简易购物车

简易购物车

就是一个简单的购物车，还可以扩展。

实现原理：

用户在ShowBook页面购书，BuyBookCl进行业务逻辑处理之后，显示在ShowMyCart上。Book是图书信息类，DB是一个内存图书数据库，用来存放初始化图书信息。



使用技术：

1、J***ASE中的ArrayList,HashMap,LinkedHashMap

2、Session技术

3、Servlet技术

4、单例

package com.pc;

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;

/**
 * @author Switch 
 * 功能：显示图书
 */
public class ShowBook extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 字符编码
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		response.setCharacterEncoding("utf-8");
		PrintWriter out = response.getWriter();

		out.println("<h1>欢迎购买</h1>");
		// 取出DB
		ArrayList<Book> db = DB.getBooks();
		for(Book book : db){
			out.println(book.getName() + "<a href='/MyCart/BuyBookCl?id="+ book.getId() + "&name=" + book.getName() + "&price=" + book.getPrice() + "'>点击购买</a><br/>");
		}
		out.flush();
		out.close();
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doGet(request, response);
	}

}

package com.pc;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * @author Switch
 * 功能：处理购书信息
 */
public class BuyBookCl extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 字符编码
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		response.setCharacterEncoding("utf-8");

		// 接收用户购书信息
		String bookname = request.getParameter("name");
		String id = request.getParameter("id");
		String price = request.getParameter("price");
		
		// 从会话获取总价
		Float totalprice = (Float) request.getSession().getAttribute("totalprice");
		// 将总价加入会话中
		if(totalprice == null){
			request.getSession().setAttribute("totalprice", Float.parseFloat(price));
		} else {
			request.getSession().setAttribute("totalprice", totalprice + Float.parseFloat(price));
		}
		
		// 从session中取出mybooks
		HashMap<String, Book> books = (HashMap<String, Book>) request.getSession().getAttribute("mybooks");
		// 如果是第一次购物 books == 空
		if(books == null){
			// 创建集合对象
			books = new LinkedHashMap<String, Book>();
			// 创建book对象
			Book book = new Book();
			book.setId(id);
			book.setName(bookname);
			// 设置图书数量为1
			book.setNum(1);
			books.put(id, book);
			
			// 将bookd加入session
			request.getSession().setAttribute("mybooks", books);
		} else {
			// 检测集合中是否有该书
			if(books.containsKey(id)){
				// 表示数已被购买过
				// 从集合中取出图书
				Book book = books.get(id);
				// 数量+1
				book.setNum(book.getNum() + 1);
			} else {
				// 该图书未被购买过
				Book book = new Book();
				book.setId(id);
				book.setName(bookname);
				book.setNum(1);
				books.put(id, book);
			}
		}
		
		
		// 转发到显示购物车界面
		request.getRequestDispatcher("/ShowMyCart").forward(request, response);

		
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doGet(request, response);
	}

}

package com.pc;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * @author Switch
 * 功能：显示购物车
 */
public class ShowMyCart extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 字符编码
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		response.setCharacterEncoding("utf-8");
		PrintWriter out = response.getWriter();

		// 从session中取出购买的书
		HashMap<String, Book> books = (HashMap<String, Book>) request.getSession().getAttribute("mybooks");
		// 测试
		// System.out.println(books);
		out.println("您的购物车有以下书籍：<br/>");
		Iterator iterator = books.keySet().iterator();
		while(iterator.hasNext()){
			Book book = books.get(iterator.next());
			out.println("书名为：" + book.getName() + " 数量为：" + book.getNum());
			out.println("<br/>");
		}
		out.println("总价为：" + request.getSession().getAttribute("totalprice"));
		out.println("<br/>");
		out.println("<a href='/MyCart/ShowBook'>返回购物大厅</a>");
		out.flush();
		out.close();
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doGet(request, response);
	}

}

package com.pc;
/**
 * @author Switch
 * 功能：存储图书信息
 * id------id号
 * name----书名
 * num-----数量
 * price---价格
 */
public class Book {
	private String id;
	private String name;
	private int num;
	private float price;
	
	// 设置器与获取器
	public String getId() {
		return id;
	}
	public float getPrice() {
		return price;
	}
	public void setPrice(float price) {
		this.price = price;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getNum() {
		return num;
	}
	public void setNum(int num) {
		this.num = num;
	}
}

package com.pc;

import java.io.Serializable;
import java.util.ArrayList;

/**
 * 
 * @author Switch
 * 功能：模拟内存数据库,单例实现
 *
 */
public final class DB implements Serializable{
	private static ArrayList<Book> books = null;
	
	private DB(){
		
	}
	
	// 静态代码块初始化图书信息
	static{
		books = new ArrayList<Book>();
		Book book1 = new Book();
		book1.setId("1");
		book1.setName("Think in Java");
		book1.setPrice(99);
		books.add(book1);
		Book book2 = new Book();
		book2.setId("2");
		book2.setName("Javascript权威指南");
		book2.setPrice(139);
		books.add(book2);
		Book book3 = new Book();
		book3.setId("3");
		book3.setName("Head First Servlet & JSP");
		book3.setPrice(129);
		books.add(book3);
		Book book4 = new Book();
		book4.setId("4");
		book4.setName("设计模式之禅");
		book4.setPrice(89);
		books.add(book4);
		Book book5 = new Book();
		book5.setId("5");
		book5.setName("Java核心技术");
		book5.setPrice(139);
		books.add(book5);
	}
	// 返回图书集合
	public static ArrayList<Book> getBooks() {
		return books;
	}
}

----------参考《韩顺平.细说Servlet》