dispatcher.java

jsp 应用开发技术光盘 是《jsp应用开发技术》这本书的源代码

package dispatcher;

import javax.servlet.http.*;
import cart.ShoppingCart;
import database.*;
import exception.*;


public class Dispatcher extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) {
        String bookId = null;
        String clear = null;
        BookDetails book = null;
        
        //从上下文中取出BookDBAO对象
        BookDBAO bookDBAO =
            (BookDBAO) getServletContext().getAttribute("bookDBAO");
        HttpSession session = request.getSession();
        String selectedScreen = request.getServletPath();
        
        //如果购物车对象不存在，实例化购一个物车对象并放入session.
        ShoppingCart cart = (ShoppingCart) session.getAttribute("cart");
        
        if (cart == null) {
        	System.out.println("error");
            cart = new ShoppingCart();
            session.setAttribute("cart", cart);
        }        

        if (selectedScreen.equals("/bookcatalog")) {
            bookId = request.getParameter("Add");
            //向购物车内添加一本书
            if (bookId!=null) {
                try {
                    book = bookDBAO.getBookDetails(bookId);
                    cart.add(bookId, book);
                } catch (BookNotFoundException ex) {                    
                }
            }
        } else if (selectedScreen.equals("/bookshowcart")) {
            bookId = request.getParameter("Remove");
            //从购物车内删除一本书
            if (bookId != null) {
                cart.remove(bookId);
            }

            clear = request.getParameter("Clear");
            //清空购物车
            if ((clear != null) && clear.equals("clear")) {
                cart.clear();
            }
        } else if (selectedScreen.equals("/bookreceipt")) {
            // 将订单存入数据库，并更新存货
            try {
                bookDBAO.buyBooks(cart);
            } catch (OrderException ex) {
                selectedScreen = "/bookordererror";
            }
        }

        String screen = selectedScreen + ".jsp";

        try {
            request.getRequestDispatcher(screen)
                   .forward(request, response);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) {
        String screen = request.getServletPath() + ".jsp";
        //把请求转发至JSP页面
        try {
            request.getRequestDispatcher(screen)
                   .forward(request, response);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}