Servlet – Hidden Form Field

Last Updated : 30 Jan, 2022

The Server embeds new hidden Fields in every dynamically generated From page for the client. when the client submits the form to the server the hidden fields identify the client. Hidden Box is an invisible text box of the form page, hidden box value goes to the server as a request parameter when the form is submitted.

Syntax for hidden fields:

<input type=hidden name=”name” value=”value”>

name: is a hidden box name or Request parameter Name.

value: is a hidden box value or Request parameter value.

Advantages of using Hidden Form Field

It’s simple.
No effect on security level setting in browsers.
Basic HTML knowledge is sufficient to work with this technique.
This technique work with all server-side technologies like Servlet, JSP, ASP.net, PHP, etc.

Disadvantages of using Hidden Form Field

The documents need to be embedded the data inside, waste bandwidth. you have to embed the result from the previous page on the next page.
Everyone can see the embedded data by viewing the original source code.
We cannot store all kinds of java objects in hidden boxes except text/string values.
Hidden boxes travel over the network along with the request and response. the indicates more network traffic.

Example

In this example, we are showing the user name and the visited time.

home.jsp

HTML

<%@page contentType="text/html" pageEncoding="UTF-8"%> 
<!DOCTYPE html> 
<html> 
  
   <head> 
       <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
       <title>Home Page</title> 
   </head> 
  
   <body> 
       <% 
           java.util.Date today= new java.util.Date(); 
           java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("hh:mm;ss"); 
           String str =sdf.format(today); 
         %> 
  
         <form action ="welcome.jsp" metgod="post"> 
             Enter your name:<input type="text" name="username"/> 
             <input type="hidden" value="<%=str%>" name="visittime"/> 
             <br> 
             <input type="submit" value="Show Message"/>     
          </form> 
   </body> 
  
</html>

Welcome.jsp

HTML

<%@page contentType="text/html" pageEncoding="UTF-8"%> 
<!DOCTYPE html> 
<html> 
  
   <head> 
       <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
       <title>JSP Page</title> 
   </head> 
  
   <body> 
       <% 
           String name=request.getParameter("username"); 
           String time=request.getParameter("visittime"); 
        %> 
        <h3>Hello <%=name%>,Welcome to our Page !</h3> 
        You visited Home page at <%= time %> 
   </body> 
  
</html>