Servlets :: Login Form - All Attributes Are Null And HTTP Status 404 Error In Some Cases

I'm a new Java user and I'm trying to code a simple login page. In first page (NewFile.jsp) users should enter their username and password and should click on "login", or click on "sign up".

1.) If user enters his username and password correctly, a login page (LoginPage.jsp) appears and says "welcome null" but it should show the name of that user instead of null.

2.) In that login page there is an edit button to edit profile information. When I clicked on it, every information is "null" and when I edit them and click on "Submit" button;

HTTP Status 404 -
type Status report
message
description The requested resource () is not available.
GlassFish Server Open Source Edition 3.1.2

that message appears.

3.) If I click on "Sign Up" button at the beginning, a registration jsp (SignUpPage.jsp) appears. After filling up text boxes and clicking on "Submit", same Status 404 screen appears.

I created a mysql database called "loginpage" using xampp. In that database there is a table called "users" and it has un, pass, name, surname, email and degree attributes.

Here is a screenshot of my project explorer:

Here is my code:

1. NewFile.jsp

<%@ page import="java.sql.*" %>
<%@ page import="java.io.*" %>
<%@ page import="java.util.*"%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>

[Code] .....