Servlet: Session tracking using HiddenFormFields

       In this Hidden Form Fields session tracking data of every individual client is given back to client browser as a dynamic form with hidden text field along with parameters and values, so that the client browser will dispatch a form by hiding those text fields.

       When the same client click a button of this hidden form field then the client browser will automatically send the value of hidden text fields along with parameters to the application.

       It will always work whether cookie is disabled or not.

Let's see the code to store value in hidden field.

<input type="hidden" name="uname" value="Mohan"> 

Here, uname is the hidden field name and Mohan is the hidden field value.

The following example demonstrate how to use this hidden form fields session tracking in servlet application.

index.html

=======

<form action="servlet1"> 

Name:<input type="text" name="userName"/><br/> 

<input type="submit" value="submit"/> 

</form>

web.xml

======

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">

   

<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>

The URL pattern of this class must be /s1, this will receive the request with one parameter "userName" and Submit as get Request.

FirstServlet.java

===========

import java.io.*; 

import javax.servlet.ServletException;

import javax.servlet.http.*; 

 

public class FirstServlet extends HttpServlet { 

public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException,ServletException{ 

     

        response.setContentType("text/html"); 

        PrintWriter out = response.getWriter();           

        String n=request.getParameter("userName"); 

        out.print("Welcome "+n); 

        out.println("<br /><br />");         

        //creating form that have invisible textfield 

        out.print("<form action='servlet2'>"); 

        out.print("<input type='hidden' name='uname' value='"+n+"'>"); 

        out.print("<br />"); 

        out.print("<input type='text' name='sname' >"); 

        out.print("<br />"); 

        out.print("<input type='submit' value='Submit'>"); 

        out.print("</form>"); 

        out.close();

    }

} 

The URL pattern of this class must be /s2, this will receive the form request with two parameters "uname" and ""sname"" when we click on Submit button.

SecondServlet.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;

public class SecondServlet extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html"); 

        PrintWriter out = response.getWriter();          

        //Getting the value from the hidden field 

        String uname=request.getParameter("uname"); 

        //Getting the value from the form field 

        String sname=request.getParameter("sname");

        out.println("Hello "+uname); 

        out.print("<br />"); 

        out.println("Hello "+sname);        

        out.close();

    }

    }