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POAdding the functionality to the servlet
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  1. POAdding the functionality to the servlet
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    copied!<p>I have developed a servlet in which user enters the name and upon clicking of a button of submit it greets the user , I also want to add the functionality that it should show the number of users currently logged in for example If i hit the servlet from one browser it should show the number of users logged in is 1 as I am the first user and if someone other hit the servlet from the next browser it should show him he is the 2 visitor , so in this way it will show him the number of users currently logged in ,please advise how to achieve that..</p> <p>The web.xml for the project is ..</p> <pre><code> &lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"&gt; &lt;display-name&gt;FirstDemo&lt;/display-name&gt; &lt;servlet&gt; &lt;servlet-name&gt;hello&lt;/servlet-name&gt; &lt;servlet-class&gt;com.saral.MyServlet&lt;/servlet-class&gt; &lt;/servlet&gt; &lt;servlet-mapping&gt; &lt;servlet-name&gt;hello&lt;/servlet-name&gt; &lt;url-pattern&gt;/helloServlet&lt;/url-pattern&gt; &lt;/servlet-mapping&gt; &lt;welcome-file-list&gt; &lt;welcome-file&gt;home.html&lt;/welcome-file&gt; &lt;/welcome-file-list&gt; &lt;/web-app&gt; </code></pre> <p>The HTML is ...</p> <pre><code>&lt;html&gt; &lt;head&gt; &lt;title&gt; A Simple web Application&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;form method="get" action="helloServlet"&gt; Name&lt;input type="text" name="txtName"&gt; &lt;br&gt;&lt;input type="submit" value="Login"&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>Please advise how to add the functionality of the numbers of users logged in. Below is the snapshot of my project structure is..<a href="http://imageshack.us/photo/my-images/685/39284405.jpg/" rel="nofollow">enter link description here</a></p> <p>I have added the counter class below as shown...</p> <pre><code>package com.saral; import javax.servlet.ServletContext; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; public class SessionCounter implements HttpSessionListener { private static int count; public SessionCounter() { } public void sessionCreated(HttpSessionEvent arg0) { count++; ServletContext sContext = arg0.getSession().getServletContext(); synchronized (sContext) { sContext.setAttribute("sessionCount", new Integer(count)); } } public void sessionDestroyed(HttpSessionEvent arg0) { count--; ServletContext sContext = arg0.getSession().getServletContext(); synchronized (sContext) { sContext.setAttribute("sessionCount", new Integer(count)); } } } </code></pre> <p>and I have modified my servlet also to this..</p> <pre><code>import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class First */ //@WebServlet("/First") public class MyServlet 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 { // TODO Auto-generated method stub String name=request.getParameter("txtName"); response.setContentType("text/html"); request.getAttribute("sessionCount"); PrintWriter out=response.getWriter(); out.println("Hello,"+name); out.println("&lt;br&gt; this output is generated by a simple servlet."); out.println("---&gt;"+(request.getAttribute("sessionCount"))); out.close(); } } </code></pre> <p>But the session I am getting is null...in output..http://imageshack.us/photo/my-images/405/sessionoutput.jpg/<a href="http://imageshack.us/photo/my-images/405/sessionoutput.jpg/" rel="nofollow">output of session</a></p> <p>Please advise how can I get the value there I am getting null rite now , I want as I MAKE first request it shoud show 1 and if I open second it should show 2 , Please advise how to achieve that as I am stuck up on this .</p>
 

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