Servlet Lab Program 1

 

------- ----------------------            Servlet Configure                   -------------------- -------------------

Copy the file "servlet-api.jar" from location YOUR_INSTILLATION_PATH\tomcat\lib\servlet-api.jar and Paste the file into your Java Directory YOUR_INSTILLATION_PATH\Java\jdk1.8.0_121\jre\lib\ext

this will work (tested).

 

--------------------                 ------------------------------------          Example to config Servlet               ------------------------------

Copy : C:\xampp\tomcat\lib\servlet-api.jar

 

Paste:  C:\Program Files\Java\jdk1.8.0_261\jre\lib\ext\servlet-api.jar

------- ---------------------- ----------------------------- ----------------------------------- -------------------

----- ----------------------------------- ----------------------------- Example 1 -------------------------------------------- ------------------------ ------

C:\xampp\tomcat\webapps\first

//My.java

import javax.servlet.*;

import javax.servlet.http.*;

import java.io.*;

 

public class My extends HttpServlet {

public void service(HttpServletRequest req, HttpServletResponse res) throws

ServletException, IOException{

               PrintWriter p = res.getWriter();

               p.println("hello servlet");

}

}

 

--------------  --------------- Compile ----------------

Class file will store in folder WEB-INF\classes as file name My.class

Javac –d WEB-INF\classes My.java

 

----------- -

 

C:\xampp\tomcat\webapps\first\WEB-INF

// WEB-INF/web.xml

<web-app>

<servlet>

               <servlet-name>My</servlet-name>

               <servlet-class>My</servlet-class>

</servlet>

<servlet-mapping>

               <servlet-name>My</servlet-name>

               <url-pattern>/My</url-pattern>

</servlet-mapping>

</web-app>

----- ----------------------------------- ----------------------------- Example 2 -------------------------------------------- ------------------------ ------

Servlets are Java classes which service HTTP requests and implement the javax.servlet.Servlet interface. Web application developers typically write servlets that extend javax.servlet.http.HttpServlet, an abstract class that implements the Servlet interface and is specially designed to handle HTTP requests.

Sample Code

Following is the sample source code structure of a servlet example to show Hello World −

// Import required java libraries

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

 

// Extend HttpServlet class

public class HelloWorld extends HttpServlet {

 

   private String message;

 

   public void init() throws ServletException {

      // Do required initialization

      message = "Hello World";

   }

 

   public void doGet(HttpServletRequest request, HttpServletResponse response)

      throws ServletException, IOException {

     

      // Set response content type

      response.setContentType("text/html");

 

      // Actual logic goes here.

      PrintWriter out = response.getWriter();

      out.println("<h1>" + message + "</h1>");

   }

 

   public void destroy() {

      // do nothing.

   }

}

 

 

Compiling a Servlet

Let us create a file with name HelloWorld.java with the code shown above. Place this file at C:\ServletDevel (in Windows) or at /usr/ServletDevel (in Unix). This path location must be added to CLASSPATH before proceeding further.

Assuming your environment is setup properly, go in ServletDevel directory and compile HelloWorld.java as follows −

$ javac HelloWorld.java

 

 

If everything goes fine, above compilation would produce HelloWorld.class file in the same directory. Next section would explain how a compiled servlet would be deployed in production.

Servlet Deployment

By default, a servlet application is located at the path <Tomcat-installationdirectory>/webapps/ROOT and the class file would reside in <Tomcat-installationdirectory>/webapps/ROOT/WEB-INF/classes.

If you have a fully qualified class name of com.myorg.MyServlet, then this servlet class must be located in WEB-INF/classes/com/myorg/MyServlet.class.

For now, let us copy HelloWorld.class into <Tomcat-installationdirectory>/webapps/ROOT/WEB-INF/classes and create following entries in web.xml file located in <Tomcat-installation-directory>/webapps/ROOT/WEB-INF/

<servlet>

   <servlet-name>HelloWorld</servlet-name>

   <servlet-class>HelloWorld</servlet-class>

</servlet>

<servlet-mapping>

   <servlet-name>HelloWorld</servlet-name>

   <url-pattern>/HelloWorld</url-pattern>

</servlet-mapping>

Above entries to be created inside <web-app>...</web-app> tags available in web.xml file. There could be various entries in this table already available, but never mind.

You are almost done, now let us start tomcat server using <Tomcat-installationdirectory>\bin\startup.bat (on Windows) or <Tomcat-installationdirectory>/bin/startup.sh (on Linux/Solaris etc.) and finally type http://localhost:8080/HelloWorld in the browser's address box. If everything goes fine, you would get the following result