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Basic concept of session- store some data of client temporarily which should be available until client destroy it.
Session management definition- It’s a mechanism used by web container to save state of client.
Session management includes-
1- session (interface)
2- cookies(class)
3- url rewriting
4- Hidden form field
| Feature | Session | Cookies | URL Rewriting | Hidden Form Field |
|---|---|---|---|---|
| Definition | A session is a way to store information (in variables) to be used across multiple pages. | Cookies are small text files stored on a user’s computer by a web server to remember stateful information. | URL rewriting is the technique of manipulating the URL in the address bar to include additional information, such as session data. | Hidden form fields are inputs in an HTML form that are not displayed to the user, but are sent to the server when the form is submitted. |
| Use Case | Storing user-specific information, such as a user’s shopping cart or login status. | Remembering user preferences, login information, and other stateful information across multiple web pages. | Maintaining stateful information, such as a user’s session, without using cookies. | Sending information to the server that is not meant to be modified by the user, such as a unique identifier for a form submission. |
| Implementation | Using HttpSession in Java Servlets. | Using the javax.servlet.http. Cookie class in Java Servlets. | Manipulating the URL in the address bar manually or using a library such as Apache UrlRewriteFilter. | Adding hidden inputs to an HTML form using the <input type="hidden"> tag. |
1-Session-
Step 1- creation of sessions-
(i)HttpSession ses=request.getsession();
-Returns existing session object else creates new session object.
(ii)HttpSession ses=request.getsession(true);
-Always returns existing session object.
(iii)HttpSession ses=request.getsession(false);
-Always creates new session object.
Step 2- Initialization of servlet-
ses.setAttribute(key, value);
Note- Remove Attribute-
ses.removeAttribute(key);
Step 3- Access of session-
ses.getAttribute(key);
4- Deletion of session-
ses.invalidate ();
Example 7- Wep app to create session at correct login, get session data from at profile page, and then logout to delete session.
Project 5 files-
1-index.html(inside WebContent)
2-Login.java(inside pacage=’ab’)
3-Profile.java(inside pacage=’ab’)
4-profile.html(inside WebContent)
5-Logout.java(inside pacage=’ab’)
1-index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form action="a">
email
<input type="text" name="e">
password
<input type="password" name="p">
<input type="submit">
<a href="b">View Profile</a>
</body>
</html>
2-Login.java(servlet)
package ab;
import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;
@WebServlet("/a")
public class Login extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String E1="mrjava@gmail.com";
String P1="java123";
String E2=request.getParameter("e");
String P2=request.getParameter("p");
if(E1.equals(E2) && P1.equals(P2)){
HttpSession ses=request.getSession();
ses.setAttribute("mail", E2);
response.sendRedirect("b");
}else{
response.sendRedirect("index.html");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
3-Profile.java(servlet)
package ab;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
@WebServlet("/b")
public class Profile extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out=response.getWriter();
HttpSession ses=request.getSession();
String m=(String) ses.getAttribute("mail");
if(m!=null){
response.sendRedirect("profile.html");
}else{
RequestDispatcher rd=request.getRequestDispatcher("index.html");
rd.include(request, response);
out.println("You are not logged in.");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
4-profile.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
Welcome user
<a href="c">Logout(remove the session)</a>
<a href="index.html">Go back(Keep the session)</a>
</body>
</html>
5-Logout.java(servlet)
package ab;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class Logout
*/
@WebServlet("/c")
public class Logout extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Logout() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession ses=request.getSession();
ses.invalidate();
response.sendRedirect("index.html");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
2- Cookies-
-cookie is a class.
-It stores textual data at client side.
-Less secure than session.
Step 1- creation of cookie-
Cookie ck= new cookie(key, value);
Step 2- send to the client side(browser)-
response. addCookie(ck);
Step 3- access the cookie-
Cookie[] c= request.getCookies();
Step 4- deletion of cookie-
ck.setAge(0);
response.addCookie(ck);
Example 8- Wep app to create cookie and add into browser at correct login, get cookies data from at profile page, and then logout to delete cookie.
output-
Project Structure-
5 files-
1-index.html(inside WebContent)
2-Login.java(inside pacage=’ab’)
3-Profile.java(inside pacage=’ab’)
4-profile.html(inside WebContent)
5-Logout.java(inside pacage=’ab’)
1-index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form action="login">
email
<input type="text" name="e">
password
<input type="password" name="p">
<input type="submit">
<a href="profile">View Profile</a>
</body>
</html>
2-Login.java(servlet)
package ab;
import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;
@WebServlet("/login")
public class Login extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String E1="mrjava@gmail.com";
String P1="java123";
String E2=request.getParameter("e");
String P2=request.getParameter("p");
if(E1.equals(E2) && P1.equals(P2)){
Cookie cookie = new Cookie("mail",E2);
response.addCookie(cookie);
response.sendRedirect("b");
}else{
response.sendRedirect("index.html");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response); } }
3-Profile.java(servlet)
package ab;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
@WebServlet("/profile")
public class Profile extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out=response.getWriter();
Cookie[] ck2=request.getCookies();
System.out.println(ck2);
if(ck2!=null){
response.sendRedirect("profile.html");
}else{
RequestDispatcher rd=request.getRequestDispatcher("index.html");
rd.include(request, response);
out.println("You are not logged in.");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
4-profile.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
Welcome user
<a href="logout">Logout(remove the session)</a>
<a href="index.html">Go back(Keep the session)</a>
</body>
</html>
5-Logout.java(servlet)
package ab;
import java.io.*;
import javax.servlet.http.*;
@WebServlet("/logout")
public class Logout extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Cookie[] ck2=request.getCookies();
for (Cookie c : ck2) {
c.setMaxAge(0);
response.addCookie(c);
}
response.sendRedirect("index.html");
}
3- Url Rewriting-
Step 1- add “?” At the end of url
Step 2 -add data in following format-
Attribute=value
Step 3- separate these attribute and value with “&” symbol
Example 9- Web app to add data with url and get it on next servlet.
output-
Project Structure-
2 files-
1-index.html(inside WebContent)
2-A.java(inside pacage=’ab’)
1-index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<a href="first?name=mr.Java&email=a@a.com">Click here</a>
</body>
</html>
2-A.java(servlet)
package ab;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
@WebServlet("/first")
public class A extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String s1=request.getParameter("name");
String s2=request.getParameter("email");
PrintWriter out=response.getWriter();
out.println(s1);
out.println(s2);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
4- hidden form field-
Step1- create input box with type=hidden
Step2- assign it’s value
Step3- get value of input box on next servlet.
Example 10- Wep app get data from hidden input box on next servlet.
output-
Project Structure-
2 files-
1-index.html(inside WebContent)
2-A.java(inside pacage=’ab’)
1-index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form action="first">
<input type="text" name="a">
</br>
<input type="password" name="b">
<input type="hidden" name="c" value="Surprise">
<input type="submit">
</body>
</html>
2-A.java(servlet)
package ab;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
@WebServlet("/first")
public class A extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String s1=request.getParameter("a");
String s2=request.getParameter("b");
String s3=request.getParameter("c");
PrintWriter out=response.getWriter();
out.println(s1);
out.println(s2);
out.println(s3);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}