CS

Java

Servlets

Http request:

enter a URL, click a link, submit a form or any event in the broswer: example: http://www.amazon.com
create the HTTP request: Developer tool -> Network, click on http://www.amazon.com, see Headers, Request header.
- Search for amazon. Open a cookie.
- Remove all shown
- New request (F5) to www.amazon.com with “Developer tool -> Network” open
  - See Request (no cookies)
  - See Response (new cookies)
- Second request to amazon (F5):
  - See Request (the previous cookies)
  - See Response (no cookies)
IP number of the address (ping in CommandPrompt ping www.casio.jp)
connection to the server (tracert in CommandPrompt: tracert www.casio.jp)
process in the server: web -> application -> thread -> process & DDBB -> application -> web
browser get the response: Developer tool -> Network, see Headers -> Response header and Response
build the DOM tree: Developer tool -> Elements
browser request other resources (images, js, css): Developer tool -> Network (second and next requests)
styles are applied (remove head node in Developer tool -> Elements)
JavaScript is applied
the page is rendered

Session in Web Applications

Hidden fields. Example in ShoppingCart.java
URL Rewriting
Cookies

Cookies

See the cookies with Browser settings and Settings ->Show advanced settings… ->Content settings… -> All cookies and site data
Cookies in the network: Console (F12), Network, reload (F5) and click url - > headers -> view source
Example with Amazon

Example of Session in applications

 public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException  {
        res.setContentType("text/html");
        String login = req.getParameter("login");
        String password = req.getParameter("password");
        String logged = check(connection, login, password);
        System.out.println("check Login logged: " + logged);
        System.out.println("check Login login, password: " + login + " " + password);
        if (logged != null) {
            HttpSession session = req.getSession(true);
            session.setAttribute("login", logged);
            res.sendRedirect("ProductList");
        } else {
        ...

Function code

    public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException  {
        res.setContentType("text/html");
        PrintWriter toClient = res.getWriter();
        String categoryId = req.getParameter("id");
        HttpSession session = req.getSession(false);
        String login = null;
        if (session != null) {
            login = (String)session.getAttribute("login");
            System.out.println("ProductList logged");
            System.out.println("ProductList login: " + login);
        }
        toClient.println(Utils.header("Products", login));
        
        ...

Logout code

    public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException  {
        res.setContentType("text/html");
        HttpSession session = req.getSession(false);
        if (session != null) {
            session.invalidate();
            res.sendRedirect("CheckLogin");
        }
    }

In folder northbrickSession