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Hidden field in servlet

Hidden field:

Hidden field is an input text with hidden type. This field will not be visible to the user.

Syntax:

How to get hidden field value in servlet?

HttpServletRequest interface’s getParameter() method is used to get hidden field value in servlet.

Syntax: String value = request.getParameter(“fieldName”);

Note: Hidden field only works in case of form submission so they will not work in case of anchor tag as no form submission is there.

Advantages of hidden field:

1. All browsers support hidden fields.
2. Simple to use.

Disadvantages of hidden fields:

1. Not secure.
2. Only work in case of form submission.

Session management example using hidden field:

SetHiddenFieldServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
* This class is used to set values in hidden fields.
* @author java tutorial point
*/
public class SetHiddenFieldServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
 
    //no-argument constructor.
    public SetHiddenFieldServlet() {
 
    }
 
    protected void doPost(HttpServletRequest request, 
 HttpServletResponse response)
              throws ServletException, IOException {
 response.setContentType("text/html"); 
     PrintWriter out = response.getWriter();
 
     //get parameters from request object.
     String userName = request.getParameter("userName").trim();
     String password = request.getParameter("password").trim();
 
     //check for null and empty values.
     if(userName == null || userName.equals("") || 
       password == null || password.equals("")){
      out.print("Please enter both username " +
        "and password. 

");
      RequestDispatcher requestDispatcher = 
       request.getRequestDispatcher("/login.html");
      requestDispatcher.include(request, response);
     }//Check for valid username and password.
     else if(userName.equals("jai") && password.equals("1234")){
         out.println("Logged in successfully.
"); 
         out.println("Click on the below button to see " +
       "the values of Username and Password.
");
         out.print("
+
           " method='POST'>");
         out.print(" +
           " value='" + userName + "'>");
         out.print(" +
           " value='" + password + "'>");
         out.print("");  
         out.print("
");
         out.close();
     }else{
      out.print("Wrong username or password. 

");
      RequestDispatcher requestDispatcher = 
       request.getRequestDispatcher("/login.html");
      requestDispatcher.include(request, response);
     }
    }
}

GetHiddenFieldServlet.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;
 
/**
* This class is used to get hidden fields values.
* @author java tutorial point
*/
public class GetHiddenFieldServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
 
    //no-argument constructor.
    public GetHiddenFieldServlet() {
 
    }
 
    protected void doPost(HttpServletRequest request, 
 HttpServletResponse response)
              throws ServletException, IOException {
 response.setContentType("text/html"); 
     PrintWriter out = response.getWriter();
 
     //get parameters from request object.
     String userName = request.getParameter("userName").trim();
     String password = request.getParameter("password").trim();
 
     out.println("Username: " + userName + "

");
     out.println("Password: " + password);
 
     out.close();
   }
}

login.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 
Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login</title>
</head>
<body>
 <form action="SetHiddenFieldServlet" method="post">
  Username:<input type="text" name="userName"/>
  <br/><br/>
  Password:<input type="password" name="password"/>
  <br/><br/> 
  <input type="submit" value="login"/> 
 </form>  
</body>
</html>

web.xml

xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" 
xmlns="http://java.sun.com/xml/ns/j2ee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 
  <servlet>
    <servlet-name>SetHiddenFieldServlet</servlet-name>
    <servlet-class>
     com.javawithease.business.SetHiddenFieldServlet
    </servlet-class>
  </servlet>
 
  <servlet-mapping>
    <servlet-name>SetHiddenFieldServlet</servlet-name>
    <url-pattern>/SetHiddenFieldServlet</url-pattern>
  </servlet-mapping>
 
  <servlet>
    <servlet-name>GetHiddenFieldServlet</servlet-name>
    <servlet-class>
     com.javawithease.business.GetHiddenFieldServlet
    </servlet-class>
  </servlet>
 
  <servlet-mapping>
    <servlet-name>GetHiddenFieldServlet</servlet-name>
    <url-pattern>/GetHiddenFieldServlet</url-pattern>
  </servlet-mapping>
 
  <welcome-file-list>
    <welcome-file>login.html</welcome-file>
  </welcome-file-list>
 
</web-app>