How to Create "HelloWorldServlet" and what are the things I need to do....... ?

What is Tomcat ?

Tomcat is webcontainer which has the capability to execute Servlets and JSP pages.
I am not going in to more details about tomcat.After downloding tomcat from internet
you will see a folder structure as in below picture.To execute our HelloWorldServlet
download tomcat which is available for free from Internet.

2)How to start tomcat server?


Go to bin folder in TOMCAT_HOME.When I say TOMCAT_HOME it means the
path which contains bin folder(C:\Tomcat7).In bin folder you will find a batch file
with name startup.If you click on it tomcat server starts.But the prerequisite is you
should set environment variable "JAVA_HOME".

Every server runs on a port.Tomcat by default starts on "8080".
If there is any thing that runs on 8080 tomcat server won't startup.

Following screen is an example of successful tomcat startup.

3)How to set JAVA_HOME ?


Go to MyComputer->Right Click on MyComputer->Choose Properties->
AdvancedSystemSettings->Advanced Tab->Click on Environment Variables
->Click on New(User Variables)


Give Variable name as:  JAVA_HOME
Variable value:              C:\Java\jdk1.7
(The folder which contains bin folder is the JAVA_HOME)

Click OK

 

4)Create HelloWorldServlet.java.

I have created in C:\test\examples\HelloWorldServlet.java
Copy the following code in Red into HelloWorldServlet.java in C:\test\examples
folder

package examples;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author Rishitha
 */
public class HelloWorldServlet extends HttpServlet {

 

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        PrintWriter writer = response.getWriter();
        writer.print("From doGet method  ");
      
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
         PrintWriter writer = response.getWriter();
        writer.print("From doPost method  ");
       
    }

}


 5)Go to C:\test\examples and compile HelloWorldServlet.java.

If you have observed HelloWorldServlet.java,it is using many classes like
HttpServletRequest,HttpServletResponse,HttpServlet.


All those classes are available in servlet-api.jar
servlet-api.jar is present in C:\tomcat7\lib folder

 So,before compiling HelloWorldServlet.java we have to set classpath to
 servlet-api.jar file which contains  HttpServletRequest,HttpServletResponse,
HttpServlet.

6)How to set classpath to servlet-api.jar ?

  a)Go to C:\test\examples
  and type set classpath=%classpath%;C:\Tomcat7\lib\servlet-api.jar

  b)Compile HelloWorldServlet.java from C:\test\examples
      javac HelloWorldServlet.java

 

 

 

 

7)To run servlet you have to place it webapplication.
    Every webapplication should follow a predetermined format.


8)How to prepare predefined webapplication format ?

    Following is the structure we have to follow for any webapplication
    -----------------------------------------------------------------------------------------

          Every web application will have WEB-INF Folder
          WEB-INF folder contains
                a)classes folder(This should contain compiled class files)
                b)web.xml
                  

  1) Create one folder with name "webexamples"
  2)In webexamples folder,Create WEB-INF folder
  3)Go inside WEB-INF folder.Create following
         a)classes folder
         b)web.xml

  4)Copy the following content into web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
    <servlet>
        <servlet-name>HelloWorldServlet</servlet-name>
        <servlet-class>examples.HelloWorldServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloWorldServlet</servlet-name>
        <url-pattern>/HelloWorldServlet</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
</web-app>

9)Go to the C:\test\.
  From there copy the examples folder in to classes folder created in above step.

Folder structure of webexamples folder should be as given in the following
pictures for your reference

 Go to WEB-INF.. It should look like in the following picture

 Classes folder should contain our examples folder which contains HelloWorldServlet.class
as in the following image.

 
10)After creating the webexamples folder in the specified format

Copy the webexamples foder to
C:\Tomcat7\webapps

And we are almost to end of this post.......... :)


11)Go to C:\tomcat7\bin\->Click on startup.bat to start tomcat server

Go to browser

Enter following URL

http://localhost:8080/webexamples/HelloWorldServlet
(If your tomcat is running on another port eg:8084,you have to give url
as
http://localhost:8084/webexamples/HelloWorldServlet


You should see the following output....
If you get "From doGet method"... that means...... You executed your first
HelloWorldServlet successfully.

 If you are first time............. doing this procedure.............. it seems very difficult...........
 but once you practice........... this will be very very easy......................


 If you have doubts you can contact me at
 anilkumar.spectrum@gmail.com

Hope you enjoyed.......... HelloWorldServlet........... 
Anil Chintha............