购物车模块

Posted 2020-08-04 行尸走肉

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学习开发购物车模块

发现一个问题，如果web.xml中配置映射路径中/servlet/***,在serlet中，跳转的时候，会在路径中自动添加/servlet，这个真是非常的恶心。下次设置映射的时候，不加/servlet.

首先给出购买页。这里用静态页面。

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP \'shoMerchandise.jsp\' starting page</title>

</head>

<body>
    <table width=424 " height="583" border="0" align="center">
        <tr>
            <td width="190"><img alt="hpcomputer"
                src="images/hppavilion.jpg"></td>
            <td width="224"><img src="images/lenovo.jpg">
            <td>
        </tr>
        <tr>
            <td>笔记本电脑</td>
            <td>移动硬盘
        </tr>
        <tr>
            <td>价格：5999.99元</td>
            <td>价格：688.88</td>
        </tr>
        <tr>
            <td>
            <a href="servlet/AddShoppingCart?id=0001&name=笔记本电脑&price=5999.00"><img src="images/buybutton.gif" width="71" height="21" border="0" /></a>
            </td>
            <td>
            <a href="servlet/AddShoppingCart?id=0002&name=移动硬盘&price=688.88"><img src="images/buybutton.gif" width="71" height="21" border="0"/></a>
        </tr>
    </table>
</body>
</html>

View Code

点击购买，跳转到addShoppingCart.java，这是一个servlet，处理的事件为把点击购买的商品添加到购物车中：

过程是，首先从session中读取shoppingcart，如果为空，则一个购物车类（通过Shop类），然后在session中新建一个购物车的信息。

session.setAttribute("shoppingcart", cart);

否则的话，就从session中读取出shoppingcart的信息。保存在javabean：ShoppingCart new cart中。

然后接收request传递到服务器的信息，并验证信息的合法性。

//获得商品的基本信息
        String id=request.getParameter("id");
        String name=request.getParameter("name");
        byte source [] = name.getBytes("iso8859-1");
         name = new String (source,"UTF-8");
        String quantity=request.getParameter("q");
        String price = request.getParameter("price");
        System.out.println(id+name+quantity+price);
        
        //检验要加入的商品信息
        if(StringTool.validateNull(id)||StringTool.validateNull("name")||StringTool.validateNull("price")||StringTool.validateNull("quantity")){
            printError(request,response);
            return;
        }
        id=StringTool.filterHtml(id);
        name=StringTool.filterHtml(name);

View Code

之后，执行cart的添加商品javebean：CartItem的addItem方法，把商品添加到cart中去。

        try{
            if(StringTool.validateNull(quantity)){
                //根据传入的商品数据创建商品，然后利用addCartItem方法添加进购物车
                cart.addItem(new CartItem(id,name,1,Double.parseDouble(price)));
                System.out.println(Double.parseDouble(price));
            }else{
                cart.addItem(new CartItem(id,name,Integer.parseInt(quantity),Double.parseDouble(price)));
            }
        }catch(NumberFormatException e){
            printError(request,response);
            return;
        }

View Code

这里并没有更新session，我这样理解：cart是建立的一个指针，它们之间（cart、session）是浅复制，所以不必更新session。

跳转到展示购物车的页面。

response.sendRedirect("GetShoppingCart");

这里就是我说的自动添加/servlet那个问题之一，按理说，按照映射的话，应该是/servlet/×××，但是由于是在servlet中跳转的，所以会自动在跳转路径中添加/servlet。

可以自己试一下。

如果商品添加失败，在输出错误信息。

下面是完整代码：AddShoppingCart.java

package com.cjg.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 com.cjg.bean.CartItem;
import com.cjg.bean.ShoppingCart;
import com.cjg.tools.*;

public class AddShoppingCart extends HttpServlet {

    /**
         * The doGet method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to get.
         * 
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        doPost(request,response);
    }        
    /**
         * The doPost method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to post.
         * 
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
          response.setCharacterEncoding("utf-8");
          
        PrintWriter out = response.getWriter();
        response.setContentType("text/html;charset:utf-8");
        HttpSession session = request.getSession();//获取session
        ShoppingCart cart=(ShoppingCart) session.getAttribute("shoppingcart");
        //当购物车为空时
        if(cart==null){
            cart=new ShoppingCart();
            session.setAttribute("shoppingcart", cart);
            
