package developerworks.ajax.servlet;import developerworks.ajax.store.Cart;import javax.servlet.http.*;import java.util.Enumeration;public class CartServlet extends HttpServlet {  /**   * Updates Cart, and outputs XML representation of contents   */  public void doPost(HttpServletRequest req, HttpServletResponse res) throws java.io.IOException {    Enumeration headers = req.getHeaderNames();    while (headers.hasMoreElements()) {      String header  =(String) headers.nextElement();      System.out.println(header+": "+req.getHeader(header));    }    Cart cart = getCartFromSession(req);    String action = req.getParameter("action");    String item = req.getParameter("item");        if ((action != null)&&(item != null)) {      if ("add".equals(action)) {        cart.addItem(item);      } else if ("remove".equals(action)) {        cart.removeItems(item);      }    }    String cartXml = cart.toXml();    res.setContentType("text/xml");    res.getWriter().write(cartXml);  }  public void doGet(HttpServletRequest req, HttpServletResponse res) throws java.io.IOException {    // Bounce to post, for debugging use    // Hit this servlet directly from the browser to see XML    doPost(req,res);  }  private Cart getCartFromSession(HttpServletRequest req) {    HttpSession session = req.getSession(true);    Cart cart = (Cart)session.getAttribute("cart");       if (cart == null) {      cart = new Cart();      session.setAttribute("cart", cart);    }    return cart;  }}