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；

2. 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：

1. 创建蛋糕类，封装蛋糕信息；
2. 创建CakeDB类，模拟保存所有蛋糕的数据库；
3. 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；
4. 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；
5. 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>