javaweb学习——session和Cookie实现购物车功能

时间：2022-05-22 09:07:47

1.创建Book类，实现对图书信息的封装。

package cn.it.sessionDemo.example1;

import java.io.Serializable;

/**

 * 该类实现对图书的封装

 *

 * @author 12428

 *

 */

public class Book implements Serializable {

    private static final long serialVersionUID = 1L;

    private String ID;

    private String name;

    public Book() {

    }

    public Book(String ID, String name) {

        this.ID = ID;

        this.name = name;

    }

    public String getID() {

        return ID;

    }

    public void setID(String iD) {

        ID = iD;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

2.创建一个BookDB类实现对图书类的操作

package cn.it.sessionDemo.example1;

import java.util.Collection;

import java.util.LinkedHashMap;

import java.util.Map;

/**

 * 该类实现数据库模拟

 *

 * @author 12428

 *

 */

public class BookDB {

    private static Map<String, Book> books = new LinkedHashMap<String, Book>();

    // 静态代码块在Java类被加载时执行，由于类只加载一次，应此静态代码块只执行一次。

    static {

        books.put("1", new Book("1", "javaweb开发"));

        books.put("2", new Book("2", "jdbc开发"));

        books.put("3", new Book("3", "java基础"));

        books.put("4", new Book("4", "struts开发"));

        books.put("5", new Book("5", "spring开发"));

    }

    // 获得所有的图书

    public static Collection<Book> getAll() {

        return books.values();

    }

    // 根据指定的ID获得图书

    public static Book getBook(String ID) {

        return books.get(ID);

    }

}

3.创建一个ListBookServlet类，用来显示可购买的图书信息。

package cn.it.sessionDemo.example1;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Collection;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * 该servlet是显示所有的图书列表。通过图书后面的购买连接可以把图书添加到购物车中

 *

 * @author 12428

 *

 */

@WebServlet("/ListBookServlet")

public class ListBookServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public ListBookServlet() {

        super();

        // TODO Auto-generated constructor stub

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=utf-8");

        PrintWriter out = response.getWriter();

        Collection<Book> books = BookDB.getAll();

        out.write("本站的图书有：");

        for (Book b : books) {

            // 将图书的id值作为参数传过去

            String url = "/SessionDemo2/PurchaseServlet?id=" + b.getID();

            out.write(b.getName() + "<a href='" + url + " '>点击购买</a><br/>");

        }

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // TODO Auto-generated method stub

        doGet(request, response);

    }

}

4.创建一个实现购物车功能的servlet类

package cn.it.sessionDemo.example1;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

/**

 * 该servlet类是用于实现购物车功能，既将用户购买的东西作为session的属性值存进去，再重定向到 到已购买商品的也买你

 *

 * @author 12428

 *

 */

@WebServlet("/PurchaseServlet")

public class PurchaseServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public PurchaseServlet() {

        super();

        // TODO Auto-generated constructor stub

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // 获得用户的购买信息

        String id = request.getParameter("id");

        // 有些用户会直接访问这个Servlet，先判断访问时是否带有书的ID

        if (id == null) {

            // 如果Id为空，返回图书列表Servlet

            String url = "/SessionDemo2/ListBookServlet";

            response.sendRedirect(url);
            //此处一定要返回，不然会出现错误

            return;

        }

        // 获取购买的图书信息

        Book book = BookDB.getBook(id);

        // 创建session对象

        HttpSession session = request.getSession();

        // 从session中获得购物车对象

        List<Book> cart = (List<Book>) session.getAttribute("cart");

        // 判断session对象是否有cart这个属性,如果没有这个属性的话，集合cart的值应为空

        if (cart == null) {

            // 没有cart属性，用户是首次购买，为用户创建一个购物车

            cart = new ArrayList<Book>();

            // 将购物车对象添加到session对象中

            session.setAttribute("cart", cart);

        }

        // 将商品放入购物车

        cart.add(book);

        // 创建一个Cookie存放session的信息

        Cookie cookie = new Cookie("JSESSION", session.getId());

        cookie.setMaxAge(60 * 30);

        cookie.setPath("/SessionDemo2");

        // 将cookie发送到客户端

        response.addCookie(cookie);

        // 重定向到已购买商品的页面。

        String url = "/SessionDemo2/CartServlet";

        response.sendRedirect(url);

    }

    /**

     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse

     *      response)

     */

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // TODO Auto-generated method stub

        doGet(request, response);

    }

}

5.创建一个展示用户购买信息的类

package cn.it.sessionDemo.example1;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

@WebServlet("/CartServlet")

public class CartServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public CartServlet() {

        super();

        // TODO Auto-generated constructor stub

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=utf-8");

        PrintWriter out = response.getWriter();

        // 变量cart引用用户的购物车

        List<Book> cart = null;

        // 创建一个变量是来判断用户是否购买过商品

        boolean Flag = true;

        // 获得用户的session,如果没有查到也不创建新的session。

        HttpSession session = request.getSession(false);

        // 如果session为空，Flag为false；

        if (session == null) {

            Flag = false;

        } else {// 不为空，就获得用户的购物车

            cart = (List<Book>) session.getAttribute("cart");

            // 如果用户的购物车为空，就设置Falg为false。

            if (cart == null) {

                Flag = false;

            }

        }

        // 如果Flag为false，表明用户没有购买过商品，重定向到ListServlet页面。

        if (!Flag) {

            out.write("对不起，你没有购买任何商品");

        } else {

            // 显示用户的购买信息

            out.write("你购买的商品有：");

            for (Book b : cart) {

                out.write(b.getName() + "<br/>");

            }

        }

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // TODO Auto-generated method stub

        doGet(request, response);

    }

}

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