Null pointer exception and servlet

Question

I cant figure out why i am getting a null pointer exception. this works if i keep my form output in the same class as my driving servlet. All i did was break off the html display to a new form and i get a null pointer exception.
this is just an excerpt. no reason to post the whole form.
Here are my two classes...
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.text.*;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.*;
import org.w3c.dom.Document;
import org.w3c.dom.DOMException;
import org.w3c.dom.Element;
public class myServlet extends HttpServlet
   implements SingleThreadModel {
        displayScreen myAddressBook;
        HttpServletRequest request;
        HttpServletResponse response;
        String displayForm = "DISPLAYFORM";
        String addForm     = "ADDFORM";
        String editForm    = "EDITFORM";
     // get function
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
          request = this.request;
          response = this.response;
        displayScreen myAddressBook = new displayScreen(this.request,this.response);
        myAddressBook.sendAddressBook(request,response,false,displayForm);
public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
     errorMsg = "";
     errCount=0;
     //stores address book in hashmap. Not currently using Address Book object
     request = this.request;
    response = this.response;
     if ((request.getParameterValues("submit")[0].equals("Next")))
        myAddressBook.sendAddressBook(request,response,false,displayForm);
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.text.*;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.*;
public class displayScreen {
     int errCount;
     String errorMsg;
     String displayForm = "DISPLAYFORM";
     String addForm     = "ADDFORM";
     String editForm    = "EDITFORM";
     HttpServletRequest request;
     HttpServletResponse response;
       displayScreen (HttpServletRequest request, HttpServletResponse response) {
           request = this.request;
           response = this.response;
public void sendAddressBook (HttpServletRequest request, HttpServletResponse response,boolean FileError,String formType)
         throws ServletException, IOException {
        request = this.request;
        response = this.response;
     response.setContentType("text/html");  /*****/ I GET A NULL POINTER EXCEPTION RIGHT HERE!!!!!!
}

Answer 1

anyway to write the system.err to an html screen with
a servlet?Why would you ask that? Surely you should have asked "Any way to write a stack trace to an HTML screen from a servlet?"
And in fact there is. I am sure you have not yet looked up the Exception class and the versions of its printStackTrace() method. But when you do, you will see that there are printStackTrace(PrintStream) and printStackTrace(PrintWriter). And you know how to write HTML (or text in general) to the servlet response so that it shows up in the client's browser, right? I will let you figure out how to put those things together.