Java servlet 实现的简易购物车

首页

2.购买页

3.购物车页

1. 首页代码发送一个post请求

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>首页</title>
</head>
<body>
<img src="/img/bookcover/shoping.png" alt="购物">
<form action="goshop.do" method="post">
    <p>欢迎您</p><br>
    <input type="submit" value="进入购物">
</form>
</body>
</html>
2.处理首页post请求的controler

package cc.openhome.controler;
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 java.io.IOException;
import java.util.LinkedHashMap;

@WebServlet("/goshop.do")
public class GoShop extends HttpServlet {

    void processRequest(HttpServletRequest req,HttpServletResponse resp)
    throws ServletException,IOException
    {
        BookDb bs = new BookDb();
        LinkedHashMap<String,Book> books = bs.getAll();
        req.setAttribute("books",books);
        req.getRequestDispatcher("shop.view").forward(req,resp);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        processRequest(req,resp);

    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        processRequest(req,resp);
    }
}
3 ,展示购物页面

package cc.openhome.view;

import cc.openhome.controler.*;
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;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedHashMap;

@WebServlet("/shop.view")
public class ShopView extends HttpServlet {

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

        String bookid = req.getParameter("bookid");
        int count = 0;
        HttpSession session = req.getSession();

        // 在点击了购买之后书的数量在加一,否则只刷新
        if(session.getAttribute("count") != null && bookid != null){
            Integer c = (Integer) session.getAttribute("count");
            count = c + 1;
        }
        session.setAttribute("count",count);

        //购物
        Cart cart = (Cart) req.getSession().getAttribute("cart");
        if(cart == null){
            cart = new Cart();
            req.getSession().setAttribute("cart",cart);
        }

        BusinessService bussiness = new BusinessService();
        if(count > 0){
            bussiness.buyBook(bookid,cart);
        }
        session.setAttribute("cart",cart);

        PrintWriter out = resp.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC '-//W3C//DTD HTML 4.01'" +
                "Transitional//EN");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>购物网页</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<form action='' method='post'>");
        out.println("<table width='100%'>");
        out.println("<td><img src='img/bookcover/shop.png' alt='小购物车' width='50'>" +
                "<a href='cart.view'>已采购"+count+"书籍</a><td>");
        out.println("</table>");
        out.println("<table width='100%'>");
        out.println("<tr>");
        out.println("<td style='color:blue'>书籍编号<td>");
        out.println("<td style='color:blue'>书名<td>");
        out.println("<td style='color:blue'>图片</td>");
        out.println("<td style='color:blue'>价格<td>");
        out.println("<td style='color:blue'>购买<td>");
        out.println("</tr>");
        int i = 0;
        LinkedHashMap <String,Book> books = (LinkedHashMap <String,Book>) req.getAttribute("books");
        for (String value : books.keySet()){
            i++;
            Book book = books.get(value);
            out.println("<tr>");
            out.println("<td>"+book.getId()+"<td>");
            out.println("<td>"+book.getName()+"<td>");
            out.println("<td><img src='/img/bookcover/book"+i+".jpeg'></td>");
            out.println("<td>"+book.getPrice()+"<td>");
            out.println("<td><a href='"+resp.encodeURL("goshop.do")+"?bookid="+book.getId()+"'>购买此书</a><td>");
            out.println("<tr>");

        }
        /*
        int i,j = 0,k = 0;
        int len = books.size();
        for(i = 0;i < len; i++,j++,k++){
            if(j % 3 == 0){
                out.println("<tr>");
            }
            out.println("<td>");
            out.println("<img src='/img/bookcover/book"+i+".jpeg'>");
            out.println("</td>");
            if(k % 3 == 0){
                out.println("</tr>");
            }
        }
        j = 0;
        k = 0;
        for( i = 0;i < len; i++,j++,k++){
            if(j % 3 == 0){
                out.println("<tr>");
            }
            out.println("<td>");
            out.println("<a href='#'>购买此书</a>");
            out.println("</td>");
            if(k % 3 == 0){
                out.println("</tr>");
            }
        }
        */
        out.println("</table>");
        out.println("</form>");
        out.println("</body>");
        out.println("</html>");
        out.close();
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        processRequest(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        processRequest(req, resp);
    }
}

4.购物车页面

package cc.openhome.controler;

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;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map;

@WebServlet("/cart.view")
public class CartShow extends HttpServlet {
    public void processRequest(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException
    {
        resp.setContentType("text/html;charset=UTF-8");
        HttpSession session = req.getSession();
        Cart carts = (Cart) session.getAttribute("cart");

