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..
The web.xml for the project is ..
<?xml version="1.0" encoding="UTF-8"?>
<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">
<display-name>FirstDemo</display-name>
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>com.saral.MyServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/helloServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>home.html</welcome-file>
</welcome-file-list>
</web-app>
The HTML is …
<html>
<head>
<title> A Simple web Application</title>
</head>
<body>
<form method="get" action="helloServlet">
Name<input type="text" name="txtName">
<br><input type="submit" value="Login">
</form>
</body>
</html>
Please advise how to add the functionality of the numbers of users logged in.
Below is the snapshot of my project structure is..enter link description here
I have added the counter class below as shown…
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));
}
}
}
and I have modified my servlet also to this..
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("<br> this output is generated by a simple servlet.");
out.println("--->"+(request.getAttribute("sessionCount")));
out.close();
}
}
But the session I am getting is null…in output..http://imageshack.us/photo/my-images/405/sessionoutput.jpg/output of session
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 .
You can store a simple POJO in application scope where you can maintain the count.