Working with Session
In this tutorial, you will learn how to handle session in JSP by using session object.
HTTP protocol is stateless. It means that there is no permanent connection between client (web browser) and Web Server. When client request a page from a web server, it opens a connection, retrieve the page and close connection. Web servers doesn't know what happen then in the client side. In addition, If another request from client is made, web server doesn't associate the new connection with the connection has been made.
In order to overcome the stateless of HTTP protocol, JSP provides you the implicit session object which is a HttpSession object. The session object resides in the server side so you can keep arbitrary data about the client and other data as well in session and later on in different requests you can retrieve the saved data for processing. JSP stores data in the server side in the session object by using a single key that client remembers.
The session object has the three most important methods which you use most as bellows:
public void setAttribute(String name, Object value)
throws IllegalStateException
public Object getAttribute(String name)
throws IllegalStateException
public void removeAttribute(String name)
throws IllegalStateException
Let's take a look at an example how to use session object. In this example, we have three pages: In the first page we collection data from user, after that user submits the form to a second page which is used to store data in session. In the last page, we get data back from the session and display it.
<html>
<head>
<title>JSP Form</title>
</head>
<body>
<form method="post" action="savetosession.jsp">
<table>
<tr>
<td>First Name</td>
<td><input type="text" name="firstname" /></td>
</tr>
<tr>
<td>Last Name</td>
<td><input type="text" name="lastName" /></td>
</tr>
<tr>
<td>Comments</td>
<td><textarea name="comments" cols="30" rows="5"></textarea></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="submit" /></td>
</tr>
</table>
</form>
</body>
</html>
In the form above, when user enters information, clicks submit button, the data goes through the page savetosession.jsp. In the savetosession.jsp page we save all the submitted data into the session object and forward the request to another page called display.jsp page
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%
String firstName = request.getParameter("firstName");
String lastName = request.getParameter("lastName");
String comments = request.getParameter("comments");
// save data into the session
session.setAttribute("firstName", firstName);
session.setAttribute("lastName", lastName);
session.setAttribute("comments", comments);
%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<%-- forward to the display.jsp page--%>
<jsp:forward page="display.jsp" />
</body>
</html>
As you see the code above, we use the setAttribute() method to save data into the session object. Here is the page for displaying data in the session object: display.jsp
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<html>
<head>
<title>Displaying data in Session</title>
</head>
<body>
<h1>Displaying data in session object</h1>
<table>
<tr>
<td>First Name</td>
<td><%= session.getAttribute("firstName")%></td>
</tr>
<tr>
<td>Last Name</td>
<td><%= session.getAttribute("lastName")%></td>
</tr>
<tr>
<td>Comments</td>
<td><td><%= session.getAttribute("comments")%></td>
</tr>
</table>
</body>
</html>
The code is obvious, we used the getAttribute() method of the session object to retrieve data which was entered in the form and displayed it on the page by using expression.
How session works
When server creates a new session, it always adds a session identifier in the form of cookie. When web browser asks for a page or makes a request, the web browser always sends cookie which are created by the web server in the request. Therefore in the server side, web server checks for that cookie and find the corresponding session that is matched to the received cookie.
The session normally short-lived so the session cookie is not saved into disk. Session also has time out. When the time is out, the session is no longer exist in the server side. You can set time out of session in configuration file in the server.