        }
        
        //获得商品的基本信息
        String id=request.getParameter("id");
        String name=request.getParameter("name");
        byte source [] = name.getBytes("iso8859-1");
         name = new String (source,"UTF-8");
        String quantity=request.getParameter("q");
        String price = request.getParameter("price");
        System.out.println(id+name+quantity+price);
        
        //检验要加入的商品信息
        if(StringTool.validateNull(id)||StringTool.validateNull("name")||StringTool.validateNull("price")||StringTool.validateNull("quantity")){
            printError(request,response);
            return;
        }
        id=StringTool.filterHtml(id);
        name=StringTool.filterHtml(name);
        try{
            if(StringTool.validateNull(quantity)){
                //根据传入的商品数据创建商品，然后利用addCartItem方法添加进购物车
                cart.addItem(new CartItem(id,name,1,Double.parseDouble(price)));
                System.out.println(Double.parseDouble(price));
            }else{
                cart.addItem(new CartItem(id,name,Integer.parseInt(quantity),Double.parseDouble(price)));
            }
        }catch(NumberFormatException e){
            printError(request,response);
            return;
        }
        response.sendRedirect("GetShoppingCart");
        //System.out.println("ssss");
    }
    
    //商品添加失败的输出信息
    private void printError(HttpServletRequest request, HttpServletResponse response)throws ServletException,IOException {
        
        response.setContentType("text/html;charset:utf-8");
        PrintWriter out =response.getWriter();
        out.println("<html>");
        out.println("<head><title>购买商品失败</title></head>");
        out.println("<body>");
        out.println("<h1>缺少商品参数或者商品参数不正确，添加商品到购物车中不成功</h1><br><br>");
        out.println("<a href=\\"/onlineshoppingcart/showMerchandise.htm\\">继续浏览商品，添加商品到购物车</a><br>");
        out.println("</body>");
        out.println("</html>");
        out.flush();
        out.close();
    }

}

View Code

解决form表单提交乱码的问题：

byte source [] = name.getBytes("iso8859-1"); 
name = new String (source,"UTF-8");

先把提交的内容以iso编码格式存储，然后保存为utf-8格式。

然后是商品展示页：

用servlet小程序处理，显示购物车的全部商品：

首先取得session

HttpSession session =request.getSession();

然后判断是否有shoppingcart记录，如果没有，显示购物车为空，如果有，显示购物车中的全部物品，并且计算几个。

在ShoppingCart中，我们每中物品只保存一次，然后更新它存在的个数。显示的时候，可以根据商品个数分别显示，也可以同种商品显示在一起。

并且调用CartItem类的getSum方法计算出总价格。

package com.cjg.servlet;

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

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 com.cjg.bean.CartItem;
import com.cjg.bean.ShoppingCart;

public class GetShoppingCartServlet extends HttpServlet {

    /**
         * The doGet method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to get.
         * 
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html; charset=utf-8");
        PrintWriter out = response.getWriter();
        doPost(request, response);
    
    }

    /**
         * The doPost method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to post.
         * 
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html;charset=utf-8");
        System.out.println(request.getContextPath());
        PrintWriter out = response.getWriter();
        //获取session
        HttpSession session =request.getSession();
        
        //从session中取出购物车信息
        ShoppingCart cart=(ShoppingCart)session.getAttribute("shoppingcart");
        
        
        out.println("<!DOCTYPE HTML PUBLIC \\"-//W3C//DTD HTML 4.01 Transitional//EN\\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        if(cart==null){
            out.println("<h1>您的购物车为空<h1>");
            out.println("<a href=\\"ShopCart/showMerchandise.jsp \\">去买几件</a> ");
            return;
        }
        out.println("<h1>您的购物车信息：<h1>");
        out.println("<a href=${pageContext.request.contextPath()}+\\"/showMerchandise.jsp\\">再买点</a>");
        printCartItem(out,cart);
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }
    /*
     * 显示购物车中的商品
     */
    private void printCartItem(PrintWriter out, ShoppingCart cart) {

        //创建一个购物车，用list接收全部上面的信息，然后循环输出出来。
        ArrayList<CartItem> items=cart.getCart();
        
        //定义一个商品对象,用于遍历的中转容器
        CartItem item=null;
        
