Thread: a null pointer exception

hi guys, I'm writing some servlets for a website, but I'm new to JSP, therefore I made alot mistakes when I was writing them, I've been fixing them for weeks, but this null pointer exception, I just don't know where the problem is, and what caused it..... so here is the code, thanks alot guys!

package Servlet;
 
import javax.servlet.*;
import javax.servlet.http.*;
 
import Model.DAO;
 
import java.io.*;
import java.sql.*;
 
public class LoginServlet extends HttpServlet
{
	Connection conn=null;
	Statement stmt=null;
 
	String username;
	String password;
 
	public void init(ServletConfig config)throws ServletException
	{
		super.init();
	}
 
	public void service(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException
	{
		DAO.getConnection(conn);
		try {
			stmt=conn.createStatement();
		} catch (SQLException e1) {
		}
		username=request.getParameter("username");
		password=request.getParameter("password");
		if(username=="admin")
		{
			try
			{
				ResultSet rs=stmt.executeQuery("select '"+username+"' from tb_user");
				if(rs.next())
				{
					ResultSet vpass=stmt.executeQuery("select '"+password+"' from tb_user where id = '"+username+"'");
					if(vpass.next())
					{
						request.getRequestDispatcher("./manage/manage_index.jsp").forward(request,response);
 
					}
					else
					{
						request.getRequestDispatcher("http://localhost:8080/form_apply_system/account/log_fail.jsp").forward(request,response);
					}
				}
 
			}catch(Exception e)
			{
				e.printStackTrace();
			}
		}
		else
		{
			try
			{
				ResultSet rs=stmt.executeQuery("select '"+username+"' from tb_user");
				if(rs.next()==true)
				{
					ResultSet vpass=stmt.executeQuery("select '"+password+"' from tb_user where id = '"+username+"'");
					if(vpass.next()==true)
					{
						request.getRequestDispatcher("http://localhost:8080/form_apply_system/account/log_success.jsp").forward(request,response);
					}
					else
					{
						request.getRequestDispatcher("http://localhost:8080/form_apply_system/account/log_fail.jsp").forward(request,response);
					}
				}
				else
				{
					request.getRequestDispatcher("http://localhost:8080/form_apply_system/account/log_fail.jsp").forward(request,response);
				}
			}catch(Exception e)
			{
				e.printStackTrace();
			}
		}
	}
}

I know this servlet sucks, so please just ignore its poor design and hard codind.....

--- Update ---

eclipse says that the null pointer exception occured at line 28, which is

stmt=conn.createStatement();

and DAO.getConnection is just a normal method used to get connection with MySQL database, here is the code of it:
[hightlight=Java]
package Model;

import java.sql.*;

public class DAO
{
public static void getConnection(Connection conn)
{
String driver="com.mysql.jdbc.Driver";
String url="jdbc:mysql://localhost:3306/web";
try
{
Class.forName(driver);
conn=DriverManager.getConnection(url,"root","12345 6");
}catch(Exception e)
{
e.printStackTrace();
}
}
}
[/highlight]

java.lang.NullPointerException
at Servlet.LoginServlet.service(LoginServlet.java:28)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:728)
at org.apache.catalina.core.ApplicationFilterChain.in ternalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.do Filter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invo ke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invo ke(StandardContextValve.java:123)
at org.apache.catalina.core.StandardHostValve.invoke( StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke (ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(A ccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invok e(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.servic e(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.p rocess(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnect ionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProce ssor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker( ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)

Sure, here it is

--- Update ---

you mean the conn in the DAO or in the servlet?

Originally Posted by Norm

conn where the NPE happens on line 28

Thanks alot man!!! You said about the non null value, so I re checked my codes trying to find such mistakes, and I found that the getConnection method didn't return an object, so the conn I'm using in the servlet is a null value, thanks!!!