Servlet Listener Example
Servlet Listener Example explains step by step details of implementing a Servlet Listener
Servlet Listener is helpful for listening various events inside a servlet container, such as add an attribute in a session, create a session, to manipulate these events you need to configure listener class in web.xml
Please see the following Java Servlet Listener Example
HttpSessionAttributeListener Example HttpSessionBindingListener Example HttpSessionListener Example ServletContextAttributeListener Example ServletContextListener Example
Package Structure
For example HttpSessionListener, we need to configure web.xml in the following way
web.xml
<listener> <listener-class>com.listener.HttpSessionListenerExample</listener-class> </listener>
HttpSessionListenerExample.java
package com.listener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class HttpSessionListenerExample implements HttpSessionListener {
private static int sessions;
public static int getTotalNoOfActiveSession() {
return sessions;
}
@Override
public void sessionCreated(HttpSessionEvent arg) {
sessions++;
System.out.println("Inside sessionCreated one session is added to counter");
}
@Override
public void sessionDestroyed(HttpSessionEvent arg) {
sessions--;
System.out.println("Inside sessionDestroyed one session is deduct from counter");
}
}
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class HttpSessionListenerExample implements HttpSessionListener {
private static int sessions;
public static int getTotalNoOfActiveSession() {
return sessions;
}
@Override
public void sessionCreated(HttpSessionEvent arg) {
sessions++;
System.out.println("Inside sessionCreated one session is added to counter");
}
@Override
public void sessionDestroyed(HttpSessionEvent arg) {
sessions--;
System.out.println("Inside sessionDestroyed one session is deduct from counter");
}
}
Invoke HttpSessionListener From Servlet
HttpSession session = request.getSession(); //sessionCreated() method is invoked
session.setAttribute("url", "www.javatips.net");
session.invalidate(); //sessionDestroyed() method is invoked