Concurring Java Problem...Please Please Help

Question

When I run my java application this error keeps coming up when trying to log in. Yer help would be much appreciated
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: Exception in JSP: /HeadNPass.jsp:19
16:
17:
18: NurseDao da = new NurseDao();
19: Nurse n = da.getNurse(userName);
20:
21: if(n != null)
22: {
Stacktrace:
     org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:504)
     org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
     org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
     org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:368)
root cause
java.lang.NullPointerException
     hospital.NurseDao.getNurse(NurseDao.java:324)
     org.apache.jsp.HeadNPass_jsp._jspService(HeadNPass_jsp.java:63)
     org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
     org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
     org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:368)
The code is as follows:
String userName = request.getParameter("username");
      String password = request.getParameter("password");
      if ((userName != null) && (password != null)){
                NurseDao da = new NurseDao();
                Nurse n = da.getNurse(userName);
                if(n != null)
                     int pw = Integer.parseInt(password);
                     if(n.getStaffId() == pw)
                        request.getSession(true).setAttribute("HEADNURSE", n);
                        response.sendRedirect("HeadNurse.jsp");
                    else
                         response.sendRedirect("error.jsp");
                else
                    response.sendRedirect("error.jsp");
                }

Answer 1

Indeed.
java.lang.NullPointerException
hospital.NurseDao.getNurse(NurseDao.java:324)Besides, I recommend to move that code to a servlet or a bean. Writing business code in JSP's is bad practice. There JSP's aren't for.