Prerequests for running a java servlet:
1. install JRE (Java Runtime Environment)
1.1 Download the JRE installation pack. Click here to download
1.2 Install the pack as per instructions.
1.3 Set the Environment Variable, JRE_HOME to the installed location.
1.3.1 Steps to set the Environment Variable in Windows XP/Vista
1.3.1.1 MyComputer-> Properties -> ADVANCED tab .
1.3.1.2 Click the "Environment Variables" button.
1.3.1.3 Add a new System Variable:
Variable name: JRE_HOME
Variable value: C:\Program Files\Java\jre1.5.0_01\
(or ur insalled location)
1.4 You have done with installing JRE
2. Install apache-tomcat.
2.1 Download a binary distribution of Tomcat from: http://tomcat.apache.org
2.2 Unpack the binary distribution into a convenient location so that the distribution resides in its own directory (conventionally named "apache-tomcat-[version]").
3. Include the servlet-api.jar to the CLASSPATH environment varialbe.
servlet-api.jar is not contained in JDK. It comes along with the apache-tomcat server. It is located "lib" folder of Tomcat installation direcotry.
eg: set classpath=C:\apache-tomcat-6.0.14\lib\servlet-api.jar;%classpath%
4. Start the ApacheTomcat server(startup.bat inside bin folder).
5. Now your server is ready and running.
Writing a Sample Java Servlet ::
Java servlets are no different from normal java programs. The servlet file is of .java extension. It uses javax.servlet package.
A sample and simple java servlet example :
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class myExample extends HttpServlet {
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("< HTML > \n" +
"< HEAD > < TITLE > Servlet Example from My-Tech-Experiments.blogspot.com </TITLE > < /HEAD >\n" +
"< BODY >\n" );
out.println( "<H1> Servlet Example < /H1 >\n" + " A simple Servlet.. <br/><br/><br/>Thought for the day: You never get a second chance to make the first impression.
</BODY></HTML >");
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
How to run the servlet :
step 1: Compile the servletName.java file using javac compiler just like anyother java file is compiled.
Step 2: Move the .class file to $java_installation_directory\webapps\ROOT\WEB-INF\classes\
If any directory is not found in the path, create it.
Step 3: Open the web.xml file in $java_installation_directory\webapps\ROOT\WEB-INF\
if it does not exist, create it. We use this file to map the servlet. It is must
Step 4: its content should look like this:
< ?xml version="1.0" encoding="ISO-8859-1"? >
<web-app 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_2_5.xsd"
version="2.5">
<display-name >Welcome to Tomcat </display-name >
<description >
Welcome to Tomcat
</description >
<servlet >
<servlet-name >HelloWWW </servlet-name >
<servlet-class >HelloWWW </servlet-class >
</servlet >
<servlet-mapping >
<servlet-name >HelloWWW </servlet-name >
<url-pattern >/servlet/HelloWWW </url-pattern >
</servlet-mapping >
</web-app >
Step 6: Enjooyyy...>!!!!
Note: You can use servlets to receive form-data as POST and GET. Do a google search on it and you will find it. Feeling too lazy to write that too here... check back late.. i might have posted it.
