购物车项目（五）——编写CartServlet类

编写思路：

1.创建CartServlet类，并继承HttpServlet

2.设置属性：action，并创建商品业务逻辑类对象

3.doGe()方法写为doPost(request,response)

4.写doPost()方法，并判断action动作

5.编写添加，删除商品的方法，并利用购物车类中的方法。

代码如下：

package Servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import dao.ItemsDAO;import entity.Cart;import entity.Items;public class CartServlet extends HttpServlet {    private String action ; //表示购物车的动作 ,add,show,delete    //商品业务逻辑类的对象    private ItemsDAO idao = new ItemsDAO();    /**     * Constructor of the object.     */    public CartServlet() {        super();    }    /**     * Destruction of the servlet. <br>     */    public void destroy() {        super.destroy(); // Just puts "destroy" string in log        // Put your code here    }    /**     * The doGet method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to get.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doPost(request,response);    }    /**     * The doPost method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to post.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setContentType("text/html;charset=utf-8");        PrintWriter out = response.getWriter();        if(request.getParameter("action")!=null)        {            this.action = request.getParameter("action");            if(action.equals("add")) //如果是添加商品进购物车            {                if(addToCart(request,response))                {                    request.getRequestDispatcher("/success.jsp").forward(request, response);                }                else                {                    request.getRequestDispatcher("/failure.jsp").forward(request, response);                }            }            if(action.equals("show"))//如果是显示购物车            {                request.getRequestDispatcher("/cart.jsp").forward(request, response);            }            if(action.equals("delete")) //如果是执行删除购物车中的商品            {                if(deleteFromCart(request,response))                {                    request.getRequestDispatcher("/cart.jsp").forward(request, response);                }                else                {                    request.getRequestDispatcher("/cart.jsp").forward(request, response);                }            }        }    }    //添加商品进购物车的方法    private boolean addToCart(HttpServletRequest request, HttpServletResponse response)    {        String id = request.getParameter("id");        String number = request.getParameter("num");        Items item = idao.getItemsById(Integer.parseInt(id));        //是否是第一次给购物车添加商品,需要给session中创建一个新的购物车对象        if(request.getSession().getAttribute("cart")==null) //getsession.getAttribute(String name)返回session对象中与指定名称绑定的对象，如果不存在则返回null        {            Cart cart = new Cart();            request.getSession().setAttribute("cart",cart);        }        Cart cart = (Cart)request.getSession().getAttribute("cart");        if(cart.addGoodinCart(item, Integer.parseInt(number)))//字符类型转换成整型        {            return true;        }        else        {            return false;        }    }    //从购物车中删除商品    private boolean deleteFromCart(HttpServletRequest request, HttpServletResponse response)    {        String id = request.getParameter("id");        Cart cart = (Cart)request.getSession().getAttribute("cart");        Items item = idao.getItemsById(Integer.parseInt(id));        if(cart.removeGoodfromCart(item))        {            return true;        }        else        {            return false;        }    }    /**     * Initialization of the servlet. <br>     *     * @throws ServletException if an error occurs     */    public void init() throws ServletException {        // Put your code here    }}