null pointer exception after response.sendRedirect() in jsp page.

[Daniel Stege Lindsjo]

Hey all

On my current project I managed to create a form that allows me to add users to a DB.
Now my only concern is that after using response.sendRedirect() I get redirected to "http://localhost:8080/dt/pages/main.jsp". But when I try to sign in via username and password i get a NULL pointer exception at adress: http://localhost:8080/dt/pages/login.do.

500 Servlet Exception


[show] java.lang.NullPointerException

java.lang.NullPointerException
at com.verify.web.LoginUser.doPost(LoginUser.java:26)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:153)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:91)
at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:103)
at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:187)
at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:265)
at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:273)
at com.caucho.server.port.TcpConnection.run(TcpConnection.java:682)
at com.caucho.util.ThreadPool$Item.runTasks(ThreadPool.java:743)
at com.caucho.util.ThreadPool$Item.run(ThreadPool.java:662)
at java.lang.Thread.run(Thread.java:637)

My Index.jsp used to send the redirect has the following content:

  <%@page contentType="text/html"%>
<%
String redirToURL = response.encodeRedirectURL("pages/main.jsp");
response.sendRedirect(redirToURL);
%>  

I've also tried to feed the relative URL directly to sendRedirect() like this:

  response.sendRedirect("pages/main.jsp");  

But I get the same result.
I'm using Resin 3.1.9 for the project.


D

[Bear Bibeault]

java.lang.NullPointerException
at com.verify.web.LoginUser.doPost(LoginUser.java:26)

What's at line 26?

[Daniel Stege Lindsjo]

At Line 26 and 27 in LoginUser.java:

  		if (uName.length() <= 0){  
		out.println("User Name cannot be empty!<BR>");}  

Just a check for an empty username.

Here is the entire code for LoginUser.java:

  package com.verify.web;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.text.*;
import java.sql.*;

public class LoginUser extends HttpServlet {

	public void doPost(HttpServletRequest request, HttpServletResponse response)
					   throws IOException, ServletException {
					   
					   String uName = request.getParameter("userName");
					   String pw = request.getParameter("password");
		
		response.setContentType("text/html");
	    response.setHeader("Cache-Control","no-cache");
		PrintWriter out = response.getWriter();
		
		boolean pass_match = false;
		boolean validUserName = false;
		boolean validPassWord = false;
		
		if (uName.length() <= 0){  
		out.println("User Name cannot be empty!<BR>");}
		if (pw.length()<=0){
		out.println("Password length is < 0 <BR>");
		pass_match = false;}
		else{}
		
		
		try {
		Class.forName("com.mysql.jdbc.Driver");
		
		Connection connection = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/yaco", "root", "obamaslammer");
        
        Statement statement = connection.createStatement();
        
        ResultSet resultset = statement.executeQuery("select * from user where userName = '" + uName + "'");
       //out.println("<BR>Preparing statement...<BR>");
       //PreparedStatement pstmt = connection.prepareStatement("SELECT * FROM user(firstName,userName,password,email,userRole,regTime,lastLogin) VALUES(?,?,?,?,?,?,?)");
       //out.println("Statement prepared...<BR>");
       
        if(resultset.next()) {
                out.println("Username was found.<BR>");
				validUserName = true;
				}
				else {out.println("Please register.<BR>");
				validUserName = false;
				}
		
		resultset = 
                statement.executeQuery("select * from user where password = '" + pw + "'") ;
        
        if(resultset.next()) {
                out.println("Password was found.<BR>");       
                validPassWord = true;
                }
                else {out.println("Password was not found.<BR>");
                validPassWord = false;}
                
                }// end try
                catch (Exception ex){
                ex.printStackTrace();
                }
                
		} //end doPost
		
		



} // end LoginUser class  

It is no where near done yet. But the class was working just fine before I had to use the reponse.redirect function.

[Ernesto Chicas]

The problem is in your servlet not in the sendRedirect, is clearly a NullPointeException because you are not sending the parameters

String uName = request.getParameter("userName"); 
String pw = request.getParameter("password");

do a

System.out.println (uName) 

in doPost, and if you do

  if (uName.length() <= 0){  

you will get NullPointerException.

Attempts to send the parameter from

 <%@page contentType="text/html"%>
<%
String redirToURL = response.encodeRedirectURL("pages/main.jsp");  
response.sendRedirect(redirToURL);  
%> 

greetings and good luck

[Daniel Stege Lindsjo]

The parameter cannot be set from the index file.
At this point the form is not accepting any data at all. No matter what I enter into userName and password the result of uName is always NULL. God this is driving me insane :S

If there is anybody out there that can see the error please respond. I've been fighting with this error for days now.


D

[Daniel Stege Lindsjo]

I finally got the error *facepalm*

The correct version of the form in main is like this:

 <form name="login_form" method="post" action="login.do">
       <input name="userName" type="text" maxlength="20" alt="userName">
       <input name="password" type="password" maxlength="20" alt="password">
         <input type="submit" name="login" id="login" value="Login">
         <a href="create_usr.jsp" title="Create New User" target="_blank">[Create User]</a>
       </form>   

Dreamweaver had messed up the form causing the fields to be outside the </form> tag.
I can't believe something so trite could drive me nuts hehe.


D

[Ernesto Chicas]

ok, try to do something like this

//String uName = request.getParameter("userName");   
//String pw = request.getParameter("password");  
String uName = "userX";   //some known value
String pw = "passUsserX";  //some known value

the problem is that you try to get the size of a string that is null

if (uName.length() <= 0){  
out.println("User Name cannot be empty!<BR>");}

NullPointerException

I hope this helps if you

[Ernesto Chicas]

Daniel Stege Lindsjo wrote:I finally got the error *facepalm*

The correct version of the form in main is like this:

 <form name="login_form" method="post" action="login.do">
       <input name="userName" type="text" maxlength="20" alt="userName">
       <input name="password" type="password" maxlength="20" alt="password">
         <input type="submit" name="login" id="login" value="Login">
         <a href="create_usr.jsp" title="Create New User" target="_blank">[Create User]</a>
       </form>   

Dreamweaver had messed up the form causing the fields to be outside the </form> tag.
I can't believe something so trite could drive me nuts hehe.


D