上一篇写模拟购物车不够详细，只写了买一个商品进购物车的场景，这次提供一个完整的模拟购物车的例子（可以选取多个商品进购物车）

(上一篇的连接:http://blog.csdn.net/acmman/article/details/43450845)

购物车的主页，有商品列表，每一个商品后面都有一个"购买"按钮，用户点击商品的购
买按钮，就会将商品加入购物车(也就是将商品加入session中)
ListBookServlet:

package cn.edu.shoping;


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


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


//代表网站首页，列出所有书
public class ListBookServlet extends HttpServlet {


	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        
        request.getSession();//给下面的url用
        
        out.print("本站有如下商品:<br/>");
        Map<String,Book> map=Db.getAll();
        for(Map.Entry<String, Book> entry:map.entrySet()){
        	Book book=entry.getValue();
        	
        	//为了防止用户禁止cookie
        	String url=response.encodeRedirectURL("/day07/BuyServlet?id="+book.getId());
        	out.print(book.getName()+"<a href='"+url+"' target='_blank'>购买</a><br/>");
        }
	}


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


}


//模拟数据库
class Db{
	private static Map<String,Book> map=new LinkedHashMap();//HashMap取


出来和存进去的顺序不是一致的（自己测试）
	//类初始化代码（写在静态代码块里）
	static{
		map.put("1",new Book("1","JAVAWEB开发","老张","一本好书！"));
		map.put("2",new Book("2","JDBC开发","老张","一本好书！"));
		map.put("3",new Book("3","Spring开发","老黎","一本好书！"));
		map.put("4",new Book("4","struts开发","老毕","一本好书！"));
		map.put("5",new Book("5","android开发","老黎","一本好书！"));
	}
	
	public static Map getAll(){
		return map;
	}
}


class Book{
	private String id;
	private String name;
	private String author;
	private String description;
	
	public Book(){
		super();
	}
	public Book(String id, String name, String author, String 


description) {
		super();
		this.id = id;
		this.name = name;
		this.author = author;
		this.description = description;
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAuthor() {
		return author;
	}
	public void setAuthor(String author) {
		this.author = author;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	
	
}

购买的Servlet，将买到的新商品加入到List集合中，然后将List集合添加到session中
(已经有了就更新session)。
BuyServlet:

package cn.edu.shoping;


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


import javax.servlet.ServletException;
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;


public class BuyServlet extends HttpServlet {


	public void doGet(HttpServletRequest request, HttpServletResponse 


response)
			throws ServletException, IOException {
       String id=request.getParameter("id");
       
       Book book=(Book) Db.getAll().get(id);
       
       HttpSession session=request.getSession(false);//session在主页已经得到，不需要在再创建
       
       //手工以cookie形式发session，以解决关闭浏览器后，上次买的东西还在
       String sessionid=session.getId();//详见sessio的id
       Cookie cookie=new Cookie("JSESSIONID",sessionid);
       cookie.setPath("/day07");
       cookie.setMaxAge(30*60);
       response.addCookie(cookie);
       
       
       //从session中得到用户用于保存所有书的集合（购物车）
       List list=(List)session.getAttribute("list");
       
       if(list==null){
    	   list=new ArrayList();
    	   session.setAttribute("list", list);
       }
       list.add(book);
       session.setAttribute("list", list);
       
       //转发(用转发只要刷新，就会买一本书，相当于重新执行该页面，重新发送了一次指令)
       //原因，转发时URL没有换，URL中带有参数，相当于又一次传参
       //所以不要用转发，要用重定向
       //request.getRequestDispatcher("/ListCarServlet").forward(request, response);
       
       //重定向，为了以后项目会改名字，故项目名字最好不要写死在程序中，用request.getContextPath()代替项目名
       String url=response.encodeRedirectURL(request.getContextPath()+"/ListCarServlet");
       response.sendRedirect(url);
	}
	
	public void doPost(HttpServletRequest request, HttpServletResponse 


response)
			throws ServletException, IOException {
      doGet(request,response);
	}


}

购物车的显示Servlet，在session中取出用户购买的商品的List列表，然后输出在界面
上。如果用户没有购买东西，就会检测到session中对应属性是null的，然后就会提醒
用户没有购买商品。

ListCarServlet:

package cn.edu.shoping;


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


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


//显示用户购买的商品
public class ListCarServlet extends HttpServlet {
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        
       HttpSession session=request.getSession();
       if(session==null){
    	   out.print("您没有购买任何商品！<br/>");
    	   return;
       }
       
       out.print("您购买了如下商品：<br/>");
       List<Book> list=(List) session.getAttribute("list");
       for(Book book:list){
    	   out.print(book.getName()+"<br/>");
       }
       
	}


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


}

 至此，实现了一个完整的购物网站的购物车小样例

转载请注明出处:http://blog.csdn.net/acmman