        PrintWriter out = resp.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC '-//W3C//DTD HTML 4.01'" +
                "Transitional//EN");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>购物结算</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<form action='' method='post'>");
        out.println("<table width='100%'>");
        out.println("<td><img src='img/bookcover/shoping.png' alt='购物车' width='100'>");
        out.println("</table>");
        out.println("<table width='100%'>");
        out.println("<tr>");
        out.println("<td style='color:blue'>书籍编号<td>");
        out.println("<td style='color:blue'>书名<td>");
        out.println("<td style='color:blue'>图片</td>");
        out.println("<td style='color:blue'>单价<td>");
        out.println("<td style='color:blue'>数量<td>");
        out.println("<td style='color:blue'>单本书总价<td>");
        out.println("</tr>");
        int i = 0;
        Map<String,CartItem> bookmap = carts.getBookMap();
        for (String value : bookmap.keySet()){
            i++;
            CartItem citem = bookmap.get(value);
            Book bk = citem.getBook();

            out.println("<tr>");
            out.println("<td>"+bk.getId()+"<td>");
            out.println("<td>"+bk.getName()+"<td>");
            out.println("<td><img src='/img/bookcover/book"+i+".jpeg'></td>");
            out.println("<td>"+bk.getPrice()+"<td>");
            out.println("<td>"+citem.getQuantity()+"<td>");
            out.println("<td>"+citem.getPrice()+"<td>");
            out.println("</tr>");
        }
        out.println("<tr>");
        out.println("<td style='color:green';font-size:200%'>总价</td>");
        out.println("<td style='color:green';font-size:200%'> "+carts.getPrice()+"</td>");
        out.println("</tr>");
        out.println("</table>");
        out.println("</form>");
        out.println("</body>");
        out.println("</html>");
        out.close();

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        processRequest(req, resp);
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        processRequest(req, resp);
    }
}

5,书籍类

package cc.openhome.controler;

import java.util.ArrayList;

public class Book {
    private String id;
    private String name;
    private double price;
    public Book(){

    }
    public Book(String id,String name, double price){
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

6,单个购物车类

package cc.openhome.controler;

public class CartItem {
    private Book book;
    private int quantity;
    private double price;

    public double getPrice() {
        return book.getPrice() * this.quantity;
    }

    public Book getBook() {
        return book;
    }

    public void setBook(Book book) {
        this.book = book;
    }

    public int getQuantity() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

7,购物车类

package cc.openhome.controler;

import java.util.LinkedHashMap;
import java.util.Map;

public class Cart {
    private Map<String,CartItem> bookMap = new LinkedHashMap<>();

    private double price;

    public void addBook(Book book){
        CartItem cartItem = bookMap.get(book.getId());

        if(cartItem == null){
            cartItem = new CartItem();
            cartItem.setBook(book);
            cartItem.setQuantity(1);

            bookMap.put(book.getId(),cartItem);
        }else {
            cartItem.setQuantity(cartItem.getQuantity() + 1);
        }
    }

    public double getPrice() {
        double totalPrice = 0;
        for(Map.Entry<String,CartItem> me : bookMap.entrySet()){
            CartItem cartItem = me.getValue();

            totalPrice += cartItem.getPrice();
        }
        return totalPrice;
    }

    public Map<String, CartItem> getBookMap() {
        return bookMap;
    }

    public void setBookMap(Map<String, CartItem> bookMap) {
        this.bookMap = bookMap;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

8图书数据源

package cc.openhome.controler;

import java.util.LinkedHashMap;

public class BookDb {
    private LinkedHashMap<String,Book> map = new LinkedHashMap<>();

    public BookDb(){
        map.put("1",new Book("1","java编程",10.00));
        map.put("2",new Book("2","C++编程",10.00));
        map.put("3",new Book("3","C编程",10.00));
    }

    public LinkedHashMap<String,Book> getAll(){
        return map;
    }
    public Book findBook(String id){
        return map.get(id);
    }
}

总结:对于个人而言:难点在于
1.页面数据的展示.
2.使用resp.encodeurl 在本页面刷新.
3.使用<a href> 重定向并且带了一个参数,把书的id发送给本页面处理.
4.http session 来存储发送数据.
5.书籍,购物车类的设计.

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原文地址：https://www.cnblogs.com/changlili/p/10000820.html