Servlet Context Basics

Context variable can access thorough the entire application. Shared across servlets and users .But session object can't be shared across the user . so it the is an advantage of the context variable  over session.

Now lets consider how context can be created and use the same across the entire application:

package servlets.first;



import java.io.IOException;

import java.io.PrintWriter;



import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;



/**

 * Servlet implementation class SessionTest

 */

@WebServlet(description = "Write data to session and read data from session and from context as well", urlPatterns = { "/SessionTest" })

public class SessionTest extends HttpServlet {

    private static final long serialVersionUID = 1L;



    /**

     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

     */

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");

        String uname=request.getParameter("uname");   

       

        PrintWriter out=response.getWriter();

       

        HttpSession session =request.getSession();// Creation of session object

        ServletContext context=request.getServletContext();//creation of context object

        if(uname !="" && uname !=null){

        session.setAttribute("Sname",uname);

        context.setAttribute("Cname",uname);

        }

        out.println("Username From session:"+ (String)session.getAttribute("Sname")+"<BR>");//Read session data

        out.println("Username From Context:"+ (String)context.getAttribute("Cname")+"<BR>");//Read context data

        out.println("Username:"+uname);

       

               

    }
}