help for making web pages using servlets

sara arif

how to make web pages using servlets and html pages. how to do session tracking, work with cookies, and invoke another pages in it?

can u give me any simple example of codding to understand these things?

DrRakha

1. Example on session tracking , is the tracking of use login overall your site , the session is tracked using the HttpSession class , session is used to save data at the server side for a limited time period .

Code:

import java.io.PrintWriter;
import java.io.IOException;
import java.util.Date;
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 SessionTracker extends HttpServlet 
{
  public void doGet(HttpServletRequest req, HttpServletResponse res)throws ServletException, IOException 
  {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();

    HttpSession session = req.getSession(true);

    String user = (String) session.getAttribute("username");
    String content=" " ;      
     
    if (user == null) {
       content="<a herf='http://www.mysite/login/'>Login</a>";
    } else {
       content="Welcome "+user+" , <a herf='http://www.mysite/logout/'>Logout</a> ";
    }

     
    out.println("<html><head><title>Site main page</title></head>");
    out.println("<body><h1>Login/Logout session tracking </h1>");
    out.println(content);// Show a link for login or logout 
    out.println("</body></html>");
  }
}

There is functions with the session object that may help you alot ,
- To get session ID

Code:

session.getId();

- Get the max time of session to be expired

Code:

session.getMaxInactiveInterval();

- Get the session created Time

Code:

session.getCreationTime();

2 .Cookies are the instances that are saved at the client side browser to keep information to be used for the next visits .In servlets , the cookies are sent using the request object .We will check if an cookie is already created otherwise we will create one . Here for example i will save the username in a cookie .

Code:

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class SettingandReadingCookies extends HttpServlet 
{

    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        
        out.println("<HTML><HEAD><TITLE>WEB_PAGE</TITLE></HEAD><BODY>");

        Cookie[] cookies = request.getCookies();
        boolean Cookiethere = false;

        for(int i = 0; i < cookies.length; i++) { 
            Cookie currentCookie = cookies[i];
            if (currentCookie.getName().equals("username")) {
                out.println("username = " + currentCookie.getValue());
                Cookiethere = true;
            }
        }  

        if (!Cookiethere) {
            Cookie newcookie = new Cookie("username", "msi_333");
           
            response.addCookie(newcookie); // Add Cookie at client
        }

         
        out.println("This page show your username when reloaded.");
        out.println("</BODY>");
        out.println("</HTML>");
}
}

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help for making web pages using servlets