自学Servlet_9_session(购物车)

先把代码附上：

public class IndexServlet extends HttpServlet {

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

		response.setContentType("text/html;charset=UTF-8");//设置浏览器以什么字符代码打开
		response.setCharacterEncoding("UTF-8");//设置response字符
		PrintWriter  out = response.getWriter();
		
		request.getSession();//这里必须要这么写一下，要获取session对象
		
		//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()){//map.entry别忘记了
			Book book = entry.getValue();
			String url = "/day07/servlet/BuyServlet?id="+book.getId();
			url = response.encodeURL(url);  //得到重写后的url

//要在浏览器后面加上session的id号码

			out.print(book.getName() + "<a href='"+url+"'>购买</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开发","老张"));
		map.put("2", new Book("2","jdbc开发","老黎"));
		map.put("3", new Book("3","struts2开发","老张"));
		map.put("4", new Book("4","spring开发","老黎"));
		map.put("5", new Book("5","hibernate开发","老张"));
	}
	
	public static Map getMap(){
		return map;
	}
	
}

class Book implements Serializable{//重点，别忘了实现序列化
	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;
	}
}

//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();
		Cookie cookie = new Cookie("JSESSIONID",session.getId());
		cookie.setMaxAge(30*60);
		cookie.setPath("/day07");
		response.addCookie(cookie);
		//cookie 没有禁用的时候这么写
		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);
		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);
	}

}

//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/>");
		
		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);
	}

}