Technical Developer: Servlet HttpSession Login and Logout Example

We can bind the objects on HttpSession instance and get the objects by using setAttribute and getAttribute methods.

In the previous page, we have learnt about what is HttpSession, How to store and get data from session object etc.

Here, we are going to create a real world login and logout application without using database code. We are assuming that password is admin123.

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In this example, we are creating 3 links: login, logout and profile. User can't go to profile page until he/she is logged in. If user is logged out, he need to login again to visit profile.

In this application, we have created following files.

index.html
link.html
login.html
LoginServlet.java
LogoutServlet.java
ProfileServlet.java
web.xml

File: index.html

<!DOCTYPE html>  
<html>  
<head>  
<meta charset="ISO-8859-1">  
<title>Servlet Login Example</title>  
</head>  
<body>  
  
<h1>Login App using HttpSession</h1>  
<a href="login.html">Login</a>|  
<a href="LogoutServlet">Logout</a>|  
<a href="ProfileServlet">Profile</a>  
  
</body>  
</html>  

File: link.html

<a href="login.html">Login</a> |  
<a href="LogoutServlet">Logout</a> |  
<a href="ProfileServlet">Profile</a>  
<hr>  

File: login.html

<form action="LoginServlet" method="post">  
Name:<input type="text" name="name"><br>  
Password:<input type="password" name="password"><br>  
<input type="submit" value="login">  
</form>  

File: LoginServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out=response.getWriter();
request.getRequestDispatcher("link.html").include(request, response);
String name=request.getParameter("name");
String password=request.getParameter("password");
if(password.equals("admin123")){
out.print("Welcome, "+name);
HttpSession session=request.getSession();
session.setAttribute("name",name);
}
else{
out.print("Sorry, username or password error!");
request.getRequestDispatcher("login.html").include(request, response);
}
out.close();
}
}

File: LogoutServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LogoutServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out=response.getWriter();
request.getRequestDispatcher("link.html").include(request, response);
HttpSession session=request.getSession();
session.invalidate();
out.print("You are successfully logged out!");
out.close();
}
}

File: ProfileServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ProfileServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out=response.getWriter();
request.getRequestDispatcher("link.html").include(request, response);
HttpSession session=request.getSession(false);
if(session!=null){
String name=(String)session.getAttribute("name");
out.print("Hello, "+name+" Welcome to Profile");
}
else{
out.print("Please login first");
request.getRequestDispatcher("login.html").include(request, response);
}
out.close();
}
}

File: web.xml

<?xml version="1.0" encoding="UTF-8"?>  
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">  
    
  <servlet>  
    <description></description>  
    <display-name>LoginServlet</display-name>  
    <servlet-name>LoginServlet</servlet-name>  
    <servlet-class>LoginServlet</servlet-class>  
  </servlet>  
  <servlet-mapping>  
    <servlet-name>LoginServlet</servlet-name>  
    <url-pattern>/LoginServlet</url-pattern>  
  </servlet-mapping>  
  <servlet>  
    <description></description>  
    <display-name>ProfileServlet</display-name>  
    <servlet-name>ProfileServlet</servlet-name>  
    <servlet-class>ProfileServlet</servlet-class>  
  </servlet>  
  <servlet-mapping>  
    <servlet-name>ProfileServlet</servlet-name>  
    <url-pattern>/ProfileServlet</url-pattern>  
  </servlet-mapping>  
  <servlet>  
    <description></description>  
    <display-name>LogoutServlet</display-name>  
    <servlet-name>LogoutServlet</servlet-name>  
    <servlet-class>LogoutServlet</servlet-class>  
  </servlet>  
  <servlet-mapping>  
    <servlet-name>LogoutServlet</servlet-name>  
    <url-pattern>/LogoutServlet</url-pattern>  
  </servlet-mapping>  
</web-app>  