Session小案例-----简单购物车的使用

同上篇一样，这里的处理请求和页面显示同样用的都是servlet.

功能实现如下：

1，显示网站的所有商品

2，用户点击购买后，能够记住用户选择的商品

3，实现了多个会话共享一个session

4, 实现了浏览器禁用cookie后数据共享问题的处理

首页：

package cn.itcast.shopping;

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

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

//首页，显示网站所有商品
public class IndexServlet extends HttpServlet {

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

		response.setContentType("text/html;charset=UTF-8");
		response.setCharacterEncoding("UTF-8");
		PrintWriter  out = response.getWriter();
		
		//为了用户第一次访问
		request.getSession();
		
		//1.显示网站所有商品
		out.print("本网站有如下书籍：<br/>");
		Map<String,Book> map = DB.getMap();
		for(Map.Entry<String, Book> entry : map.entrySet()){
			Book book = entry.getValue();
			String url = "/day07/servlet/BuyServlet?id="+book.getId();
			url = response.encodeURL(url);  //得到重写后的url
			out.print(book.getName() + "<a href=http://www.mamicode.com/'"+url+"'>购买
");>
购买页面：
package cn.itcast.shopping;

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;
//购买 
public class BuyServlet extends HttpServlet {

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

		//1.得到用户想买的书
		String id = request.getParameter("id");
		Book book = (Book) DB.getMap().get(id);
		
		//2.把用户买的书加在session中用于管理所有书的集合中了
		HttpSession session = request.getSession();

		//覆盖服务器的JSESSIONID的cookie
		Cookie cookie = new Cookie("JSESSIONID",session.getId());
		cookie.setMaxAge(30*60);
		cookie.setPath("/day07");
		response.addCookie(cookie);
		
		List list = (List) session.getAttribute("list");
		if(list==null){
			list = new ArrayList();
			session.setAttribute("list", list);
		}
		list.add(book);
		
		//3.跳转到购物车显示列表
		//request.getRequestDispatcher("/servlet/ListCartServlet").forward(request, response);

		//自动带上session的ID号
		String url  = response.encodeRedirectURL("/day07/servlet/ListCartServlet");    //实现 url重写
		response.sendRedirect(url);
		
	}

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

}

购物车列表显示页面：
package cn.itcast.shopping;

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;

//显示用户买的所有书（购物车列表显示页面）
public class ListCartServlet extends HttpServlet {

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

		response.setContentType("text/html;charset=UTF-8");
		response.setCharacterEncoding("UTF-8");
		PrintWriter  out = response.getWriter();
		out.print("您购买了如下商品:<br/>");
		

		//先判断浏览器有没以cookie的形式带sessionID过来，如果没有则判断URL地址有没有带sessionID
		List<Book> list = (List) request.getSession().getAttribute("list");
		for(Book book : list){
			out.print(book.getName() + "<br/>");
		} 
	}

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

}

Session小案例-----简单购物车的使用