Create Dynamic Web Project in Eclipse and name it SessionListener
Create Dynamic Web Project in Eclipse and name it SessionListener
Create package and session listener class
net.viralpatel.servlet.listener. Inside the package, create a Java class file called SessionListener.java. Copy following content into newly created SessionListener class. package net.viralpatel.servlet.listener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class SessionListener implements HttpSessionListener {
private int sessionCount = 0;
public void sessionCreated(HttpSessionEvent event) {
synchronized (this) {
sessionCount++;
}
System.out.println("Session Created: " + event.getSession().getId());
System.out.println("Total Sessions: " + sessionCount);
}
public void sessionDestroyed(HttpSessionEvent event) {
synchronized (this) {
sessionCount--;
}
System.out.println("Session Destroyed: " + event.getSession().getId());
System.out.println("Total Sessions: " + sessionCount);
}
}
Code language: Java (java)javax.servlet.http.HttpSessionListener and override its methods sessionCreated and sessionDestroyed. The sessionCreated() method will be called by the servlet container whenever a new session is created for this application. An object of javax.servlet.http.HttpSessionEvent class is passed as an argument to the sessionCreated method. This object can be used to get the session related information including session ID. In our example we have used a counter sessionCounter which counts the number of live session at any given point of time. Whenever a new session is created, this count gets incremented. The sessionDestroyed() method will be called by the servlet container whenever an existing session is invalidated. We have used this method in our example to decrement the session count and display the ID of session being destroyed. <listener>
<description>sessionListener</description>
<listener-class>
net.viralpatel.servlet.listener.SessionListener
</listener-class>
</listener>
Code language: HTML, XML (xml)<%@page import="java.util.List"%>
<%@page import="java.util.ArrayList"%>
<html>
<head>
<title>Servlet Session Listener example - viralpatel.net</title>
</head>
<body>
<h2>Add User Screen</h2>
<span style="float: right">
<a href="DestroySession.jsp">Destroy this session</a>
</span>
<form method="post" action="AddUser.jsp">
<h3>Enter Username to Add in List</h3>
<input type="text" name="user"/>
<input type="submit" value="Add User"/>
</form>
<%
List<String> users = (List<String>)session.getAttribute("users");
for(int i=0; null!=users && i < users.size(); i++) {
out.println("<br/>" + users.get(i));
}
%>
</body>
</html>
Code language: HTML, XML (xml)<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%
String username = request.getParameter("user");
List<String> users = (List<String>)session.getAttribute("users");
if(null == users) {
users = new ArrayList<String>();
}
users.add(username);
session.setAttribute("users", users);
response.sendRedirect("index.jsp");
%>
Code language: Java (java)<%
session.invalidate();
%>
<h2>Session Destroyed successfully.. </h2>
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View Comments
Hi Veeral,
in index.jsp , for the line List user = (List)session.getAttribute("username"); it says "Type safety: Unchecked cast from Object to List" error. ????
Hi Veeral,
sorry the above comment has been modified .... for the line List user = (List)session.getAttribute("username"); it says Type safety: Unchecked cast from Object to List” error. ????
Also, in index.jsp you've written, List users = (List)session.getAttribute("users");
please explain where did we set the attribute "users" and in this jsp file how would the container know that session is an object of HttpSession as in this file we never declared it ....
Sorry if I am being pain, but I am new ...
@digant: session is an implicit object defined by container in JSP. You can directly use it in JSP without declaring it. I will suggest you to refer http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/JSPIntro7.html
The user object is set in session in AddUser.jsp
In the sessionDestroyed method do we need to explicity call invalidate method or will it be invalidated automatically. I have a case where even after session being getting destroyed, the servlet gives the same session id.
if users close their browser window,sessions get invalidated automatically..and in that case sessionDestroyed() method never get called..is there ne solution of it??
pls post..as soon as possible..thankx in advance..
What would be the time delay between actual session invalidation and session destruction. Is it always consistent?
very nice and well explained tutorial, thanks a lot man.
SessionListen
when ever i put this code in my web.xml file it give error like
init:
deps-module-jar:
deps-ear-jar:
deps-jar:
library-inclusion-in-archive:
library-inclusion-in-manifest:
compile:
compile-jsps:
Incrementally deploying http://localhost:8084/WWAtlas
Completed incremental distribution of http://localhost:8084/WWAtlas
Incrementally redeploying http://localhost:8084/WWAtlas
Start is in progress...
start?path=/WWAtlas
FAIL - Application at context path /WWAtlas could not be started
G:\Dhiren\workspace\WWAtlas\nbproject\build-impl.xml:706: The module has not been deployed.
BUILD FAILED (total time: 3 seconds)
when i removethis its work fie
pleas any one can give me solutin for that..its very helpful for me.
Thisnt is very much important for us.
There is a huge delay for invoking the sessionDestroyed method. Is there a way to reduce it?