JSP Session Counter Using
SessionListener
Counter is a device which stores the number of times a
particular event or process has occurred. We can say that in general there is
two types of counters, first is up counters which counts upwards and the second
one is downward counter which counts from up to down.
To make a program on session counter we are making use
of the HttpSessionListener interface.This listener is a part of HttpSession
for the HttpSession object.
HttpSessionListener: By using the
HttpSessionListener for tracking the number of users who are logged into
an application. In HttpSessionListener we can implement a counter
every time a session is created and decrement it every time when the session is
destroyed.
HttpSessionListener has two methods.
- sessionCreated(HttpSessionEvent event)
- sessionDestroyed(HttpSessionEvent event)
The class HttpSessionEvent class has only one
method: getSession()
The code of the program is given below:
<html>
<head>
<title>Page 1</title>
</head>
<body>
<h1>Session Counter Demo</h1>
<a href="SessionCounterJspPage2.jsp">Click here</a> to visit second page .
</body>
</html>
|
<html>
<head>
<title>Page 1</title>
</head>
<body>
<h1>Session Demo Using HttpSessionListener</h1>
<a href="<%=response.encodeURL
("SessionCounterJspPage2.jsp")%>">Click here</a> to visit page page.
</body>
</html>
|
<html>
<head>
<title>Page 2</title>
</head>
<body>
<h1>Session Counter</h1>
<a href="<%=response.encodeURL
("SessionCounterJspPage1.jsp")%>">Click here</a> to visit first page.
</body>
</html>
|
<html>
<head>
<title>Session Counter</title>
</head>
<body>
<h1>Session Counter</h1>
There are
<%=Session.SessionCount.getNumberOfSessionsCount()%>
active sessions in the server.
</body>
</html>
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package Session;
import javax.servlet.http.*;
public class SessionCount implements HttpSessionListener{
private static int numberOfSessionsCount = 0;
public void sessionCreated (HttpSessionEvent evt){
numberOfSessionsCount++;
}
public void sessionDestroyed (HttpSessionEvent evt){
numberOfSessionsCount--;
}
// here is our own method to return the number of current sessions
public static int getNumberOfSessionsCount(){
return numberOfSessionsCount;
}
}
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The output of the program is given below:
Download this example.
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