CODEWITHSUNDEEP
javajspnullpointerexception
user3503781
user3503781

Reputation:

Validating a form using JSP

I'm completely new to JSP and am creating a simple form and validating it through JSP. Here's my code :-

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<%@page import="java.io.* , java.sql.* , java.util.* , javax.servlet.*" %>

<body>
    <h1>Login Page by JSP</h1>
    <hr>
    <form method="post" action="index_jsp">
        Enter name : <input type="text" name="user">
        Enter password : <input type="password" name="pass">
        <input type="submit" value="login">
    </form>
    <%
    String user = request.getParameter("user");
    String pass = request.getParameter("pass");

    if(user.equals("admin") && pass.equals("admin"))
    {
    response.sendRedirect("wel.html");
    }

    %>
    <br>
    <a href="new.jsp">Click here !</a>

</body>
</html>

But each and every time I run it , I get a NullPointerException . What am I doing wrong ? Immediate help would be appreciated !

Thanks!

Upvotes: 1

Views: 1916

Answers (5)

Alan
Alan

Reputation: 1751

change code：

if("admin".equals(user) && "admin".equals(pass))  {
    response.sendRedirect("wel.html");
}

When you first run jsp,it will execute the code,but user and pass is null.

Upvotes: 0

duffymo
duffymo

Reputation: 308763

First bit of advice, since you're new to JSP: Don't write scriptlet code. That's all the stuff between <% and %>. It's a 1998 vintage technology that should be discouraged. Learn JSTL and Model-2 MVC instead.

You need a servlet to orchestrate those JSPs. Every web MVC framework that I know of has what's called a front controller servlet to manage the communication and orchestration. You should, too.

You have the form POST in this JSP, sending the HTTP request to index_jsp (bad name). It's executing in the browser on the client machine.

I would expect you to send this to a servlet on the server side that gets the HTTP request, gets the username and password out, compares the values to a database to see if the user is indeed registered. Then I'd either send the next view or route to the "sorry" page. That's not what you're doing.

Upvotes: 2

planetjones
planetjones

Reputation: 12633

Don't do equals checks on the variables, rather do them against the constants:

 if("admin".equals(user) && "admin".equals(pass)) {
    response.sendRedirect("wel.html");
 }

This way you cannot get the NPE.

Upvotes: 1

Niraj Patel
Niraj Patel

Reputation: 2208

You are not checking null for request attributes.

replace 

String user = request.getParameter("user");
String pass = request.getParameter("pass");

with 

String user = request.getParameter("user") != null ? request.getParameter("user") : "";
String pass = request.getParameter("pass") != null ? request.getParameter("pass") : "";

Upvotes: 0

Macrosoft-Dev
Macrosoft-Dev

Reputation: 2185

Change this line 

if(user.equals("admin") && pass.equals("admin"))
    {
    response.sendRedirect("wel.html");
    }

with

if(user!=null){

    if(user.equals("admin") && pass.equals("admin"))
    {
    response.sendRedirect("wel.html");
    }
}

Upvotes: 0

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