Null pointer exception error in Jsp

Expert:Majid
Expert:Majid
Hi i write a login page. when i validate the login value then the nullpointer exception error is occured.

my login page code is

<%@page contentType="text/html"%>
<%@page pageEncoding="UTF-8"%>

<html>
<head>
<title>Login Page</title>
<link rel="stylesheet" href="header.css" media="all" type="text/css">
<style type="text/css" media="screen">
table
{
border: 1px solid #036;
}
th
{ color: #036;
background: lightblue;
font-size: 120%;
border-bottom: 1px solid #036;
}
td
{
padding: .5em;
}
</style>

<script LANGUAGE="JavaScript" type="text/javascript">
function validate_fields()
{
var uid=document.getElementById("userid").value;
var upwd=document.getElementById("pwd").value;

if(uid=="")
{
alert("user name should not empty");
return false;
}
else if(upwd=="")
{
alert("Password should not be empty");
return false;
}
else
{
return true;
}
}
</script>

</head>
<body>
<h1 id="header">Web-Based Bug Tracking System</h1>
<br><br>

<p align="center">Please enter your id and password to login.</p>

<form id="login" name="login" method="post" action="validateLogin.jsp" onSubmit="return validate_fields()" >

<table align="center">
<th colspan="2">Login</th>
<tr>
<td>User id:</td><td><input type="text" id="userid" size="20"></td></tr>
<tr>
<td>Password:</td><td><input type="password" id="pwd" size="21"></td></tr>
<tr>
<td></td><td><input type="submit" value="Login"></td></tr>
</table>
</form>

</body>
</html>

and the validatelogin page code is

<%@page contentType="text/html"%>
<%@page pageEncoding="UTF-8"%>
<%@ page import="java.sql.*" %>
<%@ page import="java.util.*" %>
<html>
<head><title>validateLogin Page</title>
<%

%>

</head>
<body>
<%
try
{

String id=request.getParameter("userid");
String userpwd=request.getParameter("pwd");
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String str = "select * from Member";
Connection conn = DriverManager.getConnection("jdbc:odbc:bugsdb.mdb");
Statement stt = conn.createStatement();
ResultSet res = stt.executeQuery(str);
String str1;
String str2;

while(res.next())
{
str1=res.getString("User_Id");
str2=res.getString("User_Pwd");
if(id.equals(str1) && userpwd.equals(str2) )
{
response.sendRedirect("userpage.jsp");
}
else
{
response.sendRedirect("Login.jsp");
}
}
}catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
%>
</body>
</html>

when i run this code then the following error is occured.

HTTP Status 500 -

--------------------------------------------------------------------------------

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:305)

root cause

java.lang.NullPointerException
org.apache.jsp.validateLogin_jsp._jspService(validateLogin_jsp.java:76)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:305)

note The full stack trace of the root cause is available in the Tomcat logs.

--------------------------------------------------------------------------------

Apache Tomcat/5.0.19

note i used netbean ide 3.6. Pleas help me how i finished this error. i need quick response.
Answers
Hi friend,

Error in your Code and check it :

<input type="text" id="userid" size="20">
<input type="password" id="pwd" size="21">

validatelogin page

String id=request.getParameter("userid");
String userpwd=request.getParameter("pwd");

You have not "name" attributes in the input tag
So id,userpwd gives null pointer exception.

Thanks

dear friends i used the name attribute but it still have error of runtimeNULL execption.

Please povide me a solution to this code or an alternative solution.
thanks.

Answers

Hi friend,

Error in this lines of Code because you not having attributes "name" in the
input tag.

<tr>
<td>User id:</td><td><input type="text" id="userid" size="20"></td></tr>
<tr>
<td>Password:</td><td><input type="password" id="pwd" size="21"></td></tr>
<tr>

Correct code :

<tr>
<td>User id:</td><td><input type="text" id="userid" name="userid" size="20"></td></tr>
<tr>
<td>Password:</td><td><input type="password" id="pwd" name="pwd" size="21"></td></tr>
<tr>

Thanks

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