I have jsp file that get first name, last name and phone number from the user. I want to make all of them Required field and if the field is empty, alert with the field name. for example if they don't provide the phone number, create alert with that say insert phone number.

This is my jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

"ISO-8859-1">

"center">

Employee Register Form

"<%= request.getContextPath() %>/register" method="post">

First Name	"text" name="firstName" />
Last Name	"text" name="lastName" />
Phone Number	"text" name="phoneNumber" />

"submit" value="Submit" />