Java Web实验六：实现购物车

实验六   实现购物车

一、实验目的

1. 理解Session的作用；

将Session应用到具体问题中。

二、实验内容

当用户使用浏览器访问网站的蛋糕列表页面，如果想购买某个蛋糕，首先会判断蛋糕是否存在，如果存在就加入购物车，跳转到购物车中所购买蛋糕的离了表页面，否则，返回蛋糕列表页面，流程如下：

创建蛋糕类，封装蛋糕信息；创建CakeDB类，模拟保存所有蛋糕的数据库；创建ListCakeServlet的Servlet类，该Servlet用于显示所有可购买的蛋糕的列表，单击“点击购买”链接，便可以将指定的蛋糕添添加到购物车中；创建一个名称为PurchaseServlet的Servlet类，该类实现了两个功能，一个是将用户购买的蛋糕信息保存到Session对象中，一个是在用户购买蛋糕结束后，将页面重定向到用户已经购买的蛋糕列表；创建一个名称为CartServlet的Servlet类，该类主要用于展示用户已经购买的蛋糕列表。

运行结果示例如图：

三、实验结果（源代码、运行截图）

Cake.java

package xxx;public class Cake {    private int id;    private String name;    public Cake(int id, String name) {        this.id = id;        this.name = name;    }    public int getId() {        return id;    }    public String getName() {        return name;    }

CakeDB.java

package xxx;import java.util.ArrayList;import java.util.List;public class CakeDB {    private static List<Cake> cakes = new ArrayList<>();    static {        // 初始化蛋糕列表，这里仅为示例，应从实际数据库加载          cakes.add(new Cake(1, "A类蛋糕"));        cakes.add(new Cake(2, "B类蛋糕"));        cakes.add(new Cake(3, "C类蛋糕"));        cakes.add(new Cake(4, "D类蛋糕"));        cakes.add(new Cake(5, "E类蛋糕"));    }    public static List<Cake> getAllCakes() {        return cakes;    }}

CartServlet.java

package xxx;import javax.servlet.*;import javax.servlet.http.*;import java.io.IOException;import java.util.ArrayList;import java.util.List;public class CartServlet extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        List<Cake> cart = (List<Cake>) req.getSession().getAttribute("CartServlet");        if (cart == null) {            cart = new ArrayList<>();        }        req.setAttribute("CartServlet", cart);        RequestDispatcher dispatcher = req.getRequestDispatcher("cart.jsp");        dispatcher.forward(req, resp);    }}

ListCakeServlet.java

package xxx;import javax.servlet.*;import javax.servlet.http.*;import java.io.IOException;import java.util.List;public class ListCakeServlet extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        List<Cake> cakes = CakeDB.getAllCakes();        req.setAttribute("cakes", cakes);        RequestDispatcher dispatcher = req.getRequestDispatcher("cake_list.jsp");        dispatcher.forward(req, resp);    }}

PurchaseServlet.java

package xxx;import javax.servlet.*;import javax.servlet.http.*;import java.io.IOException;import java.util.ArrayList;import java.util.List;public class PurchaseServlet extends HttpServlet {    protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {        doPost(req, res);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        int cakeId = Integer.parseInt(req.getParameter("id"));        int flag=0;        System.out.println(cakeId);        List<Cake> cart = (List<Cake>) req.getSession().getAttribute("CartServlet");        if (cart == null) {            cart = new ArrayList<>();            req.getSession().setAttribute("CartServlet", cart);        }        Cake cake = CakeDB.getAllCakes().stream()                .filter(c -> c.getId() == cakeId)                .findFirst()                .orElse(null);        if (cake != null) {                cart.add(cake);        }            resp.sendRedirect("CartServlet");    }}

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"         version="4.0">    <servlet>        <servlet-name>ListCakeServlet</servlet-name>        <servlet-class>xxx.ListCakeServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>ListCakeServlet</servlet-name>        <url-pattern>/ListCakeServlet</url-pattern>    </servlet-mapping>    <servlet>        <servlet-name>PurchaseServlet</servlet-name>        <servlet-class>xxx.PurchaseServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>PurchaseServlet</servlet-name>        <url-pattern>/purchase</url-pattern>    </servlet-mapping>    <servlet>        <servlet-name>CartServlet</servlet-name>        <servlet-class>xxx.CartServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>CartServlet</servlet-name>        <url-pattern>/CartServlet</url-pattern>    </servlet-mapping></web-app>

cake_list.jsp

<%@ page import="java.util.List" %><%@ page import="xxx.Cake" %><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>蛋糕列表</title></head><body>本站提供的蛋糕有<br>    <% for (Cake cake : (List<Cake>)request.getAttribute("cakes")) { %>    <%=cake.getName()%>    <a href="purchase?id=<%=cake.getId()%>">点击购买</a><br>    <% } %>    <a href="CartServlet">查看购物车</a></body></html>

cart.jsp

<%@ page import="java.util.List" %><%@ page import="xxx.Cake" %><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>购物车</title></head><body>您购买的蛋糕有<br>    <%        List<Cake> cart = (List<Cake>)request.getAttribute("CartServlet");        if (cart != null && !cart.isEmpty()) {            for (Cake cake : cart) {    %>        <%= cake.getName() %><br>    <%        }    } else {    %>    购物车为空    <%        }    %><a href="ListCakeServlet">返回蛋糕列表</a></body></html>