Java servlet

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ik heb onderstande servlet geschreven. ik kan ook inlogen, maar als ik een fout username of password invul, dan wordt alleen de textfield leeg, maar geen foutmelding.
blijkbaar blijf acc altijd null. kan iemand mij helpen?

import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
import Account;

public class AgendaServlet extends HttpServlet
{
private String name;
private String pass;

public void init()
{
}
public void performTask(HttpServletRequest request, HttpServletResponse response) throws IOException
{
Account acc = null;

HttpSession session = request.getSession(true);

acc = (Account)session.getAttribute("account");

name = request.getParameter("username");
pass = request.getParameter("password");

String page = request.getParameter("page");

if (acc==null || page.equals("loginpoging"))
{
System.out.println("name= "+ name + " and pasword="+ pass);
System.out.println("account is = "+ acc);
if(name!=null && pass!= null)
{
try
{
acc = LoginDBAction.getAccount(name,pass);
}
catch(Exception expe)
{
response.sendRedirect("agenda/Error.jsp");
}
System.out.println("account2 is = "+ acc + "name =" + name);
if (acc != null)
session.setAttribute("account",acc );
page="start";
}
}
if(acc != null)
{
System.out.println("page = "+ page);
if(page.equals("login"))
{
try
{
//System.out.println("login.jsp?loginok=retype&username="+ acc.getUsername());
response.sendRedirect("login.jsp?loginok=retype&username="+acc.getUsername());
}
catch (IOException ioe)
{
System.out.println("sendredirect, ioe:"+ioe);
}
}
else if (page.equals("start"))
{
try
{
response.sendRedirect("index1.jsp");
}
catch (IOException ioe)
{
System.out.println(" fout, sendredirect, ioe:"+ioe);
}
}
else
{
try
{
System.out.println("login.jsp?loginok=false&username="+ acc.getUsername());
response.sendRedirect("login.jsp?loginok=false&username="+ acc.getUsername());
}
catch(IOException e)
{
System.out.println("fout in :"+e);
}
}
}
else
{
try
{
System.out.println("account =" + acc);
if (acc != null)
response.sendRedirect("login.jsp?loginok=false&username="+acc.getUsername());
else
System.out.println("NEE!!!!!!!!!!");
response.sendRedirect("login.jsp");
}
catch (IOException ioe)
{
System.out.println("AgendaServlet fout, sendredirect, ioe:"+ioe);
}
}
}
public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
performTask(request, response);
}
}

[ACM]

Dat soort dingen kun je beter zelf debuggen gok ik zo.
Laat eventueel allerlei waarden naar de standaard-out printen zodat je ziet wat er allemaal gebeurd.