servlet之session设置

商品对象,购物车对象,servlet的实现

商品:

package app02d;
public class Product {
    private int id;
    private String name;
    private String description;
    private float price;
    
    public Product(int id, String name, String description, float price) {
        this.id = id;
        this.name = name;
        this.description = description;
        this.price = price;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }
}

购物车:

package app02d;
public class ShoppingItem {

    private Product product;
    private int quantity;
    
    public ShoppingItem(Product product, int quantity) {
        this.product = product;
        this.quantity = quantity;
    }

    public Product getProduct() {
        return product;
    }

    public void setProduct(Product product) {
        this.product = product;
    }

    public int getQuantity() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }
}
servlet的实现:

package app02d;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class ShoppingCartServlet
 */
@WebServlet( name = "ShoppingCartServlet", urlPatterns = {"/products", "/viewProductDetails","/addToCart","/viewCart"})
public class ShoppingCartServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String CART_ATTRIBUTE = "cart";
    
    private List<Product> products = new ArrayList<Product>();
    private NumberFormat currencyFormat = NumberFormat
            .getCurrencyInstance(Locale.US);
    
    // 创建商品对象,加入商品列表中(1)
    @Override
    public void init() throws ServletException {
        products.add(new Product(1, "Bravo 32' HDTV",
                "Low-cost HDTV from renowned TV manufacturer",
                159.95F));
        products.add(new Product(2, "Bravo BluRay Player",
                "High quality stylish BluRay player", 99.95F));
        products.add(new Product(3, "Bravo Stereo System",
                "5 speaker hifi system with iPod player",
                129.95F));
        products.add(new Product(4, "Bravo iPod player",
                "An iPod plug-in that can play multiple formats",
                39.95F));
    }
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ShoppingCartServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * 分支(2)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String uri = request.getRequestURI();
        if (uri.endsWith("/products")) {
            // 查询商品列表
            sendProductList(response);
        } else if (uri.endsWith("/viewProductDetails")) {
            // 显示商品详细信息
            sendProductDetails(request, response);
        } else if (uri.endsWith("viewCart")) {
            // 显示购物车
            showCart(request, response);
        }
    }
    
    
    
    

    /**
     * addToCart
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // add to cart
        int productId = 0; // 商品id
        int quantity = 1; // 商品数量(默认购买一件)
        try {
            productId = Integer.parseInt(
                    request.getParameter("id"));
            quantity = Integer.parseInt(request
                    .getParameter("quantity"));
        } catch (NumberFormatException e) {
        }

        Product product = getProduct(productId);
        if (product != null && quantity >= 0) {
            ShoppingItem shoppingItem = new ShoppingItem(product,
                    quantity);
            // 创建session对象
            HttpSession session = request.getSession();
            List<ShoppingItem> cart = (List<ShoppingItem>) session.getAttribute(CART_ATTRIBUTE);
            if (cart == null) {
                cart = new ArrayList<ShoppingItem>();
                // 设置session值
                session.setAttribute(CART_ATTRIBUTE, cart);
            }
            cart.add(shoppingItem);
        }
        sendProductList(response);
    }
    
    /**
     * 显示商品列表 (4)
     * @param response
     * @throws IOException
     */
    private void sendProductList(HttpServletResponse response)
            throws IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("<html><head><title>Products</title>" +
                "</head><body><h2>Products</h2>");
        writer.println("<ul>");
        for (Product product : products) {
            writer.println("<li>" + product.getName() + "("
                    + currencyFormat.format(product.getPrice())
                    // 商品详细信息的显示
                    + ") (" + "<a href='viewProductDetails?id="
                    + product.getId() + "'>Details</a>)");
        }
        writer.println("</ul>");
        writer.println("<a href='viewCart'>View Cart</a>");
        writer.println("</body></html>");

    }

    /**
     * 根据商品id获取商品对象
     * @param productId
     * @return
     */
    private Product getProduct(int productId) {
        for (Product product : products) {
            if (product.getId() == productId) {
                return product;
            }
        }
        return null;
    }

    /**
     * 获取商品的详细信息,并显示
     * @param request
     * @param response
     * @throws IOException
     */
    private void sendProductDetails(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        int productId = 0;
        try {
            productId = Integer.parseInt(
                    request.getParameter("id"));
        } catch (NumberFormatException e) {
        }
        Product product = getProduct(productId);

        if (product != null) {
            writer.println("<html><head>"
                    + "<title>Product Details</title></head>"
                    + "<body><h2>Product Details</h2>"
                    + "<form method='post' action='addToCart'>");
            // 隐藏域
            writer.println("<input type='hidden' name='id' "
                    + "value='" + productId + "'/>");
            writer.println("<table>");
            writer.println("<tr><td>Name:</td><td>"
                    + product.getName() + "</td></tr>");
            writer.println("<tr><td>Description:</td><td>"
                    + product.getDescription() + "</td></tr>");
            writer.println("<tr>" + "<tr>"
                    // 购买的数量
                    + "<td><input name='quantity'/></td>"
                    + "<td><input type='submit' value='Buy'/>"
                    + "</td>"
                    + "</tr>");
            writer.println("<tr><td colspan='2'>"
                    + "<a href='products'>Product List</a>"
                    + "</td></tr>");
            writer.println("</table>");
            writer.println("</form></body>");
        } else {
            writer.println("No product found");
        }

    }

    /**
     * 显示购物车
     * @param request
     * @param response
     * @throws IOException
     */
    private void showCart(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("<html><head><title>Shopping Cart</title>"
                + "</head>");
        writer.println("<body><a href='products'>" +
                "Product List</a>");
        // 创建session对象
        HttpSession session = request.getSession();
        // 获取session内容
        List<ShoppingItem> cart = (List<ShoppingItem>) session.getAttribute(CART_ATTRIBUTE);
        if (cart != null) {
            writer.println("<table>");
            writer.println("<tr><td style='width:150px'>Quantity"
                    + "</td>"
                    + "<td style='width:150px'>Product</td>"
                    + "<td style='width:150px'>Price</td>"
                    + "<td>Amount</td></tr>");
            double total = 0.0;
            for (ShoppingItem shoppingItem : cart) {
                Product product = shoppingItem.getProduct();
                int quantity = shoppingItem.getQuantity();
                if (quantity != 0) {
                    float price = product.getPrice();
                    writer.println("<tr>");
                    writer.println("<td>" + quantity + "</td>");
                    writer.println("<td>" + product.getName()
                            + "</td>");
                    writer.println("<td>"
                            + currencyFormat.format(price)
                            + "</td>");
                    double subtotal = price * quantity;

                    writer.println("<td>"
                            + currencyFormat.format(subtotal)
                            + "</td>");
                    total += subtotal;
                    writer.println("</tr>");
                }
            }
            writer.println("<tr><td colspan='4' "
                    + "style='text-align:right'>"
                    + "Total:"
                    + currencyFormat.format(total)
                    + "</td></tr>");
            writer.println("</table>");
        }
        writer.println("</table></body></html>");
    }

}