session的使用和禁止cookie时，购物车的实现

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上一篇博文中，讲到用cookie实现简单的购物车，但是有的用户，会因为不小心把cookie给禁止了，如果遇到这种情况，为了我不损失用户，那也是我们编程人员必须也能让用户感觉到，是在正常购物，下面我从原理讲起，到购物车案例

首先我教大家简单的session使用

下面先了解一下简单的使用方法Demo1创建session,并重定向到Demo2中

import java.io.IOException;

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

public class Demo1 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		HttpSession session = request.getSession();
		session.setAttribute("hello", "hello wolrd");
		response.sendRedirect(request.getContextPath() + "/servlet/Demo2");

	}

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

}

Demo2显示demo1带过来的session数据

package com.itcast.simple;

import java.io.IOException;

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

public class Demo2 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		HttpSession session = request.getSession();
		String hello = (String) session.getAttribute("hello");
		response.getWriter().write(hello);
	}

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

	}

}

简单的讲解，现在来实现，没有cookie的支持，怎么实现购物功能，这里我们用两个类来模拟数据

1.book类来封装书的属性

package cn.itcast.session.javabean;

public class Book {
	private String id;
	private String name;
	private String author;
	private String price;
package com.itcast.session.withoutcookie;

import java.io.IOException;
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 cn.itcast.session.javabean.Book;
import cn.itcast.session.javabean.DB;

public class BuyServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String id = request.getParameter("id");
		Book book = DB.Findbook(id);//通过id找到书
		System.out.println(id);
		HttpSession session = request.getSession();

		ArrayList list = (ArrayList) session.getAttribute("list");//第一次访问里面没有书
		if (list == null) {
			list = new ArrayList<Book>();

		}
		list.add(book);
		session.setAttribute("list", list);
		
		response.sendRedirect(request.getContextPath() + "/servlet/ListCart");//将url重写。使其带着sessionid数据传给ListCart

	}

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

}

 
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public Book() {
		super();
		// TODO Auto-generated constructor stub
	}
	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 getPrice() {
		return price;
	}
	public void setPrice(String price) {
		this.price = price;
	}
	public Book(String id, String name, String author, String price) {
		super();
		this.id = id;
		this.name = name;
		this.author = author;
		this.price = price;
	}
}

2.用来模拟几本书

package cn.itcast.session.javabean;

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

public class DB {
	private static Map<String, Book> books = new LinkedHashMap<String, Book>();

	public static Collection<Book> getAll() {
		return books.values();
	}

	static {
		books.put("1", new Book("1", "php实战", "老路", "hello"));
		books.put("2", new Book("2", "android开发", "老徐", "110"));
		books.put("3", new Book("3", "jdbc开发", "老黎", "106"));
		books.put("4", new Book("4", "c++算法", "老方", "107"));
	}

	public static Book Findbook(String bookid) {
		return books.get(bookid);
	}
}

3.显示购买数的列表，并在链接后面带上超连接

package com.itcast.session.withoutcookie;

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

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

import cn.itcast.session.javabean.Book;
import cn.itcast.session.javabean.DB;

public class ListBookServlet extends HttpServlet {

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

		Collection<Book> all = DB.getAll();
		for (Book book : all) {
			System.out.println(book.getId());
			out.write("<a href=/day07_sisson/servlet/BuyServlet?id="
					+ book.getId() + ">" + book.getName() + "</a></br>");
		}
	}

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

}

4.利用传过来的id，找到书，将书添加到list集合，然后存进session中，最后，将url重写，将session的数据，带到ListCart

package com.itcast.session.withoutcookie;

import java.io.IOException;
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 cn.itcast.session.javabean.Book;
import cn.itcast.session.javabean.DB;

public class BuyServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String id = request.getParameter("id");
		Book book = DB.Findbook(id);//通过id找到书
		System.out.println(id);
		HttpSession session = request.getSession();

		ArrayList list = (ArrayList) session.getAttribute("list");//第一次访问里面没有书
		if (list == null) {
			list = new ArrayList<Book>();

		}
		list.add(book);
		session.setAttribute("list", list);
		
		response.sendRedirect(request.getContextPath() + "/servlet/ListCart");//将url重写。使其带着sessionid数据传给ListCart

	}

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

}

5.展示购物车里面的数据

package com.itcast.session.withoutcookie;

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 cn.itcast.session.javabean.Book;

public class ListCart extends HttpServlet {

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

		HttpSession session = request.getSession();
		writer.write("您浏览过的商品</br>");
		ArrayList<Book> list = (ArrayList<Book>) session.getAttribute("list");
		for (Book book : list) {
			System.out.println(book.getName());
			writer.write(book.getName() + "</br>");

		}

	}

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

}