// Example 1 - Basic login processing protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String username = request.getParameter("username"); String password = request.getParameter("password"); if (username.equals("admin") && password.equals("admin123")) { // authentication HttpSession session = request.getSession(); session.setAttribute("user", username); // set session attribute response.sendRedirect("home.jsp"); // redirect to home page } else { request.setAttribute("error", "Invalid username or password"); request.getRequestDispatcher("login.jsp").forward(request, response); // show login page with error message } } // Example 2 - Logout processing protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); session.invalidate(); // invalidate session response.sendRedirect("login.jsp"); // redirect to login page }The `HttpServletRequest` is part of the `javax.servlet.http` package library, which provides classes and interfaces for servlet handling in HTTP protocol.