session实现简单的购物

短命女 2022-08-12 01:59 145阅读 0赞

j假设一个数据库和书对象

//数据库
 class Db{
 	private static Map<String, Book> map = new LinkedHashMap();
 	
 	static{
 		map.put("1", new Book("1","web开发","老张"));
 		map.put("2", new Book("2","spring","老毕"));
 		map.put("3", new Book("3","struts","老张"));
 		map.put("4", new Book("4","jdbc","老黎"));
 	}
 	
 	//拿到书
 	public static Map getAll(){
 		return map;
 	}
 }
 
 //书对象
 class Book{
 	private String id;
 	private String name;
 	private String author;
 	
 	public Book() {
 		super();
 	}
 
 	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;
 	}
 	
 }

将书的列表显示出来

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 		//设置防止乱码
 		response.setCharacterEncoding("utf-8");
 		response.setContentType("text/html;charset=utf-8");
 		PrintWriter out = response.getWriter();
 		out.write("本网站有如下商品： ");
 		
 		request.getSession();
 		
 		Map<String,Book> map = Db.getAll();
 		for(Map.Entry<String,Book> entry : map.entrySet()){
 			Book book = entry.getValue();
 			
 			//重写url防止用户禁用cookie
 			String url = response.encodeURL("BuyServlet?id="+book.getId());
 			out.write(book.getName()+"<a href='"+url+"' target='_blank'>购买</a> ");
 		}
 	}

点击购买后

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 		String id = request.getParameter("id");
 		
 		//根据id号找到书
 		Map<String, Book> map = Db.getAll();
 		Book book = map.get(id);
 		
 		HttpSession session = request.getSession(false);
 		
 		//从session得到书,使用list存放
 		List list = (List) session.getAttribute("list");
 		if(list==null){
 			list = new ArrayList();
 			session.setAttribute("list", list);
 		}
 		list.add(book);
 		
 		//重写url
 		String url = response.encodeRedirectURL("/day07/ListCartServlet");
 		response.sendRedirect(url);
 	}

最后显示购买的界面

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 		
 		//设置防止乱码
 		response.setCharacterEncoding("utf-8");
 		response.setContentType("text/html;charset=utf-8");
 		PrintWriter out = response.getWriter();
 		
 		//由session得到书目
 		HttpSession session = request.getSession(false);
 		
 		
 		//对session进行判断
 		if(session==null){
 			out.write("you do not hava to purchase any goods ");
 			return;
 		}
 		
 		out.write("You purchase the following commodity: ");
 		List<Book> list = (List) session.getAttribute("list");
 		for(Book book : list){
 			out.write(book.getName()+" ");
 		}
 	}