Session小案例-----簡單購物車的使用

Session小案例-----簡單購物車的使用

同上篇一樣，這裏的處理請求和頁面顯示同樣用的都是servlet.

功能實現如下：

1，顯示網站的所有商品

2，用戶點擊購買後，能夠記住用戶選擇的商品

3，實現了多個會話共享一個session

4, 實現了瀏覽器禁用cookie後數據共享問題的處理

首頁：

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;

//首頁，顯示網站所有商品
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();
		
		//爲了用戶第一次訪問
		request.getSession();
		
		//1.顯示網站所有商品
		out.print("本網站有如下書籍：<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);  //得到重寫後的url
			out.print(book.getName() + "<a href='"+url+"'>購買</a><br/>");
		}
		
	}

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

}

class DB{
	private static Map<String,Book> map = new HashMap();
	static{
		map.put("1", new Book("1","javaweb開發","老張"));
		map.put("2", new Book("2","jdbc開發","老黎"));
		map.put("3", new Book("3","struts2開發","老張"));
		map.put("4", new Book("4","spring開發","老黎"));
		map.put("5", new Book("5","hibernate開發","老張"));
	}
	
	public static Map getMap(){
		return map;
	}
	
}

class Book implements Serializable{
	private String id;
	private String name;
	private String author;
	
	public Book() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Book(String id, String name, String author) {
		super();
		this.id = id;
		this.name = name;
		this.author = author;
	}
	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;
	}
}

購買頁面：

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;
//購買 
public class BuyServlet extends HttpServlet {

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

		//1.得到用戶想買的書
		String id = request.getParameter("id");
		Book book = (Book) DB.getMap().get(id);
		
		//2.把用戶買的書加在session中用於管理所有書的集合中了
		HttpSession session = request.getSession();

		//覆蓋服務器的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.跳轉到購物車顯示列表
		//request.getRequestDispatcher("/servlet/ListCartServlet").forward(request, response);

		//自動帶上session的ID號
		String url  = response.encodeRedirectURL("/day07/servlet/ListCartServlet");    //實現 url重寫
		response.sendRedirect(url);
		
	}

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

}

購物車列表顯示頁面：

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;

//顯示用戶買的所有書（購物車列表顯示頁面）
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("您購買了如下商品:<br/>");
		

		//先判斷瀏覽器有沒以cookie的形式帶sessionID過來，如果沒有則判斷URL地址有沒有帶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);
	}

}