        //定义表格，输出表头
        out.println("<table width=\\"500\\" border=\\"1\\" align=\\"lefg\\" >" );
        out.println("<tr>");
            out.println("<td with=\\"200\\">商品名称</td>");
            out.println("<td with=\\"100\\">价格</td>");
            out.println("<td with=\\"100\\">数量</td>");
            out.println("<td with=\\"100\\">合计</td>");
            for(int i=0;i<items.size();i++){
                out.println("<tr>");
                item=items.get(i);
                out.println("<td>"+item.getName()+"</td>");
                out.println("<td>"+item.getPrice()+"</td>");
                out.println("<td>"+item.getQuantity()+"</td>");
                out.println("<td>"+item.getSum()+"</td>");
                out.println("</tr>");
            }
        out.println("</tr>");
        
    }

}

View Code

定义的javabean

首先是商品类：

package com.cjg.bean;

public class CartItem {
    private String name;
    private int quantity;
    private double price;
    private String id;
    private String desc;
    private double sum=0.0;
    public CartItem(String id,String name,int quantity,double price){
        this.id=id;
        this.name=name;
        this.quantity=quantity;
        this.price=price;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getQuantity() {
        return quantity;
    }
    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getDesc() {
        return desc;
    }
    public void setDesc(String desc) {
        this.desc = desc;
    }
    public double getSum(){
        return this.quantity*this.price;
    }
    
}

View Code

然后是购物车类：

package com.cjg.bean;

import java.util.ArrayList;

import javassist.bytecode.Descriptor.Iterator;

public class ShoppingCart {
    private   ArrayList<CartItem> cart;
    public ShoppingCart(){
        cart =new ArrayList<CartItem>();
        
    }
    public ArrayList<CartItem> getCart(){
        return cart;
    }
    public  void addItem(CartItem item){
        CartItem olditem=null;
        if(item!=null){
            for(int i=0;i<cart.size();i++){
                olditem=cart.get(i);
                if(olditem.getId().equals(item.getId())){
                    olditem.setQuantity(olditem.getQuantity()+item.getQuantity());
                    return;
                }
            }
        }
        cart.add(item);
    }
    public boolean removeCartItem(String id){
        CartItem item=null;
        for(int i=0;i<cart.size();i++){
            item=cart.get(i);
            if(item.getId().equals(id)){
                cart.remove(i);
                return true;
            }
        }
        return false;
    }
    public double getTotal(){
//        Iterator <CartItem> it = cart.iterator();
//        double sum=0.0;
//        CartItem item=null;
//        while(it.hasNext()){
//            item=it.next();
//            sum=sum+item.getPrice();
//        }
        double sum=0.0;
        CartItem item=null;
        for(int i=0;i<cart.size();i++){
            item=cart.get(i);
            sum=sum+item.getPrice();
        }
            
        return sum;
        
    }

}

View Code

前台展示页：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP \'shoMerchandise.jsp\' starting page</title>

</head>

<body>
    <table width=424 " height="583" border="0" align="center">
        <tr>
            <td width="190"><img alt="hpcomputer"
                src="images/hppavilion.jpg"></td>
            <td width="224"><img src="images/lenovo.jpg">
            <td>
        </tr>
        <tr>
            <td>笔记本电脑</td>
            <td>移动硬盘
        </tr>
        <tr>
            <td>价格：5999.99元</td>
            <td>价格：688.88</td>
        </tr>
        <tr>
            <td>
            <a href="servlet/AddShoppingCart?id=0001&name=笔记本电脑&price=5999.00"><img src="images/buybutton.gif" width="71" height="21" border="0" /></a>
            </td>
            <td>
            <a href="servlet/AddShoppingCart?id=0002&name=移动硬盘&price=688.88"><img src="images/buybutton.gif" width="71" height="21" border="0"/></a>
        </tr>
    </table>
</body>
</html>

View Code

web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <servlet>
    <servlet-name>AddShoppingCart</servlet-name>
    <servlet-class>com.cjg.servlet.AddShoppingCart</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>GetShoppingCart</servlet-name>
    <servlet-class>com.cjg.servlet.GetShoppingCartServlet</servlet-class>
  </servlet>


  <servlet-mapping>
    <servlet-name>AddShoppingCart</servlet-name>
    <url-pattern>/servlet/AddShoppingCart</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>GetShoppingCart</servlet-name>
    <url-pattern>/servlet/GetShoppingCart</url-pattern>
  </servlet-mapping>

</web-app>

View Code

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