win NT
- Download the distribution of Java Web Server from http://www.javasoft.com/products
. Distribution is in the form of self-extracting file.
- The Java Web Server can be installed in any directory, so you can
choose your favorite directory for installation. Move the downloaded
file into your favorite directory.
- To begin the installation just double-click on the self-extracting
file and the file extract itself and then installation begins.
- Follow the instruction and complete the installation.
To run the Web Server go to your installation
directory and then to bin directory and then double click httpd.exe. To
test the Web Server open your browser and type http://localhost:8080
in address bar and then press enter. Browser should display default
index.html into browser.
Links To Servlets Tutorials