IDEA(2020版)sevlet+session实现购物车功能

查看全文：IDEA(2020版)sevlet+session实现购物车功能 – 每天进步一点点

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【任务目标】

通过所学Session知识以及购物车的访问流程，以购买蛋糕为例，模拟实现购物车功能。

源代码下载(访问密码: 6429)：

https://url47.ctfile.com/f/64055047-1497444695-231929?p=6429

1.创建实体类

先创建一个文件夹，名称为cn.itcast.session.entity

然后右击 entity文件夹，选择New—>Java Class，名字为Cake

代码参考如下：

package cn.itcast.session.entity;public class Cake {private static final long serialVersionUID = 1L;private String id;private String name;public Cake() {}public Cake(String id, String name) {this.id = id;this.name = name;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

然后再在entity文件下创建一个数据库模拟类，CakeDB，代码参考如下：

package cn.itcast.session.entity;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;
public class CakeDB {private static Map<String, Cake> cake = new LinkedHashMap<String, Cake>();static {cake.put("1", new Cake("1", "A类蛋糕"));cake.put("2", new Cake("2", "B类蛋糕"));cake.put("3", new Cake("3", "C类蛋糕"));cake.put("4", new Cake("4", "D类蛋糕"));cake.put("5", new Cake("5", "E类蛋糕"));}// 获得所有的蛋糕public static Collection<Cake> getAll() {return cake.values();}// 根据指定的id获蛋糕public static Cake getCake(String id) {return cake.get(id);}
}

创建完后如下：

2.创建Servlet类

首先创建第一个Servlet类，用于展示所有可购买蛋糕的列表，通过点击 ”点击购买“按钮，便可以将指定蛋糕添加到购物车中。

先新建一个文件夹，右击session文件夹，选择New—>package

名称为 servlet

然后右击 servlet，选择New—>Create New Servlet，名字为ListCakeServlet

代码参考如下：

package cn.itcast.session.servlet;
import cn.itcast.session.entity.Cake;
import cn.itcast.session.entity.CakeDB;
import java.io.*;
import java.util.Collection;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;@WebServlet(name = "ListCakeServlet",urlPatterns="/ListCakeServlet")
public class ListCakeServlet extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {resp.setContentType("text/html; charset=utf-8");PrintWriter out = resp.getWriter();Collection<Cake> cakes = CakeDB.getAll();out.write("本站提供的蛋糕有：<br>");for (Cake cake : cakes) {String url = "PurchaseServlet?id=" + cake.getId();out.write(cake.getName() + "<a href='" + url+ "'>点击购买</a><br>");}}
}

再创建一个servlet，名字为PurchaseServlet

package cn.itcast.session.servlet;
import cn.itcast.session.entity.Cake;
import cn.itcast.session.entity.CakeDB;
import java.io.IOException;
import java.util.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;@WebServlet(name = "PurchaseServlet",urlPatterns="/PurchaseServlet")
public class PurchaseServlet extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// 获得用户购买的商品String id = req.getParameter("id");if (id == null) {// 如果id为null，重定向到ListBookServlet页面String url = "ListBookServlet";resp.sendRedirect(url);return;}Cake book = CakeDB.getCake(id);// 创建或者获得用户的Session对象HttpSession session = req.getSession();// 从Session对象中获得用户的购物车List<Cake> cart = (List) session.getAttribute("cart");if (cart == null) {// 首次购买，为用户创建一个购物车(List集合模拟购物车)cart = new ArrayList<Cake>();// 将购物城存入Session对象session.setAttribute("cart", cart);}// 将商品放入购物车cart.add(book);// 创建Cookie存放Session的标识号Cookie cookie = new Cookie("JSESSIONID", session.getId());cookie.setMaxAge(60 * 30);cookie.setPath("/Servlet");resp.addCookie(cookie);// 重定向到购物车页面String url = "CartServlet";resp.sendRedirect(url);}
}

最后创建一个Servlet，名字为CartServlet

package cn.itcast.session.servlet;
import cn.itcast.session.entity.Cake;
import java.io.*;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
@WebServlet(name = "CartServlet",urlPatterns="/CartServlet")
public class CartServlet extends HttpServlet {public void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {resp.setContentType("text/html;charset=utf-8");PrintWriter out = resp.getWriter();// 变量cart引用用户的购物车List<Cake> cart = null;// 变量pruFlag标记用户是否买过商品boolean purFlag = true;// 获得用户的sessionHttpSession session = req.getSession(false);// 如果session为null，purFlag置为falseif (session == null) {purFlag = false;} else {// 获得用户购物车cart = (List) session.getAttribute("cart");// 如果用的购物车为null，purFlag置为falseif (cart == null) {purFlag = false;}}/** 如果purFlag为false，表明用户没有购买蛋糕  重定向到ListServlet页面*/if (!purFlag) {out.write("对不起！您还没有购买任何商品！<br>");} else {// 否则显示用户购买蛋糕的信息out.write("您购买的蛋糕有：<br>");double price = 0;for (Cake cake : cart) {out.write(cake.getName() + "<br>");}}}
}

创建完后如下：

3.测试效果

先访问蛋糕列表

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查看全文：IDEA(2020版)sevlet+session实现购物车功能 – 每天进步一点点