Servlets : HttpSession Attribute

Click here to watch in Youtube : https://www.youtube.com/watch?v=NXMCnNxBip0

Click the below Image to Enlarge

HttpSessionAttributeDemo Project Dir Structure   

FirstServlet.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 FirstServlet extends HttpServlet
{
    private static final long serialVersionUID = 1L;

    public void init() throws ServletException
    {
        System.out.println("----------------------------------------------");
        System.out.println(" Init method is called in "
                + this.getClass().getName());
        System.out.println("--------------------------------------------");
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        String username = request.getParameter("username");
        out.print("Welcome " + username);

        HttpSession session = request.getSession();
        System.out.println("FirstServlet sessionid :" + session.getId());
        session.setAttribute("Username", username);
        session.setAttribute("Role", "Admin");

        out.print("<a href='servlet2'> : visit</a>");

        out.close();

    }

    public void destroy()
    {
        System.out.println("----------------------------------------------");
        System.out.println(" destroy method is called in "
                + this.getClass().getName());
        System.out.println("----------------------------------------------");
    }

}

SecondServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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 SecondServlet extends HttpServlet
{
    private static final long serialVersionUID = 1L;

    public void init() throws ServletException
    {
        System.out.println("----------------------------------------------");
        System.out.println(" Init method is called in "
                + this.getClass().getName());
        System.out.println("----------------------------------------------");
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        HttpSession session = request.getSession();

        System.out.println("Second Servlet sessionid :" + session.getId());

        String userName = (String) session.getAttribute("Username");
        out.print("Hello " + userName + "<br>");

        out.print("*************************************************************"
                + "<br>");

        Enumeration<String> namesEnum = session.getAttributeNames();
        while (namesEnum.hasMoreElements())
        {
            String name = (String) namesEnum.nextElement();
            String value = (String) session.getAttribute(name);
            out.print(name + ":" + value);
            out.print("<br>");

        }

        out.close();
    }

    public void destroy()
    {
        System.out.println("----------------------------------------------");
        System.out.println(" destroy method is called in "
                + this.getClass().getName());
        System.out.println("----------------------------------------------");
    }

}

web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<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_3_0.xsd"
    metadata-complete="true" version="3.0">

    <display-name>HttpSessionAttributeDemo</display-name>

    <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>

    <servlet>
        <servlet-name>s1</servlet-name>
        <servlet-class>FirstServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>s1</servlet-name>
        <url-pattern>/servlet1</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>s2</servlet-name>
        <servlet-class>SecondServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>s2</servlet-name>
        <url-pattern>/servlet2</url-pattern>
    </servlet-mapping>

</web-app>

index.html

<html lang="en">
<head>
<meta charset="UTF-8">
<title>Multiple Filters Demo</title>
</head>
<body>
    <form action="servlet1" method="GET">
        
        UserName :  <input type="text" name="username" /><br /> 
        
        Password :&nbsp; &nbsp; <input type="password" name="password" /><br /> 
            
        <input type="submit" value="login" />
        
    </form>
</body>
</html>

Environment Used 

JDK version :1.7.0_51
Tomcat version : 7.0.50 

To Download HttpSessionAttributeDemoApp Project Click the below link

https://sites.google.com/site/javaee4321/servlets/HttpSessionAttributeDemoApp.zip?attredirects=0&d=1

See also:

Servlets Tutorial

All Design Patterns Links