Session Management in JSP
As we know that the Http protocol is a stateless
protocol, that means that it can't persist the data. Http treats each request as
a new request so every time you will send a request you will be considered as a
new user. It is not reliable when we are doing any type of transactions or any
other related work where persistence of the information is necessary.
To remove these obstacles we use session management. In session management
whenever a request comes for any resource, a unique token is generated by the
server and transmitted to the client by the response object and stored on the
client machine as a cookie. We can also say that the process of managing the
state of a web based client is through the use of session IDs. Session IDs are
used to uniquely identify a client browser, while the server side processes are
used to associate the session ID with a level of access. Thus, once a client has
successfully authenticated to the web applicatiion, the session ID can be used
as a stored authentication voucher so that the client does not have to retype
their login information with each page request. Now whenever a request goes from this client again
the ID or token will also be passed through the request object so that the server can
understand from where the request is coming. Session management can be
achieved by using the following thing.
1. Cookies: cookies are small bits of textual
information that a web server sends to a browser and that browsers returns the
cookie when it visits the same site again. In cookie the information is stored
in the form of a name, value pair. By default the cookie is generated. If the
user doesn't want to use cookies then it can disable them.
2. URL rewriting: In URL rewriting we append
some extra information on the end of each URL that identifies the session. This
URL rewriting can be used where a cookie is disabled. It is a good practice to
use URL rewriting. In this session ID information is embedded in the URL, which
is recieved by the application through Http GET requests when the client clicks
on the links embedded with a page.
3. Hidden form fields: In hidden form fields the
html entry will be like this : <input type ="hidden" name =
"name" value="">. This means that when you submit the
form, the specified name and value will be get included in get or post method.
In this session ID information would be embedded within the form as a hidden
field and submitted with the Http POST command.
In JSP we have been provided a implicit object session
so we don't need to create a object of session explicitly as we do in Servlets.
In Jsp the session is by default true. The session is defined inside the
directive <%@ page session = "true/false" %>. If we don't
declare it inside the jsp page then session will be available to the page,
as it is default by true.
For the convenience to understand the concept of
session management we have made one program.
The code of the program is given below:
<html>
<head>
<title>Welcome to the first program of jsp</title>
</head>
<body>
<form method = "post" action = "FirstPageOfSession.jsp">
<font size = 6>Enter your name<input type = "text" name = "name"></font><br><br>
<font size = 6>Enter your password<input type="password" name = "pwd" >
</font><br><br>
<input type = "submit" name = "submit" value = "submit" >
</form>
</body>
</html>
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<%
String name = request.getParameter("name");
String password = request.getParameter("pwd");
if(name.equals("Williams") && password.equals("abcde"))
{
session.setAttribute("username",name);
response.sendRedirect("NextPageAfterFirst.jsp");
}
else
{
response.sendRedirect("SessionManagement.html");
}
%>
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<html>
<head>
<title>Welcome in In the program of URL rewriting</title>
</head>
<body>
<font size = 6>Hello</font> <%= session.getAttribute("username") %>
</body>
</html>
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The output of the program is given below:
When the values entered is correct.
When the entered values are incorrect, the
SessionManagement.html will be displayed again to you.
Download this
example.
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