使用session实现一个简单的购物车

Html页面：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>图书选择页面</title>
</head>
<body>
<form action="Experiment/Car" method="post">
    <input type="checkbox" name="book" value="java"/>java<br>
    <input type="checkbox" name="book" value="javaweb"/>javaWeb<br>
    <input type="checkbox" name="book" value="python"/>python<br>
    <input type="submit" name="登录"/>

</form>
</body>
</html>

实现购物车的功能：

package Experiment;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;

public class Car extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html,chardrt=UTF-8");
        PrintWriter out = resp.getWriter();
        HttpSession hs = req.getSession();
        Map<String,Integer> car = (Map<String, Integer>)hs.getAttribute("shoppingCar");
        //如果回话域没有shoppingcar,则实例化一个
        if(car==null){
            car = new HashMap<String, Integer>();
        }
        //获取用户的所选择的商品
        String[] book = req.getParameterValues("book");
//        if(book!=null&&book.length>0){
//            for(int i=0;i<book.length;i++){
//                out.println(book[i]);
//            }
//        }
        if(book!=null&&book.length>0){
            for(String bookname:book){
                //判断该物品是否在购物车中
                if(car.get(bookname)!=null){
                    int num = car.get(bookname);
                    car.put(bookname,num+1);
                }else{
                    car.put(bookname,1);
                }
            }
        }
        hs.setAttribute("shoppingCar",car);
        resp.sendRedirect("http://localhost:8080/javaWeb_war_exploded/Experiment/CarList");
    }
}

从会话域中取出购物车，并对购物车进行遍历显示。

package Experiment;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map;

public class CarList extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html,charset=UTF-8");

        PrintWriter out = resp.getWriter();
        HttpSession session = req.getSession();
        Map<String,Integer> car = (Map<String, Integer>)session.getAttribute("shoppingCar");
        if(car!=null&&car.size()>0){
            out.println("your car list:<br>");
            //遍历显示购物车里面的商品
            for (String bookname:car.keySet()){
                out.println(bookname+","+car.get(bookname)+"<br>");
            }
        }else{
            out.println("no goods+<br>");
        }
        out.println("<a href = 'http://localhost:8080/javaWeb_war_exploded/BookChoose.jsp'>keep going");
    }
}