#4_Creating_a_Servlet

--> Create a java class for servlet in your com.servlet that is also made earlier

--> ===================================== ADD SERVLET CLASS ==============================================

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AddServlet extends HttpServlet 
{

	public void doGet(HttpServletRequest req , HttpServletResponse res) throws IOException, ServletException 
	{
		int i = Integer.parseInt(req.getParameter("num1"));
		int j = Integer.parseInt(req.getParameter("num2"));
		
		int k = i + j;
		
		// Session Management --> concept used to print the added value in this case. Data is shared from one Servlet to another
		
		req.setAttribute("k", k);
		
		PrintWriter out = res.getWriter();
		out.println("Result is: " +k); 
		
		// To call servlet we have two methods:
		// 1. Request Dispatcher (Req Dis)
		// 2. Redirect (Redirect)
		
		RequestDispatcher rd = req.getRequestDispatcher("sq");
		rd.forward(req, res);
			
	}

}

=========================================== MAPPING AND SERVLET METHOD IN XML ==================================================
--> To open xml file drop down >src>main>java>webapp>META-INF



<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  
  <servlet>
  
  	<servlet-name>abc</servlet-name>
  	<servlet-class>com.servlet.AddServlet</servlet-class>
  	
  </servlet>
  
  <servlet-mapping>
  
  <servlet-name>abc</servlet-name>
  <url-pattern>/add</url-pattern>
  
  </servlet-mapping>
  
  <servlet>
  
  	<servlet-name>pqr</servlet-name>
  	<servlet-class>com.servlet.SquareServlet</servlet-class>
  	
  </servlet>
  
  <servlet-mapping>
  
  <servlet-name>pqr</servlet-name>
  <url-pattern>/sq</url-pattern>
  
  </servlet-mapping>
  
</web-app>